Comparative analysis of hollow and solid sandcrete blocks for external walling in auchi, edo state, nigeria

COMPARATIVE ANALYSIS OF HOLLOW AND SOLID SANDCRETE
BLOCKS FOR EXTERNAL WALLING IN AUCHI, EDO STATE, NIGERIA
BY
ALEGBE MARK
FES/ARC/15/19535
DEPARTMENT OF ARCHITECTURE
AMBROSE ALLI UNIVERSITY
EKPOMA
EDO STATE, NIGERIA
SEPTEMBER, 2018

ii
COMPARATIVE ANALYSIS OF HOLLOW AND SOLID SANDCRETE
BLOCKS FOR EXTERNAL WALLING IN AUCHI, EDO STATE, NIGERIA
BY
ALEGBE MARK
FES/ARC/15/19535
A THESIS SUBMITTED TO THE DEPARTMENT OF ARCHITECTURE,
AMBROSE ALLI UNIVERSITY, EKPOMA, EDO STATE IN PARTIAL
FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF
BACHELOR OF SCIENCE (B.Sc.) DEGREE IN ARCHITECTURE
SEPTEMBER, 2018

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DECLARATION
I hereby declare that this work titled: “COMPARATIVE ANALYSIS OF HOLLOW AND
SOLID SANDCRETE BLOCKS FOR EXTERNAL WALLING IN AUCHI, EDO STATE,
NIGERIA” is a collection of my original research work and it has not been presented for any
other qualification anywhere. Information from other sources (published or unpublished) has been
duly acknowledged.
ALEGBE MARK ………………………….
FES/ARC/15/19535 SIGNATURE/DATE
AMBROSE ALLI UNIVERSITY, EKPOMA

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CERTIFICATION
This research work titled: “COMPARATIVE ANALYSIS OF HOLLOW AND SOLID
SANDCRETE BLOCKS FOR EXTERNAL WALLING IN AUCHI, EDO STATE,
NIGERIA” by: ALEGBE MARK (FES/ARC/15/19535) meets the regulations
governing the award of the degree of Bachelor of Science (B.Sc.) of Ambrose Alli
University, Ekpoma and it is approved for its contribution to scientific knowledge
and literary presentation.
………………………… …………………………
SUPERVISOR SIGNATURE/DATE
………………………… …………………………
HEAD OF DEPARTMENT SIGNATURE/DATE
………………………… …………………………
DEAN OF SCHOOL SIGNATURE/DATE

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DEDICATION
To the memory of my father, Mr Friday Alegbe (1955-2010), who gave his all to ensure I be
educated.

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ACKNOWLEDGEMENT
I am grateful and highly indebted to Arc. Dr. Dimuna K.O. my supervisor and Head of
Department of Architecture, AAU for his tireless efforts towards the completion of this research
work.
Also, my sincere gratitude goes to all the lecturers of the Department of Architecture for their
support and contribution in providing a suitable environment for learning.
Notably, I want to specially thank Arc. Akhanolu A. for his assistance and advice, I am very
grateful.
Great acknowledgements are also made to Walliyu Tokpe, Momodu Dauda and Omonekhai
Habbebah for their support, advice and updates regarding matters related to the work. It was a
thing of joy working together with them.
I also want to appreciate the management of Akhoka blocks industry, Auchi for their permission
to freely carry out on site tests on their blocks and using their block moulding machines. My
appreciation also goes to management and staff of Momoh blocks, Zion blocks and Imobhigie
blocks industries for granting me interviews.
I also appreciate the assistance of Dr. Ayo-Odifiri O.S of the Department of Architectural
Technology, Auchi polytechnic, Auchi in providing some relevant research materials for this
work.
My special appreciation goes to Student volunteers of the Department of Architectural
technology, Auchi polytechnic, Auchi, Edo State for their contribution towards the distribution
and collection of the research questionnaire.
Finally, I am grateful to the Almighty God for providing me with sound health and mind during
the period of this research work.

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ABSTRACT
Sandcrete blocks are the most widely used type of blocks in the construction industry. This
research compared the use of 150mm and 225mm hollow blocks for external walling in Auchi,
Edo State, Nigeria. Specific objective is to examine the gross area of the blocks that contribute to
the varied amount of mortar consumed during bonding and to establish a mathematical model to
determining the volume of materials used in the production of a unit of solid and hollow blocks.
Primary methods of data collection were used in the study. Data collected were analysed using
frequency tables, line diagrams, percentages and degrees. The study revealed that 0.0107 cubic
meters of materials are needed to produce a unit of 225mm hollow block with 35mm thick web
while 0.0152 cubic meters of materials are needed to produce a unit of 150mm solid block. Also,
0.0048 cubic meters (41%) of mortar is needed to bond two units of 225mm hollow block while
0.0068 cubic meters (59%) of mortar is needed to bond two units of 150mm solid blocks. The
study further revealed that the volume of materials needed to produce 5 units of 150mm solid
blocks would produce 7 blocks of 225mm hollow blocks in a ratio of 1:1.4. The study concludes
that it is more expensive to build a wall entirely of 150mm solid blocks. It is therefore
recommended that the use of 225mm hollow blocks as against 150mm solid blocks should be
encouraged

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Table of Contents
DECLARATION............................................................................................................................ iii
CERTIFICATION ...........................................................................................................................iv
DEDICATION..................................................................................................................................v
ACKNOWLEDGEMENT...............................................................................................................vi
ABSTRACT....................................................................................................................................vii
List of Figures..................................................................................................................................xi
List of Tables ..................................................................................................................................xii
List of Appendices ........................................................................................................................ xiii
CHAPTER ONE...............................................................................................................................1
INTRODUCTION ............................................................................................................................1
1.1 General ...............................................................................................................................1
1.2 Statement of the Problem...................................................................................................2
1.3 Aim and Objectives of the study........................................................................................3
1.3.1 Aim ..................................................................................................................................3
1.3.2 Objectives ........................................................................................................................3
1.4 Scope of the Study..............................................................................................................3
1.5 Justification of the Study ........................................................................................................4
CHAPTER TWO ..............................................................................................................................5
LITERATURE REVIEW .................................................................................................................5
2.1 Blocks .....................................................................................................................................5
2.1.1 Sandcrete blocks ..............................................................................................................6
2.1.1.2 Constituents of Sandcrete blocks..............................................................................8
2.1.1.3 Strength and durability properties of hardened Sandcrete blocks ..........................12
2.1.1.4 Manufacture of Sandcrete blocks............................................................................15
2.1.1.5 Factors affecting the strength and of Sandcrete blocks ..........................................18
2.1.2 Sandcrete solid blocks....................................................................................................20
2.1.3 Sandcrete hollow blocks ................................................................................................20
2.1.3.1 The benefits of hollow concrete block....................................................................21
2.1.3.2 HOLLOW CONCRETE BLOCKS USED IN CONSTRUCTION........................21
2.2 Mortar ...................................................................................................................................22
2.2.1 Requirement for the use of mortar for bonding .............................................................23
CHAPTER THREE ........................................................................................................................25
RESEARCH METHODOLOGY....................................................................................................25
3.1 Introduction...........................................................................................................................25

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3.2 Research design ....................................................................................................................25
3.3 Sampling methods.................................................................................................................26
3.4 Instruments used ...................................................................................................................27
3.5 Method of data collection .....................................................................................................28
3.5.1 Surveys and interviews ..................................................................................................28
3.5.2 Field experiments...........................................................................................................29
3.6 Method of data analysis ........................................................................................................29
3.7 Conclusion ............................................................................................................................29
CHAPTER FOUR...........................................................................................................................31
RESULTS, FINDINGS AND DISCUSSIONS ..............................................................................31
4.1 Introduction...........................................................................................................................31
4.2 Respondents..........................................................................................................................31
4.3 Reasons behind choice of blocks ..........................................................................................34
4.3.1 Durability of Blocks.......................................................................................................34
4.3.2 Thermal comfort ............................................................................................................35
4.3.3 Time saving and use of mortar.......................................................................................36
4.4 Influences on choice of blocks..............................................................................................37
4.4.1 Cost as an influence .......................................................................................................37
4.4.2 Client and budget as influences .....................................................................................39
4.4.3 Project location as an influence .....................................................................................40
4.5 Comparative benefits of choice made on selection of blocks...............................................41
4.5.1 Preference ......................................................................................................................41
4.5.2 Thermal comfort and concealing pipe works.................................................................43
4.6 Improving on the quality of external walls...........................................................................44
4.7 Field experiments..................................................................................................................46
4.7.1 Volume comparison results on constituent materials ........................................................46
4.7.2 Volume comparison results on mortar...........................................................................47
4.7.3 Volume comparison per square meter of wall area .......................................................49
CHAPTER FIVE ............................................................................................................................53
CONCLUSIONS AND RECOMMENDATIONS .........................................................................53
5.1 Conclusions...........................................................................................................................53
5.2 Recommendations.................................................................................................................55
5.3 Contribution to knowledge ...................................................................................................55
REFERENCES ...............................................................................................................................57

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APPENDICES ................................................................................................................................60

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List of Figures
Figure 1 225 mm hollow block.....................................................................................................7
Figure 2 150mm hollow block......................................................................................................7
Figure 3 225mm solid block .........................................................................................................8
Figure 4 150mm solid block .........................................................................................................8
Figure 5 3D images of 225mm and 150mm solid blocks respectively.......................................20
Figure 6 3D images of 225mm and 150mm hollow blocks respectively ...................................20
Figure 7 Profession of respondents (N=43)................................................................................32
Figure 8 Years of experience of correspondents (N=43)............................................................32
Figure 9 Project handled by correspondence (N=43) .................................................................33
Figure 10 Place of residence of correspondents (N=39).............................................................33
Figure 11 225mm hollow block as the most durable (N=42).....................................................34
Figure 12 Durability as a major consideration (N=43)...............................................................35
Figure 13 Reason behind choice of 225mm hollow blocks for external walls (N=42) ..............35
Figure 14 Time savers in laying of blocks (N=43).....................................................................36
Figure 15 Savings on mortar consumption (N=43) ....................................................................37
Figure 16 How resources affect choice of blocks (N=42) ..........................................................38
Figure 17 Cost as a major reason affecting choice of blocks (N=43).........................................38
Figure 18 Reason behind selection of 150mm solid block (N=43) ............................................39
Figure 19 Client and budget as influences (N=42).....................................................................40
Figure 20 Project as an influence on selection of blocks (N=43)...............................................41
Figure 21 Level of preference to block type under study (N=43) ..............................................42
Figure 22 Comparing 225mm hollow block and 150mm solid block (N=43) ...........................42
Figure 23 Solid blocks and thermal comfort (N=43)..................................................................44
Figure 24 Solid blocks and concealment of pipe works (N=43) ................................................44
Figure 25 Safety and durability of walling units (N=39)............................................................45
Figure 26 Guarantee of quality of blocks (N=39).......................................................................45
Figure 27 Volume of constituent materials.................................................................................47
Figure 28 Percentage comparison of constituents between blocks.............................................47
Figure 29 Mortar bedding over blocks........................................................................................48
Figure 30 Volume of mortar comparison....................................................................................48
Figure 31 Square meter area of 225mm hollow block................................................................49
Figure 32 Square meter area of 150mm solid block...................................................................50
Figure 33 Volume comparison per meter square of wall............................................................50

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List of Tables
Table 1 Strengths of machine vibrated and manually compacted blocks...................................13
Table 2 Years of experience of correspondents (N=43) .............................................................32
Table 3 Time savings in laying and use of mortar (N=43).........................................................36
Table 4 Influences on selection process of blocks......................................................................39
Table 5 Volume comparison table of 225mm hollow and 150mm solid blocks ........................51

xiii
List of Appendices
APPENDICE A Questions adopted for investigation.....................................................................60
APPENDICE B Questionnaire adopted for investigation ..............................................................62
APPENDICE C Data analysis sheet ...............................................................................................72
APPENDICE D Summary sheet of analysis...................................................................................80

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CHAPTER ONE
INTRODUCTION
1.1 General
Walls are the chief element in the construction of most buildings. They are often required to be
load bearing; supporting multi-floors or non-load bearing; serving as partition, separating or
dividing walls. Sandcrete blocks are the most commonly used unit in wall construction in modern
Nigeria and, indeed, most part of Africa. The use of laterite and other forms of walling units for
the construction of modern residential buildings have not made much developmental impact when
compared to the use of Sandcrete blocks. The same can also be said of bricks. One of the major
advantages of Sandcrete blocks is the ease of production and laying of the blocks.
Okere, (2012) opined that the structural properties of blocks of interest include compressive
strength, flexural strength, water absorption, modulus of elasticity, shear modulus and split tensile
strength. Others are density, fire resistance, durability and thermal conductivity. These properties
depend to a very large extent on the relative proportions of the constituents and the method
involved in the process of production.
Sandcrete blocks are traditionally made of cement, river sand and water. The constituents are
mixed and placed in a mould which is removed immediately after compaction and leveling of the
top. The newly produced blocks are self-supporting; hence they are often referred to as zero
slump concrete. After curing, individual blocks are joined together vertically to form walls via a
process called bonding. It is often the practice to partially replace the sand portion with other
materials such as laterite, coarse aggregate or quarry dust. According to Okeke, (2012), sandcrete
blocks in which the sand portion has been partially replaced with quarry dust are often referred to
as sand-quarry dust blocks.

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1.2 Statement of the Problem
There have been a growing interest, locally on the use of solid concrete blocks as the main
building envelop and partition of internal spaces in most places in Nigeria. This is partly as a
result of the manufacturing of Sandcrete blocks without any reference to suit local building
requirement or good quality work. (Anosike et al), 2012, Anosike and Oyebode, (2012),
Omopariola, (2014) define quality as fitness for purpose or compliance with specification.
According to Alohan (2012), the majority of Sandcrete blocks used in Nigerian building industry
fall short of minimum specifications. These are some of the reasons why people opt for solidity or
rigidity of construction wall without paying much attention to other factors that compliments the
functional requirement for external walls. In addition, Omopariola (2014) stated that the rapid
increase in the cost and demand for cement has untold effect on the cost of building blocks, this
has led to many commercial block producers to compromise the standard of production in an
attempt to maximize profit.
The problem with selection of the most adequate block to be used for external walling is on the
increase, while some home owners focus their choices on the durability offered by solid sandcrete
blocks, others lay more emphasis on the cost of buying a 225mm hollow Sandcrete block.
Attempts have been made to completely replace the use of 225mm hollow blocks with 150mm or
125mm solid blocks. It goes to show that the effect the general choice of block for external
walling has is partly limited to how much cost one can save; neglecting other important factors
such as services, thermal conductivity and durability.
To decide which constructive solution for a structure is more economical, regardless of the
architectural form, requires information and indicators that help to find economically sustainable
solution. Sazedj, (2012). It is on these bases that a comparative study between hollow and solid
blocks is embarked upon to examine their economic value for external walling. To this end,
answers must be provided to such questions as;

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I. What are the basic reasons behind users‟ choice of block for external walling?
II. What are the benefits of the choice made?
III. What is the cost implication of the choice made?
1.3 Aim and Objectives of the study
1.3.1 Aim
The aim of this study is to analyze by way of comparison, the economic value derived from the
use of 150mm solid and 225mm hollow blocks for external walls.
1.3.2 Objectives
The objectives of this Study are as follows;
1. To investigate the reasons behind the choice of concrete masonry unit as a property of
external walls
2. To study the effect of the choice made on the different concrete masonry unit (CMU) for
external walling
3. To examine the gross area of solid blocks that contributes to the increased usage of mortar
during bonding
4. To establish a mathematical model to determining the volume of materials used in the
production of a unit of concrete solid and hollow blocks
1.4 Scope of the Study
This work would be limited to the comparative economic value derived from the use of solid and
hollow blocks as key materials for external walling systems. Investigations and tests would be
made to compare the amount of materials used up per unit area of wall for each block type from

4
where conclusions would be made as to which is more economical. The properties investigated
will be limited to
 Mortar consumption
 Inert material consumption
All tests will be conducted on hardened specimens of vibrated concrete blocks only. The results
of the test will serve as possible pointers to the reason why a specific type of block is used for
walling.
1.5 Justification of the Study
1. The study will provide additional information for stakeholders in the industry on the
pointers that could affect the cost of walling.
2. The relationship of considered blocks per volume would be a guide on the overall
consumption rate of materials on the production of masonry units.
3. The cost models will be of great use in optimizing the cost of material to be used for block
walling.
4. The relationship formulated between the Concrete Masonry Blocks (CMB) will be of
great help in making estimates, mostly, durability is the major factor considered when
building external walls, prompting the use of solid blocks predominantly.

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CHAPTER TWO
LITERATURE REVIEW
2.1 Blocks
Blocks are the dominant units for modern wall construction in Nigeria and most part of Africa.
They are of many types depending on the constituent materials. The constituents also determine
the integral characteristics of the blocks. The major types of blocks widely used are sandcrete
blocks (water, cement and river sand), soilcrete blocks (water, cement and laterite), concrete
blocks, bricks (burnt clay and additives) and mud blocks. The blocks come in various sizes and
shapes and are broadly classified as hollow or solid blocks and are bonded with binders, usually
sand-cement mortar or lime. Blocks, according to Project National de Researche/Development
(1994), can be regarded as a member of the concrete family. This is especially true for sandcrete
blocks which constitute a mixture of cement, water and sand and differ from concrete by the non-
inclusion of coarse aggregate in the mix.
Of the various types of blocks, the most widely used in Nigeria is sandcrete blocks. Efforts have
been made to encourage the use of the other types of blocks especially soilcrete blocks due to the
binding properties and availability of laterite. To this regards, a lot of research work has been
carried out on the use of soilcrete blocks in building projects in Nigeria. However, in spite of the
reported comparative saving in cost and the formulation of suitable mixes to meet the
requirements as walling units (Agbede and Manasseh, 2008, Adam, 2001, and Boeck et al, 2000,),
the use of soilcrete in modern building construction in Nigeria, to say the least, is not
encouraging. The same goes for bricks. The low usage of soilcrete blocks and bricks in Nigeria is
as a result of the long time spent in the production of soilcrete blocks and the bricks as compared
to the easy production of Sandcrete blocks. Sandcrete blocks also have the advantage of being
easier to place owing to its size and shape.

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2.1.1 Sandcrete blocks
Sandcrete blocks are products of a mixture of cement, sand and water, moulded into different
sizes and cured to a hardened state. Nigerian Industrial Standard (NIS): 87- 2004) defined
sandcrete as a composite material made up of water, cement and sand. It differs from concrete in
terms of material composition because of the non-inclusion of coarse aggregate in the mix, and
from mortar in that the slump is zero. As a matter of fact, Sandcrete is often referred to as zero
slump concrete. The behaviour of Sandcrete is similar to that of concrete and for this singular
reason the terms “concrete” and “Sandcrete” will be used interchangeably in this work.
Sandcrete blocks are by far the most common type of block used in modern day construction in
Nigeria. The major constituents are water, cement, and sand. The sand, according to the NIS 87:
(2004) shall be river, crushed or pit sand, clean, sharp and free from loam, dirt, organic or
chemical matter of any description. The major advantages this type of block has over others are
their easy mode of production and the speed of laying them. Their major setback is obviously
their poor thermal and hygrometric properties. This can greatly affect their durability especially
when they are permanently exposed precipitation and moisture. Rendering walls made of
sandcrete blocks with cement-sand mortar helps improve their resistance to the elements,
improving their overall performance.
Sandcrete blocks are classified as solid or hollow blocks. Hollow blocks have cavities in them
while the solid ones have no cavities. The length, width and height of the major sizes of sandcrete
blocks produced in Nigeria are as follows:

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I. 450mm x 225mm x 225mm (hollow)
Figure 1 225 mm hollow block
II. 450mm x 150mm x 225mm (hollow)
Figure 2 150mm hollow block

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III. 450mm x 150mm x 225mm (solid)
Figure 3 225mm solid block
IV. 450mm x 125mm x 225mm (solid).
Figure 4 150mm solid block
The 450mm x 225mm x 225mm hollow blocks are usually used in load bearing external walls but
that is not the case within our locality where 450mm x 150mm x 225mm or 450mm x 125mm x
225mm solid blocks serve as load bearing external walls.
2.1.1.2 Constituents of Sandcrete blocks
Sandcrete blocks are made of a mixture of water, cement and sand (fine aggregates). More
recently, sandcrete block production often includes the partial replacement of the sand with

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quarry dust or with coarse aggregates to improve the strength and water absorption properties of
the blocks.
(a) Cement.
Cement plays a vital role in concrete production as it is the major material that binds the
constituents into a compact whole (Shetty, 2005, Neville, 2011). It is a product resulting from the
burning at very high temperatures (1300ºc-1500ºc) of certain proportions of ground calcareous
materials such as limestone or chalk and argillaceous materials like clay or shale. The materials
combines into balls called clinker which is allowed to cool. The cooled clinker is then mixed with
gypsum added to improve its properties. The resulting product is what is called Ordinary Portland
cement (OPC) and is in the form of fine powder which, when mixed with water, forms a paste.
Ordinary Portland cement is the most common type of cement used in everyday construction
works. The other types of cement include: Rapid hardening cement, Sulphate resisting cement,
Low heat cement, Extra rapid hardening cement, Portland slag cement to mention but a few.
When water is mixed with cement, physical and chemical changes take place. This process is
known as hydration of the cement. It is through this process of hydration that the cement-water
paste becomes a firm and hard binding mass. During this process, the paste initially sets (stiffens)
and hardens (gain strength) with time. The different compounds hydrate at different periods,
producing heat over different lengths of time thus contributing differently to the rate of strength
development of the hydrated cement.
Cement properties can greatly be affected by the presence of moisture content or on exposure to
air. It is for this reason that it is advised that cement should always be stored in a dry place and
should never be exposed to the air.

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(b). Fine aggregates
Aggregates are inert fillers and constitute generally of at least three-quarters of the total volume of
concrete. This percentage is greater in mixes for sandcrete block production, especially for lean
mixes. Because aggregates are cheaper than cement, it is advantageous to pack as much aggregate
in the concrete as possible. Such high aggregate content “confers considerable technical
advantages on the concrete, which has a higher volume stability and better durability than
hydrated paste alone” (Neville, 2011).
Aggregates are classified into different categories as follows: (i) according to size -- into fine and
coarse aggregates, (ii) source - natural and artificial (man-made) aggregates, (iii) weight -
lightweight and dense aggregate, (iv) particle shape - rounded, irregular, angular and flaky and (v)
particle gradation - into well graded, poorly graded and gap graded.
Fine aggregates are generally those whose particle sizes fall below 5mm while coarse aggregates
are those with particle sizes greater than 5mm. The recent British and European standard (BS EN
12620, 2002) however, puts the dividing line between fine and coarse aggregates at 4mm.
Natural aggregates are those formed from naturally occurring materials such as weathering of
rocks. They include sand, gravel, and crushed rock such as granite, basalt, sandstone and
quartzite. Man-made aggregates on the other hand are manufactured and include sintered fly ash,
aluminum slag and bloated clay.
Lightweight aggregates have oven-dry particle density less than 2000kg/m3 whilst those with
densities greater than 3000kg/m3 are classified as heavy weight aggregates. In between these two
lie the medium weight aggregate (BS EN 206-1, 2000).
A well graded aggregate contains all the different sizes in appropriate ratios. Such aggregates
make better concrete as the smaller sized particles can always fill the spaces between the bigger
ones creating a more compact structure. Again, they make the concrete more workable. Gap

11
graded aggregates have some sizes missing while poorly graded aggregates have disproportionate
ratios of the sizes. Both do not make for the best concrete in terms of strength and workability.
(c) Water
Water plays a very important role in concrete production. Both the quality and quantity of the
water used is of great importance. Water is not only needed during the mixing process but also
during the curing period. The quantity of water used in concrete production is usually expressed
relatively to the cement content, hence the term water/cement (w/c) ratio. This ratio must be
carefully controlled as it greatly affects the strength, workability and durability of the concrete. A
very low w/c ratio will lead to poor hydration of the cement resulting in reduced strength and low
durability. The workability of the concrete will also be poor. Very high ratios also have similar
end effects, as the concrete will even flow.
The quality of the water is often given less attention during concrete production. Many dissolved
particles in water affect the quality and strength of the concrete. The Cement and Concrete
Association of Australia (2002) recommends the mixing water for concrete to be potable and this
is the generally accepted quality for water used in concrete production. In some instances, there
may be more stringent restrictions placed on mixing water. Impurities that if in high concentration
in water may render the water unfit for concrete production include chlorides, suspended solids
and Sulphates. Allowable maximum amount of impurities in mixing water is given in BS EN
1008 (2002) and ASTM C 1602 (2006). Water with pH value less than 6 (acidic) or higher than 9
(basic) is also not acceptable for concrete production.
Sea water contains a high level of chloride which can lead to rapid corrosion of the steel
reinforcement bars used in concrete works especially when the concrete is porous and no
adequate cover is provided for the reinforcement bars. Since these factors cannot always be taken
care of, it is advisable to avoid making reinforced concrete with sea water (Shetty, 2005). The
requirement of water for concrete curing is less stringent however, the water should not contain

12
impurities, dissolved or suspended matter which will stain or attack the hardened concrete. For
instance, water with high amount of iron if used for curing could impair the appearance of the
concrete
2.1.1.3 Strength and durability properties of hardened Sandcrete blocks
Strength and durability are two important properties of hardened concrete blocks. Whereas
strength can be considered as a short term property, durability is long term. These properties are
dependent to a large extent, on the material constituents and the mix proportions, presence of
admixtures and the manufacturing process (Oyekan and Kamiyo, 2011).
(a) Strength properties of concrete
The strength properties of concrete that are of interest are (i) Compressive strength (ii) Shear
strength
(i) Compressive strength
The compressive strength is the most important strength property of concrete used to judge its
overall concrete. It may often be the only strength property of the concrete that may be
determined since with a few exceptions almost all the properties of concrete can be related to its
compressive strength. This is usually determined by subjecting the hardened concrete after
appropriate curing, usually 28 days, to increasing compressive load until it fails by crushing, and
thereafter, determining the crushing force.
Mathematically, it is given as

13
Where;
Tables 1a and 2b respectively show the NIS 87: (2004) 28 day compressive strength requirements
for machine vibrated and manually compacted sandcrete blocks
Table 1 strengths of machine vibrated and manually compacted blocks
(a) Vibrated blocks
Types of Blocks Dimensions (mm) Strength (N/mm²)
Load bearing 450 x 225 x 225 3.45 minimum
Non-load bearing 450 x 225 x 225 Minimum
(b) Manually compacted blocks
Types of Blocks Dimensions (mm) Strength (N/mm²)
Load bearing 450 x 225 x 225 2.5 minimum
Non-load bearing 450 x 225 x 225 1.85 minimum
Many research works done to determine the compressive strength of commercially available
sandcrete blocks produced at various locations in Nigeria produced very disappointing results. For
example, Mahmoud et al (2010) carried out tests on both 450mm x 225mm x 225mm and 450mm
x 225mm x 150 mm blocks from five different manufacturers in Yola, North-eastern Nigeria.
They found that their strength ranged from 0.31 to 1.36N/mm2 and 0.12 to 1.46N/mm2
respectively. These values are far below the minimum recommended values as presented in the

14
table above The results obtained by Mahmoud et al (2010) merely corroborated those previously
obtained by Abdullahi, (2005) and Banuso and Ejeh (2008) who, respectively, investigated the
compressive strengths of commercially produced sandcrete blocks in Minna and Kaduna, both,
prominent cities in Northern Nigeria. Similar poor results were obtained in Southern Nigeria.
These are detailed in works by Olufisayo (2013), Okere (2012), Anosike and Oyebande, (2012)
and Umenwaliri and Ezenwamma (2008).
(ii) Shear strength
This is a measure of the ability of the concrete to resist forces that can cause its internal structure
to slide against itself. It can be determined from a flexural test and is given as:
fs = F/A
Where
fs= shear strength
F = Shear load at failure
A = cross-sectional area of the test specimen
(b) Durability
Durability is that property of concrete that measures its ability to “Continue to perform its
intended functions, that is, maintain its strength and serviceability, during the specified or
expected service life” (Neville, 2011). Shetty (2005) defined durability of concrete as “Its ability
to resist weathering action, chemical attacks, abrasion, or any other process of deterioration.” The
durability of the concrete can be affected by the presence of large quantity of chlorides, Sulphates
and many other natural or industrial liquids and gases. Physical factors such as high temperatures
and thermal expansion of the aggregates in the hardened concrete can also lead to extensive
deterioration of the concrete. Emphasis has been placed on the strength properties of concrete
more than any other property as durability. This may be because the strength properties usually

15
provide a better picture on the quality of the concrete. However, there may be some situations
when durability and other considerations may be of greater importance (Neville, 2011). Such may
be the case when concrete for water retaining structures is under consideration. Durable concrete
is always dense, water proof and able to resist to a reasonable extent, changes resulting from
adverse effects of the elements and mechanical damage.
2.1.1.4 Manufacture of Sandcrete blocks
The production of sandcrete blocks can be discussed under the following subheadings:
a. Batching and mixing
b. Compaction and De-moulding
c. Curing and
d. Storage and Transportation.
(a) Batching and Mixing
Batching is the process of measuring out the various quantities of the components needed for the
production of sandcrete blocks. This can be done by mass or by volume. Batching by mass is
professionally preferable to batching by volume as it eliminates errors due to the variations
contained in a specific volume. However, most producers, especially those that batch manually,
use the volume batching process because it is simpler and much more convenient than weight
batching.
Manual batching is done using head pans or wheel barrows with a bag of cement taken to be
twice the volume of a head pan and the same volume as a wheel barrow. The use of the wooden
boxes for batching is becoming obsolete. Cements are usually supplied in bags of 50kg net
weight. Batching using head pans or wheel barrows does not make for uniformity as these
volumes measured are greatly dependent on the state and size of the head pans or wheel barrows
which greatly vary with producers and locations. It should be noted that sand is usually supplied
wet and it is in this wet condition that it is most often used. The quantity of water added to the

16
mix must therefore be adjusted by reducing the amount of water to be added during mixing to
compensate for the water in the wet sand.
Furthermore, since sandcrete is a zero slump concrete, the amount of water added during mixing
is very important as too little or too much of it would lead to block failure immediately after de-
moulding.
Mixing is done either manually (with shovels or spades) or mechanically (using concrete mixers
of various capacities). Large producers of blocks generally use mixers. This offers a more
uniform and homogenous mix, especially when the volume is large. In manual mixing where
some constituents are lost, components are mixed using shovels or spades and turned over several
times until a homogenous mix is obtained. Whatever method is adopted, adequate mixing is
necessary to achieve uniform colour and texture between block batches prevent variations in
strength and minimize web cracks.
(b) Compaction.
Compaction is a very important process in block production. Compaction is achieved by
mechanically vibrating the mixture or by compacting it manually (by hand). Manual compaction
is less effective and is adopted mainly by small scale producers. One block is produced per time
using a locally constructed mould. The compaction is effected using a tamping rod. Great care is
needed while de-moulding the block in order not to introduce cracks in it.
There are basically three types of machines used in block making in Nigeria. Some of these
machines in addition to compaction also vibrate the blocks. The machine type greatly affects the
quality and the required water used in the block production. The three major types of machines
are (i) Egg laying machines (ii) Electric vibrating machine and (III) Manual hand-press machines.
I. Egg laying machine. The egg laying machines are usually of the Rosa Commetta type that
can lay up to ten blocks at a time. This is used mainly for mass production and the process

17
can be automated, leading to great output of about 300-500 blocks per hour. Both pressure
and vibration are applied resulting to the production of very high quality blocks. The
blocks are usually laid on the ground without pallets and are removed for storage after 2-3
days of production.
II. Vibrating machines: These machines are widely used by medium scale producers. They
are electrically operated or diesel powered. The majority of the machines are designed to
produce one block at a time with the block vibrated for about 10 to 15 seconds. Only few,
however, can produce up to three blocks at a time. The blocks are produced on pallets and
carried to the place of temporary storage, usually in the open. They can provide adequate
compaction. Care must be taken while moving the blocks on the pallets to the place of
temporary storage so as to prevent cracks resulting from vibration while moving the
blocks.
III. Hand-press machine. The hand-press machine is operated manually. De-moulding is
achieved through a series of levers. The hand-press machine does not compact as well as
the egg laying and vibrating machines and hence, produces blocks of lower quality. One
block is moulded at a time.
(c) Curing.
Curing of sandcrete blocks is necessary to enable the blocks develop adequate or optimum
strength by allowing for proper hydration of the cement. Fresh blocks that are exposed to high
temperatures loose water rapidly by evaporation, resulting in weak blocks. Thus, it is
recommended that newly produced blocks be placed in covered shades and protected from the
adverse effect of high temperatures. This is the most common method employed by commercial
block producers. Sprinkling of water should be done at least twice in a day. NIS 87 (2004)
requires that the blocks be left on the pallets for at least 24 hours and be cured for at least 3 days.

18
Adequate care must be taken when removing the pallets for another production so that cracks are
not induced in the blocks.
(d) Storage of cured blocks
Cured blocks are removed to storage by stacking to provide space for new productions. The
blocks need adequate care at this stage, because too much pressure beyond its bearing capacity
can result to damage while stacking. Many blocks are normally damaged at this stage due to poor
handling. NIS 87: (2004) requires that the blocks be stacked not more than 5 courses high. The
blocks are now ready for use.
2.1.1.5 Factors affecting the strength and of Sandcrete blocks
The factors that affect the quality and strength of sandcrete blocks can be divided into three
namely (i) those related to the quality and relative proportions of the constituents (ii) those related
to the manufacturing process and (iii) age of the block.
(a) Factors related to the quality and relative proportions of the constituents.
Of interest here are (a) aggregate gradation (ii) cement /aggregate ratio and (iii) water/cement
ratio.
Aggregate gradation has a great influence on the strength and physical properties of the blocks.
The ideal gradation is a well graded aggregate that will provide a dense pack where spaces
between the big particles will be filled by the smaller ones within. Such gradation also makes for
minimum volume change due to shrinkage. Poorly graded or gap graded aggregate produce less
dense blocks and may also be less workable.
The cement/aggregate ratio is one of the most important factors affecting the strength of blocks.
As discussed earlier, an increase in this ratio leads to an increase in strength. Gooding and
Thomas (1997) showed that while doubling the compaction effort produced a 23% increase in
compressive strength of sandcrete blocks, doubling the cement content produced a whopping

19
140% increase. NIS 87: (2004) recommends cement/sand ratio of 1:6 for sandcrete block
production.
The water/cement ratio also plays a vital role in sandcrete block production. Unlike concrete
which is allowed to set in forms, sandcrete blocks are de-moulded immediately after compaction.
This greatly reduces the range of water/cement ratio over which the blocks can be made. The
water/cement ratio should be such that allows for proper hydration of the cement yet allowing the
fresh blocks to stand unsupported after de-moulding. Like concrete, strength of blocks is known
to decrease with increase in water/cement ratio. Too dry a mix will lead to fracture during de-
moulding while high water/cement ratio will cause shrinkage and distortion in blocks.
(b) Factors related to the manufacturing process.
The two most important factors here are the degree of compaction and the curing process.
Omoregie (2012) showed that the strength of sandcrete blocks is improved with better
compaction. The degree of compaction is largely dependent on the type of moulding machine
used. Umenwaliri and Ezenwamma (2008) studied the effect of production methods on the
strength of sandcrete blocks and concluded that the production method (automated or manually)
affects the strength of the blocks. Strength of vibrated block is improved when additional
surcharge is provided. It should be noted, however, that increasing compaction does not
necessarily imply a more economic production (Gooding and Thomas, 1997).

20
2.1.2 Sandcrete solid blocks
Figure 5 3D images of 225mm and 150mm solid blocks respectively
2.1.3 Sandcrete hollow blocks
A hollow block is defined as one having one or more large holes or cavities which either pass
through the block (open cavity) or do not completely pass through the block (closed cavity) and
having the solid material between 50 and 75 percent of the total volume of the block calculated
from the overall dimensions. Within the limits of these requirements, it is possible to vary the
overall size of blocks and thickness of face and web shells. A large variety of shapes and sizes
have been developed in various countries. A typical example of a sandcrete hollow block is
shown below.
Figure 6 3D images of 225mm and 150mm hollow blocks respectively

21
2.1.3.1 The benefits of hollow concrete block
I. Economy in design of super-structure due to reduction of loads
II. Saving in mortar for laying of blocks as compared to solid blocks.
III. Insulation of walls is achieved due to cavities embedded within the block, which provides
energy saving for all times. Similarly, cavities result in sound insulation.
IV. No problem of the appearance of salts. Hence, there is increased savings in the
maintenance of final finishes to the walls.
V. Laying of blocks is comparatively quicker as compared to solid blocks that are more
difficult to handle
VI. Thermal insulation property of hollow concrete block is more than ordinary brick wall due
to heat transfer within the cavities.
VII. Hollow concrete block is environmentally eco-friendly.
2.1.3.2 HOLLOW CONCRETE BLOCKS USED IN CONSTRUCTION
As regards the use of hollow concrete blocks there are certain remarkable and noteworthy points
going in favor of these blocks.
I. The dead load of hollow concrete block is much lesser than a solid block; due to this, one
can work with a structural engineer to reduce steel consumption in construction.
II. Hollow concrete blocks require minimal mortar.
III. If these blocks are engineered properly during the production process, then dimensional
accuracy and high finishing quality is obtained.
IV. Hollow concrete blocks have additives to improve their water resistance and seepage
minimization.
V. Hollow concrete blocks can be engineered to achieve very high compressive strengths.
VI. Hollow concrete blocks are much sturdier.
VII. The hollow concrete block adapt to modern design forms, richness of the texture

22
VIII. Minimum maintenance cost and cost competitiveness with other materials make it a
preferred material for today‟s building.
IX. Hollow concrete blocks can effectively be used for cold storage as they are thermally
effective
2.2 Mortar
Mortar is a workable paste used to bind building blocks such as stones, bricks, blocks and other
concrete masonry units together, fill and seal the irregular gaps between them and sometimes add
excitingly decorative colours and patterns in walls. On a general note, mortar includes pitch,
asphalt and soft mud or clay such as used between mud bricks. The word “mortar” comes from
Latin “mortarium” meaning crushed.
Cement-sand mortar is the most widely used mortar in Nigeria. It consists of a proportionate
mixture of binder, sand and water. The most common binder since the early 20th
century is
Portland cement. Cement-sand mortar becomes hard when it cures, resulting in a rigid aggregate
structure. However, the mortar serves as the weaker one compared to the building blocks and
serve as the sacrificial element for the building up of the blocks. This is because the mortar is
easier and less expensive to fix than the blocks. There are several types of cement mortars and
additives used pre-historically and up until the modern age. They are;
I. Ancient mortar
II. Ordinary Portland cement mortar (OPC)
III. Polymer cement mortar
IV. Lime mortar
V. Gauged mortar
VI. Surki mortar
VII. Mud mortar
VIII. Firestop mortar

23
IX. Radiocarbon dating
The applications of mortar in various construction phases have made it a very important building
construction material. Some of the numerous functions or role mortar plays in construction are
given below.
1. Mortar is used as a binding agents to bricks, blocks and masonry units
2. It is used to give an even bed between the different layers of masonry units for an even
distribution of pressure over the bed.
3. It is used to fill up the spaces between building blocks to make the wall compact
4. It is also used in plastering works to hide the joints and to improve aesthetic appearance
5. It is also used for moulding and ornamental purposes
2.2.1 Requirement for the use of mortar for bonding
Because of the significant role it plays in the bonding of masonry units, it is always advisable that
the best mortar be used in construction. Therefore, the requirement or properties of a good mortar
must be investigated. Generally, good mortar possesses the following properties;
 Adhesion. Good mortar should be able to provide good adhesive property to building
units.
 Mortar should be water resistant. It should have the capability of resisting the penetration
of water.
 Deformative property of mortar should be significantly low
 Mortar should be relatively cheap
 Mortar should be easily workable under any given site conditions
 Mortar should possess high durability
 Mortar should be able to set quickly to increase construction speed

24
 It is desirable that mortar should last for long periods of time without losing its
appearance. Cracks should not be developed in the joints formed by mortar.

25
CHAPTER THREE
RESEARCH METHODOLOGY
3.1 Introduction
This chapter explains in details, the methodology used in gathering the information that is
pertinent to this study. It highlights the sources of data used and the design of the survey, which
includes the sampling plan and the method used in analyzing data. The steps involved were
elaborated in details and was carried out logically in order to achieve a high degree of reliability
and validity.
According to Ojo (2003), the term methodology is a system of explicit rules and procedure in
which research is based and against which claims of knowledge are evaluated. The methodology
used in a study is integral to the reliability of the findings and the validity of the study. Therefore,
this section emphasizes on the research technique adopted and implemented for this study with
the aim of achieving the research stipulated objectives. This section of the document also contains
description of the instruments used to measure various constructs applicable to this study.
The qualitative research design was used in the study. In-depth individual interviews and a well-
structured questionnaire were conducted and distributed respectively among stakeholders in the
building industry.
The experiments conducted were carried out in four different block making industries within
Auchi, Aviele and Ibie-nafe communities in Edo state. The reason was to investigate within a
closely knitted sample the quality of materials used in the production process of block from which
samples are drawn out randomly to carry out the tests.
3.2 Research design
The qualitative design using semi-structured one-to-one interviews was used for data collection.
The author sought an in-depth understanding of the perceptions of the use of both concrete solid
and concrete hollow blocks for external walling from individuals ranging from building owners,

26
architects, builders, quantity surveyors, general contractors and block making industries
managers. The choice of this design was perceived by the author as fully engaging the industry
personnel on an interview to observe their reactions towards questions designed for the purpose of
gathering facts and information concerning the study area.
The researcher also chose a survey research design because it best served to answer the questions
and the purposes of the study driven by its objectives. The survey research is one in which a
group of people or items are studied by collecting and analyzing data from only a few people or
items considered to be representative of the entire group. In other words, only a part called sample
of the entire item or population is studied, and findings from this are expected to be generalized to
the entire population, (Nworgu), 1991. Similarly, McBurney (1994) defines the survey assessing
public opinion or individual characteristics by the use of questionnaire and sampling methods.
3.3 Sampling methods
The sample is collected from few professionals in the building industry. These professionals from
the industry include architects, engineers, builders, contractors and building owners who are in
one way or the other linked with decision making as it pertains to choice of materials for a given
building project. The sample had been working in the industry for a period ranging from one to
more than ten years. The researcher wished to interview 10 building professionals; 2 each from
architects, builders, contractors, quantity surveyors and building owners but only 8 interviews
was conducted. Only 1 quantity surveyor and a builder could be interviewed. While interviewing
the other two, mid-way into the interview session, they had to leave and a meeting could not be
arranged before data collected could be analyzed. However, the data collected from the eight
parties was, nonetheless adequate enough to have meaningful results. Non-probability sampling
method was relied upon to achieve results that best align with research goals.

27
3.4 Instruments used
Semi-structured interviews which are interviews that allow the researcher to have flexibility in the
way he asked questions were utilized in interviewing the building professionals and home owners.
The researcher designed an interview schedule as one of the data collection instruments for this
study. The interview questions (see Appendix A) were aimed at eliciting relevant information
concerning the choice of block wall for external works. Questions relating to the reason behind
the choice made while selecting the best blocks to be used and the conditions that necessitated it,
perceived problems of any of the selection made as well as possible strategies that could be
adopted to enhance the selection process that would result to a better block frame of building
were asked during the interview schedule.
A questionnaire (see Appendix B) designed by the researcher titled “building blocks for external
works” was also used in the study. The content of the instrument was based on the findings of the
interview conducted (see above) with the core building professionals that have been practicing for
a period of time within Auchi, Aviele and South-Ibie communities of Edo state, Nigeria. The
questionnaire has five sections: A, B, C, D and E: · section “A”, is on demographic information of
respondents; · section “B”, is on the reasons behind choice of blocks for external walls. It has a
total of items; · section “C” contains questions on the comparative benefits of blocks chosen for
external walls. It has 4 items; · section “D”, on the other hand is on cost implication of blocks
used for external walls, which has 6 items; and finally, section “E”, made up of 2 items is on the
possible strategies for improving the quality of walling units used in construction.
The instrument was structured such that answers could be gotten to different questions. However,
while options to question could be varied, it was streamlined to ensure much closer accuracy to
expected results. Questions were structured in the following combinations in different sections as
follows;

28
a. Yes/no question type
b. Multiple choice question type
c. Agree/disagree question type
The aim of combining the different questions type is to ensure quality in delivering research
questions whilst, exposing the respondents to fewer options to choose from.
3.5 Method of data collection
The following sections explore the different methods of primary data collection and describe how
they were applied.
3.5.1 Surveys and interviews
The building professionals identified from the population were asked to decide if they are willing
to assist in the data collection process by responding to the questionnaires and accepting
interviews. From the response that the researcher received, all the parties sampled agreed to
respond to the questionnaire but only accepted the interview process under their own time and
place. The researcher divided the distribution of questionnaires into five groups with each group
consisting of three people. Most of the members of the groups are students. A pilot test was
conducted by the members to ensure it fits without errors, the purpose for which it was designed.
The questionnaires were administered directly to the chosen sample for the study. Out of the fifty
copies of questionnaires given out, forty-two were returned the same day and one, the next day.
Seven of the distributed questionnaires were not returned and response respondents could not be
reached. The possibility of retrieving much of the questionnaires was as a result of the
demography within which the sample was drawn. The opposite could have been the case if the
researcher had taken the task of distributing the questionnaires beyond a streamlined demography.
All the questionnaires were delivered by hand.

29
3.5.2 Field experiments
An experiment aims to isolate a particular event or object so that it can be investigated without
disturbance from its surroundings or activities that are related to it. They are primarily aimed at
gaining data about causes and effects and answer to questions as how? Why? When? What? To
find out how much of a thing is affected by the use of another and in what way or to what extent.
Samples of a 225mm concrete hollow block and a 150mm concrete solid block were used to
experiment on the volume of constituents that make up a unit of each of the blocks. This was done
by measuring samples and calculating the volume of materials using mathematical formulae.
Also, to examine how much mortar is used up by a unit of the samples during bonding in block
walling, mortar was mixed on site and laid over the units. The volumes of mortar used for the
samples were also taken using mathematical formulae. This is aimed at investigating how much
mortar is used on a square meter of block wall made with both sandcrete hollow and sandcrete
solid blocks. The results produced would guide on cost implication for external walling works
To ensure reliability of data collected, same experiments were done in five different prominent
block making industries in Edo state.
3.6 Method of data analysis
Data analysis occurs simultaneously with data collection Holloway & Wheeler (2002). The data
collected from the field were analyzed. Percentages of answered questions were analyzed and
presented in the form of charts, bars and columns for discussion purposes. The presentation would
guide the reader on how the effect of a certain question was perceived and reacted to, from
whence conclusion could be drawn.
3.7 Conclusion
This chapter described the research methodology. The purpose of a research design is to
maximize valid answers to a research questions. This was achieved by using qualitative,

30
exploratory-descriptive approach that was contextual. The researcher was the main data collection
instrument. Data was collected by means of surveys, Interviews and experiments. The main
purpose of the data collection methods was to investigate what influences the choice of blocks
used by building contractors, architects, surveyors and building owners. It also examines the areas
by way of comparison among solid and hollow blocks where cost is more incurred. The
assumptions as well as the findings are stated in the last section of chapter four.

31
CHAPTER FOUR
RESULTS, FINDINGS AND DISCUSSIONS
4.1 Introduction
This chapter discusses the data analysis and findings of the study. The questionnaire used in this
retrospective study was carefully analyzed to ensure that the data gathered was presented clearly
with the aid of tables, percentages, charts and graphs where possible. A chart analysis was
conducted to capture the data essential to accomplish the research objectives.
The aim of this study is to examine the value and importance on construction of the use of solid
and hollow blocks for external walls and the cost implication of the various choices made.
Research questions to answer surround the reasons behind choice of block made for external
walls, the effect of choice made and the cost implication of the choice made. Analyses of findings
are presented such that deductions can be made as regards the research questions. The
questionnaire comprised five sections with a total of 34 structured closed questions that were
developed to ensure rigor, validity and objectivity of data.
4.2 Respondents
As highlighted in section 3.3, the sample for the survey was randomly selected by the researcher
to ensure objectivity in the selection process. As shown in figure 7 below, the sample consists of
43 stakeholders in all. Architects made the highest number with 10 selections, Builders made 9
out of the selection while home owners, contractors and quantity surveyors made up the number
with 8 selections respectively.
The stakeholders as expected have varied wealth of experience in the construction industry. An
analysis carried out on the sample shows that out of the 43 selections, 47% had between 6 and 10
years of experience while 28% had experiences above 10 years.

32
Figure 7 profession of respondents (N=43)
The remaining sample that made up the least percentage had experiences between 1 and 5 years.
See table 2 below.
Table 2 years of experience of correspondents (N=43)
QUESTION Total 1 to 5 6 to 10 >10
What is your year(s) of your experience? 43 25.58% 46.51% 27.91%
20 stakeholders made up the 47% selection, 12 of them comprise 28% of the selection and 11 of
them comprise the least percentage. With a greater percent with experience between 6 and 10
years, results of data collected could be considered reliable. Nonetheless, data analyzed still
shows a good number of stakeholders who had years of experience above 10.
Figure 8 years of experience of correspondents (N=43)
8
10
9
8
8
0 2 4 6 8 10 12
Q.surveyor
Architect
Builder
Contractor
Home owner
Profession of respondents
Profession of respondents
11
20
12
1 to 5
6 to 10
>10
0 5 10 15 20 25
What is your year(s) of your experience?

33
Interestingly, 44% of the respondents had handled between 6 to10 projects in the last ten years.
That is about a project for every two years. It shows summarily, their experience in carrying out
building construction works. The pie chart below shows the percentages of projects handled by
correspondents in the last ten years. As shown in figure 10 below, majority of the correspondents
live within the area of study; Auchi, south-south part of the country. It was discovered that the
rest of the correspondents had on-going projects within the locality as at the time the
questionnaire was reached out to them.
Figure 9 project handled by correspondence (N=43)
Figure 10 place of residence of correspondents (N=39)
1 to 5
33%
6 to 10
44%
>10
23%
Number of projects handled in
the last ten years
1 to 5
6 to 10
>10
0%
10%
20%
30%
40%
50%
60%
70%
80%
North South West East
What part of the country do you reside?

34
4.3 Reasons behind choice of blocks
Contrary to what is trending in Auchi community and its environs where the use of solid blocks is
gaining dominance in building construction, the use of 225mm hollow block had been widely
used by the respondents in their most recent projects. This, the author concludes thus, to imply
that the use of 150mm solid block for external walling works could be an interference of a non-
professional who undermines the quality of 225mm hollow blocks for external walls.
However, in response to the question of blocks used for external walls, 70% agreed to the use of
225mm hollow blocks, 12% agreed to the use of 225mm solid blocks, 16% said they used 150mm
solid block and only 2% had used 150mm hollow block for external walls.
4.3.1 Durability of Blocks
As pertains to durability, it was discovered that 225mm hollow blocks were considered more
durable block to use as compared to 150mm solid blocks. This is owed to the cross sectional area
of 225mm blocks which is greater than 150mm solid blocks. It goes to show that durability is one
of the considerations given before choice of block is made. In figure 11 and figure 12, analyzed
data show that durability of blocks plays a major role when choice of block is to be made.
Figure 11 225mm hollow block as the most durable (N=42)
0% 10% 20% 30% 40% 50% 60% 70% 80%
225mm solid block
225mm hollow block
150mm solid block
150mm hollow block
Which is more durable for external wall?

35
Figure 12 durability as a major consideration (N=43)
4.3.2 Thermal comfort
For users of 225mm hollow blocks, it was discovered that the choice made was not primarily
owed to durability but thermal comfort. Thermal comfort is primarily responsible for the comfort
of occupants within a building envelope. 60% of correspondents said their decision to choose
225mm hollow block was because of the thermal comfort it guarantees, while 12% placed
durability over thermal comfort.
Figure 13 reason behind choice of 225mm hollow blocks for external walls (N=42)
The findings are consistent with Hontus (2014) at Bucharest, Romania where the author
emphasized that hollow blocks as a construction material provide good thermal and acoustic
insulation due to the air gaps in them.
0% 10% 20% 30% 40% 50% 60%
Durability
cost
workability
others
What do you consider most when external wall is to be considered?
0% 10% 20% 30% 40% 50% 60% 70%
Durability
Thermal comfort
Sound proof
To reduce cost
I do not use 225mm for external walls
Why do you choose 225mm hollow block for external walls?

36
4.3.3 Time saving and use of mortar
Time saving is another factor that affects the choice of blocks for walls construction. When
construction speed is increased, time spent is saved and invariably, the cost of construction is
lowered. Among the selected sample, it was discovered that 150mm solid block saves more time
during construction. This according to responses from interview is because of the ease with which
solid blocks are handled.
More so, an overall cost reduction in the construction work could be the reason for people to opt
for solid block during construction. Time used in construction is directly proportional to the
amount spent on construction sites, i.e. the more time is spent on site, the more money that is
used. From figure 14 and table 3, a greater number of respondents suggested that time is saved
and cost is reduced when 150mm solid blocks are used for external walls.
Figure 14 time savers in laying of blocks (N=43)
Table 3 time savings in laying and use of mortar (N=43)
QUESTIONS Total
225mm
solid
block
225mm
hollow
block
150mm
solid
block
150mm
hollow
block
Which saves your time while
laying?
43 14% 21% 42% 23%
Which saves you more on
mortar?
43 5% 35% 37% 23%
0% 10% 20% 30% 40% 50%
225mm solid block
225mm hollow block
150mm solid block
150mm hollow block
Which saves your time while laying?

37
On the use of mortar, it appears there are contrasting views on the type of block that consumes
more on mortar. It shows from data analyzed that 150mm solid block saves more on the amount
of mortar consumed during block laying. This is however contrary to field experiment carried out
where investigations of the block samples that consume more mortar were carried out. In section
4.7.2, it showed that a mortar bedded solid block consumed more material than a hollow block.
The percentages of respondents in favour of 225mm hollow and 150mm solid blocks showed
close values of 35% and 37% respectively. Such values are not contrasting enough to be
dependable.
Figure 15 savings on mortar consumption (N=43)
4.4 Influences on choice of blocks
It has been established that while cost plays a major role in every construction work, there are
other influences as to the selection of blocks used for external walls. Cost reduction has been
proven by this analysis to be one of the reasons that influences the selection of blocks, others as
discussed hereafter include the professional handling the project, Architect and client‟s budget.
4.4.1 Cost as an influence
Findings by the researcher shows that if all resources were readily available, a greater number of
people would use the more durable 225mm hollow blocks as against 150mm solid blocks. Figure
16 below shows that 93% of respondents agreed to choose 225mm hollow blocks over 150mm
0% 5% 10% 15% 20% 25% 30% 35% 40%
225mm solid block
225mm hollow block
150mm solid block
150mm hollow block
Which saves more on mortar?

38
solid blocks if the needed resources were available. This implies that the amount spent on
procuring or moulding blocks for construction has an influence on the selection made.
The use of 150mm solid blocks proves to be just an alternative only when a reduction in the
overall cost of moulding or buying blocks is considered..
Figure 16 how resources affect choice of blocks (N=42)
Figure 17 cost as a major reason affecting choice of blocks (N=43)
More so, going by the agree variance in figure 17 above, 65% of respondents were of the opinion
that cost consideration has a major influence on the selection process of blocks for construction,
while only 35% disagree. On the other hand, it was found that durability as earlier mentioned
influences the selection process made. Comparing cost and durability and the influence they both
have on the choice made, it was found that a good number of respondents were of the opinion that
durability is the greater influence. Table 4 below compares the results of analyzed data between
cost, durability, material and labour as influences to selection of blocks. In addition, the table
0% 20% 40% 60% 80% 100%
225mm hollow block
150mm solid block
If all resources were provided, which would you pick for construction of
external walls?
30%
35%
26%
9%
0% 5% 10% 15% 20% 25% 30% 35% 40%
Agree
Strongly agree
Disagree
Strongly disagree
Cost consideration is the major reason behind choice of block

39
further shows that material availability and labour cost are lesser influences to the selection of
blocks for use in walls construction.
Table 4 Influences on selection process of blocks
QUESTIONS
Total
(R)
Agree
Strongly
agree
%
Disagree
Strongly
disagree
%
Cost consideration is
the major reason
behind choice of
block
43 30% 35% 65% 26% 9% 35%
Durability is the
major reason for the
choice of block wall
43 42% 47% 89% 9% 2% 11%
Material availability
is the reason for the
choice of block made
42 31% 19% 50% 36% 14% 50%
Labour cost is the
major consideration
behind choice of
block
43 14% 2% 16% 49% 35% 84%
In addition, while 40% of respondents suggested from figure 18 below shows that they do not use
150mm solid block for external walls, 43% of the remaining respondents were of the opininon
that reduction in cost is an influence to the choice made for external wall uints.
Figure 18 reason behind selection of 150mm solid block (N=43)
4.4.2 Client and budget as influences
Sometimes, the selection of walling units used in construction site is influenced by the client and
his budget. The client may decide in some construction, especially small scale construction type
0%
10%
20%
30%
40%
50%
Durability Thermal comfort Sound proof To reduce cost I do not use
150mm for
external walls
Why do you choose 150mm solid blocks for external walls?

40
the type of block he wants the contractor or builder to use. Results of sample analyzed showed
that both the client or building owner and the budget of the project also influence the selection of
blocks made. According to Hontus (2014), the home owner, in selecting building materials for
building considers a lot of factors to suit his budget. One of his considerations could be reducing
the cost of procuring blocks. The pie charts below (figure 19) show the comparative responses
from respondents.
Figure 19 client and budget as influences (N=42)
Comparing both results, more than 70% of respondents agree that both client and budget
influence the selection of blocks made. This implies that what is seen in construction sites today
may not be as a result of ignorance on the benefits of the use of 225mm solid blocks as previously
suggested by the author.
4.4.3 Project location as an influence
The location of a project is the place where the project is been handled, built or constructed. The
location of a project was found to influence the nature and type of walls used in construction.
While it has been established that wall materials like aluminum and glass curtain walls now
dominate wall construction in developed countries, the case is not exactly so in Nigeria. Here,
there are variations in the use of sandcrete blocks which is the most dominate material used for
wall construction.
The location of a project influences the type of blocks used according to survey carried out. This
could be because of allowable standards by the approval board, planning ordinances or building
Yes
76%
No
24%
clients' influence
Yes
No Yes
71%
No
29%
budget's influence
Yes
No

41
byelaws. It shows in the figure 20 below that while a combination of 70% of respondents agreed
that where a project is located affects the choice and type of blocks used, only 30% had different
views. In the area under study, there is no specific block type used for construction. It was
observed that generally, construction of external walls can be made of 225mm hollow blocks,
150mm solid blocks, 150mm hollow blocks and 125mm solid blocks.
Figure 20 project as an influence on selection of blocks (N=43)
4.5 Comparative benefits of choice made on selection of blocks
This section discusses the better option among 225mm hollow block and 150mm solid blocks
from the results of analysis carried out on the survey. The aim is driven towards one of the
objectives of the study which is to compare the two blocks to arrive at a better option for external
walls.
4.5.1 Preference
The researcher sought the general opinion of respondents towards the better option for the
construction of external walls. Findings suggested that 96% of respondents prefer to use 225mm
sandcrete hollow blocks over 150mm solid block. Only 5% of respondents disagree with the
notion. As expected, nobody could strongly disagree that 225mm hollow blocks is a better
external walling units compared to 150mm solid blocks. Figure 21 below shows the results of
analyzed data
0% 10% 20% 30% 40% 50%
Agree
Strongly agree
Disagree
Strongly disagree
Location of project contributes to the choice of block for walling

42
This strongly aligns with results presented in section 4.4.1 and 4.4.2 where cost, client and budget
of project greatly affect the selection of block used for external walls. If this wasn‟t so, as
indicated in the chart below, a great deal of people would settle for 225mm hollow block.
Figure 21 level of preference to block type under study (N=43)
Also, the figures below show the responses of respondents when asked if they consider 225mm
hollow blocks or 150mm solid blocks better for external walls. Their responses show a very clear
preference to 225mm hollow block. 88% respondents agreed to the first question as presented in
figure 22 below while 12% agreed otherwise. In a similar fashion, while 16% think 150mm solid
block wall is better for external walls, 84% respondents think otherwise. Comparing the two
presented results, it shows that much preference is given to 225mm hollow blocks for external
walls over 150mm solid blocks.
Figure 22 comparing 225mm hollow block and 150mm solid block (N=43)
53%
42%
5%
0%
0%
20%
40%
60%
Agree Strongly agree Disagree Strongly disagree
Preference is given to 225mm Sandcrete hollow block over 150mm solid
block
Yes,
88%
No, 12%
Do you consider 225mm hollow
blocks better for external wall
Yes
No
Yes
16%
No
84%
Do you consider 150mm solid
blocks better for external wall?
Yes
No

43
4.5.2 Thermal comfort and concealing pipe works
Thermal comfort proves to be one of the reasons why people chose a certain type of block over
another. As presented in section 4.3.2, thermal comfort influences the choice made on blocks for
external walls. Solid block according to data analyzed shows that a combination of 79% of
respondents as presented in figure 23 below were of the opinion that solid block does not improve
thermal comfort.
Solid blocks are compact; therefore, thermal conductivity is increased when solid blocks are used
in the construction of external walls. They transmit heat into the internal living spaces. This heat
conducted into the building decreases the comfort level of occupants within. This, the author
believes is why a number of respondents agreed that solid blocks does not improve thermal
comfort.
On the other hand, it costs more to conceal mechanical fittings in a wall made up of solid blocks.
Openings are carved out of solid block walls to conceal pipes and thereafter covered up with
cement-sand plaster. The implication of this practice does not only increase the amount of plaster
used, it also reduces the strength and durability of solid walls. Hence, where a user goes for solid
blocks, and still carves out openings for concealing pipes, the overall durability and stability of
the wall is reduced.
As presented in figure 24 below, 67% of respondents were of the opinion that walls made of solid
blocks do not save more in concealing mechanical and electrical pipes. This implies that when
conduit works are needed during wall construction, it would cost the client more in concealing
them in walls made of solid blocks than that made with hollow blocks. Hollow blocks, because of
the presence of cavities, serve numerous purposes that include sound proofing, heat reduction by
concealment.

44
Figure 23 solid blocks and thermal comfort (N=43)
Figure 24 solid blocks and concealment of pipe works (N=43)
4.6 Improving on the quality of external walls
During the interview sessions with the building professionals, it was gathered that a lot of
deviation occur when buildings are erected on site. One of the deviations is on the type of block
used on site. While most specifications on drawings has 225mm hollow block wall, for reasons
already highlighted, a deviation is made during construction on site. The researcher went on via
the survey (Section E) to gather which among the following parameters could help improve on the
safety and quality of blocks used.
a. Drawings and specifications
b. Clients choice or specification
c. Budget
7%
14%
44%
35%
0%
10%
20%
30%
40%
50%
Agree Strongly agree Disagree Strongly disagree
Solid blocks improve thermal comfort
19%
14%
44%
23%
0%
10%
20%
30%
40%
50%
Agree Strongly agree Disagree Strongly
disagree
150mm Solid blocks saves more in concealing mechanical and
electrical piping works

45
Results of findings are presented in figure 25 and figure 26
Figure 25 safety and durability of walling units (N=39)
Figure 26 guarantee of quality of blocks (N=39)
Among three of the parameters for judging, 95% and 85% of the respondents in figure 25 and
figure 26 respectively agreed that when the type and quality of walls specified therein in the
specification sheet of the drawings are conformed to, safety, durability and quality of the walling
units are guaranteed. While 5% of the correspondents thought conforming to client‟s needs and
specification can increase durability and guarantee safety, adjusting to budget was not given any
consideration in figure 25.
From figure 25, the 0% attributed to adjusting to budget means that the client‟s budget should not
be placed above drawings specification. Usually, the cost of a building project is estimated from
the bills of quantity as prepared by a registered quantity surveyor. The client should be able to
95%
5% 0%0%
50%
100%
Conform to drawings
specifications
conform to client's
specifications
adjust to budget
In what ways can safety and durability of walling units be guaranteed?
85%
10% 5%0%
20%
40%
60%
80%
100%
Adopt drawings
specifications
adopt client's
specifications
adjust to budget
In what ways can the quality of blocks used be guaranteed?

46
fund the project in accordance with the bills of quantity; otherwise, quality and safety are both
jeopardized.
4.7 Field experiments
The aim of this qualitative primary data collection method is to examine the volume of materials
used in moulding a sample each of 225mm and 150mm sandcrete hollow blocks. Dry samples of
vibrated blocks were used in the volume comparison test and mortar consumption comparison
test.
Physical samples were measured on site and results for the comparisons per square meter area
were derived. Three-dimensional diagrammatic representations, charts and tables are included in
the presentation of findings
4.7.1 Volume comparison results on constituent materials
From the results of the comparison test on volume carried out, it was discovered that it takes more
material to produce a sample of 150mm solid block when compared to 225mm hollow block.
Mean result (35mm) of web values for 12 samples of hollow blocks was used for calculating the
volume of material used.
From figure 27 below, 0.0107 cubic meters of materials is needed to produce a sample of 225mm
hollow block with web 35mm thick, while 0.0152 cubic meters of materials is needed to produce
a sample of 150mm solid block. It goes further to imply that the volume of materials needed to
produce 5 blocks of 150mm solid block would produce 7 blocks of 225mm hollow blocks in a
ratio of 1:1.4

47
Figure 27 volume of constituent materials
The percentage ratio of one to another by volume shows the same result as presented in the chart
below, figure 28 with 59% making up the volume of the solid block and a lesser percentage of
41% making up the volume of the hollow block wall. The difference in volume ratio of 18% may
not be costly for a unit block; it would on the entire cost of any given project.
Figure 28 percentage comparison of constituents between blocks
4.7.2 Volume comparison results on mortar
The volume of mortar consumed on samples of 225mm hollow block wall and 150mm solid block
wall each was based on the standard 10mm thickness of mortar joint. Results of the volume of
mortar used were arrived at via geometrical mathematical expressions. Contrary to respondents‟
opinions in section 4.3.3, it was deduced that the amount of mortar used for samples of 225mm
0.0107
0.0152
0.0000
0.0050
0.0100
0.0150
0.0200
225mm hollow block 150mm solid
Volume of constituents used (m3)
225mm hollow
block
41%150mm solid
59%
Percentage ratio (%)

48
hollow and 150mm solid blocks as shown in the figures below was more on the latter than it was
with the former. This is because the surface area of the solid block is more than the hollow block
which is made of 52% cavity. Table 5 shows the relationship between the void area and the
compact area of the hollow block per volume.
Figure 29 mortar bedding over blocks
Also, the results of case studies carried out by Thorat (2015) showed that contrary to opinions of
respondents in 4.3.3, hollow blocks save time in laying due to ease of handling. The results
presented here agrees with the study by Thorat that „„some of the advantages of hollow concrete
block construction are reduce mortar consumption, light weight and greater speed masonry work‟‟
In addition, analyzed results shows in table 5 that while 0.048 cubic meter of mortar is used on
the surface of 225mm hollow block, 0.0020 cubic meters more of mortar was needed for mortar
bedding on a 150mm solid block. Figure 30 below shows a chart of the comparative results.
Figure 30 volume of mortar comparison
0.0000
0.0050
0.0100
225mm hollow block
150mm solid
Volume of mortar used (m3)

49
4.7.3 Volume comparison per square meter of wall area
As part of the objectives of this study, the researcher sought to examine the volume of materials
consumed per square meter of a wall area. Field experiments as described before was conducted
on the sampled blocks to determine the volume of materials that made them up. On this section,
the volume of each sample with a bed of mortar was first computed before the results each were
used to further compute for the total volume consumed per meter square of wall.
The three-dimensional visualization below in figure 31 and figure 32 show bonding of walls
constructed with both 225mm hollow block and 150mm solid block respectively. Investigation
carried out showed that it would take approximately 9½ blocks each of both hollow and solid
blocks to build a square meter of wall. This is irrespective of the difference in volume of
materials consumed by each of the samples.
Figure 31 square meter area of 225mm hollow block
More so, results indicated that a mortar bedded block of 150mm solid consumed 0.0219 cubic
meters of the constituent materials while 225mm hollow block consumed 0.0155 cubic meters of
materials. So far, it shows that each sample of a 150mm solid block would consume more
materials both as constituent material and material for mortar more than a sample of 225mm
hollow block.

50
Figure 32 square meter area of 150mm solid block
It goes further to imply that a wall built with 150mm solid block would consume more materials
than a 225mm hollow block wall. This is investigated using a meter square of wall and the
findings and results are presented in table 5. From figure 33 below, one can see the results of
materials consumed by each given block per square meter of wall. It shows that 225mm hollow
block consumed 0.1468 cubic meters of materials; 0.0606 cubic meters less than the volume of
materials consumed by its counterpart wall.
Figure 33 volume comparison per meter square of wall
0.1468
0.2074
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
Volume of total material
used up per square
meter of wall (m3)
225mm hollow block
150mm solid

51
Table 5 volume comparison table of 225mm hollow and 150mm solid blocks
Volume comparison results of material consumed making individual samples
Block
samples
Volume
(m3
)
Void
volume(m3
)
Volume of
materials
used (m3
)
Difference Percentage
(%)
225mm
hollow
block
0.0228 0.0120 0.0107
0.0044
41
150mm
solid
block
0.0152 0.0152 59
Volume comparison results of mortar consumption only
Block
samples
Volume
(m3
)
Void
volume(m3
)
Volume of
materials
used (m3
)
Difference %
225mm
hollow
block
0.0101 0.0053 0.0048
0.0020
41
150mm
solid
block
0.0068 0.0068 59
Volume comparison results of sample and mortar consumed
Block
samples
Volume
(m3
)
Volume of total material used up per
square meter of wall (m3
)
%
225mm
hollow
block
0.0155 0.1468 41
150mm
solid
block
0.0219 0.2074 59

52
The volume of materials used for a given area of wall can be duduced using the formular below;
Vm = M (0.9456) vbs
where
Vm = volume of material used for an area of wall
M = multiplier for area of wall. (use 1 for a square meter of wall, 2 for 2sqm of wall)
Vbs = volume of material for block sample (inclusive of mortar)
To conclude this chapter, results from analysed data from distributed surveys had proven to a
large extent the reasons behind the choice made during selection of blocks for external walls. This
is in line with the objectives of the study. It also presented the level of influences on the choice of
block and how the choice settled for affects the cost, safety and durability of external walls. In
addition, field experiments on volume comparison between the two samples showed that for any
given work to be done, it is more expensive to use a 150mm soild block when compared to
225mm solid block.

53
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
The aim of this study was to comparatively examine the economic value of 225 mm sandcrete
hollow and 150mm solid blocks for external walls. The reasons and influences on the choice of
block used on site were also investigated. Vibrated dry samples of blocks were used in the field
experiments carried out. The volumes of the material constituents of each block were measured
and arrived at using basic geometric formulae. The size of web, 35mm used for calculating the
volume property of 225mm block wall was a derivative of the mean value of 12 samples drawn
out from different block industries in Auchi community.
The selection of the type of block used on site is influenced by a lot of factors which include cost
of building, the building owner, the project contractor, project location, durability required,
thermal comfort, sound insulation and concealment of mechanical and electrical pipes. Blocks are
selected in a way the overall cost of building can be significantly reduced. The building owner in
a way decides for the contractor the type of block he wants to be used in his building. In the same
way, the project contractor influences the type of blocks to be used to some extent as the key
person overseeing the execution of a project. Project location was found to affect the type of
block used on site because of the varying building bye laws and regulations that change from one
part of the country to another. While compliance to building regulations is strict in some cities or
towns, it is flexible or not keenly adhered to in other places.
While analysis of results showed that thermal comfort is widely considered when choosing
225mm hollow blocks for external walls, it was concluded that durability is the major reason
behind the selection of blocks. The cavities in hollow blocks prove to be an air trap that retards
transmission of heat from the outside of the building to the interior spaces. Solid blocks on the
other hand are better sound insulators because of their compact nature.

54
Deviations were found to take place from the type of blocks specified in drawings. Such
deviations are done in most cases to reduce the amount of materials used and to reduce the cost of
carrying out the project. Therefore, one of the ways as suggested by correspondents to improve on
the safety of blocks used on site is to adapt to specifications from Architectural drawings.
The amount of material consumed per meter square area was also investigated where it was
deduced that it cost more in constituent materials and mortar usage to build up a wall made of
150mm sandcrete solid blocks when compared to 225mm sandcrete hollow blocks. This is true
because a sample of 150mm solid block has a greater surface area than a sample of 225mm
hollow block. A 150mm solid block contains 0.0152 cubic meters of materials; 0.0044 cubic
meters more than 225mm hollow block which contains 0.0107 cubic meters of constituent
materials.
On consumption of mortar, test results show that 0.0068 cubic meters of mortar is required for
bonding between 2 units of 150mm solid blocks while it requires 0.0048 cubic meters of mortar
for bonding between two units of 225mm hollow blocks. 10mm standard mortar thickness was
adopted for these tests. These differences in volume of constituent materials and in mortar
consumption are what lead to the significant increase in materials used per square meter of wall.
0.2074 cubic meters of materials would be needed to build a square meter of wall made with
150mm solid block. 0.1468 cubic meters of materials is needed to build a square meter of wall
made with 225mm hollow blocks.
Finally, It was deduced that 59% of materials is needed to produce a unit of 150mm solid block
while 41% is needed to produce a unit 225mm hollow block. A mathematical formula was
derived to guide in computation of volume of materials used for a square meter of wall which can
be used to calculate for any given area of wall.

55
5.2 Recommendations
The following recommendations are made:
1. The use of 225mm sandcrete hollow blocks for external walls is encouraged over the use
of 150mm solid blocks as they are comparatively beneficial towards improving the
stability of walls and improving thermal comforts of building occupants.
2. The use of 150mm solid blocks should be discouraged as it costs more on material
consumption to make and to also build with. It contributes significantly to an increase in
the cost of building.
3. A comparative analysis of blocks should be done to further reveal more suitable block
types for both external and internal walling processes.
4. There is need for a review of the use of blocks building projects as research revealed that
there are too many influences on the choice of blocks used. Also, regulating bodies are by
this work required to enforce compliance to building regulations towards the use and
standards of blocks for construction
5.3 Contribution to knowledge
This work has contributed to knowledge in the following ways:
1. Through this work, information on the volumetric properties of 225mm hollow and
150mm solid blocks have been revealed and compared in three ways namely;
(a) By constituent materials
(b) By sample units with mortar bedding and
(c) By square meter area of wall
2. The information gathered for the volume of material used per square meter of wall can be
used to estimate for any given size of building by multiplying values arrived at in table 5
by the area of a given wall

56
3. The formula arrived at can be used to quickly estimate for the volume of materials to be
used on any given size of block provided the volume of the unit can be derived
4. The work has provided information to influences on the selection process of blocks and
how they affect the quality of walls built

Comparative analysis of hollow and solid sandcrete blocks for external walling in auchi, edo state, nigeria

Comparative analysis of hollow and solid sandcrete blocks for external walling in auchi, edo state, nigeria

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