This document discusses cement concrete pavement and interlocking paving blocks for rural roads. It provides guidelines on designing cement concrete pavements, including recommendations for wheel load, subgrade characterization, sub-base provision, concrete strength, joint spacing, and an example design. It also outlines applications, advantages, and IRC specifications for interlocking concrete block pavements.

1. CEMENT CONCRETE PAVEMENT
AND INTERLOCKING PAVOR
BLOCKS
Dr. Pradeep Kumar
Professor
Dept. of Civil Engg.
HBTU, Kanpur - 208002

3. Wheel Load
• The legal axle load in India being 102 Kn.
• The pavement may be designed for a wheel load
of 51 kN. However, for link roads serving
isolated villages
• Where the traffic consists of agricultural tractors
and trailers and light commercial vehicles only, a
design wheel load of 30 kN may be considered.
Tyre Pressure
• The tyre pressure may be taken as 0.7 MPa
where a wheel load of 51 kN is considered and
0.5 MPa where a wheel load of 30 kN is
considered.

4. Design Period
• The design methodology given in these guidelines is
based on wheel load stresses. The repetitions of
wheel loads and the consumption of fatigue, which
form the basis of design in IRC:58-2012, need not be
considered for the very low volume of traffic
encountered on rural roads.
• Concrete pavements designed and constructed as
per the guidelines contained in this document will
have a design life of not less than 20 years, as
evidenced from the performance of roads
constructed in the past in the country.

5. Characteristics of the Subgrade
• The strength of subgrade is expressed in terms of
modulus of subgrade reaction, k, which is determined by
carrying out a plate bearing test, using 750 mm dia. Plate
according to 18:9214-1974.
• In case of homogeneous foundation, test values obtained
with a plate of 300 mm dia, k300, may be converted to
give k750, determined using the standard 750 mm dia.
plate by the following correlation:
k750= 0.5 k300... ... ... (1)
• Since, the subgrade strength is affected by the moisture
content, it is desirable to determine it during or soon
after the rainy season. An idea of the k value of a
homogeneous soil subgrade may be obtained from its
soaked CBR value using the following table.

6. Approximate k values corresponding to CBR values
Soaked
CBR%
2 3 4 5 7 10 15 20 50
K value
n/mm2/mm
21 28 35 42 48 50 62 69 140

7. Sub-Base
The provision of a sub-base below the concrete pavement has many
advantages such as:
• It provides a uniform and reasonably firm support
• It prevents mud-pumping on sub grade of clays and silts
• It acts as a levelling course on distorted, non-uniform and
undulating sub-grade
• It acts as a capillary cut-off
• Where the pavement is designed for a wheel load of 51 kN, a 150
mm thick sub-base of Water Bound Macadam (using 53-22.4 mm
aggregates), granular sub-base, gravel, soil-cement or soil-lime may
be provided. Where the traffic is light and the pavement is designed
for a wheel load of 30 kN, the thickness of the sub-base may be
reduced to 75 mm. The WBM and granular sub-base surface shall be
finished smooth.
• When the above type of sub-base is provided, the effective k value
may be taken as 20 per cent more than the k value of the sub-grade.
A plastic sheet of 125 microns thickness shall be provided over the
sub-base to act as a separation layer between the sub-base and
concrete slab

8. Concrete Strength
• Since concrete pavements fail due to bending stresses, it is
necessary that their design is based ;>n the flexural strength of
concrete. Where there are no facilities for determining the flexural
strength, the mix design may be carried out using the compressive
strength values and the following relationship:
• f= 0.7fc0.5
where,
f= flexural strength, N/mm2
f c = characteristic compressive cube strength, N/mm2
If the flexural strength observed from laboratory tests is higher than
that given by the above formula, the same may be used.
• For Rural Roads, it is suggested that the 90-day strength be used for
design instead of the 28-day strength as the traffic develops only
after the lapse of a period of time. The 90 day flexural strength may
be taken as 1.20 times the 28-day flexural strength or as determined
from laboratory tests. Heavy traffic should not be allowed for 90-
days

9. • The concrete mix should be so designed that the minimum
flexural strength requirement in the field is met at the desired
confidence level. For rural roads, the tolerance level (accepted
proportion of low results), can be taken as 1 in 20. The normal
variate, Z , for this tolerance level being 1.65, the target
average flexural strength is obtained from the following
relationship:
S = S1 + Zaσ
Where, S = target average flexural strength at 28
days MPa
S1 = charachteristic flexural strength at 28 days MPa.
Za = normal variate, having a value of 1.65, for a
tolerance factor of 1 in 20.
a = expected standard deviation of field test samples,
MPa

10. Grade of
concrete
Standard deviation for different degrees of
control, Mpa
Very good Good Fair
M30 5.0 6.0 7.0
M35 5.3 6.3 7.3
M40 5.6 6.6 7.6
Table 2: Expected values of standard deviation of compressive strength
The standard deviation of flexural strength may be derived approximately using
the formula given earlier.
For pavement construction for rural roads, it is recommended that the
characteristic 28-day compressive strength should be at least 30 MPa. The
characteristic 28-day flexural strength shall be at least 3.8 MPa

11. Modulus of Elasticity and Poisson's Ratio
The Modulus of Elasticity, E, of concrete may be taken as 3.0 x 104 MPa.
The Poisson's ratio may be taken as 0.15.
Coefficient of Thermal Expansion
The coefficient of thermal expansion of concrete , may be taken as
cc=10x10-6 per °C

13. Calculation of Stresses
Edge Stresses:
(a) Due to load: The load stress in the critical edge region may be
obtained as per Westergaard analysis as modified by Teller and
Sutherland from the following correlation (metric units):
P I σle = 0.529 —(l+0.54fi)(41og 10 +log ]0 b-0.4048) ... ... (3)
where, σ le = load stress in the edge region, MPa
P = design wheel load, N
h = pavement slab thickness, mm
µ = Poisson's ratio for concrete
E = Modulus of elasticity for concrete, MPa
k = Modulus of subgrade reaction of the pavement foundation

14. (b) Due to temperature: The temperature stress at the critical edge
region may be obtained as per Westergaard's analysis, using Bradbury's
coefficient from the following correlation:
σte = Eα x Δt
where, σte = temperature stress in the edge region, MPa
Δt = maximum temperature differential during day between top and
bottom of the slab, °C
a = Coefficient of thermal expansion of concrete, °C
C = Bradbury's coefficient, which can be ascertained directly from
Bradbury's chart against values of L/l and W/l
L = slab length or spacing between consecutive contraction joints, m
W = slab width, m
I = radius of relative stiffness, m

15. Temperature differential: Temperature differential between the top
and bottom of concrete pavements causes the concrete slab to warp,
giving rise to stresses. The temperature differential is a function of solar
radiation received by the pavement surface at the location, losses due to
wind velocity, etc., and thermal diffusivity of concrete, and is thus
affected by geographical features of the pavement location. As far as
possible, values of actually anticipated temperature differentials at the
location of the pavement should be adopted for pavement design.
Corner stresses: The load stress in the corner region may be obtained
as per
Westergaard's analysis as modified by Kelley, from the following
correlation :
where,
Σlc = 3P/h^2[1-{a(2)^1/2/l}^1.2]
Σlc = load stress in the corner region, other notations remaining the
same as in the case of the edge stress formula.

16. The temperature differential graph is shown below:

17. Zone States Temperature differentials
150 mm 200 mm 250 mm
I Punjab, UP, UK,
Rajasthan, Haryana,
Gujrat, MP
12.5 13.1 14.3
II Bihar, Jharkhand, WB,
Assam, Odisha
15.6 16.4 16.6
III Maharashtra,
Karnataka, Chatisgarh,
AP
17.3 19.0 20.3
IV Kerala, Tamil Nadu 15.0 16.4 17.6
V Coastal Areas bounded
by hills
14.6 15.8 16.2
VI Coastal Areas
unbounded by hills
15.5 17.0 19.0
RECOMMENDED TEMPERATURE DIFFERENTIALS FOR CONCRETE SLABS

19. Types of joints
• Rural Roads are generally of single-lane, and the
full lane width (3.0 m-3.75 m) is concreted in
one operation. Thus, there is no need for a
longitudinal joint for single-lane rural roads.
• As regards transverse joints, they are of three
types:
1. Contraction joints
2. Construction joints
3. Expansion joints

20. Spacing of joints
• Transverse contraction and construction joints:
The spacing of transverse contraction joints or
construction joints in alternate bay construction may be
kept 2.50 m-3.75 m. The length of the panel (in the
direction of traffic) shall not be less than the width of the
panel.
• Expansion joints: Expansion joints are necessary
where concrete slabs abut with bridges and culverts.
• Longitudinal joints: Where the width of concrete slab
exceeds 4.5 m as in the case of causeways, etc., it is
necessary to provide a longitudinal joint as per the
details given in Fig. 6 in the mid-width of the slab.

21. Load transfer at Transverse joints
• Since rural roads have low traffic with small wheel loads, the slab
thickness normally being 150-250 mm, the aggregate interlock at
the sawn joints is itself adequate for load transfer and no dowel bars
are necessary. If slabs are cast in alternate panels, keyed joints can
be formed. Day's work should normally be terminated at a
contraction joint.
• At expansion joints, where the joints width may be 20 mm, dowel
bars are required
• Dowel bars shall be 25 mm diameter, 500 mm long and spaced at
250 mm centre to centre.
• In the case of Roller Compacted Concrete Pavements, the
contraction joints may be formed by cutting joints with concrete saw
at the spacing. If aesthetics of the road is not an important
consideration, the sawing of joints may be omitted and the cracks
allowed to form on their own.

22. ILLUSTRATIVE EXAMPLE OF
DESIGN OF A CEMENT CONCRETE
PAVEMENT FOR RURAL ROADS

23. Example
A cement concrete pavement is to be designed for
a rural road in Uttar Pradesh having a traffic
volume of 150 vehicles per day consisting
vehicles like agricultural tractors/trailers, light
good vehicles, heavy trucks, buses, animal
driven vehicles, motorized two wheels and
cycles. Design the pavement. The soil has a
soaked CBR value of 4.

24. Design
Wheel load
As per para 3.1, the wheel load appropriate for the traffic conditions is 51 kN.
k value
From Table 1, the k value corresponding to a CBR value is 4 is
35×10-3 N/mm2/mm.
Sub-base
Provide a 75 mm thick WBM course.
Effective k Value
Since a sub-base is provided, the k value can be increased by 20% (para 2.5).
Effective k value = 1.20×35×10-3 = 42×10-3 kg/mm2/mm.

25. Concrete Strength
Adopt a 28 day compressive strength of 30 Mpa.
Flexural strength ff = 0.7√fc = 3.834 Mpa.
So, 28 day flexural strength = 3.834 Mpa.
90 day flexural strength = 1.20 × 3.834 Mpa
= 4.6 Mpa
Thickness
Try a thickness of 150 mm.
Edge Load Stress
From fig.4, keff= 42 × 10 -3 N/mm3, edge load stress is 4.5 MPa

26. Temperature Stress
From Table 4, the temperature differential for U. P. for a slab thickness of 150mm
is 12.5°C.
Assuming a contraction joint spacing of 3.75 m and 3.75 m width, the radius of
relative stiffness l, is as under:
L = 3750 mm
B = 3750 mm
l = radius of relative stiffness =
E = 3 × 104 N/mm2
h = 150 mm
µ = 0.15
k = 42×10-3 N/mm2/mm
l = putting values in the above formula = 673.3 mm
L/l = 3750/673.3 = 5.57
W/l = 3750/673.3 = 5.57
Both values are same,
For L/l = 5.57, Bradbury’s coefficient C = 0.834

27. Using chart in Fig. 6,
σte = 1.6 Mpa
Total Stress = Edge Load Stress + Temperature Stress
= 4.5 + 1.6 = 6.1 Mpa
This is greater than allowable flexural strength of 4.6 Mpa.
So thickness of 150 mm assumed is inadequate.
Try a thickness of 190 mm.
Edge Load Stress
From fig. 4, edge load stress σle = 2.9 Mpa.
Temperature Stress
From Table 3, the temperature differential for U. P. for a slab thickness of 200 mm is
13.1°C.
Radius of relative stiffness l =
Putting the values in the above equation;
l = 804 mm
L/l = 4.66
W/l = 4.66

28. Both values are same,
For L/l =4.66, Bradbury’s coefficient = 0.0625
Using chart at fig.1
Temperature stress, σte = 1.41 Mpa
Total Stress = 2.9+1.41 = 4.31 Mpa
The total stress is less than 4.6 Mpa and hence assumed thickness of 190 mm is OK.
Corner Stress
From fig. 5, corner load stress for wheel load of 51 kN,
k = 42×10-3 N/mm2/mm and slab thickness of 190 mm
Corner stress, σlc = 2.9 Mpa.
Since the corner stress is less than 4.6 Mpa and hence the thickness of 190 mm
is SAFE.

29. IRC SPECIFICATIONS FOR
INTERLOCKING CONCRETE BLOCK
PAVEMENTS

30. Scope
• Interlocking concrete block pavements have
been used extensively in a number of countries
for quite sometime.
• Considering their advantages and potential for
use, the guidelines have been prepared for
design and construction of such pavements,
giving the suggested applications, design
catalogues, construction practices and
specifications for their use.

31. Applications
• Footpaths and side walks
• Cycle tracks
• Residential streets
• Car parks
• Fuel stations
• Rural roads through villages
• Highway rest areas
• Toll plaza
• Bus depots
• Approaches to railway level
crossings
• Intersections
• City streets
• Truck parking areas
• Industrial floors
• Urban sections of highways
• Urban sections of highway
• Road repairs during Monsoons
• Container depots
• Port wharf and Roads
• Roads in high altitudes areas

32. Advantages
• Since the blocks are prepared in the factory, they are
of a very high quality, thus avoiding the difficulties
encountered in quality control in the field.
• Concrete block pavements restrict the speed of
vehicles to about 60 kmph, which is an advantage in
cities and intersections.
• Due to rough surface these pavements are skid
resistant.
• The block pavements are ideals for intersections
where speeds have to be restricted and cornering
stresses are high.

33. • The digging and reinstatement of trenches for
repairs for utilities is easier in the case of block
pavements.
• They are unaffected by the spillage of oil from
vehicles, and are ideal for bus stops, bus depots and
parking areas.
• They are preferred in heavily loaded areas like
container depots and ports as they can be very well
designed to withstand the high stresses induced
there.
• In India, the laying of concrete block can be
achieved at a very low cost due to availability of
cheap labour.

34. • Since they are grey in colour, they reflect more
light than the black bituminous pavements thus
reducing the cost of street lightning.
• The cost of maintenance is much lower than the
bituminous pavements.
• Block pavements do not need in-situ curing so
they can be opened to traffic soon after the
completion of construction.
• Construction is simple and labour-intensive, and
can be done using single compaction equipment.

35. • Structurally round blocks can be recycled many
times over.
• Block pavements does not exhibit very
deterioratory effect due to thermal expansion
and contraction and are free from cracking
phenomenon.
• Use of permeable block pavements in cities can
help replenish depleting underground source of
water, filter pollutants before they reach open
water sources, help reduce storm water runoff
and reduce the quantum of water drainage
structures.

36. Limitations
• Concrete block pavements cannot be used for high
speed facilities.
• The riding quality is reasonably good for low speed
traffic, but is inferior to that observed on a machine
laid bituminous or concrete pavement.
• The noise generated is high, 5-8 dB (A) higher than
bituminous surfaces.
• A very good attention to pavement drainage is
needed because the water seep through the joints.

38. The blocks can be
interlocking
horizontally and
vertically as shown
alongside:

39. Present day
interlocking blocks
have evolved in
shape after
observing their
performance. The
rectangular shape is
shown alongside. It
was intended for
imitating the stone
set blocks.

40. This is an improved version with many dentated faces for
better contact and interlocking effect resulting in enhanced
friction with the adjoining block. It also increases the shear
strength of the block system and hence load dispersal capacity.

41. This block is a further improvement over dentated
rectangular block.

42. The dentated blocks can be further grouped as
shown in the figure into three categories:
Category A:
• Dentated units are designed to key into each
other on all four faces and which, by their plan
geometry when keyed together, resist the
widening of the joint.
• These blocks can be laid in herringbone bond
pattern.

43. Category B:
• These blocks are dentated only on two sides.
Their dimensional accuracy of laying helps in
bringing about the interlock effect on other
faces.
• Generally, with some exceptions, these blocks
can only be laid in stretcher bond.

44. Category C:
• These are not dentated type but depend on
dimensional accuracy for interlocking effect.
• These blocks can be laid only in a stretcher bond.

45. DIMENSIONS
• Top surface area : 5,000 to 60,00o mm2.
• Horizontal dimension not exceeding : 28 cm.
• 1<(Mean length/Mean width)<3
• Thickness : Between 60 to 140 mm
• Length/Thickness : ≥4

46. COMPOSITION OF BLOCK
PAVEMENT
Except for the top wearing part of the pavement; the
base and sub base layers are similar to the
conventional flexible or rigid pavement. Depending
on the load coming on them, the composition of the
pavement differs.

47. Typical pavement composition
A few typical composition normally used are given in figure.

48. Block Thickness
• Interlocking concrete blocks come in different
thicknesses. These blocks serve as wearing surface
but at the same time help in reducing the stresses
imposed on subgrade and also help in resisting
pavement deformation and elastic deflections similar
to the base course of the flexible pavement.

49. • For category ‘A’ blocks used for light traffic, such as,
pedestrains , motor cars cycles, etc.,a block thickness
of 60 mm is adequate ; for medium traffic ,a
thickness of 80 mm is generally used ; for heavily
traffic roads, Category ‘B’ blocks of the thickness
100-120 mm are used. Thick blocks are best suited
where high volumes of turning movements are
involved .

50. An unevenly settled block pavement:

51. • Non uniformity in thickness of blocks affects the
evenness of the surface. A block pavement which is
initially paved to a levelled surface will settle
unevenly with the movement of vehicles. In view of
this all blocks should be of the same thickness , with
a maximum allowable tolerance limit of ±3mm.
Similarly ,variations in length and width of blocks
should be limited to ±2 to 3 mm for ensuring uniform
joint width and avoiding staggering effect.

52. Sand Bedding and Joints
A layer of sand bedding is provided between block
pavement and base/sub base for the following
reasons:
• To provide a cushion between the hard base and the
paving blocks.
• The base or sub base will have some permitted
surface unevenness. By providing a layer of sand bed
,the paved blocks can be levelled perfectly.

53. • The sand bed acts as a barrier and does not allow
propagation of cracks formed in base/sub base .
• The sand also helps to keep lower part of the joint
filled with sand and provides added interlocking
effect.

54. A layer thickness of 20 to 40 mm is found to be satisfactory for a
sand bag.
It is necessary that the lower layers are profiled to proper level
and finish and that the bedding sand layer is of uniform thickness.
Varying thickness of sand bed ultimately results in uneven
surface of the pavement.
The sand used should be free from plastic clay and should be
angular type. It should not be degradable type for e.g., sand
produced from limestone etc. is likely to get powdered under
loading.
Joints, normally 2 to 4 mm , between blocks are filled by fine
sand. Normally , the bottom 20 to 30 mm of the joint gets filled
with bedding sand, whereas, the remainder space has to be filled
with jointing sand by brooming it from the top.

55. Base and Sub-base layers
• The materials used for base construction consist of either
bound material like lean concrete or soil-cement or bituminous
layers or unbound materials like wet mix macadam or WBM.
The sub bases are generally are granular material. The sub-
base can function as drainage layer as well, provided disposal
arrangement for water is made. The base course layer is
normally provided where heavy vehicular traffic is likely.
• Besides intensity of loading, the type of soil encountered
determines the type and thickness of base and sub-bases. For
weak sub grade soils like clays, where ground water table is
shallow, bound bases are preferred.

56. Edge Restraint Blocks and Kerbs
Concrete blocks on trafficked pavements tend to move sideways
and forward due to braking and maneuvering of vehicles. The
tendency to move sideways has to be counteracted at the edges
by special edge blocks and kerbs. The edge block should be
design such that the rotation or displacement of blocks is
resisted. These are made of concrete of high strength to
withstand the traffic wheel loading without getting damaged.
These members should be manufactured or constructed in-situ
to have at least a 28 day compressive strength of 30 MPa or
flexural strength of 3.8 MPa. As far as possible the edge
blocks should have vertical face towards the inside blocks.

57. A few typical edge blocks:

58. STRUCTURAL DESIGN OF
CONCRETE BLOCK PAVEMENT
Suggested Design procedure:
Design procedures have been developed by agencies abroad based on
successful performance, or mechanistic principles. In the absence of research in
India, it is recommended that the catalogue of designs given subsequently may
be used.
Lightly trafficked pavements:
Pedestrian side walks, footpaths, cycle tracks, car parks and malls are
lightly trafficked. In such situations, the pavement can consist of blocks 60 mm
thick laid over sand bedding 20-30 mm and a base course 200 mm thick. The
base course can be WBM/WMM/crushed stone/soil cement. This design can be
adopted for the range of subgrade soils met with in india.

59. Block Pavements Subjected to Commercial Traffic:
City streets and highway sections subjected to commercial require heavy
section. Though design methods based on empirical approach and mechanistic
behaviour are available, enough work has not been done in India to evolve the
country’s own design procedure. In the absence of such knowledge, the ad-hoc
design catalogues based on international experience as given in Table 1 are
suggested for adoption. A design life of 20 years can be considered for determining
the repetitions of standard axles.
For block pavements for industrial applications like container yard and port wharf and
roads and warehouses the following thickness is recommended, based on
international experience:
Block : 100 mm
Sand Bedding : 30-50 mm
Hydraulically bound base : 300 mm
granular sub base (out of which : 300mm
the bottom 150 mm is drainage layer)

60. MATERIALS
The quality of materials, cement concrete
strength, durability, and dimensional tolerances,
etc. are of great importance for the satisfactory
performance of block pavements.

61. TABLE 1 : DESIGN CATALOUGE FOR PAVEMENT THICKNESS
Traffic and
Road type
Subgrade CBR(%)
Above 10 5-10
Cycles Tracks, Pedestrian footpaths Blocks
Sand
Bed Base
60
20-30
200
60
20-30
200
Commercial Traffic
Axle load Repetitions less than 10 msa
Residential Streets
Blocks
Sand Bed
WBM/WMM Base
Granular Sub-base
60-80
20-40
250
200
60-80
20-40
250
250
Commercial traffic Axle Load Repetitions
10-20 msa
Collector streets, Industrial streets, Bus and Truck
Parking Areas
Blocks
Sand Bed
WBM/WMMBase
Granular Sub-base
80-100
20-40
250
200
80-100
20-40
250
250
Commercial traffic Axle Load Repetitions 20-50 msa
Arterial Streets
Block
Sand Bed
WBM/WMM
Base WBM/WMM Base
DLC over it
Granular Sub-base
80-100
20-40
250
150
75
200
80-100
20-40
250
150
75
250

62. Notes:
1. Thickness of layers given above are in mm.
2. Granular sub-base should have at least 150 mm layer at the bottom which is
drainable.
3. A typical cross section is given in Fig 6.
4. If subgrade of soil has a CBR of less than 5, it should be improved by suitable
stabilisation technique to bring the CBR value to 5.
5. msa denotes repetitions in million standard axles.
Salient Mix Design Aspects
The commonly used processes for the manufacture of pre cast cement concrete paving
units require dry, low slump mixes. The desired characteristics of the mix are as
under:
water/cement ratio: 0.34 to 0.38
water content of the mix: 5 to 7 % of total mix
Quantity of cement in mix: Generally not less than 380 kg/m^3 depending on the
euipment being used for lock making. Upper limit of cement shall not be more than
425 kg/m^3. Flyash also
can be used in the mix, replacing Ordinary Portland Cement to an extent of 35
percent.

63. The above values are for general guidance only. The actual mix design has to be made
to suit each individual requirement.
Aggregate/cement ratio: 3:1 to 6:1
Aggregates: Should be sound and free from soft or honeycombed pieces. The
proportion of coarse aggregate in the mix is typically 40 % and the fine aggregate
60 %. The size of coarse aggregate should lie between 6 mm and 12 mm and the
gradation should be in the recommended range for cement concrete cement mixes
in general.
Strength: In general terms, the paving block must have adequate strength to withstand
handling, construction stresses and effects of traffic, through the strength as such is
not considered a vital factor in the satisfactory performance of a block pavement.
However, the min. compressive strength of single block should be above 30 MPa.
Addition of Pigments: To provide the desired colour to paving blocks, appropriate type
and amount of pigments are added during mixing, in the form of powder or slurry.
Although organic pigments, the former are adversely affected by the alkaline
environment of concrete and do deteriorate with time. Inorganic pigments, mostly
metal oxides, are more durable and hence preferred for consistency and purity.
Saturation of colour takes place with a pigment volume of around 5 to 9 percent of
cement content. Pigments should be finer than cement
Other Additives: Under special circumstances, super plasticizers 0.4 percent of cement
by weight may be added for high early cement. Water repellant admixtures of
calcium sterate are sometimes used to reduce water absorbtion.

64. DRAINAGE
Block pavement with joints
filed with sand is not a
waterproof layer, and so
drainage is necessary. The
surface drainage in block
pavements is shown
alongside:

65. A crossfall of 2% is generally sufficient to drain the surface run-off,
but it is desirable to provide 3% cross fall in the case of heavily
trafficked roads to avoid formation of water puddles.

66. LAYING OF BLOCKS
Blocks can be laid generally by manual labour but mechanical aids like hand
pushed trolleys can expedite the work.
Normally, laying should commence from the edge strip and proceed towards
the inner side. When dentated blocks are used, the laying done at two fronts
will create problem for matching joints
In the middle. Hence, as far as possible, laying should proceed in one
direction only, along the entire width of the area to be paved.
while locating the starting line, the following should be considered:
• On a slopping site, start from the lowest point and proceed uphill on a
continuous basis, to avoid downhill creep in complete areas
• In case of irregular shaped edge restraints or strip, it is better to start from
straight string line.
• Influence of alignment of edge restraints on achieving and maintaining
laying bond.

67. Thank You !