A Brief description on Light weight Construction Materials, types of Waste material based concrete.

1. LIGHT WEIGHT CONSTRUCTION MATERIALS
The Northcap University, Gurgaon1
UNIT-1
LECTURE - 6
Brig. S.K. Sharma (Retd.)
Pro Vice Chancellor and Professor
Department of Civil Engineering,
The Northcap University, Gurgaon

2. INDEX
WASTE MATERIAL BASED CONCRETE
 ORGANIC WASTES
 INORGANIC WASTES
2 The Northcap University, Gurgaon

3. WASTE MATERIAL-BASED CONCRETE
Recent investigations have made it possible to make
concrete using agro, urban and industrial waste
materials. Successful utilization of a waste material
depends on its use being economically competitive with the
alternate natural materials. These costs are primarily made
up of handling, processing and transportation.
The stability and durability of products made of concrete
using waste materials over the expected life span is of
utmost importance, particularly in relation to building and
structural applications. The forms in which they are used
are wide and varied: they may be used as a binder
material, as partial replacement of conventional
Portland cements or directly as aggregates in their
natural or processed states.
3 The Northcap University, Gurgaon

4. For discussion waste materials may be classified as
Organic wastes (agro-wastes), Inorganic wastes (urban
wastes) and Industrial wastes.
A. ORGANIC WASTES
The waste materials included in this category are of plant
origin, namely sawdust, coconut pith, rice husk, wheat
husk, groundnut husk, etc. It must be appreciated that
development of concrete using such aggregates is still in
early stages and published data are limited. Before using
organic wastes on a large scale as constituents in
concrete, careful investigations regarding their
structural properties and durability need be carried out.
4 The Northcap University, Gurgaon

5. Uses Of Natural Organic Waste Materials
They are used for making lighweight concrete. However,
they often contain substances (cement poisons) which
retard the hydration and hardening of cement which need
be neutralized appropriately. Moreover, it is difficult to
obtain a waste material which is not a mixture of several
species. Consequently, there is a considerable variation
in results from batch to batch. The lightweight concrete
produced using organic wastes have comparatively high
moisture movement and show relatively higher percentage
of volume changes.
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6. RICE HUSK
Huge quantities of rice husk are generated in rice mills. Each
tonne of paddy produces about 200 kg of husk. Because of its
very low density, rice husk requires large space for storage and
hauling. In India, it is disposed of by burning, thus reducing the
bulky waste to manageable volumes of ash of less than 50 per
cent of its initial volume but open burning creates severe
pollution problems.
Rick husk contains only very small quantities of water-soluble
cement poisons as compared to saw dust. It has a low bulk
density of only 100 to 150 kg/m3. The light weight concrete
of bulk density 600 kg/m3, produced using rice husk as an
aggregate is suitable mainly for making precast blocks and
slabs for walls and partitions.
6 The Northcap University, Gurgaon

7. Central building Research Institute, Roorkee has
developed a cheap cementing material from rice husk
and waste lime sludge available from the sugar and
paper industries. The dried cakes of mixture of sludge and
rice husk are burnt, and the burnt material on grinding
yields a fast-setting gray-colored cementing material
which can be used in place of cement or lime in mortars
for brick masonry work, plastering and foundation
concreting.
7 The Northcap University, Gurgaon

8. RICE-HUSK ASH CEMENT CONCRETE: The compressive
strengths of concretes made with rice-husk ash cement using
siliceous gravel and crushed limestone are given in the Table
below. The 28-day compressive strength using crushed limestone
aggregate is about 23 per cent higher than that obtained using
gravel aggregate, probably due to the formation of a stronger
interfacial bond between the cement paste and aggregate.
Because of black color of rice-husk cements, these cements
can be used to make permanent black concrete for glare-free
pavements and architectural applications. These concretes show
better long-term color stability than that obtained by using coloring
pigments.
Aggregate type
Compressive strength, MPa
3 days 7 days 28 days
Crushed
aggregate
29 39 47
Gravel
aggregate
24 33 38
8 The Northcap University, Gurgaon

9. Rice-husk ash when mixed with sand and lime in
suitable proportions with an appropriate quantity of water
can be used to cast bricks. These require air curing
followed by wet curing before being used. The rice-husk
ash bricks have a density of 1400-1600 kg/m3 and
compressive strength of 5-6 Mpa. The water absorption is
15-20 per cent.
9 The Northcap University, Gurgaon

10. B. INORGANIC WASTE
The inorganic wastes which are hard, particularly, the demolition
waste such as broken concrete, broken bricks and crushed
glass can be used to produce concretes of requisite strength
and durability.
BROKEN OR RECYCLED CONCRETE: Huge quantities of
building rubble become available each year by the way of
demolition of old structures to make way for new and modern
ones due to rapid urbanization. The quantities increase
tremendously during massive reconstruction after devastating
earthquakes. Disposal of such materials is difficult in view of the
scarcity of suitable dumping grounds, and meeting the
environmental requirements. Hence, the broken concrete is
increasingly being recycled. Recycled concrete is simply the
old concrete that has been removed from buildings,
foundations, pavements and other structures and crushed
to the specified size.10 The Northcap University, Gurgaon

11. The basic requirements for recycled aggregates for concrete
construction is that the original concrete shall be sound,
hard, normal concrete. As a rule, recycled concrete
aggregate of distinctly different qualities shall be used
separately. The cement mortar attached to the recycled
aggregate primarily determines the performance of recycled
concrete.
Finishing materials, reinforcing bars and other embedded
material, if any, in the original concrete shall be removed in
the best possible way.
Recycled aggregates shall not contain excessive amounts of
dirt, plaster of Paris or gypsum and other injurious foreign
matter like wood and asphalt which may adversely affect
recycled aggregate concrete and steel used therein.
11 The Northcap University, Gurgaon

12. PRODUCTION: The basic method of the recycling concrete
is one of crushing the debris to produce a granular product of
given particle size and then reprocessing and screening, the
degree of which depends on the level of contamination and
the application for which recycled aggregate is produced.
Recycled aggregates normally have more angular shape and
more coarser surface and exhibit more or less similar particle
size distribution as that for natural aggregate.
12 The Northcap University, Gurgaon

13. PROPERTIES OF RECYCLED AGGREGATE CONCRETE:
The concrete produced with recycled aggregate loses its
workability more rapidly than the conventional concrete,
because recycled aggregate is more porous than natural
aggregate. Thus concrete with recycled concrete aggregate
may require 5 to 10 per cent more mixing water to
achieve the same workability as the gravel concrete. If
both fine and coarse aggregates are recycled aggregates,
around 15 per cent more free water is required.
13 The Northcap University, Gurgaon

14. APPLICATIONS: Utilization of recycled concrete in the
form of aggregate is widely accepted for pavements,
base and sub-base courses and to some extent for
foundation purposes. The lean concretes produced using
recycled aggregate are called ‘econo cretes’ and have
resulted in a saving in the cost of construction of order of 30
percent.
BROKEN-BRICK AGGREGATE CONCRETE: Broken brick
is a waste product obtained as rejected overburnt or
damaged bricks in brick work and at construction sites.
Broken-brick aggregate is obtained by crushing waste
bricks and has a density varying between 1600-2000
kg/m3. It is used in concrete for foundation in light buildings,
flooring and walkways. Broken-brick aggregate may also be
used in lightweight reinforced concrete floors. Broken-brick
concrete can be designed to obtain the compressive
strength between 15 MPa to 35 Mpa generally required in
practice and such a concrete possesses satisfactory
structural properties.14 The Northcap University, Gurgaon

15. The Northcap University, Gurgaon15
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