1. Introduction
Lightweight
concrete has been successfully used now a days and it has gained its popularity
due to its lower density and superior thermal insulation properties. As Compared
with normal weight concrete, Lightweight concrete significantly reduce the dead
load of structural elements, which makes it suitable in multistory buildings.
In
practice, the density of normal weight concrete lies within the range of 2200
to 2600 kg/m3 (140 to 160 lb/ft3). Consequently, the self
weight of concrete element is high and contributes a large proportion of the
load on structure.
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Lightweight
concrete has a density between 1350 to 1900 kg/m3 (85 to120l b/ft3).
Thus using lower density concrete gives benefits in terms of small cross
section of beams and a corresponding reduction in size of load bearing
elements.
On
the other hand, lightweight concrete has higher cement content than normal
weight concrete. This represents additional cost, and so does the more
expensive lightweight aggregate. A meaningful comparison of cost should be made
on the bases of the design of the structure using lightweight concrete and it
cannot be limited to the cost of material.
The
density of Concrete can be reduced by replacing some of the solids material in
the mix by air voids. There are three possible locations of the air: (1) in the
aggregate particles, which are known as lightweight aggregates and resulting
concrete is known as lightweight aggregate concrete, (2) in the cement paste,
the resulting concrete being known as cellular concrete, (3) between the coarse
aggregate particles, the fine particles being omitted. Such concrete is known
as no-fines concrete.
The
essential characteristics of lightweight aggregate are its high porosity, which
results in a low specific gravity. I shall extend my research by using light
weight aggregates from different sources in Pakistan to make light weight
concrete.
2. Problem Statement
In concrete construction, self weight of concrete
represents major proportion of load on structure, thus there are clearly
considerable advantages in reducing weight i,e density of concrete for high
rise buildings, long span bridges and for various types of structures.
Thus there is always realizing a need to study the various
properties of lightweight aggregate concrete and developing co-relation for
these properties. So, lightweight concrete can be used for structural
applications with strength equivalent to normal weight concrete.
This research aims to study properties of light weight
concrete using lightweight aggregates found in Pakistan.
3. Objectives
1.
Influence of different types
of Lightweight aggregates on mechanical performance of Lightweight Aggregates
Concrete (LWAC) will be studied.
2.
Quality of different light
weight aggregates derived from different sources in Pakistan will be
determined.
3.
Suitability of different types
of light weight aggregates found in Pakistan with respect to different concrete
properties will be determined.
4.
Cost comparison will be
carried out for different types of light weight aggregate concretes cast in
Pakistan.
4. Literature Review
1. Muyasser M.
Jomaa’h (Civil Engineering Department – University of Tikrit), Hosam A. Daham (Civil Engineering
Department – University of Tikrit), Saad M. Rao’of (Civil
Engineering Department – University of Tikrit) in 2011 found that the elastic stage and beginning of first
cracks stages of normal weight concrete beams was smaller than others stages.
While the results of the lightweight concrete beams show this stage was longer
than other stages. The steel for lightweight concrete beams yielded before the
steel in normal weight concrete beams. Also one can conclude that the same
behavior of cracks spread, appears of crush in concrete, and failure behavior
for lightweight and normal weight of reinforced concrete beams but at different
loads.
2.
Jan Lindgård and Tor Arne Hammer (research associates, SINTEF Civil and
Environmental Engineering, Norway) concluded that LWAC structures have
potentially higher fire resistance than NDC structures, due to the lower heat
conductivity of the LWAC and thus a better insulation of the reinforcement
cover. LWAC can contain more evaporable water than NDC due to absorbed water in
the LWA particles. Thus the risk of spalling can be higher in a LWAC.
LWAC
structures may have lower fire resistance than NDC structures when exposed to
severe fire.
3.
Gunduz L (2008) made laboratory research showing that the
cube compressive strength of LWC concrete, having a 1376 kg/m3 fresh density
made with only pumice aggregate, rises up to 14 MPa at 28 days of curing time.
A higher compressive
strength
of LWC made with pumice is seemed to be impossible since the compressive
strength of its uncrushed stone restraints it. However, by adding some mineral
admixtures, using higher dosage of cement and superplasticizer and decreasing
the water to cement ratio, make possible to produce somewhat high strength LWC
from scoria aggregates
4.
.I˙lker
Bekir Topc-ua and Tayfun Uygunog lu (2007) Investigated physical and mechanical
properties of LWC produced with diatomite and pumice lightweight aggregates
after autoclave curing investigated.
5.
Al-Jabri KS, Hago AW, Al -Nuaimi AS, Al -Saidy AH (2008) investigated that
because of having large number of voids in the aggregate, LWC possesses a
relatively higher thermal insulating efficiency than the normal weight concrete
(NWC).
The
compressive strength of LWC depends on a variety factors. These are the
strength of
aggregate
stone, type of coarse, medium, fine and very fine aggregates, concrete
composition, mineral admixtures, cement quantity, water-cement ratio, curing
conditions of hardening etc.
5. References:
1. Al-Jabri
KS, Hago AW, Al -Nuaimi AS, Al -Saidy AH. “Concrete Blocks for Thermal
Insulation in Hot Climate”. Cem. Concr. Res.
2008, 35: 1472-1479.
2. Gunduz
L. “The Effects of Pumice Aggregate/Cement Ratios on The Low-Strength Concrete
Properties”. Constr. Build. Mater. 2008, 22: 721-728.
3. Al-Khaiat
H, Haque MN. “Effect of Initial Curing on Early Strength and Physical
Properties of Lightweight Concrete”. Cem. Concr. 1998, Res. 28: 859-866.
4. I’lker
Bekir Topc-ua, Tayfun Uygunog lu, “Properties of Autoclaved Lightweight
Aggregate Concrete” Building and Environment, Vol. 42, 2007, pp. 4108–4116.
5. ASTM
C330– 00, “Standard Specification for Lightweight Aggregates for Structural Concrete"
6. Neville, A.M. (1995). Properties
of Concrete. 4th ed., Essex: Longman Group Limited. 844.
7. Carryer & Associates LTD (1995) Pumice Resources of New Zealand.
8. ACI (2003) ACI 213R-03,
Guide for structural lightweight aggregate concrete., in ACI Manual of Concrete Practice, Part 1:
Materials and General Properties of Concrete. American Concrete
Institute: Farmington Hills, Michigan. p. 38.
9. Babu G. K. and Babu D. S.
Performance of fly ash concretes containing lightweight EPS aggregates, Cement
and Concrete Composites, V. 26 (2004), 605-611.
10. International Building Code (IBC),
International Code Council (ICC), Washington D.C., 2009.
6. Methodology
1- Literature
survey will be continued and expanded to the latest research made on the topic
in different parts of the world.
2- Sources
for different types of light weight aggregates like expanded shale, expanded
clay, Pumice etc will be searched out in Pakistan and availability of materials
will be made sure.
3- Concrete
mix. design will be carried out for normal strength concrete and normal weight
aggregates.
4- Physical
properties tests will be carried on cement i.e., compressive strength,
consistency, setting time, expansion, fineness etc.
5- Sieve
analysis will be carried out for sand, normal weight coarse aggregate and all
types of light weight aggregates as per British Standard. Grading curves will
be plotted and fineness modulus will be found.
6- Aggregate
tests like, Loss Angeles Abrasion Test, Bulk Density, Shape index, Acid
reactivity etc will be carried out for both normal weight and all types of
light weight coarse aggregates.
7- The
following tests will be carried out on normal weight concrete and all types of
light weight concretes.
8- If
some tests are failed for some types of lightweight aggregate concrete, Mix.
design will be revised after selecting suitable admixture or changing water
cement ratio.
9- Casting
will be carried out again for that type of concrete only by using revised Mix.
design. Tests will be revised and results confirmed.
10- Graphs
will be drawn and results will be analyzed.
11- At
the end, the whole research would be compiled into a report form.
7. Budget Description
Sr. No.
|
Description of items
|
Approximate Budget
|
1.
|
Purchase of material
|
50,000/-
|
2.
|
Experimental Expenditures
|
30,000/-
|
3.
|
Labor charges
|
20,000/-
|
Total
|
100,000/-
|
8. Proposed Work Schedule
Project
Start Date: 01-06-2012
01-06-2012
End of Literature review and Start of Practical work
01-09-2012
End of Casting of Cubes
01-010-2012
End of Curing Specimen
01-11-2012
End of Laboratory Testing of Specimens
01-12-2012
End of Comparison of Results
01-01-2013
End of Analysis, Conclusions and Recommendations
Project
Completion Date: 01-01-2013
9. Capital Expenses
Experimental Equipment:
1.
Compressive Test Machine
2.
Lab Testing
3.
Miscellaneous
Total
Amount 30000/= Rs
Material and Supplies:
1.
Light weight Aggregates
2. Fine Aggregates (Sand)
3. Cement
Total
Amount: 50000/=Rs
Human Resources
Investigators List Level of effort Total amount in
Rupees
(Principal
Investigator)
(Co-Investigator)
Lab
Technicians 3 Months PT 10000
Labour 3
Months PT
10000
Total Project Cost:
100,000/=Rs
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