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In the present context of Bangladesh, it has been seen that most of the time after
demolishing any concrete structure, demolished aggregates are hardly used or recycled for
further construction work. This demolished aggregate has a reasonable amount of monetary
value. But rather than being used for further construction work it turns into the garbage and
pollutes our environment as well as become a burden for us. This happens due to most of
the people have the idea that this recycled concrete hardly possesses any strength. Again,
in Dhaka and major cities in our country, the requirement of the road has increased
significantly inside the town area. Most of these roads are constructed demolishing the
concrete structure and producing demolished concrete as well as increasing carrying cost
of this demolished concrete. So in this thesis work it has been tried to show the relative
comparison of natural coarse aggregate(NCA) and recycled concrete aggregate(RCA) as
well as regaining strength by mixing admixture with recycled concrete aggregate(RCA) so
that recycled concrete aggregate(RCA) can be potential substitute natural coarse
aggregate(NCA). So that aggregate of demolished concrete structure can be recycled for
further construction rather than dumping. This will in one hand reduce pollution as well as
reduce the overall cost. .For the purpose of thesis work 1st class brick, 3rd class brick, and
stone chips have been used. Using this natural course aggregate (NCA) cylinder block was
cast with a simple ratio of 1:1.5:3. Then the compressive and tensile strength was checked
after 28 days. Aggregate property tests like Aggregate crushing value(ACV),Aggregate
impact value (AIV) , Elongation index(EI) , Flakiness index(FI), Los Angles abrasion
test(LAAV),unit weight, specific gravity, Absorption capacity and void ratio test were done
with both natural coarse aggregate(NCA) and recycled concrete aggregate(RCA) before
casting of cylinder. This tests were done to draw a conclusion and compare between the
natural coarse aggregate (NCA) and recycled concrete aggregate (RCA). For casting using
ii
Abstract
recycled concrete aggregate (RCA) mix ratio of 1:1.5:3, water-cement ratio, brand and type
of cement, sand, and grading of aggregate were kept same as casting using natural coarse
aggregate (NCA). After recycling once admixture was mixed with recycled concrete
aggregate (RCA) show how much strength can be regained. It is found that a significant
amount of strength was regained and it is very compatible and close to the initial strength.
Thus a cost comparison was also done using natural coarse aggregate (NCA) and recycled
concrete aggregate (RCA) and found to be very fruitful to use recycled concrete aggregate
(RCA). Finally using this dumped recycled concrete aggregate (RCA), developing country
like Bangladesh can be benefited from the point of monetary value and environmental issue
like saving the natural resource, reducing fuel consumption, low carbon emission, reuse of
waste material and stepping one step forward in green building concept. |
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