Abstract:
The recycled construction materials derived from the wastage materials during construction
and wastage due to demolition, rehabilitation, natural and technological disasters are
becoming of great interest in most project implementation. The driving force for recycling
concrete is three-fold: preserving natural resources, utilizing the growing waste, and saving
energy and money. The utilization of recycled aggregate is also an effective solution to the
problem of possessing excess waste materials while simultaneously maintaining satisfactory
concrete quality; indeed, it may also be a breakthrough towards sustainable development.
It is known that the strength of concrete depends on the quality of ingredients used. Among
those elements, the major portion is taken by coarse aggregate. This study utilizes
demolished concrete (waste laboratory test cubes for this purpose) by crushing as coarse
aggregate often termed as the recycled coarse aggregate (RCA) for investigating the effects
on compressive strength and producing industry quality concrete. Large-scale recycling can
substantially reduce the consumption of natural aggregate.
This research investigated the fresh and mechanical properties of 25 MPa recycled
aggregate concrete (RAC) made with different RCA replacement levels (i.e.,
100%NA+0%RA; 0%NA+100%RA; 50%NA+50%RA; 75%NA+25%RA; 25%NA+75%RA).
Concrete mix design (ACI mix design method) having five mix proportions for both natural
and recycled aggregate were prepared using a water-cement ratio and cement contents of
0.62, 288.71kg/m3
respectively. Total of forty-five concrete cubes (150mm*150mm*150mm)
was produced and tested at the age of 7, 14 and 28 days. Also, physical properties of all the
materials before and after replacement have been assessed.
This study reveals that, concrete produced with 75%NA+25%RA replacement level had the
highest average compressive strength with 28.1MPa. However, the performance of RAC is
decreasing with increasing RCA replacement levels, but their overall performance is
comparable to natural aggregate concrete (NAC). It can therefore, be concluded from the
findings of this research that use of recycled coarse aggregate in the construction industry
helps to prevent unnecessary damages to the environment and provide optimum exploitation
of the resources and also offers important economic advantages.
