Abstract
Sustainable trails in the building industry called for preserving the natural resources through the production of green concrete. This is concrete where waste materials are used as at least one of its components, or its production does not lead to environmental destruction through the reduction, reuse or recycling techniques. Experimental results from a study on the potential usefulness of recycled coarse aggregates (RCA) blended with locally available natural Pozzolana are outlined in this paper. Eight concrete mix scenarios were considered: a standard mix with 100% natural coarse aggregates (NCA), 25% RCA, 50% RCA, 75%RCA, 100% RCA and no Pozzolana, 100% RCA and 10% Pozzolana, 100% RCA and 20% Pozzolana, 100% RCA and 30% Pozzolana. Slump test was conducted and the results were all within the specific limits. It was conversely realized that the workability decreased in the cases of replacing NCA by RCA with no Pozzolana while an increase was recognized when the Pozzolana was add in the different percentages with the best results achieved with 100% RCA and 20% Pozzolana. The compressive strength results were consistent for the different curing ages with the highest strength being acquired with the mix that contained 100%RCA and 10% Pozzolana. The results of the durability test revealed better values for the wave length speed value when the NCA was replaced by the RCA. Considering these outcomes, the optimum result was achieved in the case of 100%RCA and 10%Pozzolana. Thus, the experimental results offer good indication for a potential usefulness of RCA proposing a reasonable way for preserving virgin natural materials.
Highlights
Concrete is a heavy, rough building material made from a mixture of cement, fine and coarse aggregates, water and maybe some additives in different proportions produced to meet certain design specifications
More water is needed to achieve similar workability to that of normal aggregate concrete (NAC) due to higher absorption capacity of recycled aggregate (RA) which can be attributed to the presence of impurities and attached cement hydrates. [11] confirmed the fact that as the RA content increases in the mix, the workability reduces especially at lower w/c ratio and in their study, it was found that the entrapped air content was similar when compared to normal concrete mix having a range of 2.4±0.2%
When recycled coarse aggregates (RCA) was introduced the workability decreased in the range of 4.2-14.3% with increasing replacement ratios of RCA up to a maximum of 20.2% with 100% RCA in comparison to natural coarse aggregates (NCA)
Summary
Rough building material made from a mixture of cement, fine and coarse aggregates, water and maybe some additives in different proportions produced to meet certain design specifications. Sustainable trails in the building industry called for preserving these natural resources through the production of eco-friendly concrete. This is concrete where waste materials are used as at least one of its components or its production does not lead to environmental destruction through the reduction, reuse or recycling techniques. Uses waste material as at least one of its components, or its production process does not lead to environment destructions” [3] As such, it employs reduce, reuse and recycle techniques to minimize greenhouse gas emission and limit the use of natural resources such as limestone, clay, natural river sand, natural rocks that are being consumed but not returned back to the earth. The effect of the RCA inclusion was verified via the check of the mechanical behavior of the produced concrete as the workability, compressive strength and durability were measured
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