Enhancement of Concrete Compressive Strength by Introducing NGPs in a Mix with Partially Substituted Recycled Coarse Aggregate for Natural Coarse Aggregate

Abstract

Concrete dominates the building sector, surpassing all other materials except water. It's estimated that the annual worldwide utilization of concrete likely exceeds 10 billion tons. Concrete easy accessibility and cost-efficiency led to its swift adoption in construction industry. Large-scale production of concrete necessitates the burning of vast quantities of fossil fuels to produce the fillers (Coarse and Fine Aggregates) causing a strain onto our environment and planet. To cater this issue researchers in past replaced Natural Coarse Aggregate with Recycled Coarse Aggregate. However, RCA concrete exhibits inferior mechanical properties unlike regular concrete, mainly due to impurities and weak cement matrix interfacial bonding leading to a drop in compressive strength by 40% was noticed. This research is conducted to study the behavior of concrete when NCA is partially replaced with RCA in conjunction with Nano-Graphite Platelets. This study emphasizes on the compressive properties of concrete when different percentages of NGPs are used in the Mix Design and its comparison with Control Mix. The Control Mix contained only conventional concrete ingredients. As far as NGPs are concerned total of three mixes were developed and studied particularly with percentages 1%, 3% and 5%.  The tests results showed that the molds prepared with Control Mix design exhibited a compressive strength of 31.57 MPa, whereas M5 mix containing inclusion of 5% Nano-Graphite Platelets with RCA exhibited a compressive strength of 32.79 MPa, gaining an increase in for about 3.86%. The results taken are evident to say that a concrete containing partial replacement of RCA with addition of 5% NGPs by the weight of its cement will provide more compressive strength as NGPs notably enhance the density and hardness of cement-based composites by decreasing porosity and reinforcing the microstructure.