Slurry infiltrated low-quality construction and demolition coarse aggregate waste in concrete – a sustainable construction

Abstract

Exponential growth in infrastructure projects, stimulated by emerging sophisticated technologies have been instrumental in the salutary proliferation of the construction sector, globally. An indubitable adversity of the rapid boom in the construction industry has been the rampant cumulative fallout of burgeoning waste during the demolition and construction phases of restoration. The current study explored the propriety of replacing natural coarse aggregate by low-quality recycled coarse aggregates (RCA) with varying proportions, along with silica fume (SF) and polypropylene (PP) fibers as admixtures, for the preparation of concrete. As the quality of RCA is determined by the history of its parent demolished structure, this investigation was preceded by assessment of the properties of RCA. A statistical approach using design of experiments, adopted to determine the coherent combinations of RCA and admixtures, yielded 16 combinations. Accordingly, concrete specimens were prepared with various quantities of RCA in place of natural coarse aggregate. Optimum proportions of the ingredients were inferred, based on the compressive strength attained by the concrete specimens. Further strength property evaluation was conducted, using these low-quality RCA treated with cement and silica fume slurry. Based on the strength results, 75% slurry infiltrated RCA, coupled with 10% SF and 0.5% PP, provided better strength in compression, tension and flexure. Scanning electron microscopy study, adopted for characterization of the micro-structural slurry-infiltrated RCA, shows the presence of strong interfacial transition zone in the treated RCA concrete. Thus, this study confirmed the efficacy of low-quality RCA as a promising material for structural construction, concurrent with a solution to various ecological disruptions precipitated by infrastructure construction and demolition wastes.