Technical, Environmental and Economical Assessment of Sustainable Concrete using Waste Burnt Clay Brick Powder as partial replacement of Cement

Abstract

The aim of this paper is to investigate the possibility of using waste burned clay bricks powder (WBCBPA) as a partial replacement of cement in concrete while maintaining its advantages. It is not only a materials issue, but also a constructionchoice issue that involves a synthesis of strength, workability, uncertainty, cost and embodied carbon. The evidence base includes published experimental programs on flow, compressive and flexural strength, setting time, soundness, shrinkage and water-transport behavior, linked here with a clearly defined local validation program for M25 concrete, with 0%, 10%, 20% and 30% cement replacement. Two variables across the compiled studies emerge as repeated factors: the replacement level and the fineness of the processed powder. At low levels of replacement, usually in the range 5-15%, the 28-day strength of the control mix is often maintained and the relative performance sometimes improves at later ages. At 20% the response is more sourcedependent, but at 30% strength and workability penalties are common. The aggregated 28-day retention values show a scatter that increases with replacement. The coefficient of variation increases from 19.4% at 10% replacement to 37.1% at 20% and 55.7% at 30%. An overall trend is described by the quadratic fit Retention (%) = 99.0 - 0.641R - 0.0371R2 , and a faster fall of the expected strength with a higher replacement is observed. In the illustrative baseline scenario, each additional 10 percentage points of WBCBP reduces the binder cost by ~7.5% and the embodied carbon by ~9.0%. But the recommendation is not based on nominal savings. Then performance, workability and reliability considerations suggest that the safest starting option is 10-15% replacement. 20% is a conditional option, to be exercised only after satisfactory local trials.