Toward Carbon-neutral Concrete: Early Age Strength of Mechanically Activated Construction and Demolition Waste-based Binders

Abstract

There is need to research and develop sustainable building materials from waste and by-products with adequate standards for increasing infrastructural and environmental need occasioned by population increase, modernization, urbanization, environmental and climatic changes concern currently. In unprocessed form it is not possible to up-cycle concrete waste, therefore mechanical activation (MA) technique can be applied to up-cycle waste, through improvement of properties for secondary raw materials.
This study focuses on effect of early age compressive strength and MA of construction and demolition waste (CDW) hence advocacy for carbon neural concrete.
MA improved the early age strengths of CDW based binder strengths. The finer CDW samples had better strength at 7 days compared to coarser. Generally, reduction of water to binder (w/b) ratio resulted to higher pozzolanic activity index for binders with 25% CDW. The 25% cement replacement with MA CDW as binder replacement was optimum, with highest respective compressive strengths of 67.02 ± 1.56 MPa and 62.82 ± 12.15 MPa, for ranges 5303–8440 cm²/g (average 6872 cm²/g) and 12,102–10,327 cm²/g (average 11214 cm²/g) geometric specific surface areas based CDW's binders respectively.
Remarkable strength for MA of CDW could be due to a combination of impact of Si reactivity and filler effect in the CDW. Water content, particle sizes and carbonation had an impact on compressive strengths for binder materials. Inconsistency in particle sizes from different batches was possibly due to the quartz amount.