Geopolymer recycled aggregate concrete: investigation on methods of aggregate treatment

Abstract

On one hand, theconstructiondemolitionwastes have constantly increased. On the other hand, the quantity of fly ash from the coal power plants have also significantly increased which need to bevalorised. This context requests the construction industry to recycle these materials in theproduction of construcion materials,that contributes to the preservation of the environment and naturalre sources. This paper presents a study on theuse of recycled concrete aggregate (RCA) to replace coarse aggregates, and on the treatment methods of RAC. Fly ash was activated by an alkaline activator solution (sodium silicateandsodiumhydroxide) to create a geopolymer binder which substitutes the Portland cement. Geopolymer recycled aggregate concrete (GRAC) with RCA from different pre-treated stateswere investigated: dry, water saturatedand lime watersaturated.The ordinary cement concrete with natural aggregates was also manufactured for the comparison. The microstructure was investigated by the SEM (Scanning Electron Microscope) technique.The results showed that samples with RAC pre-treatedby limewater significantly improved the the compressive strength 2 to 3 times when compared to samples using RAC without pre-treatment or pre-treated by water. These results are positive which show the potential for the application of GRAC.