Influence of the mix parameters on shrinkage properties of environment-friendly mortar

Cracks in concrete structures are generally initiated due to the shrinkage i.e. the volume change characteristics of the concrete structures. In this experimental study, effects of the mix parameters related to alkaline liquid (AL) and recycled fine aggregate (RFA) on the shrinkage behaviour of environment-friendly mortar mixes produced with fly ash (FA)-based geopolymer binder and RFA were investigated and reported. To find out the effects of AL, concentration of liquid sodium hydroxide (LSH) was varied from 6M to 16M, ratio of liquid sodium silicate (LSS) to LSH in AL was varied from 1.0 to 2.5 and AL/FA ratio was considered as 0.4 and 0.6. Different fly ash-based geopolymer mortar mix were produced depending on above-said combinations of mix parameters along with the RFA content (by weight) of 10%, 20%, 30%, 40% and 50% in lieu of natural fine aggregate. Prismatic specimens (25 mm x 25 mm x 285 mm) were cast and cured at ambient air temperature to determine the shrinkage behaviour. Higher RFA content in mix, higher LSS/LSH ratio in AL and higher AL/FA ratio resulted in higher shrinkage value. But, lesser shrinkage value was noticed for those specimens of mortar mix with the consideration of higher concentration of LSH in AL with varying RFA content.