Effect of superabsorbent polymers on microstructure and strength of blended cements mortars reinforced by polymeric fibre

Superabsorbent polymers (SAPs) efficiently reduce total shrinkage and cracking susceptibility of fibre reinforced mortars (FRM). This paper discusses the effects of SAPs on the microstructure and mechanical properties of FRM containing fly ash (FA) and ground granulated blast-furnace slag (GGBS) during a period of 180 days. Three types of cement including CEM I, CEM II/B-V and CEM III/A and three types of SAP with different chemical compositions and particle gradings were studied. The paper argues SAP's contribution to hydration of FA and GGBS and a subsequent deposition of these products on the fibres surface and in pores below 20 nm diameter. The analysis confirmed that SAPs provide additional water for hydration (internal curing) but also a required space for later hydration products (additional refilling of collapsed SAPs), resulting in more homogenous internal microstructure. This improvement is more prominent in mortars containing finer SAP (around 80 μm), which can facilitate strength recovery of up to 50%. The strength recovering process in FRM-SCM samples is boosted after the 2nd week, and is more dominant for samples containing CEM III/A.