Shrinkage behavior and mechanical properties of alkali activated mortar incorporating nanomaterials and polypropylene fiber

Blended ground granulated blast slag (GGBS), low-calcium fly ash (FA), nano silica (NS), and nano alumina (NA) with/without polypropylene fiber (PPF) had a significant effect on the development length of alkali activated mortar (AAM) cured at various humidity levels and curing ages. This paper presents the behavior of alkali activated mortar with 50% FA and 50% GGBFS binder materials and the alkali ratio of sodium silicate to sodium hydroxide (SS/SH) is 2.5. The molar concentration of sodium hydroxide (NaOH) used was 12 M. Feasibility Comparisons between the different humidity 60%–98% of at 23 ± 3 C° were examined. The strength behavior of alkali-activated mortar with different curing ages was also evaluated. Scanning electron microscopy (SEM) analysis and X-ray diffractions (XRD) were also conducted to clarify the effect of nanomaterials and PPF on the microstructures of AAM. It was found that the shrinkage values of AAM were decreased with the addition of polypropylene fiber and nanomaterials. The combined use of both nanomaterials had better performance than the use of nano SiO₂ and/or nano Al₂O₃ alone. The combined use of PPF with nanomaterials had a superior reduction in shrinkage and expansion and increment on strength values; the minimum shrinkage, expansion values, and maximum strength were found at AAM mix incorporating 2%NS-1%NA-0.5%PPF. The SEM analysis and XRD evaluation indicates the significant effect of nanomaterials on the microstructures and bond strength of AAM. The microstructure of the mixes incorporating both nanomaterials and PPF was denser than other mixes without nanomaterials and/or PPF and showed lower micro cracks.