Effect of sand–precursor ratio on mechanical properties and durability of geopolymer mortar with manufactured sand

The geopolymer mortar (GPM) prepared from industrial by-products and alkali activation solution (AAS) is one of the hot spots of current building materials. As a feasible alternative to natural river sand, manufactured sand (MS) alleviates the global ecological pressure. In this study, MS was used for fine aggregate. Sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) solution were used as AAS. Metakaolin (MK) and fly ash (FA) were used as the precursor to prepare MK-FA-based GPM with MS (MS-GPM), which was of great significance for saving non-renewable resources, mitigating the greenhouse effect, and recycling waste. Numerous studies were conducted to explore the effect of sand–precursor ratio (r _sp) on mechanical and durability characteristics of MS-GPM. Relationships between compressive strength and tensile or flexural strength were established by linear fitting equation. Finally, analysis of variance (ANOVA) was used to systematically calculate the effect of r _sp on performance. The results indicated that the mechanical strength and impermeability of MS-GPM decreased and crack resistance increased with r _sp from 1 to 5. The strength of MS-GPM was the best when r _sp was 1. With the increase of r _sp, the proportion of MS in MS-GPM increases, and the relative cementitious material decreases, which has an adverse impact on mechanical properties and impermeability. Linear fitting revealed that the compressive strength of MS-GPM was closely related to tensile strength and flexural strength. ANOVA results indicated that r _sp in the range of 1–5 had great effects on the performance of MS-GPM. The aim of this article is to further promote the possibility of applying MS-GPM in practical engineering by designing reasonable r _sp.