Hybrid alkali-activated fly ash-Portland cement binders with modified polymer as patch repair.

The alternative patch repair derived from hybrid alkali-activated binders (HAAB) were investigated in this paper. The HAAB mortar was produced with fly ash (FA), Portland cement (PC), and polymer-modified material (PMM). The additives (PC and PMMs) were used to replace FA at the dosage of 30 % by weight of binder. The proportions of PC-to-PMM at 30:0, 20:10, 10:20, and 0:30 were investigated. Sodium silicate (NS) and sodium hydroxide (NH) solutions were used as the alkaline activators. Constant NS-to-NH ratio of 2.0 and liquid/solid binder ratio of 0.60 were used for all mixtures. Experimental results showed that the setting time, compressive and shear bond strengths of the HAAB mortars met the requirement for repair material as specified by ASTM standard. The 7-day bond strength increased with increasing PMM replacement up to an optimum level; thereafter, it started to decline. A combination of PC and PMM in FA-based HAAB enhanced the adhesion at contact zone. Moreover, the HAAB mortars showed greater durability compared to conventional PMMs after immersion in sulfate and acid solutions, as evidenced by its relatively low strength loss. The increased formation of ettringite might be the main factor for the substantial reduction in the strength of PMM mixes. Therefore, the HAAB mortar is an attractive choice for patch repair material in terms of excellent durability, high bond strength, cost-effectiveness, and low carbon footprint compared to conventional PMM. • FA-PC-based HAAB with 10–15 % PMM satisfied the minimum 7-d compressive and bond strengths requirement as per ASTM standard. • Compressive strength of FA-PC-based HAAB decreased as PMM content increased. • Reaction product was mainly formation of hybrid C-(N)-A-S-H. • HAAB showed excellent durability, high bond strength, cost-effectiveness, and low carbon footprint compared to PMM mortar. [ABSTRACT FROM AUTHOR]