Mechanical, setting and durability properties of hybrid alkaline cements

Mechanical, setting and durability properties of hybrid alkaline cements

Hybrid alkaline cement (HAC) is composed of a significant proportion of supplementary cementitious materials (SCMs) such as fly ash (FA) and/or granulated blast furnace slag (GBFS), a minor proportion of ordinary Portland cement (OPC), and alkali activators. A series of HACs were prepared with 10-30% OPC and 90- 70%SCM using 0-8% alkali activator and curing at room temperature. The samples were then characterized using compressive strength, setting time, X-Ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), 1H Low-field NMR technology, isothermal conduction calorimetry, and thermogravimetric analysis (TG). The effects of type and dosage of activator used, and the ratio of raw materials on the mechanical, setting and durability properties of different HACs were studied. The results indicated that the setting times of HACs decreases with increasing alkali activator dosage. The HACs with high proportion of SCMs, cured at ambient temperature and activated by appropriate dosage of alkali activator perform similar or higher compressive strength than OPC. The compressive strength of HACs increases with the increasing of Na2O dosage. By selecting the type of alkali activators and adjusting their dosage, controlling the proportion of OPC in HAC system, HAC can be prepared at ambient temperature, which is useful for engineering application. The durability properties of HAC concrete are indeed crucial for its application in the construction industry. The results indicate that HAC concrete demonstrates significantly greater resistance to harsh environmental conditions compared to OPC concrete, exhibiting robust performance in both early and later stages of development. HAC concrete exhibits clear advantages over OPC in terms of resistance to chloride corrosion, sulfate penetration and alkali–silica reaction (ASR)-induced expansions.

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