Activated alkali cement based on blast furnace slag: effect of curing type and concentration of Na20

Abstract

Recent studies highlight the feasibility of using activated alkali cement (AAC) as a substitute for Portland cement. In this context, the objective of this article is to evaluate the influence of the type of curing on the mechanical properties of ACC based on blast furnace slag. For this, cylindrical specimens measuring 50 × 100 mm were made using blast furnace slag activated by sodium hydroxide with different mass concentrations (2.5–15%). Normal curing at room temperature, thermal curing at 65 °C, solution curing with distilled water (saturated curing), hydrated lime (lime curing) and sodium hydroxide (sodium curing), and compound curing were carried out. The compressive strength results at 7 and 28 days indicate that the AAC presents a superior behavior to the OPC. Regarding the curing mechanisms, the most advantageous were thermal curing, which promoted greater thermal energy, and curing in sodium solution, which prevented the loss of alkaline ions from the AAC. In these types of healing, there was greater formation of tobermorite and hydrotalcite, with an increase in alkaline activation rates, as evidenced by the results of XRD, FTIR and TDG. In situations of inefficient curing, such as saturated and lime curing, ettringite and efflorescence were formed, impairing the mechanical properties of the material. It was concluded that the best AAC cure was thermal or sodium cure depending on the Na2O concentration.

Keywords

• Blast furnace slag
• Thermal cure
• Tobermorite
• Alkaline activation