Use of slag (GBFS) generated in charcoal blast furnace as raw material in alkali-activated cement

Alkali-activated cements are low-environmental-impact binders and can be obtained from the alkaline activation of wastes such as slags and fly ashes, and solutions of hydroxides and silicates. In this study, two types of slag, A and B, generated in charcoal and coke blast furnaces, respectively, were activated with NaOH in contents of 4, 5 and 6% to obtain alkali-activated slag (AAS). Samples were submitted to calorimetry and compressive strength tests, and investigative microstructure analysis. The results showed that cement obtained with slag A (AAS_A) presented a much superior performance than AAS_B, which was related to the higher degree of hydration, higher formation of amorphous CSH with a higher incorporation of aluminum ions (C–(A)S–H). For AAS_B, the activator content was not able to improve the compressive strength. Calorimetry measurements showed a small interaction between slag B and the activator. The results contribute to the appreciation of slags generated in charcoal blast furnaces, which may become raw material for low-environmental-impact cements, in this case, AAS.