Characterization of alkali-activated hybrid slag/cement concrete

Abstract

This paper presents characterization of ambient cured Alkali Activated Concrete (AAC) mixes based on workability and compressive strength using Taguchi method. The aluminosilicate source was a mix of slag (GBFS) and cement (OPC), while the alkaline activator was made with a mix of sodium hydroxide (SH) and sodium silicate (SS). The four parameters considered in this study were: slag to cement ratio (GBFS:OPC), Na2O ratio, solution modulus (Ms) and water to binder ratio (W/B). Nine series of experiments were conducted using L9 Taguchi array. Slump test and compression test were conducted on all mixes. In addition, the microstructural analysis was applied using SEM and EDS spot to examine the microstructure properties. Based on Signal-to-Noise (S/N) ratio, the results were evaluated using ANOVA analysis to investigate the optimum level for each parameter. It was found that using alkali activator with hybrid cement (GBFS + OPC) is not effective method to produce AAC because of the very low workability obtained. On the other hand, using GBFS only as a binder was effective to produce AAC with high compressive strength and desirable workability. Moreover, the inclusion of OPC in mixes increased significantly the cracking level at the microscale. In addition, the hydration products of developed mixes with 100% GBFS were more homogenous than mixes contained OPC.