Performance of Calcium Aluminate and Calcium Sulfoaluminate Cement Mortars Incorporating Fly Ash and Limestone Powder

This study assesses the performance of calcium aluminate (CAC) and calcium sulfoaluminate (CSA) cement mortars, particularly when blended with fly ash (FA) and limestone powder (LP). The effects of incorporating 20% FA, 15% LP, and their combination (FA 20% and LP 15%), using a water-binder ratio of 0.40 were explored. The study meticulously evaluates the performance of the mortar mixtures in terms of setting time and mechanical properties, including compressive strength, flexural strength, and direct tensile strength. Additionally, the study investigated the alkali-silica reaction (ASR) and autogenous shrinkage. Advanced analytical methods such as X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) were employed to further understand the microstructural changes. The study reveals a significant correlation between compressive, flexural, and direct tensile strengths of the mortar mixtures. Notably, CSA and CAC mortar mixtures with SCMs showed an ASR value lower than the recommended 0.10%, while the autogenous shrinkage for both CAC and CSA mixtures was less compared to Ordinary Portland Cement (OPC). The influence of SCMs, though not substantial, was clearly observed. TGA results corroborated the phases identified in XRD and those observed in SEM, through the thermal decomposition of the phases present in the mixtures. This study contributes valuable insights into the use of SCMs in improving the performance and sustainability of CAC and CSA cement mortars.