Evaluation of Performance of Plain and Slag Cement Mortars Modified with Superabsorbent Polymers and Nanosilica

Abstract

One of the sustainable strategies for enhancing the durability and service life of concrete infrastructure is to improve the quality of the microstructure through internal curing. This can be achieved by the use of superabsorbent polymers (SAPs), which act as internal water reservoirs within the concrete. As cement hydrates, these reservoirs release additional water, enhancing the degree of hydration, refining the microstructure, and ultimately improving the overall performance of the concrete. This research investigates the effects of SAPs and nanosilica (NS) admixtures on plain and slag cement mortars by evaluating hydration kinetics, workability, water absorption, strength properties, drying shrinkage, and microstructural quality and integrity using the ultrasonic pulse velocity (UPV) method. The SAP-modified mortars exhibited enhanced performance attributed to improved hydration resulting from internal curing, especially when compared with mixtures without SAP. Results show that, relative to reference mixtures, mortars with SAP developed higher strength, attained higher UPV values, and demonstrated lower water absorption and drying shrinkage. These findings suggest a refinement and densification of the microstructure resulting from improved hydration. In plain and slag cement mortars, the addition of NS admixtures alone increased water absorption and drying shrinkage while reducing UPV and strength values. However, in some cases, the combination of colloidal NS with SAP improved performance, suggesting potential synergistic effects between these two additives.