Influence of nano alumina reinforced superabsorbent polymer on mechanical, durability, microstructural and rheological properties of cementitious materials

Superabsorbent polymers (SAPs) are widely used in concrete for their promising effect in internal curing and crack sealing. Nano materials are efficient in improving the permeability and porosity of concrete with their smaller size and larger surface area. In this research , polyacrylamide (PAM) as superabsorbent polymer (SAP) along with nano alumina (NA) is proposed for small percentage of replacement in cement and their effects on mortar concrete were studied for mechanical and microstructural properties under self-curing and wet curing conditions. This study investigates the combined influence of nano alumina and polyacrylamide superabsorbent polymer hydrogel on chemical durability of cement mortar with HCl, CaCl2, and Na2SO4 immersion for 180 days. The effectiveness of replacing cement by composite mixture of polyacrylamide superabsorbent polymer and nano alumina at 0.1%, 0.2%, 0.3%, 0.4% and 0.5%, by weight, was investigated. Nano alumina modified by SAP was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) studies. Results indicate that NA/SAP combination in concrete improves hydration of cement enhancing the mechanical properties in concrete and similar properties are obtained in self-curing conditions indicating that SAP is good internal curing agent in concrete and NA is useful in filling up micro pores in concrete enhancing their strength. Hence, a composite admixture is proposed in concrete through this work for low-shrinkage, compact and dense concrete for the application in practical engineering.