Insights into the effects of polyurethane for sustainable cementitious materials: Experimental study, microstructural and numerical modeling

Polyurethane polymer-modified cementitious materials (PUCM) have demonstrated promise in improving the pore structure characteristics and mechanical properties of construction materials. The mix design procedures remain subjective due to the limited investigation of their pore structures. Furthermore, the mechanical and essential properties of concrete are directly influenced by pore structure features, such as porosity and pore size distributions. This study examined the microstructures, porosities, and pore-size distributions of polyurethane (PU)- modified mortars using mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Four levels of PU content (0%, 10%, 15%, and 25% by cement weight) were incorporated into the mortar mixture. Moreover, a finite element (FE) model was developed to analyze the equivalent principal behavior of the PUCM under compression and flexural loads. The results indicated that the inclusion of PU materials reduced compressive strength. Whereas the flexural strength was slightly improved at the optimum polyurethane content (15%PU). The reference mortar exhibits the lowest cumulative intrusion mercury of 0.0443 mL/g. While PUCM-25PU exhibits the highest cumulative intrusion mercury value of 0.0531 mL/g, resulting in more porosity. The microstructural analysis results showed that the adsorption of cement particles onto the PU matrix inhibited hydration. The FE results were in good agreement with the test results, indicating a minimum error of 3% and a maximum error of 11% % at the ultimate flexural stress for the PUCM-0PU and PUCM-15PU specimens, respectively. The research highlighted the application of polyurethane in cementitious repair materials with remarkable advancements in the construction industry, providing effective and long-lasting solutions for maintaining civil engineering infrastructure.