The influence of SAP particle size and extra water on the dynamic mechanical behavior of SAP-modified cement-based composites

• Raising SAP size and adding extra water increase the total and macropore porosity. • Increasing SAP size and adding extra water reduce the dynamic compressive strength. • Dynamic compressive strength of composites increases with a rise in strain rate. • Raising SAP size and adding extra water elevate the DIF-f c and DIF-E values. • Raising SAP size and adding extra water raise the fracture degree of composites. Superabsorbent polymers (SAP)-modified cement-based composites (abbreviated as composites) have excellent frost resistance, internal curing efficiency, self-sealing and self-healing capacity. However, the effects of SAP particle size and extra water on the dynamic mechanical behavior of composites are still unclear. In this study, the total porosity and macropore (>100 μm) porosity of composites were studied with a mercury intrusion porosimetry test and an image analysis. The influence of SAP particle size and extra water on the quasi-static and dynamic mechanical properties of composites was analyzed. The fracture behavior of composites was investigated based on the fractal dimension and crack morphology. The results reveal that adding extra water can respectively raise the total porosity and macropore porosity by 33 %–39 % and 36 %–50 %, thereby declining the compressive strength and elastic modulus of composites under quasi-static and dynamic compression. The rise of strain rate from 63 s −1 to 102 s −1 elevates the dynamic compressive strength, elastic modulus, and fracture degree of composites by 39 %–44 %, 4.9 %–6.0 %, and 5.2 %–7.4 %, respectively. Raising particle size of SAP and adding extra water can raise the dynamic increase factor of compressive strength and elastic modulus. Which originates from the change of crack path, the increase of fracture degree, and the delayed response of strain induced by the rise of total and macropore porosity.