Properties and characterization of high-performance steam-cured cement-based materials modified by phase change materials

Steam-cured concrete is widely used in precast element production due to its high early strength and efficiency, but its long-term performance is often poor. Integrating phase change materials (PCMs) into steam-cured samples is a potential solution. The influences of six PCMs on the fluidity, mechanical strength, toughness, water absorption, and pore structure of steam-cured mortars are investigated by a series of experiments. PCMs employed are paraffin (P-45 and P-58), fatty acids (lauric acid, LA and myristic acid, MA), and polyethylene glycol (PEG1500 and PEG4000). The results show that PEG powder can improve the fluidity of fresh mortar, while the fluidity reduces as the amount of LA or MA increases. The addition of appropriate PCMs slightly reduces the strength of steam-cured mortar but effectively improves the toughness. Incorporating proper PCMs significantly decreases the capillary water absorption of the steam-cured mortar due to the modification of the surface characteristics of pore walls by paraffin and fatty acids. Compared with specimens containing PEG and fatty acids in this study, mortar containing paraffin have higher strength, especially for the one-day early strength. Employing an appropriate amount (not more than 5%) of paraffin is an excellent way to develop high-performance steam-cured cement-based materials, which extend the service life and reduce an environmental load of steam-cured cement-based materials. •Except for LA or MA, the addition of paraffin or PEG does not adversely affect the fluidity of fresh mortar.•Compared with fatty acids and PEG, the mortar with paraffin has higher mechanical properties.•The impermeability of mortar is improved due to the surface modification of pore walls by paraffin or fatty acids.•Employing an appropriate amount of paraffin is an excellent way to improve the durability of steam-cured mortar.