Evolution of temperature stress and tensile properties of concrete during steam-curing process

Abstract

Nowadays, steam curing is widely used in the production of prefabricated components. However, studies have shown that steam curing can lead to micro or macro-cracks in concrete caused by the curing regime which can affect the performance of the concrete in all aspects. Herein, the internal stress and tensile strength development of concrete during the steam-curing process was studied, so as to evaluate the crack risk of concrete during steam curing. To evaluate the internal stress during the steam curing, the internal temperature and thermal deformation of the concrete were tested. Considering the difficulty of measuring the tensile properties of early-age cement-based materials, a mortar tensile test device combined with digital image correlation (DIC) was designed in the paper. Meanwhile, thermal analysis tests were done to analyse the CH content of the concrete during steam curing. The results indicated that the mortar tensile test device in combination with the DIC designed in the paper was an effective method for testing the early tensile properties of cement-based materials. In the four stages of steam curing, micro-cracks in the concrete were most likely to occur in the cooling process. The addition of supplementary cementitious material is an effective method for restraining surface cracking in steam-cured concrete, and to ensure the tensile strength, sufficient water vapour is needed in the steam-curing process for a concrete mixture with large mineral admixtures, otherwise, a reduction in the tensile strength of more than 50% will occur.