Effects of ambient temperature, formwork type, and demolding time on the thermal deformation of sidewall concrete in underground engineering: Experiment, simulation, and engineering practice

Abstract

Formwork type (FT) and demolding time (DT) profoundly affect sidewall concrete's thermal deformation and stress. However, FT and DT are mostly based on subjective judgments, and lack of quantitative research data. Therefore, this paper proposes a method combining laboratory experiments, computer simulation, and engineering practice to study the effects of ambient temperature, different FTs, and DT on the sidewall's temperature change with time, temperature distribution in space, displacement change with time, thermal deformation, temperature stress for the first time. Results show that: the hydration heat release of cementitious material is the driving force for thermal deformation; in the height and depth directions, sidewall temperature is high in the middle and low on both sides; the use of steel formwork produces less thermal deformation and lower temperature stress than the use of wood formwork; when using steel formwork, it is recommended that the DT be 9 d in winter and 7 d in summer; for wood formwork, the DT be 12 d in winter and 10 d in summer. The recommended DT for the specific FT in different ambient temperature can be calculated by applying the research method in this paper. The research results can provide helpful thinking for decision-making on the engineering site.