Development of low drying shrinkage foamed concrete and hygro-mechanical finite element model for prefabricated building fasçade applications

Prefabricated lightweight concrete building fasçade can improve the energy efficiency of buildings and reduce the carbon emission of transportation. However, it is essential to maintain the dimensional stability of the full scale element. The drying shrinkage of lightweight foamed concrete was investigated in this study. The hypothesis of using the drying shrinkage of normal weight concrete to approximate that of lightweight foamed concrete of dry density about 1500 kg/m3 counterpart was verified. Three different strategies of reducing drying shrinkage were studied. The drying shrinkage of common ingredients of ordinary Portland cement (OPC) and ground granulated blast-furnace slag (GGBS) was commonly up to 2000-3000 με. The use of magnesium expansive agent with different calcination conditions could not reduce the drying shrinkage. The use of calcium sulfoaluminate (CSA) cement with OPC and GGBS could significantly reduce the drying shrinkage within 1000 με in standard testing environment. The formulation developed in laboratory was scaled up in a concrete production plant for prefabricated concrete elements. A lightweight full scale panel (the wet density was about 1700 kg/m3) was fabricated. The drying shrinkage of the developed formulation with CSA cement was only 161 με in the field test. A hygro-mechanical model was developed to model the diffusion, shrinkage and plastic strain evolution. The incremental stress-strain constitutive relationship of the hygro-mechanical model was derived for incorporating it into general finite element routine. The model parameters were calibrated by the drying shrinkage measurements in this study. The calibrated model demonstrated the cracking potential of three typical reinforced concrete panels of three different formulations studied in this study.