Drying kinetic and shrinkage of sand-concrete applied by shooting process

The aim of this study is to bring some answers to the questions about the delayed deformation of the shooting sand concrete (SC), which is made of aggregates up to 5 mm. Comparison of the results shows that the endogenous shrinkage (eES) of both SC and vibrated concrete (VC) is similar. Drying shrinkage (eDS) results, revealed that eDS of SC is higher than that of VC in the short term. In the long term, eDS of SC becomes lower than eDS of VC. However, the SC loses more water during the period of shrinkage measurements than VC. Furthermore, pore size distribution shows that the mesoporous structure of SC lost more water than the bimodal structure of VC, which includes macropores and mesopores. These particular porometric structures of SC and VC are the main factor behind the difference of the drying shrinkage behaviour of the two mixtures. This is an interesting and unexpected result, which is not in accordance with the commonly accepted relationship between shrinkage and weight change of samples, and between moisture loss and porometric structure. This work provides an explanation for this phenomenon by taking into account the kinetics of drying and the porometry of the concrete.