The effects of superabsorbent polymers on the shrinkage and mechanical properties of concrete were investigated.Results of shrinkage tests show that SAP addition reduces the shrinkage.Especially,for the concrete with 3.84 kg SAP/m3 concrete,the shrinkage is little.Compressive strength of concrete with SAP is lower than that of concrete without SAP.However,for the concrete with SAP,the ratio of compressive strength at 90 days to one at 3 days is larger than that of concrete without SAP.
To investigate the early-age behaviors of concrete under a restrained condition,a set of apparatus was developed.In this way,the tensile creep and other early-age properties can be investigated in depth.By measuring the modulus of elasticity of concrete,synchronous shrinkage of concrete and steel rings and free shrinkage of concrete,the deformations of concrete ring can be quantified respectively.The experimental results show the tensile stress in concrete is time-dependent,and the stress at cracking is much lower than the tensile strength at that age;the tensile creep plays an important role in relaxing the tensile stress and postponing the cracking of concrete.
For a better understanding of the strains and stresses,numerical simulation was conducted by using ANSYS under the assumption of absolute bond between the steel and concrete.The results show that the stresses and strains in such concrete and steel rings are uneven;the curves of strains and stresses change gradually around the interface.To ease numerical computation,the mechanical system was simplified under the assumptions of synchronous deformation and uniform strains and stresses.The results of the numerical simulation and simplified stress calculation can match almost perfectly.It means that the simplified mechanical model can be used in stress and visco-elastic behavior quantification.
