Effect of super absorbent polymers and fiber on drying shrinkage of spontaneous combustion coal gangue concrete

In order to explore the effective method of reducing the shrinkage of spontaneous combustion coal gangue concrete, seven groups of samples were designed with the different dosage of super absorbent polymers (SAP)and polypropylene (PP)fibers, the drying shrinkage test and the internal humidity test were carried out. The effect of SAP and PP fibers on shrinkage performance of spontaneous combustion coal gangue concrete was investigated, the influence of SAP and PP fibers on the internal humidity of the matrix was analyzed, and the law of change between the drying shrinkage strain and the internal relative humidity of the matrix was revealed. The shrinkage prediction model of spontaneous combustion coal gangue concrete was proposed. The results show that the addition of SAP and PP fibers can significantly reduce the drying shrinkage of spontaneous combustion coal gangue concrete. The shrinkage value of the matrix first decreases and then increases with the increasing of the SAP addition; the shrinkage value of the matrix gradually decreases with the increment of PP fibers dosage. At the age of 90 days, when the volume content of SAP is 0.2%, the shrinkage reduction effect of matrix is the best, and the shrinkage strain of the sample is reduced by 31.3% compared with the plain concrete. The addition of SAP and PP fibers can inhibit the decay of the internal humidity; the shrinkage strain and the internal relative humidity of the matrix vary linearly. By introducing the influence coefficient of spontaneous combustion coal gangue aggregate, the AFREM shrinkage prediction model is modified, the predicted results are in good agreement with the experimental results, and the modified shrinkage model can be used for the calculation of dry shrinkage of spontaneous combustion coal gangue aggregate concrete.