Study On Influence Mechanism Of Ground Granulated Blast Furnace Slag On Shrinkage And Cracking Of Self-Compacting Concrete

The hydration heat and shrinkage of self-compacting concrete(SCC)are higher than that of normal concrete,which will increase the cracking risk of structure or component and affect the serviceability of building.Using supplementary cementitious materials to replace part of cement can effectively solve the above problems.Because of its pozzolanic effect and filling effect,ground granulated blast furnace slag(GGBFS)can not only improve the macro-performance of concrete,but also realize the resource treatment of solid waste,which is beneficial to the environment.In this study,the equivalent volume of 0-30%GGBFS was selected to replace cement,and the influence of different GGBFS content on the workability of SCC was investigated,the influence of GGBFS content on the mechanical properties of SCC was studied by compressive and flexural strength tests,combined with the heat of hydration,X-ray diffraction(XRD)and Scanning electron microscope(SEM)tests,the effects of macro-properties were analyzed at the micro-scale,the shrinkage and cracking resistance of SCC with different GGBFS content were obtained by using temperature-humidity integrated shrinkage test and steel ring restrained test device,and compared with the shrinkage models at home and abroad,an integrated prediction model of shrinkage and relative internal humidity(ε_s-RH)was established,and a stress calculation model was established based on the steel ring confined test.The results show that GGBFS can significantly improve the filling capacity,passing ability and wet packing density of SCC,and the optimum content of GGBFS is 30%,the multi-parameter coupling model can well characterize the performance of SCC.The early strength of the SCC is similar to that of the control group after adding less than 30%GGBFS,and the later strength increases with the increase of the amount of GGBFS,because the GGBFS can fully hydrate with the increase of age,increasing the amount of hydration products,resulting in continuous increase in late strength.Through hydration heat test,XRD test and SEM test,it is found that the pore structure of SCC is improved,the pore distribution is more reasonable,the interfacial transition zone is better,which is more conducive to the strength development.The autogenous shrinkage and drying shrinkage of SCC decrease with the increase of GGBFS content,and they are in good agreement withε_s-RH prediction model.The initial cracking time of SCC ring containing GGBFS was delayed or did not crack,and the number and width of cracks were decreased.