Influence Of Binding Materials Composition On The Performance Of Shrinkage-Compensating Concrete

The preparation method of concrete expansion agent SCEA using the waste Ca O produced by the manufacture of sulfuric acid was invented. Expansive mortar and concrete of composite cementitious materials were investigated. The influence rules of binding materials composition on the restrained expansion ratio, drying shrinkage, compressive strength, and durability were studied. The hydration process and hydration products of shrinkage-compensating composite binder were studied by hydration heat, SEM. Looking forward to the research can provide guidance and reference to the application of concrete expansion agent SCEA in engineering and promote its development and application.The main contents and results are listed as follows:① SCEA expansive agent can produce a greater expansion speed at early ages. Proper dosage of fly ash(FA) was benefit to the development of restrained expansion rat(RER), whereas larger dosage of FA decreased the increase variation of expansion because of low early strength. On the other hand, granulated blast furnace slag(BFS) was adverse to the development of RER. Some amount of FA or BFS replacement can shorten the stage of rapid development of RER. By adjusting the composition of binding materials, the different expansion expectation can be achieved.② SCEA expansion agent is of great benefit to the compressive strength of concrete. It can significantly reduce drying shrinkage of concrete, improve concrete carbonation resistance and resistance to chloride ion permeability. But it is adverse to the frost resistance of concrete.③ High temperature can not only improve the hydration of cement, but also improve the hydration of expansive agent. So the contradictions between the expansion and strength came into being. The large expansion in the early stage can hinder compressive strength of mortar. In high temperature, the RER can be closed to or reach the maximum value at 1~2 and the expansion was so large that it no longer agree with the development of strength.④ According to the Knudson kinetics model and Krstulovic-Dabic hydration kinetics model, some kinetic parameters were calculated. The hydration process of composite binders can involve NG stage, I stage and D stage. The effects of fly ash and slag on NG stage, I stage and D stag were different, which can further influence the expansive efficiency.