Experimental Study On Development And Performance Of Self-compacting And Self-curing Concrete

In recent years, the concrete-filled steel tube are applied in high-rise buildings and super high-rise buildings continuously, but the quality of concrete pouring and the concrete curing has been the blind spot in the practical application. The appearance of self-compacting and self-curing concrete is a new way to solve the quality of concrete pouring and the later concrete curing. This paper study the concrete by adding super-absorbent polymer(SAP) based on the self-compacting concrete to satisfy both properties and self-curing properties though a large number of experiments. In this paper, the law of SAP dosage and additional amount of water are two basic parameters. This paper study on mechanical properties, volume stability and self-curing effect when added different SAP dosage and additional amount of water to self-compacting concrete. This paper established the specific didderential equation of concerte inernal humidity field in the SAP release water before and after. The equation can provide a certain theoretical basis for explaining the SAP self-curing mechanism and can provide an idea for quantitative analysis of the SAP self-curing.Based on the standard method, the SCC mix proportion is calculated. On this basis, the Power’s theory is used to get the theoretical SAP dosage and additional water, and the SAP-SCC mix design has been done, the results show that the completely meet the requirements of the working ability and mechanical properties.The tests on mechanical property of SAP-SCC show that the proper amount of SAP dosage and the additional amount of water will not cause the concrete strength to decrease obviously and the 28 d strength also increased slightly. But the SAP dosage and the additional amount of water are not too large, otherwise it will cause the concrete strength decreased significantly in each age. In this paper, the best dosage of SAP is about 0.15%(the percentage of cementitious materials), the best additional amount of water is about 10~15 times(the quality of SAP).The test on volume stability of SAP-SCC show that the free shrinkage and self shrinkage can be reduced after the incorporation of SAP into SAP-SCC. Before the SAP release water, the free shrinkage and self shrinkage between the test group and the blank reference group were all basically the same. After the SAP release water, the shrinkage gap between the test group and the blank reference group began to appear. In this paper, the free shrinkage and the self shrinkage of SAP-SCC reducing shrinkage effect is the best when the SAP dosage is about 0.15% and the additional amount of water is about 15 times.In this paper, based on Fick’s second law, we established the specific didderential equation of concerte inernal humidity field by using the moisture diffusion law and moisture conservation law when the SAP release water before and after, and found that the different equation has the same form. This shows that the diffusion of SAP-SCC internal humidity field is similar before and after the SAP release water. Then through the capillary pressure theory, according to the Laplace equation and the Kelvin equation established the relationship between the concrete relative humidity and the nonporous surface tension, and according to the relation of stress and strain should be to establish a relationship between the internal relative humidity of SAP-SCC and the relative shrinkage.The curing efficiency test of the SAP-SCC lead to the result that no matter the SAP dosage or the additional amount of water, they both have effect on the resistivity. The influence of the SAP dosage and the additional amount of water on the curing effect is related to the internal depth of concrete. And the effect is concered about the buried depth of the electrode. The right SAP dosage and the additional amount of water both can obviously promote the humidity inside the concrete when the buried depth of the electrode is less than 3cm, which can reduce the resistivity of concrete. It can be considered that the self curing effect is obvious when the depth is less than 3cm and the self curing effect is not obvious when the depth is larger than 3cm. Based on this, it can be considered that joining the SAP and the additional amount of water has played a certain role in self curing and using join the SAP to achieve the effect of self-curing is feasible.