Research On Early-age Shrinkage Of Magnetite Concrete

The apparent density of the heavy concrete is generally2500kg/m3or more, mainly used for national defense, atomic energy reactors and so on, such as the816underground nuclear engineering decrypted in the April2002. Preparation of heavy concrete requires heavy and solid ore blocks, usually magnetite or hematite block. In present. Application of heavy concrete has been many reports, but mainly focuses on the workability of heavy concrete. Research on its early-age shrinkage is very little.The main difference between heavy concrete and normal concrete is the difference of coarse and fine aggregate.Heavy concrete is consisted of coarse and fine aggregate with high density such as iron ore, and barite, and its method of mix design and construction is more mature, and heavy concrete is same as ordinary concrete:from the economic aspects, Generally, according to the requirements of materials, we can make heavy concrete with the local materials which are easy to take. this paper focus on the early-age shrinkage of magnetite concrete,and make comparison between the early-age shrinkage of normal concrete.Concrete technology is developing to a direction of high-strength and high-performance, but with concrete technology development, the difficulty of crack control increases, its reason is:an increase in the amount of cement, concrete tensile strength improves lags compressive strength, the usage of admixture which may reduce the volume stability.Concrete shrinkage crack is due to concrete shrinkage deformation caused by constraints, several major factors restricting the occurrence and development of concrete crack are:the concrete shrinkage deformation size, concrete tensile performance level and the constraint conditions of concrete deformation. This paper mainly studies magnetite concrete’s shrinkage deformation.The main function of super plasticizer is to increase concrete slump, which is beneficial to the pumping, but at the same time the shrinkage of concrete increases, which is approved by lots of engineering practice.For magnetite concrete, the increase of inner humidity caused by the addition of super plasticizer promote the chemical reaction, which causes inflation phenomenon.this paper studies the influence of super plasticizer on early-age shrinkage of magnetite concrete in quantitative terms.Reasonable curing method can not only improve the strength concrete,but also reduce the shrinkage,we can get reasonable curing time and start curing ages through experiments in the curing time and start curing ages’s influence on early-age shrinkage of magnetite concrete.