Study On The High-strength Lightweight Aggregate Concrete Shrinkage Cracking Test

Lightweight Aggregate Concrete is refers to the Lightweight Aggregate Concrete,which is made from Lightweight Aggregate,light sand(or common),cement and water.Its dry apparent density is less than 1950 kg/m3.Because of Lightweight aggregate concrete,its concrete density is less than conventional low 20% ~ 30% density of ordinary concrete.For the lots need of concrete construction,LAC has the advantage of low density,high strength lightweight aggregate concrete.But compared with ordinary concrete,the late great shrinkage is a great disadvantage of lightweight aggregate concrete,which is lead to not a lot of popularity of lightweight aggregate concrete.In a free state,the contraction made of Lightweight Aggregate Concrete does not have side effects on the object itself.And applied in the structure of concrete,the concrete pouring into the structure of the component due to under statically indeterminate state,when their contraction deformation occurs,will produce contraction stress,and under the condition of constraint shrinkage stress cannot be released,when is greater than the tensile strength of concrete itself,can produce cracks,which finally impact on the durability of structures.This paper has studied the lightweight aggregate concrete on some aspects.The experimental study is mainly for the following:(1)In this paper,experimental purposes required to configure a high-strength lightweight aggregate concrete of LC60,and we made some study about high-strength ceramic concrete's free shrinkage in the free state.The free shrinkage test involves eight different mix of lightweight aggregate concrete.We carefully studied the contraction status LC60 expansive lightweight aggregate concrete of different content and different dosage under polypropylene.The results showed that: expanders for lightweight aggregate concrete has a significant anti-shrink property.And we find out that the 8% of mixing is best after mechanical test.And we also find that the polypropylene fiber has infections on shrinkage,which can reduce moisture loss.(2)The cracking is one of the key factors influencing the durability of concrete,and lightweight aggregate concrete undoubtedly exacerbate the shrinkage cracking.The experiment's instructs is using professor Zhu Han's group's,which is improved after several times test.The polypropylene fiber and expanders both can improve the performance of lightweight aggregate concrete,But the two substances to prevent the cracks of concrete is from two mechanism playing a role in the direction.This paper studied under the different content of polypropylene fiber and expansion agent affect how the craze of lightweight aggregate.And the experiment also joined the traditional C60 concrete,and the light aggregate concrete are compared with those of the traditional C60 concrete research.Results show that adding expansive agent and polypropylene can improve the cracking resistance of concrete,adding 0.9Kg/m3 of polypropylene fiber and 8% content of expansion agent on the cracking resistance of high strength lightweight aggregate concrete is greatly improved.(3)We also study the mechanical performance of lightweight aggregate concrete.The research involves the cube compressive strength,splitting tensile strength,bending strength and the influence of modulus of elasticity.