Experimental Study On Durability Performance Of Lightweight Aggragate Concrete With Double Mineraladmixtures

With the development of modern civil engineering structure in the direction of high-rise and long-span,and the requirement of lightweight and energy saving of building materials,the self-weight shortcomings of ordinary concrete no longer meet the needs of engineering,and the development of lightweight aggregate concrete has become an inevitable trend.Lightweight aggregate concrete with lightweight,durable performance is good,and low coefficient of thermal conductivity,application of lightweight aggregate concrete in construction engineering in satisfy the intensity and other performance requirements at the same time can reduce weight,and is unceasingly thorough along with the idea of sustainable development and demand for building energy efficiency is higher and higher,the use of artificial light aggregate mixture of lightweight aggregate concrete has the economic benefits.Improving the durability of concrete structures in harsh environments has practical guiding significance for structural design.In this paper,fly ash and slag powder double mixing technology is used to replace part of cement with the total content of 30%,40%,and the incorporation ratio of fly ash and slag powder is set as 1:1,2:3,1:2,respectively,to prepare LC30 lightweight aggregate concrete by loose volume method.The slump of fresh lightweight aggregate concrete and compressive strength at different curing age were measured,and the fluidity and mechanical characteristics of lightweight aggregate concrete were studied.In accordance with the ? Standard for test methods of long-term performance and durability ordinary concrete?,has carried on the fast freeze-thaw test,accelerated carbonation test,water permeate test and shrinkage deformation test.And research of fly ash and slag powders under different quantity of different mixing ratio of the lightweight aggregate concrete durability performance,finally by means of scanning electron microscopy(SEM)technology to analysis the different group of lightweight aggregate concrete microstructure.The results show that :(1)Double mineral admixtures can significantly improve the fluidity of lightweight aggregate concrete.When the total admixture remains unchanged,slump increases with the increase of fly ash content.When the incorporation ratio remains unchanged,the total content of fly ash and slag powder increases,and the slump shows a downward trend.The compressive strength of early age reference concrete is higher than that of the test group with mineral admixtures.When the ratio of fly ash and slag powder is 2:3,the 28 d compressive strength value is the highest,followed by the ratio of 1:1,and the lowest when the ratio of 1:2.(2)Mixing fly ash and slag powder can improve the frost resistance and impermeability of lightweight aggregate concrete.When the total content of fly ash and slag powder is 40%,theimprovement effect on the frost resistance of lightweight aggregate concrete is better than 30%.When the total content of fly ash and slag powder is 30% and the ratio is 2:3,it is the best to improve the impermeability of lightweight aggregate concrete.(3)The addition of fly ash and slag powder has an adverse effect on the carbonation resistance and free shrinkage performance of lightweight aggregate concrete.With the increase of the total content of fly ash and slag powder,the carbonation depth and shrinkage strain value of lightweight aggregate concrete increase.Light aggregate concrete has the best durability when the proportion of fly ash and slag powder is 2:3.(4)It can be seen from the SEM image that when the total content of fly ash and slag powder is 30% and the proportion is 2:3,the hydration product has the highest concentration,the internal structure of concrete is the densest,and the internal pores of concrete increase with the total content.