Experimental Study Of Additive Components On The Shrinkage And Crack-Resistance Of Foamed Concrete

In recent years, foamed concrete has been increasingly used in the engineering construction, but it tends to crack during its use. As an important means of improving cement-based materials, the addition of additional components can solve the cracking problem in these materials. Nevertheless, few studies focus on the influence of additional components on shrinkage and cracking of foamed concrete. Therefore, it is quite necessary for researchers to explore the effect of additional components on the shrinkage and crack-resistance performance of foamed concrete.In this paper, the author conducts a systematic study of the effects of fibers and admixtures on the shrinkage and crack-resistance performance of foamed concrete, and analyzes the impact of coupling mechanism between additional components on the performance of foamed concrete. Variance analysis is conducted to probe into the influence of various factors on the performance of foamed concrete; strength tests are carried out to check the influence of additional components on the strength and toughness of foamed concrete; non-contact concrete shrinkage deformation tester and comparator are used to evaluate the influence of additional components on initial shrinkage of foamed concrete; annular constraint test method is adopted to explore the effect of additional components on crack-resistance performance of foamed concrete; scanning electron microscope is utilized to study the microstructure of foamed concrete and dissect the mechanism of actions for the changes in the shrinkage and crack-resistance performance of foamed concrete.The results suggest that, the initial shrinkage deformation curve of foamed concrete show regular fluctuations, which can be divided into three stages:shrinkage stage, expansion stage and drying shrinkage stage. Fibers can significantly inhibit the initial shrinkage of foamed concrete and enhance its strength among which hybrid fiber has better improvement effects than single-doped basalt fiber; as it is highly compatible with foamed concrete, polycarboxylate superplasticizer is able to greatly increase the strength of foamed concrete and suppress expansion and shrinkage stages in initial shrinkage, thereby improving the shrinkage performance of foamed concrete; the water-retaining agent HPMC can enhance the strength and initial shrinkage performance of foamed concrete with an ideal admixture content of 0.04%; the shrinkage reducing agent can compensate the shrinkage of foamed concrete and improve the shrinkage performance of this kind of concrete.As an indicator, ICT can evaluate the cracking sensitivity of foamed concrete and judge the cracking risk level. The experiments show that, with the changes in fiber content and length-diameter ratio, hybrid fiber has a more significant influence on crack resistance performance of foamed concrete than single-doped fiber and can reduce the risk level of foamed concrete; the water-retaining agent HPMC can reduce the ratio of compressive strength to flexural strength of foamed concrete, improve its toughness and increase its crack-resistance performance; different couplings can be found between different additional components, which are able to greatly improve the shrinkage and crack-resistance performance of foamed concrete. Range analysis shows that hybrid fiber is the major influencing factor and that the optimum hybrid proportion is 2:1, the powder content 0.4% and the shrinkage-reducing agent content 0.5%.