Experiment And Modeling On Early Shrinkage Of High Ductile Fiber Reinforced Concrete

HDC(High Ductile Fiber Reinforced Concrete)is a kind of high performance concrete.For obtaining the abilities of strain hardening and multiple cracking,a mass of fibers are added in HDC which is designed and based on the theory of mesomechanics.Moreover,HDC has the characteristics of low water blinder ratio,high cement content and high dosage of admixture,and there are no coarse aggregates in HDC.These characteristics enlarge the shrinkage value of HDC during the process of setting and hardening of HDC.And shrinkage performance has strong influence on usability of HDC.In addition,early shrinkage progress fastly in HDC,which would directly affect the final volume stability and the formation of cracks of HDC.But there are just few researches have been done on the shrinkage performance of HDC.In order to predict the development tendency of early shrinkage in HDC and enhance volume stability of HDC and control cracks formation in it.Effect of fiber volume fraction on early plastic shrinkage,autogenous and drying shrinkage of HDC were experimentally studied.And then shrinkage models were presented based on test results.The three models are respectively suitable for early plastic shrinkage,autogenous and drying shrinkage.The main research contents are as follow:Firstly,the relationship between the temperature rise of the hydration and setting time of HDC was researched,and then the test ending time of plastic shrinkage of HDC and the test starting time of HDC were determined by variation of the temperature rise of the hydration.Secondly,the rules of prehardening plastic shrinkage of HDC were studied.The results show: the minimum shrinkage appears when the fiber volume fraction is0.9%.And the shrinkage decreases in terms of the increase of fiber volume fractionuntil the volume reaches 0.9%,after that the shrinkage will show up trend as the rise of fiber content.Thirdly,the paper researched autogenous and drying shrinkage of HDC.With the increase of fiber volume fraction,both autogenous and drying shrinkage have certainly decreasing tendency respectively.At the same time,how the mechanical properties are affected by fiber volume were studied,the results indicate:With the increase of fiber volume fraction,compression strength of HDC is decreasing,but shear strength and bending strength are increasing.Finally,a suitable model for early plastic shrinkage of HDC was presented by computer simulation.For autogenous and drying shrinkage,the models suitable for HDC were also presented based on the test results,existing shrinkage models and Matlab software.The given models can be well used to HDC,and have a good agreement with the test results.