Investigation On Properties Of PVA Fiber Reinforced Strain Hardening Cementitious Composites

Traditional cement concrete is brittle which limits its application.Based on fracture mechanics and micromechanics,the strain hardening cementitious composites?SHCC?exhibits high ductility and excellent toughness,but there are still some problems such as the bad performance on volume stability and durability need investigating.In this paper,the influence of matrix composition on the basic mechanical properties of OPC-SHCC was studied.Then according to the micro-expansion characteristics of sulphoaluminate cement?SAC?,the internal curing effect of super absorbent polymer?SAP?and the high bondability of redispersible emulsion powder?VAE?,the effects of changing binding material,the addition of SAP and VAE on the basic mechanical properties,volume stability and durability of SHCC were investigated,revealing the intrinsic mechanism,and put forward the technical method which both considers mechanical properties,volume stability and durability.The main work of this paper and the main conclusions are listed as follows:?1?The influence of matrix composition such as water to binder ratio,sand to binder ratio and fly ash content on the basic mechanical properties of SHCC was studied by using basic mechanical properties tests.The results show that the increase of water to binder ratio and fly ash content,and the decrease of sand to binder ratio are beneficial to the SHCC multiple cracking and strain hardening performance,improving the ultimate tensile strain of SHCC.But at the same time it will reduce the compressive strength and flexural strength of SHCC.The basic mechanical properties of SAC-SHCC,SAP-SHCC and VAE-SHCC were studied.The results show that compared with OPC-SHCC,SAC-SHCC has better ductility,and its ultimate tensile strain can reach 4.4%which increases of 39%,but its compressive strength and flexural strength decreased slightly;the addition of SAP can improve the ultimate tensile strain of SAP-OPC-SHCC,and when the SAP content is 0.4%,the ultimate tensile strain of SAP-SAC-SHCC reached 4.4%and 5.0%respectively.The compressive strength and the flexural strength decrease with the increase of SAP content.In the uniaxial tensile test,the ultimate tensile strain of the VAE-SHCC can be maintained at more than 3%in the case of less cracks,and the average width of the carcks increases.With the increase of the VAE,the compressive strength decreases while the flexural strength increases slightly.?2?The influence of SAC,SAP and VAE on the volume stability of SHCC was studied by drying shrinkage deformation test.The results show that compared with OPC-SHCC,the SAC-SHCC exhibits good volume stability.The drying shrinkage deformation of SAC-SHCC within 90 days is reduced by 72%than that of OPC-SHCC,which can remain below400?10^-6.SAP and VAE have the water retention performance,which can effectively reduce the drying shrinkage deformation of SHCC.With the increase of SAP content and VAE content,the drying shrinkage strain of SAP-SHCC and VAE-SHCC decreases,and SAP is better than VAE for improving the volume stability.?3?The effects of SAC,SAP and VAE on the durability of SHCC were studied by anti-chloride ion permeation test and sulfate attack test.The results show that SAC-SHCC has the better resistance to chloride ion permeability and the addition of SAP has no significant effect on the resistance to chloride ion permeability of SHCC,while the addition of VAE can increase matrix porosity of SHCC,thereby reducing its resistance to chloride ion permeability.Under the action of sulfate,SAC-SHCC has good ductility,while SAP and VAE have no significant improvement effect on the sulfate resistance of OPC-SHCC.