Research On The Impact Of Fine Aggregate And Chloride Solution Immersion On The Mechanical Properties Of SHCC

Strain Hardening Cement-based Composites(SHCC)has great ability to control the crack width,which is of great significance to improve the durability of offshore engineering structures.But the practical application of SHCC is limited by its high material cost.The purpose of this thesis aims to cut down its cost by adopting local fine aggregates and domestic PVA fibers.Then,mechanical properties of SHCC after specimens are immersed in chlorine solution in different periods is investigated.First of all,the effect of particle size of fine aggregates on the mechanical behavior of SHCC is tested so as to select a suitable aggregate gradation.Then,by preloading different tensile or compressive stress,the influence of preload stress,soak time and concentration of chlorine on the mechanical behavior of SHCC with different damage induced by preload is examined.Finally,on the basis of the mechanical properties of PVA fiber/matrix interface,the theoretical model is set up to predict the tensile strength of the SHCC.The main results obtained are as follows:(1)PVA fibers have been dispersed into the cement matrix equally when six different gradation SHCC specimens of fine aggregate are prepared.It is obvious that different grading fine aggregate has great influence on the tensile properties of SHCC but make less effect on compressive strength and elastic modulus.The SHCC made by domestic PVA fibers and sand with particle less than 0.6 mm shows strain hardening behaviour and multiple micro cracks characteristics under uniaxial tension.(2)The influence of preload,solution concentration and soak time on mechanical properties of SHCC after chloride solution soak is different.The ultimate tensile strain of SHCC increases with increasing preload tensile stress & soaking time,but the tendency of tensile strength is not obvious.(3)The compressive strength of SHCC first increases with the increase in preload stress then decreases,but increase with soak time.Elastic modulus increases with preload stress and soak time.The chloride penetration depth increases as the soak time,preload pressure stress and the concentration of chloride increases.(4)The interface parameters such as the interfacial chemical bond,interfacial frictional bond,slip-hardening coefficient and the critical length of fiber between PVA fiber and cement matrix is derived from load-displacement relationship during monofilament pull-out test.The strength effective coefficient is put forward.The predicted tensile strength of SHCC is in agreement with the experimental result.