| In this paper,high strength high modulus PVA fiber reinforced cementitous composites were prepare in order to improve the toughness of cement matrix composite.Considering the problem of environmental protection and energy saving,large dosage of fly ash 60%(mass ratio)and low dosage of PVA fiber(volume ratio2% or less)was used.PVA fiber surface sizing and lubrication treatment have been studied with regards to fiber mechanical properties,surface characteristics,and compressive strength,flexural mechanical properties of cement based composite materials.Single fiber pullout experiments were conducted to evaluate the interfacical bonding between PVA fiber and cement matrix before and after the surface treatment.Through experimental analysis,the following conclusions were obtained:1)The SEM photos showed that PVA fiber surface was enclosed with a coated membrane after different concentrations of sizing agent and lubricants treatment.2)After sizing agent(100 g/L)treatment,the PVA fiber sizing add-up ratio,water contact angle,fiber tensile strength is 1.9%,84.12 ° and 1700.8 MPa respectively,the PVA fiber hydrophilic was greatly reduced.PVA fiber after lubricant(100 g/L)treatment,PVA fiber weight add-up ratio,water contact angle,fiber tensile strength were 1.5%,68.55 ° and 1696.3 MPa,the fiber hydrophilic was slightly lowered.After treating with the sizing and lubrication agents,the strength of PVA fiber was dropped about 2%,and modulus was decreased by 14%,the elongation at break was increased by 20%.3)With the increase of sizing and lubricant add-up ratio,the compression strength of the PVA fiber reinforced cementitous composite was decreased to some degree.Compressive strength of PVA fiber reinforced cement after sizing agent(100g/L)and(100 g/L)of lube treating respectively,can still reach about 20 MPa.4)PVA fiber toughening cement three point bending test showed that knowable PVA fiber surface after sizing agent and lubricant processing respectively,with the constant improvement of the concentration of sizing agent and lubricant processing and its fiber toughening the flexural strength of cement sample a downward trend overall.PVA fiber surface,respectively,after sizing agent(100 g/L)and the lubricant(100 g/L),while maintaining the certain flexural strength,the fracture toughness of fiber reinforced cement is best.According to the crack propagation characteristics of the PVA fiber reinforced cement samples,known as the increase of the concentration of the sizing agent and lubricant in the PVA fiber reinforced cement block cracks from the above three increased,which respectively after sizing agent(100 g/L)and lubricant(100 g/L)processing of PVA fiber reinforced cement samples,respectively appeared a lot of tiny crack,even more shows(100 g/L)after sizing agent and lubricant(100 g/L)processing of PVA fiber cement base sample,its toughness is improved.5)By PVA single fiber pullout test,with the improvement of the sizing agent and lubricant processing concentration,the interface strength,debonding energy,sliding hardening coefficient of PVA fiber toughened cement samples showed downward trending.After PVA fiber treated with sizing agent(100 g/L),the bonding between fiber and cement to improve the toughening effect of fiber,the fiber interface strength 1.7 MPa,debonding energy of 1.8 J / ?,slip hardening coefficient of 0.5.At the same time,PVA fiber treated with lubricant(100 g/L),the bonding between the fiber cement to improve the toughening effect of PVA fiber is the best,the fiber interface strength 1.8 MPa,debonding energy of 1.9 J / ?,slip hardening coefficient of 0.4.Combined with the fracture morphology of PVA fiber reinforced cement,PVA fibre in respectively after sizing agent(100 g/L)and lubricant(100 g/L),fiber in cement has good dispersibility in the matrix,and is suitable for cohesive force,make the most of the fiber in cement is pumped out,the PVA fiber reinforced cement toughness got obvious improvement. |
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