Study On Pseudo Strain-Hardening And Fracture Characteristic Of Polyvinyl Alcohol Fiber Reinforced Cementitious Composites

High strength and high modulus polyvinyl alcohol (PVA, in short) fiber (KURALON K-II, REC15) exploited by Japanese company can enhance the ductility to matrix in many ways. PVA fiber reinforced cementitious composites(PVA-FRCCs, in short) is a kind of composites reinforced by PVA fiber less than 2%～4% volume ratio.Furthermore, the matrix is just cement, cement adding some admixture, or extra adding some small particle diameter fine aggregate.Above all, the characteristic of the composites is ultra-high ductility whose ultimate tensile strain is about 100 times to concrete. Moreover, inherent pseudo strain-hardening character of the composites is the result of stable cracking and the reason of its unique ductility. In addition, the saturated multiple crack width of the composites is less than 100μm. Accordingly, a series of tests and analytical work about the composites have been completed in order to put the composites into hydraulic structure preventing cracking and improving durability:1. Material component performance, feeding sequence and mixing technology are described in detail. Based on a large number of tests, the optimal compounding method which can reduce the mixing time, make fiber dispersed uniformly and get better flowability can be acquired.2. Complete stress-strain curves of uniaxial compressive cylinder test of PVA-FRCCs are drawed. Although compressive strength is much low between 16MPa and 33MPa, tensile strain at peak load is 3 to 6 times to concrete and ultimate strain is almost 100 times to concrete.3. Uniaxial direct tensile test of nonotched and double-edged notched thin sheets which individually employ grip jaw and bended steel plate method are carried on 1000kN microcomputer control hydraulic servo machine and 250kN MTS-NEW. As a result, pseudo hardening stress-strain complete curves can be got and ultimate tensile strain is 0.7% at the most. Accompanyingly, densely multiple crack occurred whose width is only less than 100 μm. Furthermore, the analysis and simulation of stress-strain curves are carried out. In addition, the formula of calculating tensile stress is established.4. Uniaxial direct tensile test of single-notched thin sheet whose geometric dimension is the same to that used in foregoing direct tensile test is also done on 1000kN microcomputer control hydraulic servo machine. Pseudo hardening Load P-crack mouth opening displacement (P-CMOD, in short) is gained. Besides, not only multiple dispersive cracks...