Experimental Research On The Mechanical Properties Of PVA-Fiber Reinforced Cementitious Composites

Based on ECC design theory, this thesis adopts polyvinyl alcohol(PVA) fiber as toughening materials, makes up PVA fiber reinforced cementitious composites(PVAFRCC), researches lots of mechanical performance indexes such as the bending, compressive and four-point bending, direct tensile, the following works have been completed:1.After many tries to match, constantly adjusted the selection of raw materials, mixing sequence and process, got the excellent mixture ratio of both working performance and mechanical performance and the mixing method, with PVA fiber dosage, sand grain size, water/cement ratio for the biggest influence factor of the orthogonal experiment was designed.2.The bending tests of PVA- FRCC specimens are conducted, the specimens show multiple cracks and strain- hardening phenomenon, bending load-deformation curves are obtained, bending strength values increased by 52%, the consistency of mixture decreased by 30.3%. The orthogonal experiment results are analyzed, considering the bending strength and consistency, got the best mixture ratio for the fiber content is 1%, the maximum particle size of sand is 0.63 mm, water/cement ratio is 0.40.3.The compression tests of PVA-FRCC specimens are conducted, Compressive load-deformation curves are obtained, the split phenomenon does not appear when the specimens damage, along the axis direction the specimens are compressed, and bulging along the lateral. The compressive strength values of Specimens decreased by 21.27%, the peak compressive strain increased by 2.55%, about 12 times that of ordinary concrete. Analyzed the result of the orthogonal experiment and got the best mixture ratio for the fiber content is 2%, the maximum particle size of sand is 0.09 mm, water/cement ratio is 0.29.4.The four-point bending tests of PVA- FRCC specimens are conducted, all four-point bending specimens show multiple cracks, cracks width is about 0.04-0.1 mm, spacing is 1-2 cm, evenly distributed in the center of specimens, the distribution width is about 7 to 14 cm, the overall trend for is the more the cracks, the cracks width is smaller, the spacing is smaller, the greater the distribution width. The average initial cracking load of PVA- FRCC specimens is 0.36 KN; the average peak load is 0.49 KN; the average Initial cracking deflection is 0.38 mm; the average corresponding deflection of peak load is 3.62mm; the average bending scale ultimate strength is 4.69 Mpa; the average bending strength is 6.40 Mpa; the average elastic modulus is 11.33 Gpa. Proportion considering the bending scale ultimate strength, bending strength, peak deflection, analyzed the result of the orthogonal experiment and got the best mixture ratio for the fiber content is 2%, the maximum particle size is 0.63 mm. The four-point bending load- deformation curves are obtained.5.The direct tensile tests of PVA- FRCC specimens are conducted, the specimens break in the middle of the straight segment, the slits number for 2-3, the average peak tensile strain of 7 days is 0.65%, about 43-65 times that of concrete tensile strain of 28 days, the direct tensile load-deformation curves are obtained, the strain- hardening phenomenon is obvious.