Research On Preparation And Mechanical Properties Of Domestic PVA Reinforced Engineered Cementitious Composites

Cementitious Composites Engineered (ECC) is a new type of building material with pseudo strain hardening and multiple cracking, which is characterized by a remarkable nonlinear deformation and excellent toughness. ECC with a fiber volume of 2% shows an ultimate strain of 3%-5%, and its crack width remains about 60μm at failure under tention. With the appication of high strength steel, the ECC material has been applied in practical engineering, and it is expected to solve the structure’s durability problem of the modern concrete structure. In this paper, the performance of domestic PVA-ECC was studied by experimental research and theoretical analysis:(1) Referring to the existing research results of ECC, the components and molding process of domestic PVA-ECC were determined. Based on micromechanics,9 kinds of different mixture were employed for preparing the specimens. The compression test and four point bending test were carried to characterize the mechanical behavior of ECC, water-cement ratio, sand-cement ratio, the volume of fly and the quality of PVA fiber were investigated to determine their effects on the compressive strength and toughness of ECC. Comprehensive test results, the best proportion of mixture G2 was determined to be:cement/fly ash/silica fume/sand/water/ superlasticiczer/domestic PVA fiber (Vf)=0.2/06/0.2/0.36/0.35/0.004/2%.(2) Based on the best proportion of mixture G2, the direct tensile test and the uniaxial test were carried to domestic PVA-ECC. Based on the test results, domestic PVA-ECC tensile and compressive stress-strain curve were drawed, and domestic PVA-ECC tensile and compressive constitutive model were established.(3) The pull test was based on the best proportion of mixture G2. Anchorage length and diameter of high strength steel bar, protective layer thickness of ECC were investigated to determine their effects on the bond-slip performance between high strength steel bar and domestic PVA-ECC. A formula for calculating the strength and a bond-slip constitutive model of 500MPa steel bars and domestic PVA-ECC was put forward. Research shows that 500MPa steel bars and domestic PVA-ECC have better deformation compatibility and better bond anchoring performance.(4) Based on plane assumption, no relative slip between steel and ECC, and no debonding between concrete and ECC, the load carrying capacity of ECC/RC functionally-graded concrete beams in different stages was analyzed in detail based on plastic-elastic theory, and the load capacity of ECC/RC functionally-graded concrete beams in different stages were analyzed.