Experimental Study On Properties Of PVA Fiber Super High Toughness Cementitious Composites

Ordinary concrete and mortar have the shortcomings of brittleness,low tensile strength,easy to crack.These shortcomings often lead to structural damage and affect their normal use in the project.Control the crack development,increase the toughness and improve the durability of the concrete become the issues of common concern present.ECC(Engineered Cementitious Composites)reinforced of Polyvinyl alcohol(PVA)fiber is a ultra-high toughness cementitious composites materials.The direct tension makes the cement-based material rather a single cracking than multi seam cracking.ECC has strain hardening characteristics and good toughness characteristics.When the fiber content is 2%,the ultimate strain is up to 3%which is hundreds times of ordinary concrete and mortar.Since the cracking of this material is very small(width<100?m),ECC can effectively improve the durability in the repair and strengthening of the hydraulic structures.So it has broad application prospects.Based on this,we have done the following research:1)In this paper,we get the PVA-ECC which has strain hardening characteristics,ultra-high toughness.PVA-ECC can produce a number of fine cracks under the tensile loads,and the ultimate strain is stable for more than 3%.2)In this paper,we have studied the method of mixing of the PVA-ECC by adding an appropriate amount of thickener to improve the performance.The result is PVA fibers are uniformly dispersed in the matrix.3)In this paper,we have studied the PVA-ECC materials with the ratio,including the thickener dosage,fly ash,water-cement ratio,sand-cement ratio,sand particle size and the PVA dosage.Though the ultimate tensile test,compressive test,flexural test and other mechanical properties,we get to establish the optimum mix design parameters.We also have studied the deformation properties of the PVA-ECC(including the coefficient of linear expansion,autogenous volume deformation,etc.)and durability of ECC(including impermeability,frost resistance,etc.).These have laid the foundation for future practical engineering applications in the PVA-ECC.4)Types of PVA fibers have a great impact on the ECC.In this paper,we have the comparison test by the PVA fibers which are made in Japan and China to promote the application of domestic fiber.It also can reduce the costs of practical engineering.