Study On The Preparation And Properties Of Polypropylene Fiber/ Cement Composite Material

Cement is the building materials which the largest amount application and the most widely used in human society. Cement-based materials with high compressive strength, but there are some disadvantages, such as low tensile strength, high shrinkage rate, low deformation, high brittle performance and poor impact resistance, and so on, the tensile strength of cement-based materials is only 1/10-1/7 of the compressive strength, it is easy to occur plastic cracking in low tensile deformation As the compressive strength of cement-based materials are raised greatly, the disadvantages of shrinkage cracking are more prominent. But the disadvantages of cement-based materials is congenital, it is impossible solved by improved the performance of material itself, only by adopting the technical way of "compound" Thus developed a series of cement base composite materials, it is one kind of important ways by using synthetic fiber production cement base composite materialsThe parameters of the optimum content and optimal molding process of polypropylene fiber were obtained by studying the impact of polypropylene fiber and modified ordinary cement-based polypropylene fiber with composite material performance. And discussed the enhancement mechanism of polypropylene fiber on cement base composite materials, make the polypropylene fiber get more extensive application. in practical projects.This paper focuses on the impact of unmodified polypropylene fibers and modified polypropylene fibers on the cement base composite materials performance, the main contents include: (1) Determine the best water-cement ratio through the comparison and research the mechanics performance of cement-based composites under the different water-cement ratio; Determine the best adding process through research first mixing method and after mixing method; (2) the effects of different modification methods to polypropylene fiber, and the effects to the property of the composite materials were studied in order to determine the best modification method; (3) Research the dosage changes of polypropylene fiber on the flexural strength, compressive strength, shock resistance, drying shrinkage performance, and shrinkage performance of cement composite materials;(4) Use scanning electron microscopy (SEM), FTIR, according to the basic theory, combined with the test results to study the mechanism of PP fibers improving mortar's performances and discuss the reinforced effect of other composite constituents.Studies have shown that, Pre-adding polypropylene fiber can make fiber disperse better and enhance the concrete performance better. Polypropylene fibers were modified by using different methods to make the combination of fibers and cement mortar matrix improved get a different degree, and the method of surface grafting is best. The acrylic acid was grafted on surfaces of the PP fibers by using the method of surface grafting , the hydrophilic of fibers were improved, make the combine with cement mortar closely and make the surface roughening, increases the interface bonding with cement the, on macroscopic, the mechanical performance of the cement mortar are improved significantly.Compared with cement mortar reinforced by ordinary PP fibers, the flexural strength, compressive strength, shock resistance drying shrinkage performance, and shrinkage cracking of cement mortar reinforced by modified PP fibers are better. To 28d sample bending and compressive strength as the index, the best component ratio of polypropylene fiber reinforced mortar in this task conditions is 0.6kg/m3, water-reducing admixture is 0.8% and the water-cement ratio is 0.44.The morphology of polypropylene fibers modified polypropylene fibers and composites are observed by SEM and IR; The microscopic interaction of polypropylene fibers and cement matrix, and the mechanism of polypropylene fiber reinforced cement mortar were studied.