Properties And Mechanism Study Of Polypropylene Fiber Reinforced Cement Composite Material

Compared to timber, steel and other building materials, cement composite materials (such as cement mortar, concrete, etc.) are the current building materials with the biggest application scope, and cement composite materials have hard to combustion, anti-high pressure, durable, low cost, security, stability and other advantages, but such materials also have some obvious weaknesses, such as its low tensile strength, low fracture energy, the high requirements of basic, the impact of admixtures on concrete quality, long conservation cycle length, big own weight, its impact on construction speed, bad toughness, the large impact of the construction process on structural quality, and so on. Nowadays, filling some fibers in cement composites is the gradually popularized means to strength cement composites. Construction industry group wish by adoptiong that strength means, the mechanical property, impermeability, anti-freeze-thaw performance and other performance index of cement composite matrix could be improved.This topic was carried out against such background. Through the research on the effect of polypropylene fibers on cement composite material properties,it is in order to obtain the relationship between cement composite material performances and polypropylene fiber content, construction technique, the mechanism of filling polypropylene fibers intensifies cement composite materials is explored, so that works of polypropylene fiber in cement practice can be more widely applied.This topic was focused on impact of modified polypropylene fibers on cement composite materials performance, as well as the impact of mixing polymer emulsion on polypropylene fiber reinforced cement composite materials. Main research contents include: (1) the used raw materials was determined in accordance with the application sites of cement-based composite materials; (2) the effects of different water-cement ratios on properties of cement composite materials were studied in order to determine appropriate water-cement ratio, the impacts of two different fiber mixing processes on the polypropylene fiber dispersion and the cement composite material strengths were determined, and the appropriate fiber mixing process was found; (3) with the use of the scientific method-orthogonal experiment analysis, the effects of polymer emulsion, water-reducing agent and polypropylene fiber contents on cement composites mechanical properties were studied, and by making the mechanical properties of polypropylene fiber reinforced cement composites as the index, the optimum proportion of polypropylene fiber reinforced cement composites in this task conditions was determined; (4) it was studied the effect of the changes in polypropylene fiber content on cement composite materials shock resistance, drying shrinkage performance, impermeability, creep strain performance, anti-freeze-thaw performance, and shrinkage cracking performance; (5) the mechanism of mixing appropriate amount of polypropylene fibers and polymer emulsion can enhance cement composite material properties was analysised.Studies have shown that compared to other fibers with round or rectangular cross-section , modified polypropylene fiber with clover-type cross-section has the greater specific surface area and the stronger bond strength to the matrix, such modified polypropylene fiber was selected as reinforce materials in cement composite materials,so the enhancing effect of fiber can be more fully exerted; polypropylene fiber mixing process should be selected the first doped law, the first law process makes fiber uniformly distributed in single filament and enables fibers to exert the maximum effect; made sample 28d flexural strength and 28d compressive strength as the index, the best component ratio of polypropylene fiber reinforced mortar in this task conditons is 1.5kg/m3 polypropylene fiber, 2% polymer emulsion, 1% water-reducing admixture,100% cement, 250% sand and 0.44 water-cement ratio; made sample 28d compressive strength as the index, the best component ratio of polypropylene fiber reinforced concrete in this task condition is 0.7kg/m3 polypropylene fiber, 3% polymer emulsion, 0.1% water-reducing admixture, 0.44 water-cement ratio, 720kg/m3 sand and 1280kg/m3 detritus. Mixing an appropriate amount of poly propylene fiber and polymer emulsion, can significantly improve cement composites the shock resistance, anti-drying shrinkage performance, strain and creep resistance properties, anti-freeze-thaw performance, and anti-shrinkage cracking performance; polypropylene fibers are evenly scattered in cement composite material system so that tensile strength of hardened cement composites is significantly improved, at the same time the stress concentration on crack tip is effective alleviated, and there is a great help to improve the performance of cement composites; if the polypropylene fiber mixing volume reaches a certain extent, some fibers will not play its role effectively, and continuing to enhance the mixing volume of polypropylene fiber will improve cement composites performance little; mixing polymer emulsion can markedly improve the interface microstructure between the fiber and cement composites matrix, the enhance effect of polypropylene fiber will also be full played ; the polymer film and the interface transition layer formed by mixed polymer emulsion can significantly reduce the possibility of the internal crack in cement composite generation and expansion, enhance its ability to resist the external environment, and significantly enhance the performance of cement composites.