The primary reason for the seizure of three concrete cracks: external load stress directly causing cracks, the primary stress that causes cracks in the usual accounting; under the effect of external load, causing stress fractures program times: the cracks caused by the deformation, such as temperature, shortening and swell, resulting in uneven settlement cracks and other factors. Cracks generally consists of one or more elements together during constitute effect, while elements of cracks in three episodes, especially crack causing the most deformation changes, accounting for more than 80%.

         To advancing concrete cracking talent, may be appropriate to increase with planned reinforcement, but this approach is only to withstand the stress caused the cracks because of external loads of useful, while about a third crack, especially plastic shortening crack alone, with plans to be reinforced difficult to be effective, because the steel is difficult to fine spread, while polypropylene fibers can compensate this lack. When properly incorporated polypropylene fibers in concrete after, because polypropylene fibers and cement-based aggregates have a strong binding force, capable of active and easily mixed with concrete data, spread evenly and fine.

        Polypropylene fiber concrete in handling the primary effect of the crack on the plastic shortening is: blocking the onset of plastic shortening and bundling crack crack open. Plastic concrete cracking concrete to harden before the primary attack, especially in the 4 to 5 hours after the pouring of concrete, this time because of moisture transpiration and handling, interior concrete tensile strain talent below the onset of plastic strain shortened, thus resulting in Plastic Cracks in concrete attack. And after the incorporation of polypropylene fibers, polypropylene fibers since spread evenly, played a similar screen effect, slowing the cracks because of the rapid onset of coarse aggregate loss, delay the first cracks in the plastic shortening presented moment. And when the cracks showing the presence of polypropylene fibers also makes the top of the open fractures were tied, cracks can bypass the fiber or the fiber pull off to continue to open, which needs to spend immeasurable energy to defeat the fiber crack open bundling effect, the greater the fiber volume content, the stronger the effect this bundle. In general there is no concrete cracks the top was so bundled effects, comfortable open, which makes general cracks in concrete than participate fiber concrete cracks wider, longer. 1, as shown in the cracks of concrete plasticity shorten area, the largest crack Aperture and water loss rate increases were followed by fiber volume fraction and decreased clarify polypropylene fiber function usefully traveled crack concrete.

        In addition, the effect of polypropylene fibers and refined crack crack resistance, significantly improved the cement plan to make cement natively microcracks cuts, crack width decreases, it must make the impermeability of the hardened cement and resistance to a considerable degree of travel.