Study On Mechanical Properties Of Modified Polypropylene Fiber Cement Mortar

Cement mortar has been widely used in engineering,but its exposed shortcomings also often cause problems.Cement mortar is a kind of brittle material with poor toughness and crack resistance.The addition of high ductility fibers can not only increase its bending resistance and crack resistance,but also significantly improve in durability,and retains the original compressive strength.There have been many cases of fiber addition being added in concrete or mortar,and they have achieved remarkable results.Combined with the characteristics of the modified polypropylene fiber super-high ductility and the elastic modulus,This thesis selects 2 fiber length,3 diameters and3 volume content(%V)to study the basic mechanical properties and durability of fiber cement mortar and compare the data with plain mortar.The conclusion is as follows:(1)When mixing cement mortar,the fluidity of fiber cement mortar decreases a lot,because the fluidity of fiber mortar is inversely proportional to fiber content in a certain range,and the setting time of corresponding fiber mortar will also decrease greatly.(2)The rupture strength of cement mortar mixed with modified polypropylene fiber is obviously increased under the condition of loss of partial compressive strength,the rupture strength of 0.35% V-Φ30μm(fiber length has no significant effect)is the best,and the rupture compressive strength is 7.9 MPa,compression strength is 39.2MPa.(3)Since fine fly ash particles and fibers are filled with all the narrow passage after hydration,the impermeability of mortar is improved by the mixing of fiber-flyash,in which the maximum seepage pressure of 0.35% V-L8mm-Φ30μm test group is the best,impermeability grade reaching 1.0Mpa.(4)After the formation of mortar,the evaporation of internal moisture will produce shrinkage stress.The fibers dispersed in cement mortar resist deformation and crack by virtue of super toughness.The effect of 0.35% V-φ20μm(fiber length is not significant)is the best.The drying shrinkage rate is only 0.14% in 60 days.(5)Because of the strong crack resistance of the fiber,the random distribution of the fiber improves the integrity of the mortar,and the impact times in the drop hammer impact experiment are significantly higher than those in the control group.The effect of0.40% V-L8mm(fiber diameter is not significant)is the best.Initial cracks reached 37 times and final cracks reached 49 times.