Properties Of Polypropylene Fiber Compositing Latex Powder Modified Concrete

Aiming at the engineering problems of cement concrete pavement easy to denudate in mainland China cold saline areas, a cement-based composite material for repairing damaged cement concrete pavement named polypropylene fiber compositing latex powder modified concrete (PFCLPC) is researched. Two single factor experiments of fiber dosage and latex powder dosage is used for researching the mechanical properties of PFCLPC. In addition, an orthogonal experiment of four factors (fiber dosage, fiber length, latex powder dosage and silicon powder dosage) and three levels is used for researching the mechanical property and durability of PFCLPC, such as bending strength, compressive strength, splitting tensile strength, elastic modulus, the abrasion resistance, shrinkage or expanding, the freezing resistance, microcosmic structure and so on.At last, the optimal mix proportion parameters of concrete pavement overlay repairing materials in cold saline areas were determined through the optimization analysis method of efficacy coefficient. Several important conclusions are shown as follows:(1) The influence of latex powder 5044N for bending strength and compressive strength of PFCLPC is highly significant, and bending strength and compressive strength decrease with latex powder dosage increase in a certain extent. The latex powder has optimal dosage for splitting tensile strength is 5%.(2) Polypropylene fibers and latex powder 5044N can improve the toughness of PFCLPC significantly. Elastic modulus and compressive strength of PFCLPC fit the relationship of linear function Ec=0.278fc+19.209, and correlation is significantly.(3) Latex powder can improve the freezing resistance of PFCLPC significantly by forming the latex thin film and introducing gas while the cement hydrates. Silica fume can enhance the freezing resistance of concrete by improving the pore structure of internal concrete. Both polypropylene fiber and latex powder can alleviate the tensile stress of latex powder when the micro-cracks appear in concrete so that it can effectively prolong the time of resistance of freezing-thawing damage.(4)The most significant factor to the salt resistance of PFCLPC is fiber dosage, and when it is 0.1%, the performance is the best. The influence of latex powder to the salt resistance is next to fiber dosage. At meantime, when latex powder dosage is 5%, the performance salt resistance is the best.(5) Shrinkage ratio εt and the testing age t of PFCLPC fit the relationship of exponential function εt=β1·exp(-t/β2)+α0, and the correlation is significant when the significant level a is 0.01. Latex powder takes the greatest influence on shrinkage of concrete, dosage of fiber does in the second, silica powder in the third and length of fiber in the last. Latex powder can increase the shrinkage of concrete. On the contrary, with the increase of fiber dosage, the shrinkage of concrete can reduce effectively. When dosage of silica fume is 2.5% or fiber length is 6mm, shrinkage of PFCLPC is the minimum.(6) Optimizing of fiber dosage 0.1%, fiber length 9mm, latex powder dosage 5% and silicon powder dosage 2.5% as mixing parameters of PFCLPC, its comprehensive mechanical performance is good relatively.(7) Although the latex powder has a certain impact for the mineral ash reaction of silicon powder in concrete, but the effecting of latex powder, silicon powde and fiber composited to form the uniform distribution and closed matrix pore in concrete and around the concrete fiber web structre, so as to improve the mechanical properties and durability of PFCLPC effectively.