Research On The Design And Performance Of Fiber Reinforced High Toughness Cementitious Materials

By the demand of the building materials to the modern architecture are more and more strict, the development of traditional concrete are restricted due to its brittleness, poor toughness and so on. The service life and safety issues of concrete have become increasingly prominent. Therefore, the study of high toughness cementitious materials and the approach of how to improve the flexibility and bending deformation of concrete are significante to the service life and service security of modern architecture.This paper aims at solving the problems of big stiffness and poor flexibility of traditional concrete, the manufacturing process, material design and performance test of SBR modified steel fiber-reinforced concrete and PVA fiber reinforced high toughness cementitious materials are investigated in this article. By compositing SBR and steel fiber to achieve the same increasing of the flexible of the concrete matrix and the bonding strength of the concrete and steel fiber to achieve the purpose of reinforce the concrete's toughness. Microhardness testing and scanning electronic microscopy(SEM) were employed to characterize the effect of SBR on the microhardness and morphology of the interface transition zone(ITZ) and the surface area of the steel fiber pulled-out from the concrete. Starting from the properties of the experimental materials, through the pre-processing of materials and mixing technology selection, PVA fiber reinforced high toughness cementitious materials that have high bending ability and multiple cracking phenomenon are producted. And the bending toughness index and crack form are evaluated of cement base plate and bending in different proportions. The status of the two high toughness cementitious composite materials are tested. Come to the conclusions:1. SBR could improve the performance of the fresh concrete. The addition of polymer leads to a salient decrease in compressive strength and an increase in flexural strength. The composite of 15%SBR and 1% steel fiber can significantly improve the flexural strength, impact toughness and flexural toughness of the concrete.2. Microhardness testing shows that 15%SBR can improve the aggregate-mortar interface transition zone(ITZ) of the concrete after curing 28 days. Scanning electronic microscopy(SEM) were employed to characterize the microstructure of the polymer and the morphology of the steel fiber pulling-out from the concrete and the interface transition zone between mortar and fiber. The results show that SBR are filmed interlaced in the concrete to increase the compactness of slurry and slutty-aggregate zone. The interfacial bond strength between steel fiber can concrete is enhanced.3. The SBR made the crest of incremental intrusion volume of concrete go left. The porosity of the pore size within the range of 100-1000 nm are increased. Continuous polymer network film structure communicating larger pores. Large holes are divided into closed pores. Therefore the porosity of gel pores within the pore size< 10 nm is increased. When in air curing, a large number of cracks were formed because of drying shrinkage. Hence porosity within the pore size>100nm was significantly increased relative to the concrete at standard curing.4. By selecting fly ash as mineral admixtures, PVA fiber's surface treated with silicone oil and fiber pre-dispersion, the cement-based plates bending deformation could reach 10.7mm. The crack has an obvious roll-out phase. Fiber slippage is the important reason for the cement-based material for deformation ability. The cement-based material's bending performance was severely reduced by the mixing of SBR. Plate thickness is the main reason to determine the amount of bending deformation and fracture morphology.5. PVA fiber reinforced high toughness cementitious materials could disperse cracks of the cement into many tiny cracks. The composite of these two materials has good prospects for development.