Preparation And Properties Of Cement-based Materials Reinforced With Carbon Nanotubes And PVA Fibers

As we all know, technology is an important technology of fiber reinforcedconcrete means to improve toughness and reduce the risk of cracking. On this basis,the American scholar Victor Li by optimizing the micro-mechanics, forming a cementmatrix bond strength of the fiber tip is slightly larger than assumed fiber tensile forceexpansion ideal state, which has developed a strain hardening cement performancecharacteristics based materials ECC (Engineered Cementitious Composite), the materialand method in research interest in recent years increasingly attracted domestic scholars.At present, the domestic development of strength and ultimate deformation capacityECC overall low, there is a large room for improvement.In order to obtain a higher overall strength, ultimate deformation capacity betterfiber reinforced cement-based materials, the preparation of this paper in the originalECC technology, based on the use of carbon nanotubes to further enhance the strengthand deformation capacity cement matrix from the nanometer scale, producing carbonnano tube and PVA fiber reinforced cement-based composite materials. By changingthe way of feeding, changing water reducer type, change the water-cement ratio,change the fiber content, such as carbon nanotubes reinforced matrix approach tobending, compression and bending performance indicators for the main expedition tostudy the water-cement ratio, fiber content, such as carbon nanotubes and influence ofPVA fiber reinforced cement-based composite material properties.By studying the impact of enhancements to its content of carbon nanotubes andfound that the higher the dosage, the more significant enhancements. Compared withthe reference group of non-doped carbon nanotubes,28days flexural strength of carbonnanotubes doped with1.5‰increase in cement-based materials15%. Enhance theeffect of carbon nanotubes dispersed by its extent. After passing discovery of carbonnanotubes dispersed by ultrasonic dispersion for better dispersion of the carbonnanotubes in the other types of mechanical dispersion, admixtures in the carbonnanotube dispersion solution, a stabilizing effect.By changing the content of polyvinyl alcohol fiber content and carbon nanotubes,two-factor orthogonal test conducted after the experiment, it was found under the samefiber content, increased dosage of the flexural strength of carbon nanotubes have acertain role to improve, compressive strength is small. Compared to two factors, polyvinyl alcohol fiber content for the ultimate flexural strength and compressivestrength of the reinforcing effect is greater than the carbon nanotubes.By order of addition of the impact study found that adding fiber performanceparameters of mixing time for the big Γ2material impact, should adopt the first mixedmethod, although this method is prone to dust. The admixture is added time for mixingthings work performance parameters Γ2less affected, we recommend using the samemethod or mixed method after doping, because more convenient with the mixedmethod or mixed method.By studying the impact of admixture species found in different water reducing itsoptimum dosage varies polycarboxylate superplasticizer1%, naphthalenesuperplasticizer was1.5%. Polycarboxylate superplasticizer more than naphthalenesuperplasticizer produced entraining phenomenon, leading to internal specimen producemore pores, therefore, the best performance naphthalene superplasticizer achievesuperior efficiency polycarboxylate water reduction agents, cement-based material ismore stable.Discovered by studying the impact of water-cement ratio, cement ratio mixingmaterial impact on work performance and strength significantly. When a lowwater-cement ratio, mixing thick material is too dry, poor work performance, notforming dense, low intensity; higher water-cement ratio, mixing things slightlybleeding, after more than a pore forming strength is also low. Only a range ofwater-cement ratio to get a good mix material performance, high strength cement-basedmaterials. Mixing cement ratio test results combined with physical performance impactand3d,7d,28d flexural strength and compressive strength to determine water-cementratio should be controlled between0.3-0.4.By studying the effects of each component content found polyvinyl alcohol fibercontent is low, with increasing content, the strength of cement-based materialscontinues to improve, but performance did not change significantly. But the fibercontent greater than2.5%, mixing physical performance and physical properties ofhardened significantly reduced, the hardened body was found after the break this timethe fiber cross section produced a significant agglomeration, fiber reinforced efficiencyis significantly reduced.Experimental determination of the water-cement ratio of0.4, naphthalenesuperplasticizer dosage is2%, the first doped polyvinyl alcohol fiber,2%ash, carbonnanotubes using ultrasonic dispersion, the dosage is1.5‰, its28days compressive strength52MPa, three-point flexural strength (bending strength) is14MPa, four-pointflexural strength8.2MPa, corresponding to the maximum displacement four-pointbending is20mm.