Advanced Materials Research Vols. 919-921

Abstract: This paper presents an investigation of the effect of emulsified waste cooking oil on the porosity, EDEX results and the reduction of autogenous shrinkage of the high strength concrete with W/B of 20% incorporating 20% of fly ash and 10% of silica fume. Two different types of shrinkage reducing agents, the existing glyeol based shrinkage reducing agent (SR) and the waste cooking oil (WCO) were applied and compared. The effect of emulsification of the WCO with two emulsifying speeds, 2000 rpm and 4000 rpm were also investigated. It is found that the emulsified WCO has desirable shrinkage reduction effect than un-emulsified WCO and existing SR. Test results also indicated that emulsified WCO could also reduce pore volume due to saponification reaction

Abstract: This thesis discusses the influence of fly ash content, fiber content and fiber types on the performance of fiber reinforced concrete, through the flexural and compressive tests on fiber reinforced cement mortar, and the splitting tensile and bending tests on the fiber reinforced concrete. The test result shows that the adding of fly ash can better play the enhancement of polypropylene fiber; the change of the fiber content affects the flexural strength of cement mortar and obviously improves the splitting tensile strength of the reinforced concrete; and the polypropylene fiber and steel fiber have different enhancement on cement mortar due to their qualitative differences.

Abstract: A number of rubber cement concrete specimens that rubber powder dosage different were obtained using same cement, water and fine aggregates, by adjusting the dosage of rubber powder. Then it was used to research the influence of rubber powder dosage on performance of cement concrete by measuring its liquidity, strength and toughness. The results show that: when water-cement ratio was equal and rubber powder replacing the same volume sand, the fluidity of cement concrete almost linear increased with rubber powder dosage increasing. With dosage of rubber powder increasing, compressive strength and flexural strength reduced, but toughness linear growth trend when dosage of rubber powder less 30%.

Abstract: Basalt fiber reinforced concrete has excellent basic mechanical properties. It has become a hot topic of engineering studies. Based on the freeze-thaw resistance of durability indices, through the comparative experiment on the dynamic elastic modulus and mass loss of plain concrete and basalt fiber reinforced concrete in the freeze-thaw cycles, this paper had discussed the impact of basalt fiber on the freeze-thaw resistance of concrete, and have considered whether the specimens were mixed with fly ash. The results showed that basalt fibers can improve the freeze-thaw resistance of concrete specimens significantly. After 100 freeze-thaw cycles, the dynamic elastic modulus of basalt fiber reinforced concrete specimens was 1.47 times as much as that of plain concrete specimens, and mass loss of basalt fiber reinforced concrete specimens was 0.64 times as much as that of plain concrete specimens. Fly ash had an influence on the freeze-thaw resistance of basalt fiber reinforced concrete. In engineering applications, the mixing amount of fly ash should be taken into consideration. This research had a certain reference value on the engineering applications of basalt fiber reinforced concrete.

Abstract: The cementitiousness between rubber particles and cement-based material could be raised because of the surface modification of rubber,thus enhance the mechanical property of crumb rubber concrete and improve the interface effect of rubber particles.We had researched the change regulation of the ratio between tensile strength and compressive strength of the Crumb Rubber Concrete Modified by latex,the concrete with various quantity of rubber,under the condition Dosage of latex is 0.5% of cement quality.The result of Experimental prove that,compressive strength, splitting tensile and flexural strength could be enhanced because of latex injecting,and the ratio between tensile strength and compressive strength could be enhanced at the same time.

Abstract: Organic molecule and Inorganic molecular could be bind by silane coupling agent,the cementitiousness between rubber particles and cement-based material could be raised because of the surface modification of rubber,thus enhance the mechanical property of crumb rubber concrete.We had researched the change regulation of Mechanical Properties,such as compressive strength,splitting tensile strength and flexural strength of the Crumb Rubber Concrete Modified by silane coupling agent with various quantity of rubber,under the condition Dosage of silane coupling agent is 0.5% of cement quality.

Abstract: The strategic concrete structures are often required to resist impact loads arising from the projectile strike, falling weight, blast generated missile etc. The existing structures found deficient in resisting these loads are required to be retrofitted whereas the upcoming structures are required to be designed for expected impact loads. This paper explores the ways of strengthening existing reinforced concrete (RC) structures using externally bonded carbon fiber reinforced polymer (CFRP) sheets and improving the impact resistance of concrete by mixing hybrid fibers in its production. The impact response of concrete structures is assessed using experiments involving the impact of projectiles of different nose shapes on slab specimens. The material behavior at high strain rate is established using split Hopkinson pressure bar (SHPB) testing at varying strain rates. Analytical models are developed for predicting penetration depth, scabbing thickness, ballistic limit velocity and ejected mass. The experimental results were also validated through numerical modeling using LS-DYNA.

Abstract: In order to discuss the effect of different cooling methods, dosage and length of PP fiber on the splitting tensile strength of PPHSC after high temperatures, experiments were carried out on the splitting tensile strength of C60 HSC mixed with PP fibers with different dosage ( 1.0kg/m³, 1.5 kg/m³, 2.0kg/m³, 2.5 kg/m³) and length (8mm,19mm) before and after high temperatures. The test results indicated that the relative residual splitting tensile strength of PPHSC totally declined with the increase of temperature, meanwhile, the strength value of HSC cooled in air was higher than that cooled in water on the whole. The addition of PP fiber with the length of 8mm contributed to the enhancement of the relative residual splitting tensile strength of HSC after high temperatures, whereas, only the HSC mixed with 1.0 kg/m³ PP fibers had a greater strength than plain concrete when the length of fiber was 19mm. After exposure to high temperatures, the relative residual splitting tensile strength of HSC with PP fibers 8mm in length was completely higher than those with 19mm.

Abstract: In this study,silica fume and fly ash were used to replace part of cement, the 28-days compressive strength and the permeability coefficient were tested to study influences of mineral admixture on properties of porous pervious concrete made of recycled aggregates.The results show the best effect is to multiplexed mix with fly ash and silica fume, the 28-day compressive strengths of concrete is higher than those single mixed or doesn’t mix any mineral admixture.

Abstract: Based on the existed research and analysis methods of air entraining natural pumice concrete freeze-thaw damage, nuclear magnetic resonance (NMR) detection technique was introduced in the present study. From the research of essence of freeze-thaw coupling-induced concrete damage in saline solution, natural pumice concrete porosity and transversal relaxation time T2 spectral parameters were used as criteria, and nuclear magnetic resonance imaging (NMRI) technology, an intuitive method was used to determine freeze-thaw damage quantitatively.