Papers by Keyword: Anti-Permeability

Abstract: Active admixture recycled-concrete (AARC) is one of green high performance concretes, which took active admixture and fly ash into recycled concrete to replace part of cement. This paper researches the relationship of seepage resistance grade and chloride diffusion coefficient of recycled concrete by the regressive analysis of experimental data from NEL and gradually pressure method. The mufti-factor (slag powder, fly ash, air-entraining agent, polypropylene fiber, recycled coarse aggregate) and multi-level experiments of anti-permeability of concrete were carried out by orthogonal experiment method, and the optimum proportion of concrete is determined. The results show that seepage resistance grade of 16 groups AARC all reached W13, and chloride diffusion coefficient was between 0.5~1×10^-8cm²/s, the permeability grade is IV. The impermeability of the AARC is excellent. The rate of recycled coarse aggregate and slag powder were the most important factors for the impermeability properties of concrete, the optimum proportion of concrete was 10% slag powder, 20% fly ash, 1/10000 air-entraining agent, 1.0 kg/m3 polypropylene fiber and 40% recycled coarse aggregate.

Abstract: Concrete multi-step mixing technology means the construction technology of multi-step material mixing and multi-step stirring. Based on the tests about impermeability, frost resistance and anti-carbonization in the same material and the same proportioning using the method of aggregate enveloped with cement of multi-step mixing technology, it demonstrated that the method of aggregate enveloped with cement can obviously improve the performance of concrete on impermeability, frost resistance and carbonization resistance.

Abstract: The use of styrene butadiene rubber (SBR) emulsions in concrete has been increasing in concrete construction and repair work due to its benefits to flexure strength, adhesion and impermeability. This research evaluated the influence of different contents (0%, 5%, 10%, 15%, and 20% by cement) of SBR on the mechanical properties and anti-permeability of the paste, mortar and concrete with the same water-to-cement ratio to analysis the SBR on the properties of them. For the mechanical properties, the compressive strength, flexure strength and elastic modulus were studied. The permeability was assessed by total charge-passed derived from rapid chloride permeability test (RCPT), all the samples were prepared and measured complying with the corresponding Chinese Industry Standard. Experimental results showed that the properties of the SBR modified concrete were associated with the corresponding properties of the SBR modified mortar and paste, and their properties changed in the same way with the incorporation of the SBR latex.

Abstract: In order to improve the durability of concrete for mechane engineering, the experimental investigation of the preparation process condition of concrete have been reported.The effect of mix proportion design and chemical admixture on the strength of concrete are studied, the anti-permeability and anti-erosion by acid are analyzed. The results indicated that the addition of 1% water-reducing admixture and 3% organic Si waterproof (the precent of admixture and cement in mass) are useful to improve the mechanics property and durability of the concrete, the compressive strength after dipped in water 48 h enhance 100% , the permaebility grade enhance from P4 to P10, the erosion coefficient K decrease from 6.1% to 2.2% and the erosion degree R decrease from 57.5% to 32.8%, respectively, compare with that without dopant the water-reducing admixture. The results gained in this study are helpful for improving the the durability of the concrete and enlarge application the mechane engineering in rural areas.

Abstract: The anti-permeability of concrete is one of important indexes of the durability of concrete. The experiment on anti-permeability of cellulose fiber concrete and hybrid fiber concrete were made. And the rule of the anti-permeability of concrete with the different fiber types and mix amount of fiber was researched. The factors of influencing the anti-permeability of concrete were analyzed. The experimental results indicate that the anti-permeability of concrete is improved because of the cellulose fiber, and the permeability coefficient of concrete decrease with the increasing of content of fiber. Even the content of fiber is 0.9kg/m³, the anti-permeability of cellulose fiber concrete is obvious improved, while the steel fiber has less reinforcement effect.

Abstract: Through experiments, in concrete reasonable use efficient jianshuiji, fly ash and slag powders and adding mixed materials thereof after the concrete can be greatly increased the anti-permeability and improve the durability of concrete.

Abstract: The effect of VAE latex modification on the physical properties of cement mortar is investigated. The porosity problem in cement mortar modified by vinyl acetate ester-ethylene (VAE) copolymer emulsion was successfully resolved by reasonable defoaming technique. It is shown that the bond strength and water resistance properties of modified cement mortar are better than unmodified cement mortar. When polymer-cement ratios ranged from 0 to 0.25, the bond strength and anti-permeability increased first and then decreased. The best value appeared at 0.1(polymer-cement ratio). SEM shows that the modified sample has compacted structure, polymeric films wrap the cement body and fill in the gap between cement and sand to improve the interfacial bond.

Abstract: Anti-permeability, durability even strength of cement-based composites are closely related with the material pore structure. Polyvinyl alcohol (PVA) fiber reinforced strain hardening cement-based composites (SHCC) are provided with high ductility and multi- micro-crack propagation mode. Due to fibers adding, much more interface and tiny fracture had been drawn into SHCC, although it has some advantages such as high tensile strength, ductility and energy consumption under seismic load or other cyclic force. Water repellent treatment can improve the anti-permeability of SHCC. Investigations have been made through Mercury injection experiment to reveal influence on microstructure of PVA-SHCC by silane water repellence. Results show that, the pore structure of SHCC can be fined by inside water repellent agent. That is, water repellent infiltrate through the relative big hole or defect of cement paste and react with the alkali substance. Then the resultant colloids reduce the big hole, pore or fracture and reform the pore structure of the cement paste. Because the fine pore structure can prevent air, water and ions defuse into interior of cement-based composites, water repellent treatment is benefit to increase anti-permeability of high ductile SHCC.

Abstract: The aim of this study was to evaluate the influence of mix proportion parameters on anti-permeability of green high performance concrete (GHPC) and find out the main influencing factors. Applying grey relational analysis method, the relational grades between the influencing factors and diffusion coefficient of Cl^- of GHPC were calculated. Besides, the sequence result of influencing degree of the factors to affect the anti-permeability was obtained. The result shows that the importance of the factors affecting anti-permeability of GHPC has following sequence: water-binder ratio> sand ratio > dosage of cement> dosage of water reducing admixture > dosage of mineral fillers > dosage of fly ash. In order to improve anti-permeability of GHPC, water-binder ratio and sand ratio must be controlled strictly.