Advanced Materials Research Vols. 168-170

Abstract: The interface bond between steel fibers and concrete matrix is the key of carrying capacity of steel fiber reinforced concrete(SFRC). In marine tidal fluctuation zone and splashed area, steel fibers will be rusty, and the bending toughness of SFRC was weakened. In this study, we tried to improve corrosion resistance of steel fiber and the interface bond strength by depositing zinc phosphate coating on steel fiber. These zinc phosphate steel fiber reinforced concrete(ZSFRC) have higher anti-corrosion ability. After corrosion they still have higher bending toughness than common SFRC.

Abstract: The effects of different content of rubber powder, silica fume, cellulose ether, dihydrate gypsum, water reducing agent , defoamer on the dry-mixed mortar were studied according to orthogonal experiments. The results show that the compressive strength of 1 d is up to 38.4 MPa and the flexural strength to 6.4 MPa. Therefore the super-high mortar studied is mainly used for rush repairing engineering. It has great economical benefit and society benefit.

Abstract: Fly ash aerated-concrete is a new kind of energy-saving and environmental material, when compared with other traditional building materials, it can save above 65% energy. But when fly ash aerated-concrete block is used to build walls, it often cracks. This document analyzes crack formation on fly ash aerated-concrete, and explains some reinforcing techniques on how to solve these problems.

Abstract: In recent years aluminum bridges have been constructed in China, but lack of aluminum design and construction standards limits its development. Traditional design theory of concrete and steel can’t be completely adopted for its application in bearing structures. In order to solve technical difficulty, material type, deflection under live load, frequency and bucking of aluminum bridges are analyzed based on aluminum half-opened truss bridges constructed in China. Compared with related design standards at home and abroad, recommendations are put forward to provide theoretical basis for further application and research of aluminum truss bridges.

Abstract: The pre-modification of SiO2 aerogels and polystyrene using microwave heating method, then make use of the ultrasonic dispersion method preparing for dispersion polymerization SiO2 / PS nano-composite microspheres. Analysis the size distribution of composite structure by TEM charactering the samples; using the weight ton method evaluate the curve of PS conversion with temporal change and calculate the coating rate of core-shell structure, and research the various factors.

Abstract: In order to study the fracture toughness of steel fiber reinforced concrete (SFRC) and the postcracking toughness evaluation method, the fracture toughness tests were done for the four types of steel fibers and three kinds of matrix strength. According to the experiment curves of the load and the crack mouth opening displacement (Load-CMOD), the fracture toughness of SFRC was studied; the formulas of the postcracking toughness coefficient and the Fracture-CMOD toughness index were established. The experiment results show that the Fracture-CMOD toughness index can reflect sensitively to the effect on concrete toughness of the type of the steel fiber, and then it is avoid that the estimation error of the initial cracking point led to the evaluation error of the toughness.Comparison with other fibers B fiber shows the best crack resistance and the toughening ability.

Abstract: The deformation of rubberized concrete under uniaxial compression and three-point flexure is studied in this paper by test, and the load-deflection curves and load-strain curves under three-point flexure are obtained. Three rubberized concrete, with 5%, 10% and 15% rubber contents, were tested. The test results show that rubber powder influences the compressive strength and flexural strength of concrete. The greater of the rubber dosage, the greater of the strength decreasing of concrete. The decline of compressive strength is greater than flexural strength, the ratio of flexural strength to compressive strength of rubberized concrete is 1.08, 1.16, 1.26 times of the normal concrete for three different rubber contents respectively. And the ultimate tensile strain of rubberized concrete is 1.62, 2.25, 2.80 times of the normal concrete respectively. The addition of rubber improved the toughness and deformation ability of the normal concrete.

Abstract: The number of steel-frame buildings is increasing as a result of development of social economy. However, the fire-resistant property of steel-frame buildings is much weaker than that of brick-frame buildings and RC-frame buildings. In response to such demand, fire-resistant steel has been developed since the last two decades. Mo is one of the most effective strengthening elements for the high-temperature strength of steels. With the increase of the Mo content in steels, there is a dramatic increase in costs which is unacceptable for the cost-sensitive construction area. Therefore, a fire-resistant steel with a low Mo content is highly desired. Two fire-resistant steels with low Mo content (<0.3%) were designed in this paper. The interdependence of microstructure, properties and temperature was studied and analyzed in hot-rolled testing steels. The results show that the low-Mo fire-resistant steels have improved elevated temperature strength (The yield strength of Nb content steel is 240MPa, which can met the requirements of grade Q345 fire-resistant steel), low yield ratio (<0.6) and good welding performance (Ceq≈0.40). The bainite and fine grains are mainly beneficial to the elevated temperature UTS. Nb is an alloying element effective in increasing elevated temperature strength (especially for YS) as well as Mo.

Abstract: The introduction of hydrophilic groups, such as -COOH, -SO3, -OH, -O-, into the polyurethane resin, so that waterborne polyurethane products in the water resistance, solvent resistance, weather and other aspects of performance are worse than solvent borne systems. In our work, to improve the water resistance of the films for waterborne polyurethane, we incorporated C=C bond into the side chain of polyurethane by using pentaerythritol diacrylate as an extension agent. By measuring the cured polyurethane films absorption and mechanical properties, we determine the conditions for UV curing, 3% TMPME, photoinitiator (2959) and to UV light application time for 30s. With the increase of the amount PEDA, water resistance, hardness and tensile strength increase. Furthermore, with the improved water resistance, it is hoped that the performance of waterborne polyurethane can be comparative or superior to the solvent-borne systems.

Abstract: Through the corrosion-damaged experiment of steel fiber reinforced concrete (SFRC) in simulation domestic sewage, the corrosion resistance of SFRC placed in domestic sewage were investigated. The results show that high concentration domestic sewage would cause the properties of SFRC to deteriorate, and the corrosion coefficients of compressive and flexural strength of SFRC decrease gradually with the increase of corroding age. The steel fiber can not inhibit obviously the degradation of concrete compressive and flexural strength unless the steel fiber volume fraction is more than 1.0%. The size effect on compressive and flexural strength of SFRC after corroding in domestic sewage is existent.