Advanced Materials Research Vols. 450-451

Abstract: Corrosion resistance coefficient and expansion ratio of different cementitious materials are tested under the sulphate corrosion experimental condition, sulphate resistance of often-used cementitious material of high performance concrete for marine is studied and evaluated. The results show that sulphate resistance of portland cement is better than ordinary portland cement, and both of them are low, often-used cementitious material of high performance concrete for marine have certain sulphate resistance, which are better than ordinary portland cement and portland cement, and some of them have strong or very strong sulphate resistance. The evaluation results of the sulphate resistance of often-used cementitious material of high performance concrete for marine are not unanimous completely by corrosion resistance coefficient method and expansion rate method. Sulphate corrosion mechanism of different kinds of cementitious material is analyzed.

Abstract: Abstract. The anti-frost property of concrete is one of the major parts of study on the durability of concrete. By viewing all over the world, due to the alternation of external temperature upon and under zero centigrade, concrete structures located on the areas of high latitude are usually unavoidable to suffer the damage caused by freeze-thaw cycles. Due to the insufficiency of theoretical foundation and the complexity of freeze-thaw durability itself, the contemporary studies are far from integrity in respect to the theoretical consensus. What is more, the researching measures concentrate more on the experimental approach. Based on this, it would be necessary to carry out relevant theoretical study on the freeze-thaw durability of concrete. The freeze-thaw damage of concrete is equivalent to that when internally generated hydrostatic pressure during freezing thawing process is greater than the destruction produced by then tensile strength of concrete. Although hydrostatic pressure is uniform in all directions, concrete is a kind of uneven brittle material. When it's under the stress by three even directions, the final destruction always happens in the weakest section, which is very similar to tensile breakage. In this case, unilateral tensile can be used to simulate the internal hydrostatic pressure affection of concrete during freezing and thawing process. In this article, one-dimensional micromechanical model of random damage will be used to the research of freeze-thaw damage and try to quantify it.

Abstract: In this paper, the correlation between limestone powder content and MB value in manufactured sand is analyzed and the effect of limestone powder content and clay content of manufactured sand on the MB value is studied, the results show that with the increase of pure limestone powder content, the MB values remained almost unchanged, and were less than 1.0; when the limestone powder content increased from 5% to 15%, with the increase of clay content, the MB value increased gradually; when the limestone powder content was taken as 7%, 12% and 15%, the clay content was taken as1.8%, 2.7% and 2.3% respectively with the MB value kept at 1.0, which still could meet the requirement of the engineering construction standard JGJ52-2006 about clay content.

Abstract: The preliminary experimental studies on the effects of two kinds of industrial waste slag of iron tailings and fly ash which have different characteristics on the scumming degree of sea mud sintered perforated brick were carried out in this paper. And the influence mechanism of two kinds of industrial waste slag on the scumming degree of sea mud sintered perforated brick were analyzed combinated with interrelated references. The test and theory analyzed demonstrated that iron tailings have more advantageous factors to alleviate the scumming degree of sea mud sintered brick and fly ash has more disadvantageous factors to enhance the scumming degree of sea mud sintered brick. A vast development world would be provide for the resources reuse of huge dredging sludge come from sea engineering by strengthening the basic study on the scumming resistance technique of sea mud sintered brick.

Abstract: In this study, the effect of loading rate on the bonding strength between rebar and concrete substrate is investigated through pull-out test on 24 concrete cylinders. The load capacity, shear deformation and fracture characteristics of the interface are examined carefully. It is found that with the increase of loading rate, the load capacity increases correspondingly and their relationship can be characterized with a semi-logarithm equation. The load-deflection curves expand with the increase of loading rate, which is an indication of a gradually increasing energy absorption capacity with the increase of loading rate. Generally, with higher loading rate, more energy is dissipated.

Abstract: The cyclic wetting-drying environment affects the internal microstructure and durability of hardened concrete. The carbonation behavior of concrete in cyclic wetting-drying condition and standard condition is investigated in this study. The concrete specimens are designed with different contents of mixed mineral and carbonated in different curing condition. The carbonation depth is tested to study the carbonation process in combination of pore structure analysis and microstructural observations. The experimental results show that the carbonation reaction of concrete in cyclic wetting-drying condition proceeds more rapidly. When mixed mineral is added, difference in the curing condition shows less effect on the carbonation behavior of concrete.

Abstract: Phenyl isocyanate is used to react with 1,2-propanediol in different temperatures. Toluene is used as solvent and triethylamine is used as catalyst. In-situ FT-IR is used to monitor the reaction to work out rate constant, Arrhenius equation and Eyring equation. The urethane reaction has been found to be a second order reaction, and the rate constant seems different between initial stage and final stage. The activation energy (E_a), activation enthalpy (ΔH) and activation entropy (ΔS) for the urethane reaction are calculated out, which are 74.1 kJ•mol^-1, 71.3 kJ•mol^-1 and -30.5 J•mol^-1•k^-1, respectively. They are very useful to reveal the reaction mechanism.

Abstract: In this paper the influence of mineral admixtures on early shrinkage of ordinary concrete with the same water-binder ratio is studied by self-made equipment and CABR-NES deformation instrument developed by China Academy of Building Research Institute. All concrete specimens are cured with one surface exposed to air and others are covered with plastic film. The replacement ratio of mineral admixtures is 10%, 20% and 30%, respectively, and a mixture of a combination of both fly ash and slag is also studied. The results indicate fly ash reducing the early shrinkage of ordinary concrete, and the shrinkage decreases with the increasing of replacement ratio, but the effect is not so significant when the replacement ratio is above 20%. Slag also reduces the early shrinkage of ordinary concrete, and the shrinkage decreases with the increasing of replacement ratio, but the effect is not so significant when the replacement ratio is below 20%. Mixture with a combination of both fly ash and slag has lower shrinkage than mixture with fly ash.

Abstract: Construction market in Korea has been decreased for 3 or 4 years, and it brought the problem in supply and demand of workforce. Therefore, new workforce in construction industry could not been enter, and some of them have been employed in non-major area. This research intends to analyze construction industry as well as demand and status of construction companies and to diagnose status of new workforce for architectural works, and a survey is conducted for enrolled students and graduates to diagnose problems of current status in order to suggest the alternatives in Korea.

Abstract: Effects of operating temperature on the fineness and yields of the ultrafine circulating fluid bed fly ashes (CFBAes) have been studied. Results show that the temperature of selection zone increased faster than that of crushing zone. Introduction of secondary air decreased the temperature of crushing zone, which would make the classifier invalid. Also, ambient temperature and insulation measures have a great impact on the ultrafine grinding in superheated steam jet mill