Advanced Materials Research Vols. 450-451

Abstract: The capillary porous structures of the pre-cast concrete with different initial steam-curing duration were analyzed with MIP techniques. Then the hydration degree of cement, fly ash and slag in pre-cast concrete versus time were obtained respectively by combing the hydrochlorides and EDTA selecting dissolution methods, based on which the corresponding evolution of capillary porosity was determined. The comparison between calculated results and experimental capillary porosity showed that the proposed evolution model of capillary porosity could be adopted to reveal the developing trend of capillary porosity of pre-cast concrete with fly ash and slag under certain curing conditions

Abstract: Attack of sulfate crystallization and chemical interaction between sulfate and hydration product is one of the most important factors responsible for degradation of cementitious materials. This study investigates the effects of emulsified asphalt and fly ash as well as their combination on resistance of mortar to physicochemical attack of sulfate in order to develop high performance cementitious materials with high resistance to sulfate attack. The partly-submerged experiment with 5% Na2SO4 solution is designed to simulate physicochemical attack of sulfate salt on sample. Results indicate that, compared with fly ash, addition of emulsified asphalt is more effective in improving the resistance of mortar sample to physical crystallization role and chemical attack of sulfate. Moreover, a combination of fly ash and emulsified asphalt can further enhance the resistance of cementitious materials to physicochemical attack of sulfate, which results from the improvement of microstructure, reduction of CH product and increase of ductility of sample.

Abstract: To study the effect of concentration and type of de-icing salt on salt scaling based on the mechanism of glue spaling proposed by John J. Valenza II and George W. Scherer, the de-icing solution of NaCI andCaCI2 on the concentration of 1%、3%、5% and 7% were frozen into brine ice . Order to obtain the relationship of elastic modulus between the type and concentration of de-icing ,all brine ice specimens were tested under uni-axial compressive loading. The test results show: with the increase of concentration, the elastic modulus and peak stress of bring ice were decreased;when the same concentration ,the elastic modulus and peak stress of NaCl brine ice were higher than CaCI2.Based on the test results ,a reasonable explanation of the following phenomenon were given:The different type of de-icing salt all can lead to salt scaling of concrete;when the concentration of de-icing salt is moderate,it is will occur the most serious salt scaling.

Abstract: Chloride ion migration tests, or so called electrical accelerated tests, for testing chloride diffusion coefficient of cementitious materials are reviewed. The ion migration theory of electrical accelerated tests is presented. Four main representative measures, chloride penetration test, steady state migration test, unsteady state migration test and salt saturated conductivity test, are introduced and their theoretical calculations of chloride diffusion coefficient are described. Through analysis of the theoretical calculations, it could be found that all electrical accelerated tests are based on ion migration theory although different suppositions are adopted. Steady state migration test is the most suitable measure to determine chloride diffusion coefficient among the migration tests. DCIPT, DRCM and DSSCT calculated by chloride penetration test, unsteady state migration test and salt saturated conductivity test could be used to identify the resistance to chloride ion penetration of cementitious materials but are not the real diffusion coefficient.

Abstract: With L-glutamic acid as raw materials, N-carboxy-L-glutamic acid-benzyl-anhydride (BLG-NCA) was synthesized by triethanolamine. With triethanolamine as the initiator in the anhydrous dichloromethane, ring-opening polymerization of BLG-NCA was initiated, poly-l-glutamic acid benzyl ester was obtained. The amount of initiators, molar ratio of monomer/initiators, reaction temperature and reaction time to the effect of poly-l-glutamic acid benzyl ester in the ring-opening polymerization of BLG-NCA were studied. At last, poly L-glutamate was got, after the debenzylation in HBr solution. Through infrared spectroscopy, Ubbelohde viscometer, ¹H NMR spectra, polymerization product was characterized and analysized. Results showed that in dichloromethane, ring-opening polymerization of BLG-NCA could be initiated by triethanolamine.

Abstract: Concrete is the largest amount of artificial building materials in the world today. According to incomplete statistics, the construction waste produced in china each year can reach about one hundred million tons, and it can reach hundreds of millions of tons due to the long accumulation, which has become a serious social and environmental issues. In this paper, the technology of separation and recycle of waste concrete is studied, and the components of waste concrete are separated effectively, which provides a technical guarantee for the recycling of waste concrete. The waste concrete is disposed through the process of crushing, shelling and sieving and so on, the coarse aggregate and fine aggregate are separated effectively, the properties of coarse aggregate are nearly the same as natural aggregate. When the shelled fines is milled into ultrafine powder and used as concrete admixture, the performance of concrete can be improved. These all provide a new effective way for the recycling of waste concrete.

Abstract: This document outlined the development of concrete mixing water at first. And then it discussed some properties of concrete prepared with adding sea water and impacts of sea water on effectiveness of concrete. The article also tried to explain some reasons of these impacts. The author emphasized on analyzing the effect to the function of concrete by using seawater as mixing water and the reasons and separately elaborated on the different effects to plain concretes and reinforced concretes. At last, the article predicted the development trend of using seawater as concrete mixing water.

Abstract: The urethane reaction kinetics of 1,2-propanediol with phenyl isocyanate are investigated in different solvents, such as xylene, toluene and dimethylformamide. In-situ FT-IR is used to monitor the reaction to work out rate constant. It showsthat the urethane reaction has been found to be a second order reaction, solvents largely affects reaction rates. The reaction is largely accelerated in polar solvents, following the order of dimethylformamide > toluene > xylene. Further more, when dimethylformamide is used as solvent, the rate constants are different between initial stage and final stage, which belongs to different hydroxyls in 1,2-propanediol. However, when toluene or xylene is used as solvent, the rate constant is the same. That is, there is no reactivity difference for hydroxyls in 1,2-propanediol.

Abstract: Calcium-magnesium-silicate glass fiber is a kind of candidate materials for aluminosilicate ceramic fiber in high temperature resistant field. However, the large thermal shrinkage limits its rapid development and industrial application in high temperature insulation field. It has been known that the shrinkage under high temperatures is mainly affected by the structure and crystallization mechanisms of glass fibers. Thus, Al2O3 was chosen as additive in the chemical composition of glass fiber to investigate the glassy network structure, crystallization and dissolution properties of calcium-magnesium-silicate glass fiber by DTA, XRD and ICP-AES techniques. The results show that with the addition of Al2O3, the glassy network structure was strengthened and the precipitation of crystals was inhibited for heat-treated fibers. As for the dissolution properties in physiological fluids, though the weight losses, changes of pH values and leached ions concentration lowered slightly with the addition of Al2O3 for the intensified network structure, fibers still present high dissolution rates.