Advanced Materials Research Vols. 450-451

Abstract: The leaching behavior of hexavalent chromium (Cr(VI)) and major metal elements relevant to Cr(VI) leaching from chromite ore processing residue (COPR) to HNO3 are investigated by batch leaching tests. According to the test results, aqueous Cr(VI) accounted for 70-80% of the content of total Cr. Cr(VI) concentration was controlled by the dissolution degree of Cr(VI)-bearing minerals (such as hydroandradite) as the pH value ranged from 7.58 to 10.47, and by the adsorption degree of Cr(VI) on metal amorphous precipitates as pH value ranged from 6.18 to 7.58. It takes time for the penetration of acid into COPR and the release of alkalinity from the interior zone of particles. So, it could be speculated that the fine-sized particles would react with acid more effectively. 14mol HNO3 per 1kg COPR is needed to maintain the pH value to achieve 7.5 for 48 hours. This indicates the acid neutralization capacity of the test sample is relatively large. It suggests that the application of acid treatment method for COPR disposal is feasible but costly.

Abstract: The carboxymethylcellulose/montmorillonite (CMC/MMT) nanocomposite was prepared by a solution intercalation technique. The effects of contact temperature, the initial pH value of dye solution, contact time and the initial dye concentration on the adsorption capacitiy of CMC/MMT nanocomposite for Congo red (CR) were investigated. The adsorption kinetics and isotherms of nanocomposite were also studied. The results indicated that with the contact temperature increasing and the initial pH value decreasing, the adsorption capacity of the CMC/MMT nanocomposite increased. Compared with the adsorption capacity of CMC (62.42 mg/g), the nanocomposite exhibited the higher adsorption capacity (161.08 mg/g). The adsorption behaviors of CMC/MMT nanocomposite showed that the adsorption kinetics and isotherms were in good agreement with pseudo-second-order equation and the Langmuir equation.

Abstract: Taking the mix proportion of rammed earth dwellings in Anji as the basic standard, the physical properties, thermal properties, mechanical properties of rammed earth in various mix proportion have been tested by means of experiments. The results showed that the proportion of hydrated lime added to the rammed earth have a direct influence on the thermal conductivity, specific heat, compressive strength and shear strength of rammed earth specimens, the thermal and mechanical properties of modified rammed earth material is better when hydrated lime in the proportion of 10%～20%.

Abstract: The durability of alkali-activated slag mortar in seawater environment, compared with that of ordinary portland cement mortar, was studied by drying-wetting test in accelerated laboratory seawater. The drying-wetting resistance, porosity, performance mechanism, and depth of chloride ingress were analyzed. The results show the mechanical properties of the AAS mortars were improved after 40 cycles, opposite to that of the OPC mortar, which is mostly due to the difference of porosity and pore structure. The chloride penetration resistance of AAS mortar was better, comparing to conventional OPC mortar.

Abstract: This manuscript briefly introduces an engineering example.The method of fly-ash concrete presumption at early age is used in mixing proportion design. we can control concrete quality and improve accuracy of the early evaluating presumption concrete among measures and results.

Abstract: The development and research of new thermal insulation materials become a hot point due to the demand of building energy efficiency and high hygrothermal environment. Although there are many kinds of insulation materials in Chinese market, most of them are made from oil. It is very important to develop new thermal insulation materials to decrease the emission of CO2 and the use of non-renewable energy. The new materials have the function of reducing carbon emissions, improving the insulation performance of building envelope and indoor hygrothermal environment. However the research on hygrothermal characteristic of eco-fiber production is still kind of new work, such as water vapor permeability, thermal conductivity, water absorption coefficient, and isothermal sorption curve and so on, especially water absorption coefficient which doesn’t obey the classical model, according to the classical standards.

Abstract: The molar ratio of MgO and MgCl2 affects prominently on the strength of Magnesium Oxychloride Cement Concrete. Different ratios were used to explore the optimum mixture proportion with the highest uniaxial compressive strength. The influence of the MgCl2 solution concentration is presented. XRD (X-ray diffraction) and SEM (scanning electron microscope) was used to analyze the micro-mechanism.

Abstract: Magnesium phosphate cement (MPC) was modified by fly ash, silica fume and re-dispersible latex powder and the properties of modified MPC, such as fluidity, setting time and compressive strength, were tested. Based on the experimental results, the contents of 50% fly ash, 10% silica fume and 2% re-dispersible latex powder were chosen to modify MPC and the water resistance of the modified MPC was studied. The experimental results showed that the addition of fly ash prolonged the setting time and significantly increased the compressive strength of MPC. The addition of silica fume improved only the water resistance of MPC. The addition of the re-dispersible latex powder prolonged the setting time and improved the water resistance of MPC.

Abstract: This manuscript makes experiments on the relation between each index and fly-ash concrete strength, such as W/B, Sa, S/A and so on. At the same time we applicate artificial neural networks into HPFC The main research is on the relationship between component material and performance of the high-performance fly ash concrete, and also on the fly ash high-performance concrete quality control system and method, which promotes fly ash in foundation and basement construction engineering application. This text introduces the treatment technology of the non-linear artificial neural network, utilizing mixing ratio of existing concrete (import) and data as the performance index (output) to train the network, setting up concrete to non-linear import--Output mode relation, constructing concrete performance model, promoting prediction precision of concrete performance further.

Abstract: Presently large amount of slurry are generated in natural stone processing plants with an important on the environment and humans. But relative to normal concrete, the Recycled Aggregate Concrete (RAC) has unstable properties and weaker strength. Such inadequacies can be overcome though applied the confinement to the RAC. In this paper, several reinforcement systems are introduced to be used in the RAC. Analysis showed that the strength and deformation capacity are highly increased, while the shrinkage is reduced and deformation is obviously improved.