Advanced Materials Research Vols. 476-478

Abstract: Based on the established linear 2-DOF dynamics model of three-axle steering vehicle, the relationships between the gain of main transient and steady-state characteristic parameters of three-axle steering vehicle based on Zero Vehicle Sideslip Angle Control (ZVSC), vehicle speed and the deviation of the instantaneous steering center are deduced, and the influences of the control method and system inherent characteristics on steering transient response and stability are discussed. The main characteristic parameters of all wheels steering vehicles and front wheels steering vehicles are compared by quantative analysis using MATLAB with the consistency with theoretical analysis proofed.

Abstract: Based on the mechanism of concrete carbonation, the effects of content of fly ash in the binder, the water to binder ratios, compound activator, and long-term curing on the carbonation depth of fly ash high-performance concrete are investigated. Experiment results are analyzed and compared with compressive strength development characteristic of fly ash high-performance concrete, and some valuable conclusions are gained.

Abstract: This study explores the effects of the limestone addition on the mechanical properties and durability of the cement. Portions of the Portland cements were replaced by the limestone powders. Results showed that the compressive strengths of the mortar were reduced by the limestone addition. In general, the addition of limestone helps to reduce the shrinkage and improve the sulfate attack resistance. The lowest sulfate-expansion occurred at the specimens with a limestone addition of 10%. Moreover, with additions of 10% or less, the reductions in strength were likely recovered by the addition of fly ash.

Abstract: The ring-test was used to evaluate the plastic shrinkage crack tendency of paste specimen added with silica fume in this investigation. Silica fume was used as a partial replacement by weight of cement from 0% to 30%. The compressive strength and drying shrinkage were also examined. The test results show that the addition of SF (up to 30%) increases the compressive strength of paste. No significant influence of silica fume was found on the drying shrinkage of paste. The crack index is significantly increased in the paste specimen added with 10% and 20% replacement. This shows that the addition of SF increases the plastic shrinkage cracking tendency of paste. Using the ring-test method to detect the plastic shrinkage cracking of SF paste can provide more accurate measurements, which is helpful to understand the plastic shrinkage crack tendency of paste added with SF.

Abstract: Organic substances containing hydroxyl group and alcohol amine group were chosen in this paper and the effects of different organic group on powder properties and physical performance of cement pastes were studied using various methods of analysis, such as particle size analysis, fluidness analysis and XRD. The results show that monohydric alcohols have a neglectable aid-grinding effect. For Polyhydric alcohols and ethanol amine, the absorption capacity of the hydroxyl group or amido on the surface of the powder may increase in relation to the increase in groups, which can increase fineness but cannot improve the fluidity. For Diethanolamine and Triethanolamine, the absorption on the powder mainly depends on the hydroxyl group, but the amido has a strong electrostatic repulsive force, so the dispersion of the powder not only comes from high steric hindrance effect, but also the electrostatic repulsive force, which can improve the powder’s dispersity, reduce sieve residue and increase the fluidity. This research paper provides a theoretical guide for the application of grinding aids.

Abstract: Effect of hydroxypropyl methyl cellulose ether (HPMC) on early stage process of cement pastes and its mechanism were studied by hydration heat, chemical combined water, calcium ion concentration, TG-DTG and Ca (OH) 2 content. Results show that HPMC can significantly delay hydration acceleration period of cement pastes. Hydration acceleration period of cement pastes gradually goes back, with the dosage increasing. However, changes of HPMC dosage has little effect on deceleration period and stabilization period of cement hydration. When hydration time is less than 6 hours, chemical combined water slowly increases. Chemical combined water dramatically increases when hydration time is between 6 hours and 24 hours. After 4 hours hydration, calcium ion concentration reaches maximum 26.8mm/L in blank sample. Calcium ion concentration gradually decreases when hydration time is more than 4 hours and reach minimum 9.2 mm/L after 24 hours hydration. Calcium ion concentration of cement pastes which modified with HPMC showed the same change law. When hydration time is less than 4 hours, the content of Ca (OH) 2 in cement pastes slowly enlarges along with hydration time prolonging. The content of Ca (OH) 2 significantly increases when hydration time is more than 4 hours. At the same age, the more the dosage of HPMC is, the less the chemical combined water, calcium ion concentration and Ca (OH) 2 content.

Abstract: Raw soil is a kind of good ecological building material. But in fact abundant adobe houses in Western China have many defects such as bad indoor environment. This paper discusses from the point of view the ecological characteristics and thinks of that these defects are not the fault of soil itself but the limitation of its constructor’s knowledge. So the author analyses the indoor and outdoor environment of adobe houses and proposes new points that raw soil is a sustainable material which could be absolutely used in rural houses of Western China and at the same time its economic effectiveness is incomparable to other building materials.

Abstract: The attrition rate of a TBM cutter connects with the economic benefits of the TBM application and digging efficiency. The main influence factor of the attrition rate of the TBM cutter is rock abrastivity. The rock abrastivity is in contact with the physical and mechanical indexes of rock and rock attributes. The relationship between the rock abrastivity and the physical and mechanical indexes of rock is studied by experiments and mathematical statistics. The experimental samples are collected in the Qingdao subway tunnel and done rock mechanics room experimentation and rock abrastivity experimentation separately in the lab Based on calculation and analyses of the test data. We obtain a mathematic model describing the relationship between rock abrastivity and physical and mechanical indexes of rock and summarize and interpret the correlativity between them.

Abstract: The use of self-compacting concrete (SCC) is spreading worldwide due to its attractive properties in the fresh state as well as after hardening. Two application examples were introduced, one was reinforced concrete (RC) column strengthening with reinforced self-compacting concrete, and the other was with steel jacket and SCC. Economical and social benefits of the two application examples were analyzed. Project examples and applicable analysis show that RC column strengthening with SCC has attractive advantage, such as economy of technique, convenient construction, good construction quality, as well as bearing capacity improved significantly. The second strengthening method can make the best of advantage of SCC and steel material, and has strong global performance, high utilization ratio of the additional new materials, seismic behavior improved obviously, and so on.

Abstract: BaTiO3 nanoparticles were synthesized by hydrothermal process at various temperatures for 8 h, starting from a mixture of Ti(OBu)4 + BaCl2. The structure analytic results showed that all the prepared powders are well crystallized. Meanwhile, the phase change ratio from metastable cubic to tetragonal phases increased with the increase of hydrothermal temperatures.