Advanced Materials Research Vols. 838-841

Abstract: Study of Constitutive relations of concrete based on Chinese and foreign scholars. This paper put forward constitutive equation that more close to the stress-strain data of high strength concrete under uniaxial compression, and make a comparison between the theoretical results and experimental data, and promising results were obtained. It can be used as a basis for researching of high strength and high performance concrete of other mechanical properties.

Abstract: The basic mechanical properties of RAP used as semi-rigid cement stabilized macadam base were researched. To add fiber to improve the crack resistance of the cement stable macadam mixture, reduce pavement reflection crack. Sixteen groups orthogonal experiment were arranged by the factors as cement, fiber, waste asphalt concrete and fly ash, the unconfined compression test, split test and drying shrinkage experiment were carried out. The results showed that the effect of the factors on the sensitivity of unconfined compression strength is obviously different, and from large to small order is cement, fly ash, fiber, waste asphalt concrete. RAP fiber cement stabilized macadam can satisfied with the strength requriments of base and subbase of all levels of the road. It should set cement and fly ash as the main control factors in the optimization design of RAP fiber cement stabilized macadam.

Abstract: The paper reports a study of the impact of moisture and age of pellets, as well as an external condition, on the thermal degradation of the thermoplastic polyurethane elastomers. Because thermoplastic polyurethane elastomers are hydroscopic polymer, moisture will have a significant impact on thermal degradation. For determination of the effect of moisture and age were used the thermo gravimetric analysis, differential scanning calorimeter and ISO STN 871: Plastics. Determination of ignition temperature using a hot-air furnace.

Abstract: In 110-190°C for 15-75 min of excess sludge thermal hydrolysis experiment, inspected the volatile suspended solid dissolution rate, the concentration of sludge SCOD, TCOD, components of organic acids in the supernatant fluid changes,such as sewage thermal hydrolysis characteristics, analysis the effect to improve the performance of sludge anaerobic digestion. The results show that with the increase of thermal hydrolysis temperature and time, SCOD and VFA in the sludge supernatant on rising. Under the condition of 190°C,75min, SCOD and VFA reached a maximum of 6674 mg/L,2630 mg/L; Release of sludge organic dissolved solids,COD and other major completed in the first 45 min,after 45 min changed little; Thermal hydrolysis temperature was between 90~170°C,sludge anaerobic digestion performance increases with temperature,when the temperature was higher than 170°C,sludge anaerobic digestion performance began to decline.

Abstract: Plain concrete pavements under heavy impact loading will induce flexure, crack and direct shear failure. To obtain dynamic response and failure mode of plain concrete pavement under heavy impact loading, the concrete brittle crack model is adopted and finite element model of plain concrete pavements is established; the dynamic response and failure mode under heavy impact loading in different loading points and different loading times are studied; the production, stretching and extension of cracking are researched; which is a powerful reference for practical engineering application.

Abstract: With regards to the quality problem of concrete that cant be found out earlier in the quality control, this paper discussed the principle to rapidly detect composition of concrete mixture and analyzed the measurement accuracy of water checker for fresh concrete through laboratory test. Experiments showed that the error in unit cement and unit water measured by instruments is relatively small and able to meet the accuracy requirements. And, the application of rapid detection techniques to the concrete quality control in practical engineering has achieved good results.

Abstract: Experiments for studying the shrinkage of concrete cured under three conditions were designed, and the impact of different curing conditions on the 28-day shrinkage and 180-day long-term shrinkage of concrete was researched. The results are as follows: There are significant influences of different curing conditions on shrinkage of concrete; The variation rule of 28-day shrinkage of concrete is consistent with that of 180-day shrinkage of concrete, the shrinkage of the concrete cured under standard condition is less than that cured under indoor natural condition, and larger than that cured under totally enclosed condition; In addition to mixing polypropylene fiber and expansive agents to optimize the proportions of concrete mix in the manufacturing process of concrete, adequate curing, after placing, is quite necessary for effectively controlling the shrinkage development of concrete, reducing the risk of concrete cracking and improving the quality of concrete structure.

Abstract: The influence of metakaolin (MK) on strength and microstructure of steam-cured high-strength concrete has been investigated using compressive strength test, XRD, MIP and SEM. Three MK replacement levels were considered in the study: 5%, 10% and 15% by weight of cement. A mix double blended with 10% MK and 10% slag was prepared too. Test results have indicated that MK can increase the compressive strength of steam-cured concrete, especially at early age. Compressive strength up to 90MPa at 1 and 28 days is obtained with the incorporation of 10% MK and 10% slag. When the replacement level of MK is higher than 10%, the enhancement of strength becomes less significant. Content of Ca (OH)₂ crystals is decreased while content of hydrates with Al is increased due to the pozzolanic reactivity of MK. Concrete pore structure is significantly refined and a denser hydrates structure is obtained due to the pozzolanic reaction and filler effect of MK. Meanwhile, combination of aggregate and paste is enhanced too. The improvements of strength and microstructure become more obvious when MK and slag are double incorporated.

Abstract: In order to systemic study the normalized stress-strain relationship behavior of Yingkou clay. By the consolidated undrained triaxial sherar test of Yingkou clay, obtaining that stress-strain relationship is strain hardening under different confining pressures.A kind of cementation structure in the soil directly affects soft soil strength.And the paper contrast four kinds of normalized factors to study stress-strain characteristics,which are confining pressurethe average consolidation pressureand the ultimate value of principal stress.The results indicate that the normalized degree is more accurate when used value of principal stress and as normalized factor. Meanwhile the normalized stress-strain relationship of Yingkou clay under consolidated undrained condition is established,which can well predict the stress-strain relationship under different confining pressure.