Advanced Materials Research Vols. 168-170

Abstract: In this paper, using river silt from Ningbo as main material, through studying the properties and mixture ratio of raw material and sintering parameters, successfully sintered high mixing volume of silt, large range of sintering temperature, low-water-absorption and high-strength lightweight aggregates, and analyzed its microstructure, providing a better way of resourcization for the Yongjiang silt. The results show that Yongjiang silt supplemented with fly ash and other supplementary materials can be sintered high performance ceramsite, lightweight high-strength low water absorption ceramisite is because the ceramsite has dense enamel structure on surface and honeycomb closed fine porous structure in internal.

Abstract: In this paper, The cueved surface equation of the traditional combined parabolical is established by means of step function and the inclined coordinates. And then, the calculating formulas of the internal forces and deflection of the roof are derived from the throry of shallow shell and Navier method. Finally, a numerical example is given.

Abstract: By adopting the method of orthogonal experimental design, the effect of three independent variables, that is steel fiber fraction, polypropylene fiber fraction and silica fume fraction on the compressive strength, flexural strength and shrinkage of cement mortar was studied. The results indicate that steel fiber is one of the most important factors affecting compressive strength and shrinkage, and polypropylene fiber is one of the most important factors affecting flexural strength and shrinkage of cement mortar. By using deviation analysis to analyze the orthogonal experiment results, the optimized mix proportion of hybrid fiber reinforced cement mortar is determined. The hybrid effect of steel fiber and polypropylene fiber on the properties of cement mortar is discussed.

Abstract: The mineral structure and performance of belite-barium calcium sulphoaluminate cement clinker were investigated by petrographic analysis, X-ray diffraction and scanning electron microscopy, while raw materials were studied by differential thermal analysis, thermogravimetric analysis and X-ray diffraction. The results show that high-silicon limestone has low decomposition temperature which can promote the development of alite by adding small quantity. The formation and development of C3S is hindered in α-quartz while C3S is formed easily by mixing magnesite and dolomite in the low temperature. The proper proportions of high-silicon limestone and ordinary limestone is 1:5, and the compressive of this cement at 3, 7, 28 d are 37.9, 60.3, 87.9 MPa, which shows excellent mechanical properties.

Abstract: Alite-strontium calcium sulphoaluminate cement, a new type of cementitious material, is synthesized by combining strontium calcium sulphoaluminate with minerals of Portland cement clinker. The influences of excessive SO₃ and SrO on the microstructure and performances of this cement are studied by XRD, SEM-EDS and lithofacies. The results show that the optimal excessive mass fraction of SO3 and SrO are 50% and 80%. The compressive strength of the cement prepared under the testing conditions reaches to 32.8MPa, 66.8MPa and 126.4MPa at 1d, 3d and 28d curing ages, respectively. The additions of SO₃ and SrO are benefit to improve the content of strontium calcium sulphoaluminate, and promote the formation of alite at low sintering temperature.

Abstract: The influence of MgO on the composition, structure and properties of alite-calcium strontium sulphoaluminate cement were investigated by means of X-ray diffraction, SEM–EDS and light analysis. The results show that when the mass fraction of MgO is 1~5%, the early strength of cement can be enhanced significantly. The optimal content of MgO in the cement clinker is 2% and the compressive strengths of the cement at 3, 28 d are 64.3, 103.6 MPa respectively. A suitable amount of MgO can promote the formation of C1.5Sr2.5A3 , while the formation of C1.5Sr2.5A3 can be hindered if the content of MgO is excessive. The existence of MgO can improve the formation of C3S, increasing the mechanical property of the cement. Compared with the Portland cement, alite-calcium strontium sulphoaluminate cement has a higher capacity to dissolve MgO, which indicates that low-quality high-magnesium limestone can be efficiently used in the cement production.

Abstract: Effect of the vinyl acetate - ethylene copolymer emulsion (VAE emulsion), styrene-acrylic emulsion and paraffin emulsion were studied on waterproof properties and mechanical properties of calcined gypsum from flue gas desulfurization (FGD). The results showed that waterproof properties of samples which mixed paraffin emulsion were most excellent, but mixing paraffin emulsion caused the negative effect to the mechanics properties of samples. Adding appropriate content of VAE emulsion was advantageous to waterproof properties and mechanical properties of samples. Scanning electron microscope was used to observe the microstructure of samples, and the mechanism of waterproof emulsion was discussed.

Abstract: The synthesis conditions and mechanical performance of alite-rich cement clinker were investigated by the orthogonal test method. Sintering temperature, sintering time and contents of strontium oxide or strontium sulfate were taken as the influencing factors for the orthogonal test. The experimental results show that the optimal sintering temperature and sintering time are 1450 °C and 60 min, and the best strontium oxide or strontium sulfate content in the clinker is 1.5% and 0.5%, respectively. The doping of strontium oxide or strontium sulfate can promote the formation of alite mineral. That is beneficial to the increase of cement strength. The early strength of cement can be improved by addition of strontium oxide, and the long strength of cement can be increased through adding a little of strontium sulfate.

Abstract: The fatigue behavior of the asphalt mixtures beams is experimented by sine wave load, and the fatigue life is predicted by ultrasonic ware theories. Test results show that ultrasonic ware can reflect better fatigue process, and it is an effective method to analyze and forecast fatigue property.

Abstract: Piles formed by tamped concrete are a kind of technology in foundation treatment. In order to study the difference of strength characteristics between tamped and ordinary poured concrete, optimum parameters of mix proportion on tamped concrete are obtained by heavy compaction test in laboratory, then unconfined compressive strength tests are accomplished on the basis of optimum parameters of mix proportion. Influence factors of strength characteristics of tamped concrete are studied, such as cement-aggregate ratio, curing age, curing condition and so on. Finally, strength characteristics of tamped and ordinary poured concrete are compared. The test results indicate that the tamped concrete is hardened quickly and early-strength. In standard, water and saturated soil curing condition, compressive strength all grows sufficiency, thus tamped concrete can be used in ground and underground environment. At the same time, a higher strength can be obtained by smaller cement content, and the cost of tamped concrete can be reduced effectively.