Applied Mechanics and Materials Vols. 275-277

Abstract: In view of the present situation of high energy consumption from buildings in China, we study the thermal performances of the different wall systems of steel public buildings. We test on insulation tests for the different wall systems by protective thermal box law in the laboratory. According to the test data, we analyze differences between test values and theoretical values in order to determine the different wall systems for the different climatic regions and provide foundation to choose the wall systems of steel public buildings for energy savings.

Abstract: High performance nano-binder cementitious composites (HPNCC) are ultra-ductile fiber reinforced cementitious composites with special matrix. The compressive strength and flexural properties of HPNCC containing nano-SiO2 particles were investigated at age of 3d, 7d, 14d and 28d. According to the results, HPNCC exhibited excellent mechanical properties in the test. The compressive strength, flexural strength and first crack strain of HPNCC were all increased obviously at early age except the ultimate strain. In the flexural test, both crack extension width and the number of fine cracks decrease along with the curing age. However, the average crack spacing has no remarkable changes. Nano-SiO2 particles in HPNCC acted as ultra-fine fillers and catalyzers to strengthen the interfacial bond between the matrix and PVA fiber which improved the mechanical properties and would make HPNCC be widely used in the engineering.

Abstract: In this paper, the key parameters and functions for quantification of temperature creep stress were offered. These key parameters established the creep-heat-change fluctuation on fully graded concrete. The information is helpful for simulation of super arch dam concrete pouring process.

Abstract: Pore characteristics of pavement concrete with nano-particles (TiO2 or SiO2) are experimentally studied and compared with that of plain pavement concrete. The test results indicate that the addition of nano-particles improves the pore structure of concrete. The refined extent of pore structure of concretes increase with decreasing content of nano-particles. The pore structure of concrete with nano-TiO2 is better than that of concrete with the same content of nano-SiO2.

Abstract: Measure the temperature change of concrete-filled steel tubular with high strength low heat micro-expansive in its hardening process with different mix proportion. Study self-stress of high strength low-heat micro-expansive and study the relations of the expansive admixtures quantity and its changing regularity with the time. Observe the fail of axial compression short column of concrete-filled steel tubular with high strength expansive under vertical loading, study the changing regularity of its stress under loading.

Abstract: Hydration activity of silica fume(SF) and its effect on the structure of C-S-H gel in silica fume-cement (SFC)pastes was studied by FTIR and 29Si MAS NMR combined with deconvoluton technique, respectively. The experimental results indicate that the cement of 48% and the SF of 41% can react in the paste with SF replacement for cement was 10% by weight and the average chain length (ACL) of SiO4 and/or AlO4 tetrahedra in C-S-H was 3.0 at 3d. At 120d, the cement of 65% and the SF of 96% could react, and the ACL of C-S-H was 3.7, which was higher than that in the plain cement paste (ACL was 3.1). In the highly alkaline environment of the cement paste, pozzolanic reaction of silica fume can potentially occur in two ways, the monosilicate formed after the structure of silica fume were broken can combine with Ca cations to form C-S-H directly. Moreover, these chemical species can also connect C-S-H dimers into highly polymerized C-S-H and increase the ACL of C-S-H.

Abstract: Damage of cement paste under attack of sodium sulfate solution with different temperature and regime were carried out in this paper. Experimental study was executed on cement paste admixed by fly ash and GGBS. Sulfate concentration is 33.8g/l SO42- solution (5% by mass of Na2SO4). Two exposure regimes are employed in this study including immersion and drying-immersion cycles. In immersion regime, the temperature of sulfate solution is room temperature, 50°C and 80°C. Physical properties and sulfate ion distribution of paste were systematically tested during 150 days of sulfate exposure. And effects of raised temperature and drying-immersion cycles on deterioration of paste were also determined. The experimental results show that the strength, mass and expansion rate of paste improves initially and then progressively degrade until failure in sulfate environment. Beside chemical attack, which is major damage factor to paste in immersion regime, crystallized thenardite results in surface scaling of paste in drying-immersion cycles. Raised temperature and drying-immersion cycles accelerate the physical properties evolution process and increase the effective sulfate diffusion coefficient.

Abstract: Derived calculation formula of plastic strength, and used mortar consistency instrument to determine plastic strength. Through experiment, the fly ash and silicon powder that desulfurized or denitrated as grouting materials, its change rules of plastic strength were studid under different water cement ratio and different dosage conditions. Results shows that, between the two factors of water cement ratio and dosage, the water cement ratio affect significantly the plastic strength. The smaller the water cement ratio, the more obvious the increase of the plastic strength as time growth. Early plastic strength of silicon powder grouts is growing rapidly.

Abstract: The objective of this research was to investigate the influence of Warm Mix Asphalt (WMA) additives on asphalt mixture properties through the laboratory testing programs such as air voids, tensile strength ratio (TSR), dynamic stability, and low temperature bending failure strain tests. The experimental design included the use of three WMA additives of Sasobit, Evotherm and Rediset, one base (unmodified) binder source, and one modified binder source. The WMA mixtures were compared to those of controls, i.e., mixtures without the additives. Results from this study showed that: (1) WMA mixtures with Rediset, Evotherm, and Sasobit had slightly higher air voids than Hot Mix Asphalt （HMA）; (2) All WMA mixtures with SBS modified asphalt have lower TSR values than the original ones. The TSR of the WMA mixtures with base (unmodified) asphalt is not significantly different from HMA; (3) The WMA mixtures with SBS modified asphalt have lower values of the dynamic stability and bending failure strain than HMA, while the WMA mixtures with base asphalt are contrary, except with Rediset additives.

Abstract: In view of the issue that Heat Conductivity Coefficient (HCC) value of Thick-typed Fireproofing Coating (TFC) for tunnel at elevated temperature is not unknown, which makes researchers unable to make right fireproofing design and analysis for structure, starting from composition of TFC for tunnel, regarding it as complex of insulation aggregate and adhesive material, and using series model and parallel model, formulas of HCC at elevated temperature are established. The temperature field in three specimens is calculated by above HCC value, and is compared with testing results. Analysis result shows that HCC value from series model is the most reasonable. This paper provides an effective Solution for HCC value of TFC for tunnel at elevated temperature.