Advanced Materials Research Vols. 250-253

Abstract: The compression tests were carried out to investigate the compression behavior of steel fiber reinforced ultra high strength concrete(SFRUHSC). Cubic and axial compression specimens were tested at room tempreture, in terms of load control. The result shouwed that the compression strength of 150×150×150mm³and 100×100×100mm³ cubic specimens is 108.4MPa and 94.7MPa, while the 100×100×300mm³ axial specimens’ is 73.4MPa. The above data demonstrated that the different size effect from that of strength of steel fiber reinforced concrete(SFRC), namely the strength of 100×100×100mm is larger than that of 150×150×150mm³. Two kinds of compression specimens showed various fracture mode: ductile tension fracture of cubic specimens and the brittle shearing fracture of axial ones. But the steel fibers inside the specimens had been pulled out from the matrix.

Abstract: This paper presented the results of a comparative study aiming to investigate the effect of reflective coatings on lowering surface temperatures of matrix. Moreover, the important factors of the amount and the color of colored hollow-ceramic micro sphere were discussed. It was demonstrated that the use of reflective coatings could reduce a white surface temperature by 6.5 °C compared to a sample. The temperature difference became to reduce while the color of coatings turned to dark from the white to the yellow.

Abstract: At present, masonry and plaster of AAC blocks are still carried out by traditional construction methods which often lead to some quality defects such as cracking and leaking in the wall and hollowing and spalling in the plaster layer, etc. and hinder greatly the popularization and application of AAC blocks. On the basis of the characteristics of AAC blocks and the dry masonry thin-bed mortar, a kind of high performance dry-mixed Mortar for dry masonry process of AAC blocks was developed. The mortar has excellent workability, high water-retention, property, good mechanical properties and good construction properties. It solves the problems caused by traditional construction methods. The mechanism for these is discussed.

Abstract: In ordinary processing condition, using small amount (2%) of polymer to modify reactive powder concrete (RPC), the performance of modified and unmodified RPC was studied for their corrosion resistance with water-dip-in, acid-dip-in and sulphate solution-dip-in tests and was verified by the strength loss rate. The results show that not only the corrosion resistance but also the strength, especially the flexural strength, has been improved obviously after the polymer modification. The mechanism has been studied with SEM and EDS analysis.

Abstract: Sintered magnesia with different particle sizes, fused MgAl₂O₄ and FeAl₂O₄ were used as the raw materials. FeAl₂O₄ is added in MgO-MgAl₂O₄ bricks at different ratios to gradually replace MgAl₂O₄. After the raw materials were molded and sintered at the tunnel furnace with the temperature 1 530°C for 10 hours, the MgO-MgAl₂O₄-FeAl₂O₄ bricks could be made. After the analysis of the phase composition, microstructure and routine performance of the specimens, the influence by adding FeAl₂O₄ to the samples on the properties such as thermal shock resistance, adhesion strength of kiln crust are discussed as the key point. The result shows that the addition of FeAl₂O₄ has no evidently influence on the apparent porosity and volume density. The cold compressive strength of the samples reduces gradually with the addition of FeAl₂O₄, and it decreases obviously when the amount of FeAl₂O₄ is more than 8%. When the addition of FeAl₂O₄ is 5% FeAl₂O₄ in the MgO-MgAl₂O₄-FeAl₂O₄ bricks, MgAl₂O₄ and FeAl₂O₄ can combine each other’s advantages. The thermal shock resistance not only decreased obviously but the adhesion strength to kiln crust is increased.

Abstract: The aluminium foam is reinforced by compositing ZrO₂ ceramic balls with high hardness. The production process includes preparing precursor using NaCl particles and ZrO₂ ceramic balls, infiltrating molten aluminium into precursor and cleaning NaCl particles. The defects presented during the process make the structure inhomogeneous and influence the performance of aluminium foam composite. The defects consist of inner and surface shrinkage caused by insufficient infiltration and inhomogeneous distribution of ZrO₂ ceramic balls in the composite. By analyzing the forming mechanism, offering right control of process and choosing correct parameters, the sound aluminium foam composite was prepared. The optimum value of pouring temperature, preheating temperature of die and particles and the suction was determined as 740°C-760°C, 480°C-500°C and -0.04Mpa, respectively. The composite has the structure with 0.8-1.2mm pore size, 60-70% porosity and ZrO₂ ceramic balls of 40 percent by volume. The research makes a basis for the application of the new aluminium foam composite.

Abstract: The influences of silane impregnation on water adsorption, bonding force between ice and concrete surface and resistance to freeze-thaw of concretes were studied. Two strength grades (C30 and C50) and the air entrainment were considered for concrete preparation. The results show that surface impregnation with silane reduces the final water adsorption of concrete by more than 90% when compared with the untreated specimen. The silane treatment significantly decreases the bonding force between ice and concrete surface. The resistance to freeze-thaw of both new and old concretes can be improved by the silane treatment. Therefore, the surface treatment with silane is suggested as an effective method to improve the durability of concrete structures in cold regions.

Abstract: The introduction of foam into concrete, made the concrete have a small internal, closed independent uniform bubbles, which can form light weight, good insulation properties of foamed concrete, mainly used for roofing, non-load-bearing walls and thermal insulation layer pipeline. The purpose of this study is to obtain basic data on the properties of the development of lightweight foamed concrete containing a novel and high-efficiency foaming agent for various applications. The results show that this novel complex foaming agent have high foam expansion and stable foam. Lightweight foamed concrete based on LC foaming agent exhibits high compressive strength, low thermal conductivity and low water absorption after 28-day curing. Furthermore, it can be found that micropores is homogenously distributed into the LC foamed concrete with density of 400kg/m³.

Abstract: Currently, brittle mechanics and designing methods of high-strength construction-structure steel and its weld at low temperature are little studied at home or abroad. In addition, global climatic anomalies bring with extremely low temperature at cold region from time to time in recent winters; therefore it is imminent to research about the rule of the brittle fracture of high-strength construction-structure steel at low temperature. The main mechanical properties of steel are precondition and foundation for its toughness studying. In this paper, uniaxial tensile test of Q460C(14mm at thick), the high-strength construction-structure steel has been carried out at the low temperature to obtaining the intensity index (including yield strength σ_s, tensile strength R_m), the plastic index (including elongation at break A, reduction of area Z), and the rule of these index along the temperature changing, as well as calculating the Q460C steel’s temperature sensitive coefficient, which may be used to forecast the intensity index of Q460C at low temperature. The experimental data show that: The yield ratio of the Q460C was found to increase with the elongation at break A and the reduction of area Z decreasing while the plasticity and toughness decrease as the testing temperature drops. The result indicates that the Q460C steel is inclined to low temperature brittle fracture, so brittle fracture prevention measures should be strengthened.

Abstract: At present, wall materials innovation and energy-saving building construction face the new situation in China. Using local rich natural resources and industrial waste to make light-weight concrete buliding block instead of clay brick is one of the most effective measures. This paper expounds the research on pumice and its concrete, and the testing result indicates the pumice after being properly machined and spheroidizing hole sealing can be used to make hollow block, which performance can well meet the need of wall materials.