Applied Mechanics and Materials Vols. 423-426

Abstract: Stream sediments from the upper Chi River basin, including Chi and Nam Phong sub-watershed, are applicable to be a source of raw materials to produce fired clay bricks. The sampling locations of clay materials are generally found along the river terrace where are covering three different regions (upper-, mid-and lower sub-watershed) nearby brickyards. Quartz is the main mineral of all samples. Moreover, mainly clay mineral groups consist of mica, kaolinite, and chlorite group composing totally around 5%. Other mineral compositions, such as carbonate, evaporite, corundum, hematite and pyrolusite are normally found both in fine stream sediments and fired clay bricks. Additional minerals in fired bricks are forsterite, zircon and mullite group which are less than 0.2%. Their strength in submersion test expressed in the air-dried to pure water both 1 day and 5 days is revealed that their strength and strain intend to increase with the submersed brick. Besides, prism compressive strength decreases in half related to a fired brick unit. Their impact resistances are significantly distinctive by mineral composition of clay mineral group and silica. The compressive strength of air-dried fired brick at the ultimate stress and strain corresponding by time in water absorption test show that water filled in void or pore can enhance their strength and strain. Thus, fired clay bricks are capable to resist compressive force than the normal condition.

Abstract: In this paper, a new type of nano-SiO₂/silicone-acrylate emulsion composite coatings were synthesized through the modification and dispersion of nano-SiO₂ mixed with waterborne resin, dispersant, etc., and successive compounding with silicone-acrylate emulsion. The effects of dispersant concentration, PH value and the addition of waterborne resin on the dispersion stability of the nano-SiO₂ aqueous suspension were explored through infrared spectrum, X-ray diffraction techniques and sedimentation test, as well as the influence of thickener and defoamer agent on the performance of the composite coatings. It was found that the nano-SiO₂/silicone-acrylate emulsion composite coatings had good properties of weather resistance, anti-abrasion, acid and alkaline resistance and water resistance and so on, which could effectively improve the durability of concrete. So they can be widely used in surface protection of hydraulic constructions.

Abstract: A fractal model to simulate cement paste internal pore structure, and on this basis deduce that fractal dimension is D and the corresponding pore is r, the relationship between porosity is P. MIP was measured test. Then calculated the different ages of the fractal dimension of cement and concrete compressive strength, tensile strength and permeability coefficient. The results showed that: compressive strength, permeability and fractal dimension has a good correlation. Whey in cement in the process of hydration of cement products continue to fill the pores, making the compressive strength increased 70%, permeability is declining.

Abstract: In this paper, digital imaging technology is used to research the specimen deformation in asphalt mixture unconfined compressive strength test. We compare of the differences in the average vertical strain with a narrower range of local under three groups different specimens conditions, diameter height ratio of 1:1 specimens which are of specification and end untreateddiameter height ratio of 1:1 specimens which are wax to seal the deal and diameter height ratio of 1:1.5 specimens which are end untreated. We discover that the first two states can be easier to achieve the relatively stable state and better reflect the true stress-strain relationship than the last.

Abstract: In the actual structure, the concrete materials are mainly in multi-axial stress state. Because of the rapid development of concrete structures and the continuous improvement of structural engineering analysis theory, engineers have put forward higher requirements for concrete performance under multi-axial stress research. Based on stress space, this paper studies strength failure criterion of concrete, analyzed its limitations, and proposed concrete strength failure criterion research directions. It plays a strong practical role in scientific research.

Abstract: Beam bending fatigue test was done by MTS810 using stress control mode, the double logarithm fatigue equations and Weibull fatigue equations of three types of modified asphalt mixtures for intermediate course under different design method are gained. Good performance of the modified asphalt mix design programs are choose to use in the Northeast region to explore the modified asphalt mix design method for the use of intermediate course through a comparative study of 3 types of modified asphalt mixture fatigue performance.

Abstract: Concrete strength theory under complex stress is mostly expressed by stress. However, the destruction of concrete depends mainly on strain; failure criterion based on strain space can essentially describe the failure mechanism of concrete. It is also the basis for concrete constitutive strain space. This paper studies the strength failure criterion based on strain space and proposes directions for future research, which has guiding significance for theoretical research.

Abstract: This paper discusses waste production of recycled aggregate concrete is used as the recycled concrete, experiment with different recycled aggregate instead of natural aggregate, the ratio of recycled concrete workability and compressive strength etc performance compared with ordinary concrete, analyzing the change of the recycled aggregate replacement rate on the influence of concrete strength.

Abstract: Limestone filler and aggregates are used widely in cement production and concrete mixing nowadays, which could be connected with thaumasite formation, and lead to a lack of durability further in sulfate environment. This work deals with the deterioration of cement pastes containing 35% w/w limestone powder with different fineness immersed in MgSO₄ solution at 5°C±2°C for 15 weeks by. Erosion phases are discussed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). Test results show that visual deterioration of three kinds of cement pastes containing 400-mesh, 800-mesh and 1250-mesh limestone powders has little distinction, and erosion phases are all compound of ettringite, thaumasite, gypsum and brucite. Limestone powders with fineness of 400-mesh could supply enough carbonate needed for thaumastie formation. Increase of limestone fineness further could not accelerate deterioration of cement paste during the external magnesium sulfate attack at low temperature.

Abstract: The influences which were caused by difference of produced methods and original concrete on the performance of recycled aggregate have been studied in this paper. Moderate reprocessing of recycled aggregate can effectively improve the performance. Higher strength matrix concrete, better the performance of recycled aggregate, and the recycled concrete strength will be higher also. Original concrete has little effect on the performance of recycled aggregate.