Applied Mechanics and Materials Vols. 584-586

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. This work deals with the sulfate minerals including of thaumasite, ettringite and gypsum in two types of cement pastes containing 35% w/w limestone powder immersed in MgSO₄ solution at 5°C±2°C for 15 weeks by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). Two types of cements were used: (i) ordinary Portland cement (P·O), (ii) typeII Portland cement (P·II). Test results show that thaumasite is present in two types of cement pastes, amount of thaumasite as well as amount of portlandite reacted with external SO₄^2- in P·II cement paste are more than those in P·O cement paste. It indicates that P·II cement is more susceptible to thaumasite formation than P·O cement containing the same amount of limestone powder, and more gypsum formation could contribute to thaumasite formation possibly during the external MgSO₄ attack at low temperature.

Abstract: This paper test the strength intensity,water absorption property of 10 baking—free bricks using the matrix cementing component in waster concrete as the material,studies the effect of m~ing ratio and maintenance time on pmpe~y to get the best mKing ratio of this kind of brick.It also analyzes the intension resources of this brick.

Abstract: Through lots of triaxial and a single-line wetting path experiments for slaking deformation of the remolded laterite , behaviors of stress-strain and volumetric strain-axial strain are studied at different level values of wetting stress.The test results indicate that the modulus of deformation and the strength of samples are reduced by wetting, that the value of wetting deformation is relation to the stress state and that the logarithmic relationship between wetting axial strain of the type of laterite and wetting stress levels meets . The test results obtained have an important reference value for actual projects in Jiangxi laterite area.

Abstract:

Asphaltic concrete is a composite material in which its mineral components: gravel, quartz sand and mineral powder is coupled by using bitumen. The experimentally determined that the quality of adhesion depends on the temperature at which all components had been mixing of hot asphalt mixes. However, the influence heating time remains unexplored. In this work the strength of compound was investigated on the samples of granite glued with using bitumen in a large range of temperature and time. It has been found that at a temperature of 140 degrees the strength increases significantly with time, but then starts to decline. The authors argue that the process of formation and destruction of adhesive compound bitumen and minerals can be described by the thermofluctuational theory of strength. Bitumen molecules on the boundary surface of the mineral become in a compressed state. The thickness of this layer can achieve 100 µm. The durability of road surfaces and the bond strength of all components asphalt concrete depends from quality of this indicator. Researches were conducted of the influence of the same temperature and time on the mechanical properties of the bitumen, but don’t found significant changes.

Abstract: In order to manufacture high-value added materials from steel slag, a steel slag-based ceramic was prepared in the paper. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were carried out to characterize the phase formation and the microstructure of the steel slag-based ceramics. Besides, the line shrinkage, flexural strength and water absorption were also determined.Results show that the variation of the line shrinkage and the flexural strength had a positive correlation with the increase of the temperature at the interval 1160°C~1210°C, which was opposite to the change of the water absorption. 1210°C was proved to be the optimum sintering temperature in this work, at which the maximum flexural strength was obtained with a value of 99.39MPa. With the temperature increasing, the quartz phase gradually decreased, participating in the sintering reaction, and the diopside become dominant phase with columnar crystals in 2-5μm at length, which would contribute to the fine performance of the ceramics.

Abstract: Concrete structure is widely used in civil engineering. Concrete cracking, a common and frequently occurring disease, is one of the main factors that cause impaired concrete structure durability. This paper analyzes the generation process and features of non-longitudinal concrete cracking. With on-site investigation of selected buildings in Ningbo, the paper discusses the main existing non-longitudinal cracks and their impact on the durability of concrete structure.

Abstract: The unqualified corrugated pipe grouting quality in bridges will lead to serious safety accidents. The sound field propagation in corrugated pipe structure was simulated and analyzed using finite element method, a much complex wave propagation characteristic is demonstrated, and the scattering signals caused by grouting defect are hardly distinguished. The collected impact-echo signals were processed by signal processing of information entropy technology. It is found the defect size is directly related to the information entropy. Several simulated models are constructed and measured, and the bigger size defect is, the lower entropy value is.

Abstract: Effects of structural characteristics of two different types of fly ash on performance of ready-mixed concrete were studied.Results indicated that, comparing with fly ash containing round spherical micro-Pearl 80% around , fly ash containing round spherical micro-Pearl below 20% will reduced work performance of pre-mix concrete clearly, water requirement increases 16% around, slump loss 0.5h for 100mm around, 1h for 140mm around, and because needed using excessive of pumping agent and makes setting time of concrete extended. Major accident hazards exist in actual pumping concrete. Respectively 40% two types of fly ash cement hydration morphology comparative studies showed that, mixed with fly ash containing round spherical micro-Pearl below 20% ,hardened cement paste with high porosity, density is low, such ash failed to improve performance of cement matrix.

Abstract: In the paper , the combined aggregate concrete is regarded as a three-phase composite material based on the meso-scale level, it consists of lightweight aggregate, ordinary aggregate and mortar. According to Fuller’s grading curve, the number of aggregate with different size could be obtained. And the randomly aggregates model is generated base on the Monte Carlo method. APDL program is developed to generate finite element model of combined aggregate concrete, On the basis, the stress characteristics of combined aggregate concrete is studied.

Abstract: Modifying of the surface of pine wood with aqueous solutions boron-nitrogen compounds was empirically found to provide a 100% biological stability of wood for at least 20 years. Durability of the protective effect of the modifiers developed is due to the formation of hydrolytically stable compounds on the surface of the wood.