Applied Mechanics and Materials Vols. 357-360

Abstract: Rubber particles were dipped into NaOH solution in order to wipe the zinc stearate generated in the process of preparation of rubber power. Rubber with different particle diameters and mixing amount (sand replaced in equal volume percentage) was adopted to produce rubberized concrete specimens. A series of tests including compressive strength tests, flexural strength tests, elastic modulus tests and ultimate strain ratio tests were done respectively. The results of tests showed that the value of the compressive strength, flexural strength and elastic modulus decreased with the increase of the mixing amount of rubber, while the decrease amplitude was different from each other. The value of ultimate strain increased a little and the ability of toughness and deformation of rubberized concrete were enhanced obviously through dipping rubber particles into NaOH solution.

Abstract: Recently, the safety of existing civil engineering structures attracts more and more attention. The long-term strength of concrete plays a key role during the assessment of safety and durability for civil engineering structures. The strength of concrete will gradually decrease during the service of civil engineering structures. It is significant to accurately predict the strength deterioration of concrete for correctly evaluating the safety of structures. The factors affecting the long-term strength of concrete include environment type, age, climate, water cement ratio, amount of cementing material and so on. In this paper, artificial neural network with powerful mapping ability has been selected to predict the long-term strength of concrete. First, there-layer BP neural network with age, water cement ratio, amount of cementing material as input and long-term strength as output was built. Then, the neural network was trained by the samples measured in real structures and the well-trained neural network was test. From the test results, the trained neural network can accurately predict the long-term strength of concrete with the error less then 9%.

Abstract: In order to make full use of stone chippings, alleviate the contradiction of increased demand and supply shortage of river sand. On the basis of the method of dense aggregate packing, this paper explores a way utilizing stone chippings with high fine content(more than 10% fine content), poor graded crushed stone, grade II flyash and S95 slag powder to prepare HPC with stone chippings 100% replacing river sand. The experiment results show that this mix design method is feasible, and its designed concrete has good workability, high dosage of mineral admixtures, high strength, high chloride ion penetration resistance, low cement content, low cost and so on.

Abstract: Using electrochemical impedance spectroscop (EIS) and polarization curve technique, the electrochemical behavior of prestressed reinforcement under different stress levels was studied in simulated concrete solution. The results show that: As the stress increasing, the impedance spectroscopy changes significantly, the entire impedance spectroscopy shows an elongated semi-circular deformation, high-frequency capacitance arc radius corrosion decreases with the corrosion progress, in other words, the reaction resistance decreases, the corrosion rate of the sample increases. And when the galvanized steel is in 1064MPa stresss condition, corrosion current density reaches the maximum, is 9 times larger than that of none stress corrosions condition. Under the combined effects of the external stress and corrosive media, dislocation can be emitted, value-added and moves. When it reached a critical state, it would lead to the crack nucleation of Stress corrosion cracking (SCC).

Abstract: Under the premise of sustainable development, construction waste is taken as recycled aggregates used in U-shaped lining channel project. In this paper, illustrated by an actual case, we applied the method of orthogonal experiments to research the influence on the compressive strength of the Recycled Aggregate Concrete caused by different aggregate and various amount of additional materials used. Variance analysis and range analysis adopted to conclude the main influence factor and optimal combination, to provide theoretical support for further study.

Abstract: Xiaolangdi sediment tunnel is the first waterway engineering used un-bonded circumferential pre-stressed lining in China. Based on data obtained by concrete strain meters over tensioning and operation periods, strain of concrete creep of sediment tunnel lining was analyzed. The results show that concrete creep developed over tensioning period is 26.4% of total strain and 35.8% of elastic strain respectively; Creep strain had a good linear relation with pre-stress and loading time and can be calculated by εc=ασiti , which are agree with the measured results; Over operation period, concrete creep strain can be analyzed by rejecting the effect of temperature and water level from the total strain.

Abstract: The geopolymer building blocks were prepared with fly ash, steel slag, pulverized blast furnace slag, sand and activator by the pressure molding process. Effects of activator on the microstructure and properties of the samples were analyzed by SEM-EDS and other methods. The results showed that the samples activated by sodium hydroxide with the best comprehensive performance: the compressive strength and flexural strength at 28days are 89.9MPa and7.9MPa, the water absorption and softening coefficient are 6.99% and 0.93, and its volume density is 2124Kg/m³. The compressive strength loss and weight loss are 9.20% and 2.44% after 25 freeze-thaw cycles, which meet the requirement JCT/422-2007 Non-fired rubbish gangue brick.

Abstract: Based on the coupling testing program of freeze-thaw and carbonation, the laboratory simulation test is carried out. The laws of carbonation depth of the fly ash concrete suffered the freeze-thaw cycle in different test modes and the influence of fly ash dosage on concrete carbonation depth after the freeze-thaw cycle are studied. Defining the influence coefficient of the freeze-thaw cycles on carbonation depth of concrete, the mechanism of coupling of freeze-thaw and carbonation is analyzed,and the role of freeze-thaw and carbonation in the coupling process are obtained.

Abstract: Compressive performance test of lightweight aggregate concrete with different quantity of steel fiber and plastics-steel fiber is carried out, and the following conclusions are obtained. It is not obvious that the change of compressive strength when LC30 light weight aggregate concrete mixed with plastics-steel fiber. Compressive strength is enhanced steadily to light weight aggregate concrete with steel fiber, but the amplitude is not large. The compressive deformation and failure characteristic of lightweight aggregate concrete are greatly improved as a result of mixed with plastics-steel fiber and steel fiber, and the failure pattern of lightweight aggregate concrete changed from brittle failure into a certain plastic failure.

Abstract: In this paper, the low-silicon coal gangue fly ash is used to produce autoclaved aerated concrete. The influences of water binder ratio, coal gangue fly ash content, calcareous content and conditioning agents on the compressive strength of the autoclaved aerated concrete are investigated. Optimal raw material formulation and procedure are determined for the autoclaved aerated concrete. The compressive strength and frost resistance of autoclaved aerated concrete made by the optimal raw material formulation and procedure meet with the requirements of autoclaved aerated concretes of B05 grade, and its thermal conductivity, drying shrinkage reach the requirements of the relevant national standards of China.