Advanced Materials Research Vols. 261-263

Abstract: Analysis of the contrast tests on the property of three test pieces of fabric-reinforced FQQB and observation of the development of slab crack, as well as the analysis of the mechanical mechanism lying in the improvement in crack resistance property of FQQB by fabric. Analysis results show that it is effective to reinforce FQQB by fabric as it not only enhances the moment resistance of wallboard, but also apparently improves the cracking phenomenon of test specimen in the bottom of the board, and improves the anti-cracking ability of an entire building system.

Abstract: According to a series experiment for bending resistance of hydraulic concrete and RC element of mixing short-chopped basalt fiber, the reinforcing effect of bending strength and flexural elastic modulus of short-chopped basalt fiber concrete are analyzed, and increased cracking-resistance loads of short-chopped basalt fiber RC beams is also researched. Experimental results show that bending resistances of short-chopped basalt fiber concrete are increased, short-chopped basalt fiber in concrete is useful to reinforce the bending strength of concrete and cracking loads of RC beams.

Abstract: People often use superplasticizer and mineral admixtures (such as steel slag, slag, etc.) to increase the density of concrete and improve concrete strength, but don’t use coarse aggregate gradding. The paper selects the coarse aggregate of skeleton structure from several grading concept, and uses Uniform Design to test high strength concrete workability, and analyses results. It is shown from the results that the method of Uniform Design can significantly reduce the workload, and concrete mixture slump increases linearly with the water-cement ratio and sand percentage, but decreases linearly with steel slag addition, and the water released from the flocculation of cement by superplasticizer can increase the slump, and most of water plays the role of lubricant before it reacts with cement, and the effect of slump that sand extends coarse aggregate skeleton are greater than that sand surface area increases.

Abstract: This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.

Abstract: A dynamic elastic-plastic microplane constitutive model for concrete based on M2 which is proposed by B.P. Bazant etc., is presented in this paper. The state of each microplane is characterized by normal deviatoric and volumetric strains and shear strain.The strain-stress relations for deviatoric and shear component is described as elastic-plastic model. A new concept: failure strain has been introduced. The stress shall be zero after the microplane stress reaches failure stain level. The reinforced effect of steel fiber on concrete is taken account in this paper. Finally 2 calculation examples have been adopted to verify the rationality and correctness of the proposed module.

Abstract: An exhaustive literature survey shows, that a very little effort has been done towards Artificial Neural Network (ANN) approach in the area of concrete technology [1, 2, 3]. In the present investigation, development of ANN approach for prognostication of concrete mix proportion in lieu of conventional laboratory approach. The traditional lab approach attracts some drawbacks such as lot of manual involvement, time consuming, chances of creeping of human errors, uncertain prediction and always invasive in nature. Hence to reduce above said drawbacks, this study is undertaken to develop a ANN between concrete mix ingredient properties namely maximum size of aggregate, degree of quality control, degree of workability, type of exposure, characteristic compressive strength required in the field at 28 days and concrete mix proportion. Prognostication of concrete mix proportion is essential for all structural works. The present work deals with collection of huge input data base from literatures, ANN’s training and its testing are adopted to fix the appropriate weighted matrix (Illustrated in Fig [1]) which in turn Prognosticates the appropriate concrete mix proportion. Indian standard code (IS 10262:1982) procedure is also adopted to compare the concrete mix proportions of same samples. The Prognosticated concrete mix proportion from ANN approach yielded very high accuracy results (As shown in fig [2]) compared with IS code method. To account for larger sample data the results of this work will contribute for the prognostication of concrete mix proportions up to a certain degree of level, which will assist a structural engineer in estimation of concrete mix proportion, with minimum effort and non- invasive technique.

Abstract: The hydration of slag in Portland cement is studied by considering the interaction between the hydrations of slag and Portland cement clinker. The slag hydration heat value that the different dosage of slag is in Portland cement is measured with isothermal calorimetry method as quartz sand sample contrast. The kinetic analysis was used to obtain parameters, which were employed to find out the influence of the slag content on the reaction rate constant value. The reaction stages have been analyzed and explained in accordance with kinetic models. The model predictions show that as the slag proportions in the blended cement changes, water retention in the hydration products changes only slightly if compared to that of Portland cement, The investigations have shown that the addition of silica fume of more than 30 mass% reduces the duration of the phase boundary interaction as a rate-determined process resulting in the fast diffusion rate-determining process. The results of this study have also revealed evidence of the accelerator effect of slag during the first 24 h of hydration when it still exists as chemically inert filler.

Abstract: The application of steel fiber reinforced concrete as a new type of structural material, has unique advantages and wide application prospects. A special structural engineering, the use of high strength steel fiber reinforced concrete, to explore this technology for the construction of a key node in the construction process to elaborate.

Abstract: The disposal of waste rubber produced each year is a critical issue for any country, because this material doesn't resolve easily and leads to more environmental pollution. Utilizing waste rubber in industry is an alternative for the disposal of this matter. In the present study 5%, 10% and 15% of coarse aggregate is replaced with crumb rubber by volume along with 5%, 10% and 15% silica fume as cement replacement by weight in self compacting concrete. There were several rheological tests carried out on fresh concrete such as slump flow test, T₅₀, J-ring, L-box and V-funnel test. Mechanical properties of specimens were also examined; compressive strength at 7 and 28 days of curing and modulus of elasticity and density of hardened cylindrical specimens at 28 days of curing.

Abstract: The influence of synchronous use of coarse and fine recycled concrete aggregates on durable performance of recycled aggregate concrete (RAC) in air environment were determined. In this study, three series of concrete mixtures were prepared, in which the coarse recycled aggregate was used as 0%, 30%, 60% and 90% replacements of coarse natural aggregate and fine recycled aggregate as 0%, 10%, 20%, and 30% replacements of fine natural aggregate. Meanwhile, fly ash and slag were used as 15%, 25%, 35% and 45% replacements of cement, respectively. The carbonation depths, compressive cube strength, workability of RACs were tested. The experimental results showed that RAC with synchronous use of coarse and fine recycled concrete aggregates had satisfactory durable performance. When RAC was used as structural concrete in air environment, the optimum synchronous replacements are 60% for coarse recycled aggregate and 20% for fine recycled aggregate.