Applied Mechanics and Materials Vols. 438-439

Abstract: A Si-Mn Slag Cementitious Material was prepared by mixing Si-Mn slag, circulating fluidization bed slag as raw material. The results shows that circulating fluidization bed slag and Si-Mn slag has a preferably additive effect in a certain range by combination of lime, anhydrite and anhydrous sodium sulfate as activator, and the strength of samples reach the peak at circulating fluidization bed slag of 8%, Si-Mn slag of 70%, anhydrous sodium sulfate of 2%, anhydrite of 10%, lime of 10%. The strength, setting time and soundness were also tested and the results can meet most of the requirements of OPC standard (42.5) GB/T 175-2007.

Abstract: This paper selected two kinds of alkali-free liquid concrete accelerators and tested their compatibility with ordinary Portland cement, Portland cement and moderate heat Portland cement by measuring the setting times, compressive strength and compressive strength ratio of samples. The results showed that the compatibility is good between alkali-free accelerators and two types of cement: ordinary Portland cement and moderate heat Portland cement. However, the compatibility of two accelerators and Portland cement are quite different, the compatibility of AFA-2 accelerator is excellent, but AFA-1 accelerator is very poor. The setting times of alkali-free accelerators is mainly influenced by the mixing materials content, gypsum content, C₃A and C₃S content. In order to ensure the mechanical properties and durability of concrete, the setting times of new concrete accelerator is not the shorter the better, the appropriate initial and final setting times are 1min30s~5min and 4min~ 12min respectively.

Abstract: Ultrahigh performance concretes (UHPC) are promising materials for the next generation infrastructures due to their superior mechanical properties and durability. In this paper, comparison studies were conducted to show the potential of UHPC for sustainable constructions in chloride environments in view of service life. For reinforced concrete, the service life was calculated with analytical solution of Ficks second law on diffusion. And for reinforced concrete with nonlinear initial chloride profiles and depth-dependent chloride diffusion coefficient, a numerical method based on the Crank-Nicholson numerical scheme was adopted to predict the service life. The results show that the reinforced concrete structures constructed and repaired with UHPC have much longer service life than that of normal concrete (NC) and high performance concrete (HPC). It hence needs less cost for maintenance and reconstruction, which fulfills the requirements of sustainable construction.

Abstract: In order to improve the volume stability of high performance concrete, the effects of deformation behavior of high performance concrete containing CaO-based expansive agent were investigated. Concrete samples prepared without or with CaO-based expansive agent were compared through expansion under water curing at 20°C, drying shrinkage and autogenous shrinkage measurements. According to the experimental and analytical results, the new type expansive agent can control volume stability for high performance concrete. The addition of 10% CaO-based expansive agent not only built effective expansion in high performance concrete whatever under saturated condition or under sealed condition, but also substantially reduced its drying shrinkage.

Abstract: Corrosion of the steel reinforcement in the concrete structure caused by chloride ion penetration becomes more serious in the marine environment. Metakaolin has been widely used in the concrete structure to improve the strength and durability. The combination of metakaolin (MK) and fine fly ash (FA) was studied in the article and the penetration behavior of concrete with various contents of metakaolin-based modifier is investigated. The penetration resistance of concrete was tested in combination of electric flux test. The improving mechanism was studied with mercury intrusion porosimetry analysis (MIP). The experiment results indicate that metakaolin-based modifier improved the penetration resistance of concrete obviously. The combination of fine fly ash weakened the water sucking action of metakaolin and preserved the working performance of concrete. The pore size distribution of concrete containing metakaolin-based modifier has been optimized to improve the microstructure and enhance the penetration resistance of concrete.

Abstract: Active admixture recycled-concrete (AARC) is one of green high performance concretes, which took active admixture and fly ash into recycled concrete to replace part of cement. This paper researches the relationship of seepage resistance grade and chloride diffusion coefficient of recycled concrete by the regressive analysis of experimental data from NEL and gradually pressure method. The mufti-factor (slag powder, fly ash, air-entraining agent, polypropylene fiber, recycled coarse aggregate) and multi-level experiments of anti-permeability of concrete were carried out by orthogonal experiment method, and the optimum proportion of concrete is determined. The results show that seepage resistance grade of 16 groups AARC all reached W13, and chloride diffusion coefficient was between 0.5~1×10^-8cm²/s, the permeability grade is IV. The impermeability of the AARC is excellent. The rate of recycled coarse aggregate and slag powder were the most important factors for the impermeability properties of concrete, the optimum proportion of concrete was 10% slag powder, 20% fly ash, 1/10000 air-entraining agent, 1.0 kg/m3 polypropylene fiber and 40% recycled coarse aggregate.

Abstract: To improve the road performance of lime-flyash stabilized aggregate (LFSA), mix design method for skeleton close-grained LFSA is proposed by the method of multi-level filling theory and particle interference theory. Road performance of it is verified by indoor test. The results show that the designed LFSA, with the mix design method of strong interlocked skeleton close-grained (SISC) LFSA proposed in this article, has good road performance. Compared with LFSA of the gradation of Chinese technical specification for construction of highway asphalt pavements (CS gradation), the late strength of LFSA of SISC gradation increases 18%, the temperature shrinkage coefficient and dry shrinkage coefficient respectively increase by 15% and 45%, the scour resistance increases by 20%. Therefore, the SISC LFSA has a broad application prospect.

Abstract: An algorithm for arbitrary polygonal aggregate generation is proposed based on secondary development of ANSYS in this paper. It is established on the basis of circular aggregate model, and the central angle is the control parameter to generate poristic polygon as the coarse aggregate of concrete. The concrete numerical samples with first gradation of aggregate and two gradation of aggregate are generated. The aggregate fraction of polygon sample is lower about 20% than the original circular aggregate sample in the statistical sense. The results show that the proposed method can simulate gravel aggregate appropriately as long as the central angle and the aggregate percentage of original circular aggregate sample is reasonable controlled.

Abstract: By comparing the permeability test results between the autoclam method introduced by Queens University Belfast and the seepage method specified in China standard, it was found that water permeability index given by autoclam test had a better correlation with seepage value than air permeability index and water absorption index.

Abstract: In this paper, shrinkage deformation of concrete with recycled crushed brick coarse aggregate was experimental studied, effects of curing age, strength of concrete and environmental conditions on shrinkage of concrete are analyzed. Based on regression analysis of test data, the formulas for estimating the shrinkage deformation of recycled coarse aggregates concrete are given out, which provide the basis for engineering applications.