Papers by Keyword: Recycled Concrete (RC)

Abstract: In order to study the frost-resistant durability of recycled concrete, This test of freezing and thawing cycle were conducted to normal concrete specimens, recycled concrete specimens and include 2% LJ115 liquid anti-freezing mixture recycled concrete specimens respectively by quickly freezing method at±20±2°C. On the basis of this ,to the four kinds of specimens, analyse the mass loss rate and the dynamic modulus of elasticity.The result indicates that the frost-resistant durability of include antifreeze recycled concrete had improved greatly, even more than the normal concrete.

Abstract: Recycled concrete is the concrete mixed with crush aggregate recycled by waste concrete. This study investigates the effect of long term duration at high temperature on the mechanical properties and behavior of recycled concrete. The result shows that recycled concrete shrank after heating to temperatures below 500°C. Because the silicate aggregates expand over 573°C, recycled concrete expanded at 750°C. Recycled concrete contained the more recycled aggregates, the less expanded. The mechanical behavior of recycled concrete was worse than conventional concrete at treatments below 500°C. However, over 500oC, the resistivity of recycled concrete from construction sites, which contains some red brick, was better than conventional concrete. The property difference tends to decrease with elevated temperature.

Abstract: The use of recycled aggregate to produce new concretes has become increasingly widespread, and numerous studies have demonstrated that the final product performs similarly to traditional concrete. However, construction and demolition waste (CDW) presents certain characteristics which could limit its acceptance in the construction sector due to worse performance than natural aggregates. One example of this is water absorption, which in recycled aggregates reaches such high values that the amount of free water calculated for mixing the concrete is affected, consequently impacting on the concrete's properties, especially consistency. This paper reports the possibility of solving this problem with a simple and inexpensive method; pre-saturation of recycled aggregates prior to adding them to the mix. The results of two different pre-treatments are compared; one consisted of immersing the aggregates in water for 10 minutes and the other, in addition to the above procedure, included a brief period of air drying and subsequent elimination of surface water from the aggregate. Both pre-treatments were found to solve the problem of consistency.

Abstract: When recycled aggregates are used appropriately, it is possible to obtain good quality, economic and environmentally friendly building materials. The emergence in recent years of the use of recycled materials in the construction industry, specifically in the production of concrete, has met with varying degrees of success due to the barriers that the market for recycled products has still to overcome. Scientific studies have focused on the good properties presented by the coarse fraction of construction and demolition waste (CDW), leading to the formulation of various international recommendations which, although still insufficient, provide a stimulus to the use of recycled aggregates in concrete.

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: Influence of replacement ratio and water-cement ratio on the recycled concrete mechanical properties were analyzed by testing the compressive strength and tensile strength of the recycled concrete. Results show that the mechanical properties of recycled concrete, compared with common concrete, can meet the requirements of the project. Water-cement ratio has great influence on compressive strength and tensile strength, replacement ratio has obvious influence on compressive strength but little on tensile.

Abstract: This paper addresses problems of aggregate concrete of construction wastes, which were featured as large water absorption, quick slump loss, as well as easy bleeding and low strength of concrete. A comparative analysis by experiment between recycled aggregate concrete and ordinary concrete was made on aspects of water absorbability, compressive strength, slump loss, bleeding rate, drying shrinkage and economic efficiency. It has found possible to preparing the recycled aggregate concrete of high performance through the prewetting recycled aggregate. It is concluded that construction wastes can be recycled by obtaining the optimum mole of preparing recycled aggregate concrete of construction wastes and evaluating their reliability on cost-lefficiency and mechanic capability，thus, it also recycled the limited resources and solve some environment problems.

Abstract: In order to study ribbed thin-walled square steel tube recycled concrete eccentric compression column, used the mechanical properties of ANSYS software, conduct the nonlinear numerical simulation. The analysis of the ribbed and ribbed, recycled coarse aggregate replacement ratio and eccentricity, three factors on the eccentric compression column mechanical performance, proved the thin-walled square steel tube that recycled concrete composite column the effectiveness of three-dimensional finite element simulation. The result shows that: when aggregate replace rate was 0%, ribbed specimen than not ribbed specimen axial displacement and displacement to the reduced to 5.77% and 2.33% respectively. When the aggregate replace rate was 50%, ribbed specimen than not ribbed specimen shaft voltage and bias displacement has been reduced by 6.53% and 4.22%; When the aggregate replace rate was 0%, ribbed specimen than not ribbed specimen axis pressure bearing capacity and bias the bearing capacity increased by 1.21% and 2.74%. When the aggregate replace rate was 50%, ribbed specimen than not ribbed specimen axis pressure bearing capacity and bias the ultimate bearing capacity increased by 1.04% and 2.82%.

Abstract: The complete stress-strain curves of recycled aggregate concrete with different recycled coarse aggregate replacement percentages were tested and investigated. An analysis was made of the influence of varying recycled coarse aggregate contents on the complete stress-strain curve, peak stress, peak strain and elastic modulus etc. The elastic modulus of RC is lower than natural concrete (NC), and with the recycled coarse aggregate contents increase, it reduces. While with the increase of water-cement ratio (W/C), recycled concrete compressive strength and elastic modulus improve significantly. In addition, put forward a new equation on the relationship between Ec and fcu of the RC.

Abstract: The recovery and utilization to building solid waste is the current hot issues in the construction of towns. In this paper, 30 groups of fly ash recycled concrete test cube were designed and produced, through the mechanical performance test research, we analysised the main influence factors to the strength and performances of fly ash regeneration concrete test cube,such as recycled aggregate category, water cement ratio, the admix proportion of recycled aggregate. The test results would lay a solid foundation for the test research and engineering application of recycled concrete.