scholarly journals Stress–Strain Curve and Carbonation Resistance of Recycled Aggregate Concrete after Using Different RCA Treatment Techniques

2021 ◽  
Vol 11 (9) ◽  
pp. 4283
Author(s):  
Long Li ◽  
Dongxing Xuan ◽  
Chisun Poon
Keyword(s):  
Elastic Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Treatment Techniques ◽  
Carbonation Resistance

Five recycled coarse aggregate (RCA) treatment techniques including flow-through carbonation, pressurized carbonation, wet carbonation, nano silica (NS) pre-spraying and combined pressurized carbonation with NS pre-spraying, were utilized to improve the performance of recycled aggregate concrete (RAC). The characteristics of the stress–strain curves of RACs including peak stress, peak strain, elastic modulus, ultimate strain and toughness were evaluated after using the above RCA treatment techniques. A theoretical model for natural aggregate concrete was used to analyse the stress–strain curve of RAC. Additionally, the carbonation resistance of RAC after using different RCA treatment techniques were investigated. The results showed that the calculated stress–strain curve of RAC based on the theoretical model matched well with the experimental results. Among the three types of carbonation techniques, pressurized carbonation caused the highest improvement in peak stress and elastic modulus of RAC, followed by flow-through carbonation, the last was wet carbonation. The NS pre-spraying method contributed to even higher improvement in peak stress and elastic modulus of RAC than the pressurized carbonation method. The combined pressurized carbonation with NS pre-spraying exhibited the highest enhancement of RAC because both the RCA and the new interface transition zone (ITZ) were improved. The carbonation resistance of RAC was improved after using all the studied RCA treatment techniques.

Experimental Research on Mechanical Properties of Recycled Aggregate Concrete under Uniaxial Loading

2013 ◽  
Vol 671-674 ◽  
pp. 1736-1740
Author(s):  
Xue Yong Zhao ◽  
Mei Ling Duan
Keyword(s):  
Elastic Modulus ◽  
Coarse Aggregate ◽  
Strain Curve ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Peak Strain ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Recycled Coarse Aggregate

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.

Mathematical Model for Compressive Stress-Strain Curve of Recycled Aggregate Concrete

2008 ◽  
Vol 385-387 ◽  
pp. 521-524 ◽  
Author(s):  
Wei Wang ◽  
Li Jun Yang ◽  
Xiao Ni Wang
Keyword(s):  
Mathematical Model ◽  
Compressive Stress ◽  
Strain Curve ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Experimental Investigations ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
New Model

For the effective utilization of recycled aggregate concrete (RAC), it is necessary to correctly describe its compressive stress-strain curve (SSC) in theoretical and numerical analysis as well as engineering design of RAC structures. The objective of this study is to establish a good mathematical model for SSC of RAC. Based on energy dissipation theory, the differential governing equation of SSC is deduced and a new mathematical model is obtained. The new model can well describe both hardening type SSC and softening type SSC. It can overcome the shortcoming of the traditional model. Finally, good agreements have been found between the new model and the experimental investigations.

Analysis of Stress - Strain Curve on Recycled Aggregate Concrete under Uniaxial and Conventional Triaxial Compression

2010 ◽  
Vol 168-170 ◽  
pp. 900-905 ◽  
Author(s):  
Hai Feng Yang ◽  
Zhi Heng Deng ◽  
Ying Huang
Keyword(s):  
Lateral Pressure ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Confining Pressures

43 Φ50mm × 100mm column stress - strain curve tests are completed through RMT-201, which studied the compressive stress - strain curves of recycled aggregate concretes at distinct confining pressures under conventional triaxial stress state. This article, has analyzed the influence of different water-cement ratios, confining pressures on the curves, and raised constitutive equations of triaxial compression stress - strain curves for the different strength of recycled aggregate concretes.The brittleness indexes for recycled aggregate concrete under distinct confining pressures were analyzed contrastively. The result showed that: the failure modes of recycled aggregate concrete specimens are similar to those of ordinary concretes, but the final failure patterns of recycled aggregate and ordinary aggregate are quite different; with the increase of lateral pressure, the peak stress and peak strain of recycled aggregate concrete show linear growth; recycled aggregate concrete compressive stress - strain curves under the uniaxial and triaxial stress states are similar to ordinary aggregate concrete, yet peak strain shows signs of larger growth; with the increase of lateral pressure, the brittleness of recycled aggregate concrete reduces. The brittleness index of high-strength recycled aggregate concrete is larger wholly than that of ordinary recycled aggregate concrete and with confining pressure reaching a certain value, the brittleness index remains stable.

scholarly journals Axial Stress-Strain Performance of Recycled Aggregate Concrete Reinforced with Macro-Polypropylene Fibres

2021 ◽  
Vol 13 (10) ◽  
pp. 5741
Author(s):  
Muhammad Junaid Munir ◽  
Syed Minhaj Saleem Kazmi ◽  
Yu-Fei Wu ◽  
Xiaoshan Lin ◽  
Muhammad Riaz Ahmad
Keyword(s):  
Axial Stress ◽  
Peak Stress ◽  
Polypropylene Fibre ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Peak Strain ◽  
Stress Strain ◽  
Polypropylene Fibres ◽  
Aggregate Concrete

The addition of macro-polypropylene fibres improves the stress-strain performance of natural aggregate concrete (NAC). However, limited studies focus on the stress-strain performance of macro-polypropylene fibre-reinforced recycled aggregate concrete (RAC). Considering the variability of coarse recycled aggregates (CRA), more studies are needed to investigate the stress-strain performance of macro-polypropylene fibre-reinforced RAC. In this study, a new type of 48 mm long BarChip macro-polypropylene fibre with a continuously embossed surface texture is used to produce BarChip fibre-reinforced NAC (BFNAC) and RAC (BFRAC). The stress-strain performance of BFNAC and BFRAC is studied for varying dosages of BarChip fibres. Results show that the increase in energy dissipation capacity (i.e., area under the curve), peak stress, and peak strain of samples is observed with an increase in fibre dosage, indicating the positive effect of fibre addition on the stress-strain performance of concrete. The strength enhancement due to the addition of fibres is higher for BFRAC samples than BFNAC samples. The reduction in peak stress, ultimate strain, toughness and specific toughness of concrete samples due to the utilisation of CRA also reduces with the addition of fibres. Hence, the negative effect of CRA on the properties of concrete samples can be minimised by adding BarChip macro-polypropylene fibres. The applicability of the stress-strain model previously developed for macro-synthetic and steel fibre-reinforced NAC and RAC to BFNAC and BFRAC is also examined.

scholarly journals Experimental and Theoretical Investigation on the Thermo-Mechanical Properties of Recycled Aggregate Concrete Containing Recycled Rubber

2021 ◽  
Vol 8 ◽  
Author(s):  
Yunchao Tang ◽  
Wanhui Feng ◽  
Zheng Chen ◽  
Yumei Nong ◽  
Minhui Yao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Microstructural Analysis ◽  
Strain Curve ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Recycled Rubber

The utilization of recycled aggregates made from construction wastes and recycled rubber made from waste tires is an effective method to realize the sustainable development. Thus, this study aims to determine the feasibility of using recycled aggregate concrete containing rubber, named rubberized recycled aggregate concrete (RRAC) as a new type of green-building material. The experimental carbon emissions test verified RRAC as a low-carbon material. In addition, the residual mechanical properties of RRAC were investigated under elevated temperatures. After exposure at 200, 400, and 600 C for 60 min, the stress−strain curve, compressive strength, energy absorption capacity, and spalling resistance of RRAC with recycled aggregate replacement ratios of 50 and 100%, rubber contents of 0, 5, 10, and 15% were explored with microstructural analysis. Moreover, empirical models were proposed to describe the effects of heated temperatures and rubber contents on the stress–strain relationship of RRAC. The results indicated that the rubber particles could reduce the spalling of specimens based on the vapor pressure theory. Therefore, this study provided scientific guidance for the design of structures made with RRAC for resisting high temperatures.

scholarly journals Evaluasi Blok Tegangan Tekan Ekuivalen Balok Beton Bertulang Agregat Limbah Batu Onyx Tulungagung

2021 ◽  
Vol 15 (1) ◽  
pp. 45-50
Author(s):  
Bobby Asukmajaya R. ◽  
◽  
Edhi Wahjuni S. ◽  
Wisnumurti Wisnumurti ◽  
◽  
...  
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Coarse Aggregate ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Normal Concrete ◽  
Aggregate Concrete ◽  
Average Compressive Strength ◽  
Stress Block

Normal aggregate replacement to the onyx waste aggregate will certainly make the compressive strength and modulus of elasticity different, so it will affect the value of the compressive stress block equivalent (β1) as a result of the extent of the changing stress strain curve. In this study, trying to compare between the experimental β1 value of onyx concrete, while analytically the β1 value for normal concrete was obtained in accordance with SNI 2847 - 2019. To get the experimental β1 value from onyx concrete, it is made by looking for the compressive strength, elastic modulus and ꜫ0, for later the stress strain curve of the concrete is made to find the experimental β1 value of the onyx concrete. The results were obtained if the average β1 value of 18 specimens of onyx coarse aggregate concrete with an average compressive strength of 32.92 MPa was 0.868 while the analytical β1 value based on SNI 2847-2019 was 0.839, This shows that the B1 value for concrete with other aggregates is different, so it needs to be checked experimentally.

scholarly journals Compressive Behavior, Microstructural Properties, and Freeze–Thaw Behavior of Tailing Recycled Aggregate Concrete with Waste Polypropylene Fiber Addition

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6712
Author(s):  
Fan Xu ◽  
Tao Li ◽  
Chenghua Li ◽  
Zhijun Li ◽  
Sheliang Wang ◽  
...  
Keyword(s):  
Polypropylene Fiber ◽  
Strain Curve ◽  
Peak Stress ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Cement Matrix ◽  
Peak Strain ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Thaw Cycle

To improve the high brittleness of recycled aggregate concrete containing iron ore tailings (TRAC), the feasibility of adding polypropylene fiber (PPF) to TRAC was studied by performing a compression stress–strain curve test, scanning electron microscope characterization, and a freeze–thaw cycle test. The results indicated that PPF had a beneficial impact on reducing the brittleness of TRAC. With the increase in PPF content, the peak strain increased, the elastic modulus decreased, and the peak stress and energy absorption capacity increased at first and then decreased. Furthermore, the microstructure investigation revealed that the interface friction between the PPF, aggregate, and cement matrix was the main source of energy dissipation. When the load acted on the concrete, the stress was dispersed to the fiber monofilaments, thus effectively enhancing the peak stress and peak strain of concrete and suppressing the generation and development of cracks in the concrete. In terms of freeze–thaw resistance, adding a small amount of PPF could reduce the negative effects of the freeze–thaw process on the cement matrix. On the premise of ensuring strength, the waste utilization should be as high as possible. Therefore, it was suggested that the content of PPF in fiber-reinforced tailings recycled aggregate concrete (TRAC-PP) should be 0.6%.

Material yield strain identification using energy absorption

2018 ◽  
Vol 53 (6) ◽  
pp. 463-469
Author(s):  
S Abdul Jalil ◽  
A Anwar ◽  
SM Chou ◽  
K Tai
Keyword(s):  
Elastic Modulus ◽  
Yield Point ◽  
Gold Standard ◽  
Strain Curve ◽  
Peak Stress ◽  
Strain Identification ◽  
Stress Strain Curve ◽  
Yield Strain ◽  
Stress Strain ◽  
Mathematical Process

The current gold standard of identifying yield points from stress strain curves involves identifying a significant change in elastic modulus or using an arbitrary strain offset (0.1%, 0.2% or 2%) of the elastic modulus. The development of the offset method was due to the ambiguous definitions of yield point. The result is an arbitrary yield point which is prone to various human-related errors. This article presents a method to identify a unique yield point consistently using energy absorbed by the material up to first peak stress. This mathematical process idealises the stress strain curve for easy identification of the yield point. The method was tested on three possible types of stress strain curves with either a distinct yield point or without a distinct yield point (with peak stress closer to elastic region or closer to fracture). The yield points obtained by the proposed method are shown to be robust, consistent and unaffected by variations of the stress strain curves and data noises.

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