MECHANICAL PROPERTIES OF RECYCLED COARSE AGGREGATE CONCRETE REINFORCED WITH STEEL FIBERS

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Nancy Kachouh ◽  
Hilal El-Hassan ◽  
Tamer El-Maaddawy
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Compression Strength ◽  
Recycled Concrete ◽  
Steel Fibers ◽  
Flexural Stress ◽  
Flexural Toughness ◽  
Splitting Strength ◽  
Concrete Mix ◽  
Tensile Splitting Strength

This paper presents the combined influence of natural aggregates (NA) replacement with recycled concrete aggregates (RCA) and incorporating steel fiber reinforcement on the mechanical properties of normal-strength (30 MPa) concrete mixes. Hooked-end steel fibers were added in a 2% volumetric fraction to promote 100% RCA replacement. Fine aggregates were in the form of locally-abundant desert dune sand. Mechanical properties of 28-day concrete samples were assessed, including compression strength, tensile splitting strength, elastic modulus, flexural stress, and flexural toughness. For plain concrete mixes, the replacement of NA by RCA resulted in 18, 27, and 5% reductions in the respective design compression strength, elastic modulus, and tensile splitting strength. Nevertheless, the addition of steel fibers could restore the aforementioned properties by up to 90, 77, and 164%. Compared to the control mix made with NA, the flexural strength of the plain RCA-based concrete mix decreased by 33%, while the flexural toughness increased by 100%. In turn, the corresponding flexural properties of RCA concrete mix reinforced with steel fibers were 2 and 56 times those of the control made with NA. Findings provide evidence of the ability to produce concrete made with 100% RCA and reinforced with steel fibers with comparable compression properties and improved tensile and flexural performance compared to those of NA-based concrete.

Optimization of the Concrete Mix Proportions Centered on Performance after Exposure to High Temperature

2011 ◽  
Vol 268-270 ◽  
pp. 372-376 ◽  
Author(s):  
A. Chaboki-Khiabani ◽  
M. Bastami ◽  
M. Baghbadrani ◽  
M. Kordi
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
Statistical Study ◽  
High Strength ◽  
Taguchi Approach ◽  
Effective Parameters ◽  
Mix Proportion ◽  
Concrete Mix ◽  
Tensile Splitting Strength ◽  
Considerable Loss

This paper presents the results of an experimental and statistical study on the effect of high temperatures on the retained mechanical properties of high-strength concretes (HSC). The mechanical properties of HSC significantly change during and later than exposure to elevated temperature. The compressive and splitting tensile strength of more than 400 HSC cylindrical specimens with sixteen mix proportion have investigated to study the effect of mix proportion on the retained mechanical properties of HSC specimens after heating. According to these results, a considerable loss was observed for all mixes and specimens in strength particularly in tensile splitting strength. In addition, these experimental data were investigated using Taguchi approach to find the effective parameters of mix proportion. Also, the most optimum mix proportion was found and checked experimentally. According to our results, by controlling some factors in the mix proportion, it is possible to reduce the retained destructive effects of elevated temperature on HSC specimens.

Analysis and optimization of mechanical properties of recycled concrete based on aggregate characteristics

2021 ◽  
Vol 28 (1) ◽  
pp. 516-527
Author(s):  
Jiangwei Bian ◽  
Wenbing Zhang ◽  
Zhenzhong Shen ◽  
Song Li ◽  
Zhanglan Chen
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Coarse Aggregate ◽  
Aggregate Size ◽  
Peak Stress ◽  
Recycled Concrete ◽  
Maximum Aggregate Size ◽  
Coarse Aggregates ◽  
Aggregate Content ◽  
Aggregate Shape

Abstract The most significant difference between recycled and natural concretes lies in aggregates. The performance of recycled coarse aggregates directly affects the characteristics of recycled concrete. Therefore, an in-depth study of aggregate characteristics is of great significance for improving the quality of recycled concrete. Based on the coarse aggregate content, maximum aggregate size, and aggregate shape, this study uses experiments, theoretical analysis, and numerical simulation to reveal the impact of aggregate characteristics on the mechanical properties of recycled concrete. In this study, we selected the coarse aggregate content, maximum aggregate size, and the aggregate shape as design variables to establish the regression equations of the peak stress and elastic modulus of recycled concrete using the response surface methodology. The results showed that the peak stress and elastic modulus of recycled concrete reach the best when the coarse aggregate content is 45%, the maximum coarse aggregate size is 16 mm, and the regular round coarse aggregates occupy 75%. Such results provide a theoretical basis for the resource utilization and engineering design of recycled aggregates.

Effect of Silica Fume on Mechanical Properties and Carbonation Resistance of Concrete

2012 ◽  
Vol 238 ◽  
pp. 161-164 ◽  
Author(s):  
Qing Long Wang ◽  
Jun Chao Bao
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Elastic Modulus ◽  
Silica Fume ◽  
Compression Strength ◽  
Considerable Increase ◽  
Carbonation Resistance

A designed experimental study has been conducted to investigate the effect of silica fume on mechanical properties and carbonation resistance of concrete, a large number of experiments have been carried out in this study. The results indicate that the addition of silica fume has improved the compression strength and elastic modulus of concrete. A considerable increase for the compression strength and elastic modulus of the concrete was observed by increasing the dosage of silica fume. Besides, the addition of silica fume can improve the carbonation resistance of the concrete composite evidently, and the carbonation resistance is becoming better and better as the silica fume content is increasing gradually.

scholarly journals Mechanical Properties of Recycled Concrete in Marine Environment

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Jianxiu Wang ◽  
Tianrong Huang ◽  
Xiaotian Liu ◽  
Pengcheng Wu ◽  
Zhiying Guo
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Marine Environment ◽  
Recycled Concrete ◽  
Grey Model ◽  
Time Intervals ◽  
Normal Concrete ◽  
Equal Time ◽  
Peak Value

Experimental work was carried out to develop information about mechanical properties of recycled concrete (RC) in marine environment. By using the seawater and dry-wet circulation to simulate the marine environment, specimens of RC were tested with different replacement percentages of 0%, 30%, and 60% after immersing in seawater for 4, 8, 12, and 16 months, respectively. Based on the analysis of the stress-strain curves (SSCs) and compressive strength, it is revealed that RC’ peak value and elastic modulus decreased with the increase of replacement percentage and corroding time in marine environment. And the failure of recycled concrete was speeded up with more obvious cracks and larger angles of 65° to 85° in the surface when compared with normal concrete. Finally, the grey model (GM) with equal time intervals was constructed to investigate the law of compressive strength of recycled concrete in marine environment, and it is found that the GM is accurate and feasible for the prediction of RC compressive strength in marine environment.

scholarly journals REVIEW ON CORBONDIOXIDE CURING OF CONCRETE

2021 ◽  
Vol 5 (10) ◽  
Author(s):  
Vijaya Kumar Y.M ◽  
Seema B S
Keyword(s):  
Mechanical Properties ◽  
Carbon Dioxide ◽  
Experimental Study ◽  
Global Warming ◽  
Compression Strength ◽  
Industrial Activities ◽  
Concrete Mix ◽  
Water Curing ◽  
Carbon Dioxide Co2 ◽  
Stable Forms

Carbon dioxide (CO2) is the reason of increasing the global warming resulting from human industrial activities, to reduce these emissions of CO2 there is a necessity for sequestration of CO2 into stable forms. The paper summarizes the mechanical properties of concrete when cured on CO2 that is by using CO2 chamber. The research includes designing a concrete mix of M25 and M30 grade as per IS 10262:2009. The experimental study on water cured and CO2 specimens for compression strength were carried out. The results show that for M25 and M30 grade of concrete has achieved increasing value as comparing with 7days of water curing and the duration of 4hour CO2 curing. For M25 grade of concrete has achieved 70% of compression strength and M30 grade of concrete has achieved 65% of compression strength in the duration of 4hours of CO2 cured specimens when compared to 28days of water cured specimens.

scholarly journals Investigation on the Mechanical Properties of Fiber Reinforced Recycled Concrete

2016 ◽  
Vol 2 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Hasan Jalilifar ◽  
Fatholla Sajedi ◽  
Sadegh Kazemi
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Experimental Test ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Fiber Content ◽  
Recycled Concrete ◽  
Test Results ◽  
Fiber Volume ◽  
Flexural Toughness

The flexural strength of conventional concrete material is known to be enhanced by incorporating a moderate volume-fraction of randomly distributed fibers. However, there is limited information on describing the influence of fiber volume-fraction on the compressive and flexural strength of recycled coarse aggregate concrete (RCA-C) material. This paper reports on experimental test results of the RCA-C material replaced with 0, 30, 50 and 100% recycled aggregate and 0, 0.5, 1 and 1.5% steel fiber volume fraction. Three-point flexural tests of notched prism specimens were completed. The mechanical properties in compression were characterized using cube specimens. Significant improvement in compressive and flexural strength of RCA-C was found as fiber content increased from 0 to 1.5%. The experimental test results of RCA-C were further evaluated to investigate the influence of fiber content on flexural toughness. According to test results, the addition of steel fibers to RCA-C material appreciably increased the flexural toughness.

scholarly journals Experimental Study on Physical-mechanical Properties and Fracture Behaviors of Saturated Yellow Sandstone Considering Coupling Effect of Freeze-Thaw and Specimen Inclination

2020 ◽  
Vol 12 (3) ◽  
pp. 1029 ◽  
Author(s):  
Liang Chen ◽  
Peng Wu ◽  
Yanlong Chen ◽  
Wei Zhang
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Elastic Modulus ◽  
Failure Mode ◽  
Inclination Angle ◽  
Compression Strength ◽  
Shear Loading ◽  
Cold Regions ◽  
Freeze Thaw ◽  
Peak Compression

The effect of freeze-thaw on the physical-mechanical properties and fracture behavior of rock under combined compression and shear loading was crucial for revealing the instability mechanism and optimizing the structure design of rock engineering in cold regions. However, there were few reports on the failure behavior of rock treated by freeze-thaw under combined compression and shear loading due to the lack of test equipment. In this work, a novel combined compression and shear test (C-CAST) system was introduced to carry out a series of uniaxial compression tests on saturated yellow sandstone under various inclination angles (θ = 0°, 5°, 10°, and 15°) and the number of freeze-thaw cycles (N = 0, 20, 40, and 60). The test results showed that the P-wave velocity dramatically decreased, while the rock quality and porosity increased gradually as N increased; the peak compression strength and elastic modulus obviously decreased with the increasing θ and N, while the peak shear stress increased gradually with the increasing θ and decreased with the increase of N, indicating that the shear stress component can accelerate the crack propagation and reduce its resistance to deformation. The acoustic emission (AE) results revealed that the change of crack initiation (CI) stress and crack damage (CD) stress with the θ and N had a similar trend as that of the peak compression strength and elastic modulus. Particularly, the CI and CD thresholds at 60 cycles were only 81.31% and 84.47% of that at 0° cycle and indicated a serious freeze-thaw damage phenomenon, which was consistent with the results of scanning electron microscopy (SEM) with the appearance of some large-size damage cracks. The fracture mode of sandstone was dependent on the inclination angle. The failure mode developed from both the tensile mode (0°) and combined tensile-shear mode (5°) to a pure shear failure (10°–15°) with the increasing inclination angle. Meanwhile, the freeze-thaw cycle only had an obvious effect on the failure mode of the specimen at a 5° inclination. Finally, a novel multivariate regression analysis method was used to predict the peak compression strength and elastic modulus based on the initial strength parameters (θ = 0°, N = 0). The study results can provide an important reference for the engineering design of rock subjected to a complex stress environment in cold regions.

scholarly journals The Effect of Mixing Technique and Prolonged Mixing Time on Strength Characteristics of Concrete

Proceedings ◽  
2018 ◽  
Vol 2 (20) ◽  
pp. 1290
Author(s):  
Karol Urban ◽  
Alena Sicakova
Keyword(s):  
Compressive Strength ◽  
Mixing Time ◽  
Strength Properties ◽  
Recycled Concrete ◽  
Strength Characteristics ◽  
Concrete Aggregate ◽  
Splitting Strength ◽  
Mixing Method ◽  
Tensile Splitting Strength ◽  
The Impact

The experiment aims to test the triple mixing (3M) technique to produce the concrete with recycled concrete aggregate (RCA). Then, the impact prolonged mixing, representing the influence of delivery and discharge time in praxis, is analysed by the change in strength properties. Both the 28-day compressive strength and tensile splitting strength are evaluated in two aspects: the prolonged mixing time (0, 45 and 90 min after initial mixing), and the mixing method (normal and triple). Prolonged mixing time brought both the positive and negative changes in strength characteristics however the worst difference between initial mixing (0′) and 90′ minutes of mixing was only 8.4% for compressive strength and 8.5% for tensile splitting strength.

Experimental Study of Strengthening and Toughening for Recycled Steel Fiber Reinforced Ultra-High Performance Concrete

2014 ◽  
Vol 629-630 ◽  
pp. 104-111 ◽  
Author(s):  
Gai Fei Peng ◽  
Xu Jing Niu ◽  
Qian Qian Long
Keyword(s):  
Mechanical Properties ◽  
Fracture Energy ◽  
High Performance ◽  
Steel Fiber ◽  
High Performance Concrete ◽  
Steel Fibers ◽  
Fiber Reinforced ◽  
Ultra High Performance Concrete ◽  
Tensile Splitting Strength ◽  
Recycled Steel

This paper presents an experimental investigation on mechanical properties (including compressive strength, tensile splitting strength and fracture energy) of ultra-high performance concrete (UHPC) with recycled steel fiber, compared with none fiber and industrial steel fiber reinforced UHPC. Moreover, the microscopic observation of fracture energy was carried out. All specimens were prepared at 0.18 water /binder (W/B) ratio and the dosage of steel fiber was controlled at 60 kg/m3. The results indicate that recycled steel fiber has a significant effect on enhancing strength and toughness of UHPC. And owing to the crimped shape, higher tensile strength (1800-2000 MPa) and appropriate diameter (1 mm) of recycled steel fiber, the steel fibers of UHPRSFRC will not immediately be pulled off and necking phenomenon is distinct.

Probabilistic Modelling of Strength of Concretes with RCA

2016 ◽  
Vol 722 ◽  
pp. 207-215
Author(s):  
Roman Jaskulski ◽  
Anna Stępień ◽  
Marlena Sobocińska
Keyword(s):  
Tensile Strength ◽  
Recycled Concrete ◽  
Design Parameters ◽  
Concrete Aggregate ◽  
Probabilistic Modelling ◽  
Test Results ◽  
Aggregate Fraction ◽  
Natural Aggregate ◽  
Concrete Mix ◽  
Tensile Splitting Strength

The subject of the work is research and probabilistic modelling of compressive and tensile strength of concrete with recycled concrete aggregate (RCA). Sixteen series of concrete containing natural aggregate and RCA of 50% by mass of coarse aggregate (fraction 4 – 16 mm). Concrete specimens were tested for compressive and tensile splitting strength. In the study also the absorptivity of recycled and natural aggregate was tested, which is the amount of water that both types of aggregates can absorb during concrete mix. Based on the results models were formulated describing the compressive and tensile strength of concrete with RCA. These models are based on the design parameters of the concrete mix. In order to determine the coefficients of the models an estimating of a function of several variables by linear regression was performed. Compliance of the values ​​calculated using the models with the values ​​obtained from the tests was determined by Monte Carlo simulation. The results indicated a possibility of obtaining a high compliance of the test results with results obtained from simulations based on formulated models.

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