scholarly journals Structural Behavior of Concrete Beams Containing Recycled Coarse Aggregates under Flexure

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
In-Hwan Yang ◽  
Jihun Park ◽  
Kyoung-Chul Kim ◽  
Hyungbae Lee
Keyword(s):  
Experimental Data ◽  
Flexural Strength ◽  
Concrete Beams ◽  
Crack Pattern ◽  
Crack Spacing ◽  
Experimental Results ◽  
Structural Behavior ◽  
Experimental Program ◽  
Coarse Aggregates

The structural behavior of concrete beams containing recycled coarse aggregates (RCAs) was investigated in this study using detailed experimental data. Twelve concrete beams were tested in the experimental program: nine beams with varying RCA contents and three control beams with natural coarse aggregates (NCAs). The parameters for investigating the structural behavior of the RCA concrete beams under flexure were the RCA content (30%, 50%, and 100%) and tensile rebar ratio (0.50%, 0.79%, and 1.14%). The crack pattern of the RCA beams was similar to that of the NCA beams; however, the RCA beams exhibited smaller crack spacing than the NCA beams. The flexural strength was slightly affected by the RCA content. However, the ductility of the beam was not significantly influenced by the RCA content. A comparison of the experimental results and the calculations from the ACI 318 and EC 2 provisions for the flexural strength showed that the current provisions conservatively predicted the flexural strength of the RCA concrete beams.

scholarly journals 24-hour Fire Produced Effect on Reinforced Recycled Aggregates Concrete Beams

2019 ◽  
Vol 9 (3) ◽  
pp. 4213-4217 ◽  
Author(s):  
A. H. Buller ◽  
M. Oad ◽  
B. A. Memon ◽  
S. Sohu
Keyword(s):  
Flexural Strength ◽  
Concrete Beams ◽  
Testing Machine ◽  
Maximum Load ◽  
Reinforced Concrete Beams ◽  
Recycled Aggregates ◽  
Equal Proportion ◽  
Load Testing ◽  
Coarse Aggregates ◽  
Natural Aggregates

In this article, the effect of prolonged fire (24-hour duration) on reinforced concrete beams made with recycled aggregates from demolished concrete was experimentally investigated. Demolished concrete was used recycled coarse aggregates in equal proportion with natural coarse aggregates. Normal and rich mix concrete with water-cement ratio equal to 0.54 were used. As a control specimen, beams with all-natural aggregates were also cast to compare with the results of the proposed beams. All beams were cured for 28 days and exposed to fire at 1000°C in an oven for 24 hours. After the elapse of this fire period, the beams were allowed to air cool, followed by testing till failure in a universal load testing machine. Comparison of the test results shows that rich mix concrete beams more reduction in flexural strength, more increase in maximum load carrying capacity and deflection than normal mix beams. The maximum reduction in flexural strength was 32.41% for beams cast with 50% RCA and rich mix. Although the fire duration used in this study is rare, yet the outcome provides guidelines for taking proper decisions for retrofitting/strengthening of the fire affected structure before putting it back in service.

Research in the Preparation of Paving Bricks with Construction Garbage

2013 ◽  
Vol 712-715 ◽  
pp. 917-920
Author(s):  
Lian Xi Wang ◽  
Guang Hui Pan ◽  
Fu Yong Li ◽  
Hai Ming Wang ◽  
Guo Zhong Li
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Experimental Results ◽  
Replacement Rate ◽  
Coarse Aggregates ◽  
Waste Concrete ◽  
Fine Aggregates ◽  
Binder Ratio ◽  
Water Binder Ratio

Construction garbage paving bricks were made of recycled coarse and fine aggregates which were prepared by the waste concrete. The influence of replacement rate of recycled coarse aggregates, water-binder ratio and excitation agent dosage on the compressive strength and flexural strength of construction garbage paving bricks were researched. The experimental results show that optimum replacement rate of recycled coarse aggregates, water-binder ratio and excitation agent dosage were 100%, 0.43 and 1.5% respectively. In this proportion, the 7d, 28d compressive strength of the products were 15.6MPa, 37.5MPa respectively, and the 7d, 28d flexural strength were 2.0MPa, 4.3MPa respectively, which fit the requirements of the Cc30 level of compressive strength and the Cf4.0 level of flexural strength involved in JCT 446-2000 "concrete pavers".

scholarly journals Assessing the Instantaneous Stiffness of Cracked Reinforced Concrete Beams Based on a Gradual Change in Strain Distributions

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Chunyu Fu ◽  
Dawei Tong ◽  
Yuyang Wang
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Cross Section ◽  
Concrete Beams ◽  
Internal Force ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Gradual Change ◽  
Concrete Cracking ◽  
Good Agreement

Concrete cracking causes a gradual change in strain distributions along the cross section height of reinforced concrete beams, which will finally affect their instantaneous stiffness. A method for assessing the stiffness is proposed based on the gradual change, which is considered through modeling different strain distributions for key sections in cracked regions. Internal force equilibria are adopted to find a solution to top strains and neutral axes in the models, and then the inertias of the key sections are calculated to assess the beam stiffness. The proposed method has been validated using experimental results obtained from tests on five reinforced concrete beams. The predicted stiffness and displacements are shown to provide a good agreement with experimental data. The instantaneous stiffness is proven to greatly depend on the crack number and depth. This dependence can be exactly reflected by the proposed method through simulating the gradual change in concrete strain distributions.

scholarly journals Mechanical Properties of Polypropylene Fiber Cement Mortar under Different Loading Speeds

2021 ◽  
Vol 13 (7) ◽  
pp. 3697
Author(s):  
Hui Chen ◽  
Xin Huang ◽  
Rui He ◽  
Zhenheng Zhou ◽  
Chuanqing Fu ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Relative Error ◽  
Cement Mortar ◽  
Polypropylene Fiber ◽  
Experimental Results ◽  
Strength Tests ◽  
Sample Age

In this work, the relationships between the mechanical properties (i.e., compressive strength and flexural strength) and loading speed of polypropylene fiber (PPF)-incorporated cement mortar at different ages (before 28 days) were studied. A total of 162 cubic samples for compressive strength tests and 162 cuboid samples for flexural strength tests were casted and tested. Analytical relationships between the sample properties (i.e., sample age, PPF content, and loading speed) and compressive and flexural strength were proposed based on the experimental data, respectively. Of the predicted compressive and flexural strength results, 70.4% and 75.9% showed less than 15% relative error compared with the experimental results, respectively.

Crack Self-Healing Properties of Concrete with Adhesive

2014 ◽  
Vol 919-921 ◽  
pp. 1880-1884 ◽  
Author(s):  
Qing Yu Cao ◽  
Ting Yu Hao ◽  
Bo Su
Keyword(s):  
Flexural Strength ◽  
Vinyl Acetate ◽  
Ethylene Vinyl Acetate ◽  
Experimental Results ◽  
Experimental Program ◽  
Cement Matrix ◽  
Self Healing ◽  
Repair Efficiency ◽  
Healing Agent ◽  
Strength And Toughness

An experimental program was carried out to investigate whether EVA (ethylene vinyl acetate) heat-melt adhesive can potentially act as a self-healing agent in cement-based material. The effects of incorporation of EVA and heating on the properties of mortar were studied. Experimental results show that the interface between EVA and cement matrix was well improved after heating, which allows a significant improvement in flexural strength and toughness of specimen; Pre-damaged specimens in various degrees (30%, 50% and 70%) were effectively repaired by EVA and the repair efficiency all exceeded 100%. Keywords:crack; heat-melt adhesive; self-repairing

An Experimental Study on Flexural Behavior of Reinforced Concrete Beams with GFRP Bars and Recycled Coarse Aggregate

2013 ◽  
Vol 319 ◽  
pp. 440-443
Author(s):  
Seung Hun Kim ◽  
Yong Taeg Lee ◽  
Tae Soo Kim ◽  
Seong Uk Hong
Keyword(s):  
Reinforced Concrete ◽  
Flexural Strength ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Flexural Performance ◽  
Coarse Aggregates ◽  
Glass Fiber Reinforced ◽  
Load Carrying ◽  
Cracking Pattern

This study evaluates the flexural performance of reinforced concrete beams with GFRP(Glass Fiber Reinforced Polymer) bars and RCA(Recycled Coarse Aggregates). A total of four specimens with various replacement ratios of RCA (0%, 30%, 50%, and 100%) were tested. An investigation was performed on the influence of RCA with various replacement ratios on load-carrying capacity, post cracking stiffness, cracking pattern, and ductility. The test results showed that replacement ratios of RCA had not a bad effect on concrete compressive strength or flexural strength of beams. They were compared with the design flexural strength and the nominal moment predictions of ACI Code.

scholarly journals Experimental Study on Calculation Methods for Short-term Cracks in High-strength Reinforced Concrete Beams

2017 ◽  
Vol 11 (1) ◽  
pp. 187-194
Author(s):  
Ruliang Zheng ◽  
Degao Tang ◽  
Yulong Xue ◽  
Zhen Liao
Keyword(s):  
Reinforced Concrete ◽  
Crack Width ◽  
Concrete Beams ◽  
High Strength ◽  
Crack Spacing ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Calculation Methods ◽  
Short Term ◽  
Average Crack

High-strength steel has increasingly become widely used among various engineering practices, but the relevant provisions of the codes lag behind its development. Six sets of experiments on simple supported beams reinforced with HTB600 and HTB700 rebars subject to bending loading were conducted in this study to 1) investigate the conditions of crack development, 2) contrast the calculating modes of short-term crack width between Chinese and European concrete codes, and 3) analyze European applicability and precision pertaining to high-strength reinforcement of beams. According to the experiments and research, when the calculation formulae obtained from Chinese codes were used to calculate the average crack spacing of high-strength reinforced concrete beams, the error relative to that obtained in the experiment reached approximately 20%. Based on this, a revised formula for the calculation of average crack spacing is proposed in this article, and the results of these calculations align with the results obtained from the experiment. In addition, this study also demonstrates that the maximum cracking spacing calculated by adhering to Eurocode standards yielded no significant deviation as compared to the experimental results. However, owing to a difference in the crack width exceeding 20% being observed between the results obtained under Eurocode standards and the experimental results, the calculation methods need to be further improved for better applicability of high-strength reinforced rebars.

scholarly journals Effect of Water-Cement Ratio on Flexural Strength of RC Beams Made with Partial Replacement of Coarse Aggregates with Coarse Aggregates from Old Concrete

2019 ◽  
Vol 9 (1) ◽  
pp. 3826-3831
Author(s):  
M. Oad ◽  
A. H. Buller ◽  
B. A. Memon ◽  
N. A. Memon ◽  
Z. A. Tunio ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Flexural Strength ◽  
Concrete Beams ◽  
Recycled Concrete ◽  
Reinforced Concrete Beams ◽  
Partial Replacement ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Coarse Aggregates ◽  
Effect Of Water

This research paper presents an experimental evaluation of the effect of water-cement ratio on the flexural strength of reinforced concrete beams made with 50% replacement of coarse aggregates with recycled concrete aggregates (RCA). 72 reinforced concrete beams were cast using 0.54, 0.6, 0.65 and 0.70 water-cement ratio. In each ratio, 12 beams were cast using RCA and 3 beams were cast using all-natural coarse aggregates (NCA). Beams were cured for 7 and 28 days. After curing, all beams were tested with central point load in a universal load testing machine. From the obtained results, it is observed that the maximum reduction in flexural strength of RCA beams is about 28% when compared to the 0.54 w/c ratio beams of the same group and 31.75% in comparison to NCA beams cast with same w/c ratio. The maximum deflection and average strain in beams remained within limits. The observed cracking pattern shows shear failure of all beams.

scholarly journals Behavior Of A Confined Tension Lap Splice In High-Strength Reinforced Concrete Beams

2015 ◽  
Vol 23 (3) ◽  
pp. 1-8 ◽  
Author(s):  
Ahmed H. Abdel-Kareem ◽  
Hala Abousafa ◽  
Omaia S. El-Hadidi
Keyword(s):  
Compressive Strength ◽  
High Strength Concrete ◽  
Concrete Beams ◽  
High Strength ◽  
Experimental Results ◽  
Experimental Program ◽  
Transverse Reinforcement ◽  
Displacement Ductility ◽  
Lap Splice ◽  
Strength Concrete

Abstract The results of an experimental program conducted on seventeen simply supported concrete beams to study the effect of transverse reinforcement on the behavior of the lap splice of a steel reinforcement in tension zones in high-strength concrete beams are presented. The parameters included in the experimental program were the concrete compressive strength, the lap splice length, the amount of transverse reinforcement provided within the splice region, and the shape of the transverse reinforcement around the spliced bars. The experimental results showed that the displacement ductility increased and the mode of failure changed from a splitting bond failure to a flexural failure when the amount of the transverse reinforcement in the splice region increased, and the compressive strength increased up to 100 MPa. The presence of the transverse reinforcement around the spliced bars had a pronounced effect on increasing the ultimate load, the ultimate deflection, and the displacement ductility. The prediction of maximum steel stresses for spliced bars using the ACI 318-05 building code was compared with the experimental results. The comparison showed that the effect of the transverse reinforcement around spliced bars has to be considered into the design equations for lap splice length in high-strength concrete beams.

scholarly journals Intelligent Predicting System for Modeling of Flexurally – Strengthened Reinforced Concrete Beams with CFRP Laminates

2014 ◽  
Vol 61 (1) ◽  
pp. 25-42
Author(s):  
Ibrahim M. Metwally
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Artificial Neural Network ◽  
Reinforced Concrete ◽  
Flexural Strength ◽  
Concrete Beams ◽  
Rc Beams ◽  
Ann Model ◽  
Flexural Strengthening ◽  
Cfrp Laminates

Abstract In the last years, a great number of experimental tests have been performed to determine the ultimate strength of reinforced concrete (RC) beams retrofitted in flexure by means of externally bonded carbon fiber-reinforced polymers (CFRP). Most of design proposals for flexural strengthening are based on a regression analysis from experimental data corresponding to specific configurations which makes it very difficult to capture the real interrelation among the involved parameters. To avoid this, an intelligent predicting system such as artificial neural network (ANN) has been developed to predict the flexural capacity of concrete beams reinforced with this method. An artificial neural network model was developed using past experimental data on flexural failure of RC beams strengthened by CFRP laminates. Fourteen input parameters cover the CFRP properties, beam geometrical properties and reinforcement properties; the corresponding output is the ultimate load capacity. The proposed ANN model considers the effect of these parameters which are not generally account together in the current existing design codes with the purpose of reaching more reliable designs. This paper presents a short review of the well-known American building code provisions (ACI 440.2R-08) for the flexural strengthening of RC beams using FRP laminates. The accuracy of the code in predicting the flexural capacity of strengthened beams was also examined with comparable way by using same test data. The study shows that the ANN model gives reasonable predictions of the ultimate flexural strength of the strengthened RC beams. Moreover, the study concludes that the ANN model predicts the flexural strength of FRPstrengthened beams better than the design formulas provided by ACI 440

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