scholarly journals Flexural Stress-Strain Behavior of RC Beams made with Partial Replacement of Coarse Aggregates with Coarse Aggregates from Old Concrete: Part-2: Rich Mix

2018 ◽  
Vol 8 (5) ◽  
pp. 3338-3343 ◽  
Author(s):  
M. Oad ◽  
A. H. Buller ◽  
B. A. Memon ◽  
N. A. Memon ◽  
S. Sohu
Keyword(s):  
Construction Industry ◽  
Research Work ◽  
Testing Machine ◽  
Reinforced Concrete Beams ◽  
Partial Replacement ◽  
Flexural Stress ◽  
Stress Strain ◽  
Failure Patterns ◽  
Strain Behavior ◽  
Coarse Aggregates

Crowded city centers pose serious problems of infrastructure and associated facilities. Construction industry is obliged to opt for vertical construction in place of short height structures in order to meet with the needs. This leads to the generation of huge quantities of demolishing waste whose management is a serious issue. One of its best uses is its utilization in new concrete. Concrete is widely used in construction industry. Normally 1:2:4 mix is used, but the use of rich mix is also common in columns and elsewhere. Therefore, this research work focuses on evaluating the flexural stress-strain behavior of rich concrete mix beams made with 50% replacement of natural coarse aggregates with coarse aggregates from old concrete. A total of 12 reinforced concrete beams 1:1.5:3 ratio mix and 0.54 w/c ratio are prepared in two batches in 0.9mx0.15mx0.15m beams. In the first batch, natural coarse aggregates are replaced in 50% with coarse aggregates from demolished concrete and the second batch contains beams made with all-natural coarse aggregates. To reinforce the beams, 2#4 deformed bars are used in compression and tension zone along with #3 stirrups at 15cm c/c all along the length of the beam. In each batch, half of the beams are cured for 7 days and half for 28 days. After curing, all beams are tested for load, deflection, and strain in a universal load testing machine. All parameters are recorded at regular intervals and cracking and failure patterns are monitored. From obtained results, it is analyzed that the beams presented 11.68% reduction in flexural capacity. Cracking pattern and failure mode of the beams is similar to those of the control specimen.

scholarly journals Flexural Stress-Strain Behavior of RC Beams Made with Partial Replacement of Coarse Aggregates with Coarse Aggregates from Old Concrete: Part-1: 1:2:4 Ratio

2018 ◽  
Vol 8 (3) ◽  
pp. 3048-3053 ◽  
Author(s):  
M. Oad ◽  
A. H. Buller ◽  
B. A. Memon ◽  
N. A. Memon
Keyword(s):  
Reinforced Concrete ◽  
Urban Areas ◽  
Concrete Beams ◽  
Research Work ◽  
Reinforced Concrete Beams ◽  
Partial Replacement ◽  
Flexural Stress ◽  
Stress Strain ◽  
Strain Behavior ◽  
Coarse Aggregates

Occupancy, particularly in urban areas, requires more space than ever. Space constraints need erection of high rise buildings in place of short height buildings. This need demolishing of old structures which creates huge quantities of demolished concrete. One of its best disposals is its use in new concrete. Therefore, this research work uses 50% replacement of natural coarse aggregates with coarse aggregates from old concrete to study the flexural stress-strain behavior of reinforced concrete beams. Total of 12 reinforced concrete beams (900x150x150 mm) were cast with 2#4 bars in tension and 2#4 bars in compression zones. Ordinary Portland cement with hill sand and crush aggregate was used in 1:2:4 proportions. Water cement ratio used is 0.54. The beams were cast in two batches, one with 100% natural aggregates and another with 50% natural coarse aggregates replaced with coarse aggregates from old concrete. In each batch 3 beams were cured for 7 and 28 days respectively. After curing all beams were tested with central point load. The beams were monitored at regular intervals for load, displacement, strain and load until first crack. The beams under study were compared with the controlled specimen. The results were in good agreement with the normal concrete specimen. Maximum reduction in flexural stress is recorded as 8.8% for 7-day cured beams and 5.52% for 28-day cured specimen. Thus, the use of coarse aggregates from demolished concrete in new concrete is proved to be promising partial replacement of coarse aggregate in terms of flexural stress-strain relationship.

scholarly journals Effect of 12-hour fire on Flexural Behavior of Recyclable Aggregate Reinforced Concrete Beams

2019 ◽  
Vol 5 (7) ◽  
pp. 1533-1542 ◽  
Author(s):  
Abdul Hafeez Buller ◽  
Bashir Ahmed Memon ◽  
Mahboob Oad
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Research Work ◽  
Testing Machine ◽  
Point Load ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Partial Replacement ◽  
Load Testing ◽  
Coarse Aggregates

Fire being one of the hazards causes external and internal adverse effects on concrete. On the other hand, demolishing waste causes numerous environmental issues due to lack of proper disposal management. Therefore, this research work presents experimental evaluation of effect of 12-hur fire on flexural behavior of reinforced concrete beams made with partial replacement of natural coarse aggregates with coarse aggregates from demolished concrete. The model beams are prepared using both normal and rich mix. Natural coarse aggregates are replaced in 50% dosage. Also, the beams without recyclable aggregates are prepared to check the results of proposed beams. After 28-day curing all the beams are exposed to fire for 12-hour at 1000°C in purpose made oven, followed by testing in universal load testing machine under central point load. During the testing deflection, load, and cracks are monitored. Analysis of flexural behavior and cracking reveals that after 12-hour fire residual strength of the beams is 52%. This shows loss of the strength of reinforced concrete beams thus requires appropriate retrofitting decision before putting again the structure in service after fire. Observation of cracks shows that most of the beams failed in shear with minor flexural cracks. In comparison to the results of control specimen the proposed beams show good fire resistance. The outcome of the research will prove landmark for future scholars and help the industry personals in understanding the behavior of the material in fire.

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.

Nonlinear Rate-Dependent Stress-Strain Behavior of Light-Weight Textile Conveyor Belt

2011 ◽  
Vol 675-677 ◽  
pp. 453-456
Author(s):  
Ze Xing Wang ◽  
Jin Hua Jiang ◽  
Nan Liang Chen
Keyword(s):  
Loading Rate ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Conveyor Belt ◽  
Uniaxial Tensile ◽  
Stress Strain ◽  
Strain Behavior ◽  
Rate Dependent ◽  
Dependent Behavior

In order to investigate the effect of loading rate on the tensile performance, the uniaxial tensile experiments were conducted on universal testing machine under different loading rates (5 mm/min, 10mm/min, 50 mm/min, 100 mm/min and 150 mm/min), and a constant gage length equal to 200mm, resulting in loading strain rate of 4.17×10-4, 8.33×10-4/s, 4.17×10-3/s, 8.33×10-3/s,1.25×10-2/s, and the tensile stress-strain curves were obtained. The experimental results show that the tensile properties of the conveyor belt exhibit obvious rate-dependent behavior. In this paper, the rate sensitivity coefficient varied with loading rate, was calculated, and the nonlinear rate-dependent behavior was also investigated.

scholarly journals Incorporation of Rice Husk Ash as Partial Replacement of Cement in M40 Grade Concrete

2021 ◽  
Vol 9 (9) ◽  
pp. 1444-1447
Author(s):  
Musaib Bashir Dar
Keyword(s):  
Compressive Strength ◽  
Construction Industry ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Cement Mortar ◽  
Cement Content ◽  
Research Work ◽  
Industrial Wastes ◽  
Partial Replacement ◽  
Alternative Materials

Abstract: In this developing era concrete and cement mortar are widely used by the construction industry, with this development. Large number of industrial wastes are generated and if these wastes are not properly used it will create severe problems, keeping the environment in mind, concrete engineers are trying to find some alternative materials which will not only replaces the cement content but also improves strength of concrete. As we also know that during the manufacturing of cement large amount of Co2 is released into the environment, but if we use such material that will replace the quantity of cement content therefore indirectly, we are contributing towards the prevention of our planet from global warming and other pollutions. Also, in this research work the Rice Husk Ash is used. the rice husk ash obtained from the rice processing units, by adding this product with concrete, not only replaces the cement content but also increases the strength of concrete like compressive strength etc. The Rice husk ash was incorporated with concrete with varying percentages of 2.5% ,5% ,7.5%, & 10%. the proper codal precautions were followed during the manufacture of concrete cubes of 150x150x150mm. it was concluded that the strength of concrete increased by incorporated the rice husk ash. Keywords: Concrete, RHA, Compressive strength, Industrial wastes, Cement etc

scholarly journals Flexural Behavior of Reinforced RAC Beams Exposed to 1000°C Fire for 18 Hours

2019 ◽  
Vol 9 (3) ◽  
pp. 4225-4229
Author(s):  
A. H. Buller ◽  
M. Oad ◽  
B. A. Memon
Keyword(s):  
Shear Failure ◽  
Research Work ◽  
Testing Machine ◽  
Point Load ◽  
Recycled Aggregate ◽  
Flexural Behavior ◽  
Load Testing ◽  
Test Results ◽  
Coarse Aggregates ◽  
Fast Pace

In order to meet the socio-economic demands around the globe, construction industry not only consumes concrete at a very fast pace but also yields huge amounts of construction and demolishing waste. The phenomenon gives rise to environmental issues due to production of concrete ingredients and due to dumping of the waste. Therefore, one of the solutions is the production of green concrete utilizing demolished waste. This research work studies the effect of prolonged fire (18 hours) on the flexural behavior of reinforced concrete–recycled aggregate beams. The beams were using 50% replacement of natural coarse aggregates with demolished concrete. The beam samples were cast as both normal and rich mix concrete and were cured for 28 days. After curing, the beams were exposed to fire at 1000°C in a purpose made oven, followed by testing in a universal load testing machine under central point load. The test results show that the proposed beams (cast with rich mix) exhibited about 22% reduction in flexural strength. The failure mode of the beams was observed as shear failure.

scholarly journals Long Term Impact in Reinforced Recycled Concrete Beams Under 9-Month Loading

2019 ◽  
Vol 9 (3) ◽  
pp. 4140-4143
Author(s):  
M. Oad ◽  
A. H. Buller ◽  
B. A. Memon ◽  
N. A. Memon ◽  
S. Sohu
Keyword(s):  
Urban Areas ◽  
Concrete Beams ◽  
Testing Machine ◽  
Maximum Load ◽  
Point Load ◽  
Recycled Concrete ◽  
Partial Replacement ◽  
Green Concrete ◽  
Coarse Aggregates

Green concrete is an active area of research. Structural demolishing waste is a global serious problem, particularly in urban areas. This research paper presents the experimental evaluation of the effect of long term loading on reinforced green concrete beams. Three beams were cast with partial replacement of natural coarse aggregates with demolished old concrete. Three beams were cast with all-natural coarse aggregates to compare the results. The beams were mounted on purpose made frames for 9 months. Deflection, strain and cracking in beams were monitored on a daily basis. After 9 months, the beams were tested until failure in a universal load testing machine under central point load. It was observed that the proposed beams exhibited 3.55% reduction in maximum load caring capacity compared to control specimens. The obtained results show good performance of the proposed green concrete beams under 9-month long term loading.

Modeling of stress-strain relation of cement-treated sand under compression

2021 ◽  
Author(s):  
Khawaja Adeel Tariq ◽  
Takeshi Maki
Keyword(s):  
Research Work ◽  
Fixed Ratio ◽  
Uniaxial Stress ◽  
Limestone Powder ◽  
Compressive Behavior ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Behavior ◽  
Stress Strain Relation ◽  
Uniaxial Compressive Stress

AbstractThis research work has been conducted to model the uniaxial stress-strain compressive behavior of cement-treated sand and its post-peak softening area. The cylindrical specimens were produced by using limestone powder, sand and high early strength cement. The mixtures were made by using different ratios of water to cement with fixed ratio of limestone powder to cement and cement to sand. The stress-strain behavior in post-peak zone of cement-treated is adjusted with introduction of compression softening factor. Uniaxial compressive stress-strain relationships after amending the Japanese Society of Civil Engineers model are proposed. Finite element analysis shows that the suggested model estimates well the compressive behavior of cement-treated sand.

New Model for Hyper-Elastic Materials Behavior With an Application on Natural Rubber

2017 ◽  
Author(s):  
Ahmed G. Korba ◽  
Mark E. Barkey
Keyword(s):  
Natural Rubber ◽  
Test Data ◽  
Pure Shear ◽  
Testing Machine ◽  
Shear Loading ◽  
Least Square ◽  
Elastic Materials ◽  
Stress Strain ◽  
Strain Behavior ◽  
Hyper Elastic

This paper is concerned with defining a new Weight Function Based model (WFB), which describes the hyper-elastic materials stress-strain behavior. Numerous hyper-elastic theoretical material models have been proposed over the past 60 years capturing the stress-strain behavior of large deformation incompressible isotropic materials. The newly proposed method has been verified against the historic Treloar’s test data for uni-axial, bi-axial and pure shear loadings of Treloar’s vulcanized rubber material, showing a promising level of confidence compared to the Ogden and the Yeoh methods. A non-linear least square optimization Matlab tool was used to determine the WFB, Yeoh and Ogden models material parameters. A comparison between the results of the three models was performed showing that the newly proposed model is more accurate for uni-axial tension as it has an error value which is less than the Ogden and Yeoh models by 1.0 to 39%. Also, the parameters calculation by more than 95%, for the bi-axial and pure shear loading cases compared to the Ogden model. Natural rubber test specimens have been tensioned using a tensile testing machine and the WFB model was applied to fit the test data results showing a very good curve fitting with an average error of 0.44%.WFB model has reduced processing time for the model.

Experimental Research on Mechanical Performance of Self-Compacting Reinforced Concrete Beam with Recycled Coarse Aggregates

2011 ◽  
Vol 374-377 ◽  
pp. 1887-1890 ◽  
Author(s):  
Jing Li ◽  
Xian Feng Qu ◽  
Hai Yang Chen ◽  
Juan Li ◽  
Lin Jiang
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beam ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Testing Machine ◽  
Reinforced Concrete Beam ◽  
Recycled Concrete ◽  
The Self ◽  
Reinforced Concrete Beams ◽  
Coarse Aggregates

In order to study the mechanical performance of self-compacting reinforced concrete beam with recycled coarse aggregates, recycled concrete and recycled gravel were taken as coarse aggregates with the particle size from 50 to150mm, two groups of specimen of self-compacting reinforced concrete beams with recycled coarse aggregates were made. After seven days, their bending strength were tested using method of one-third point loaded of simple beam on the testing machine. The results showed that the recycled coarse aggregates are bonded closely with the self-compacting concrete, its bond performance is good; Compared to ordinary reinforced concrete beam, it shows a smaller stiffness and a bigger mid-span deflection. In addition, the different combination of recycled concrete could reduce the self-compacting reinforced concrete’s stiffness with recycled coarse aggregate and increase its deflection.

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