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 Impact of Long-Term Loading on Reinforced Concrete Beams Made with Partial Replacement of Coarse Aggregates with Recycled Aggregates from Old Concrete

2019 ◽  
Vol 9 (1) ◽  
pp. 3818-3821 ◽  
Author(s):  
M. Oad ◽  
A. H. Buller ◽  
B. A. Memon ◽  
N. A. Memon
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Recycled Concrete ◽  
Reinforced Concrete Beams ◽  
Partial Replacement ◽  
Short Term ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Coarse Aggregates ◽  
Sustained Loading

This research work presents an experimental evaluation of the effect of sustained loading on reinforced concrete beams made with 50% replacement of natural coarse aggregates with aggregates from old concrete. A total of 9 RC beams were cast, 6 with natural coarse aggregates and 3 with recycled concrete aggregates. All beams were cured for 28 days in standard fashion. Among the first batch, 3 beams were used to test under short term loading till failure. An application of 50% of short-term loading followed on all beams assembled on purpose made frames. All beams were monitored for deflection, strain, and cracking. Both deflection and strain remained within limits. Crack monitoring revealed maximum crack width 0.5 mm. After six months of sustained load, beams were removed from the frames and tested in universal load testing machine with central point load till failure. The load-deflection pattern of all beams was observed to be almost similar and 22.12% higher in recycled concrete beams than all-natural aggregate beams. The results show promising use of recycled concrete aggregates in new concrete subjected to sustained loading.

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 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 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.

Air-coupled Nonlinear Ultrasonic Test for Reinforced Concrete Beams

2018 ◽  
Author(s):  
Jason Maximino C. Ongpeng ◽  
Kenneth Guevarra ◽  
Sohichi Hirose
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Second Harmonic ◽  
Ultrasonic Test ◽  
Test Method ◽  
Reinforced Concrete Beams ◽  
Bending Test ◽  
Harmonic Amplitude ◽  
Cement Ratio ◽  
Water Cement Ratio

<p>Air-coupled ultrasonic test is a non-destructive test method for investigating damage in material. In this paper, reinforced concrete beams with one 8-mm diameter rounded bar were casted and tested under four-point bending test with water-cement ratio of 40% and 60%. The transducers were placed and focused on the horizontal surface with induced 3mm notch at the midpoint where maximum tension occurred and crack formation was located. Frequency domain waveform was used specifically to analyze second harmonic generation (SHG). There were two metrics used under the SHG, these were: second harmonic amplitude (SHA) and second harmonic ratio (SHR). The SHR proved to be consistent for both water-cement ratio and it behaved increasing as damage in tension increases.</p>

scholarly journals Influence of recycled concrete aggregates on the shear strength of reinforced concrete beams

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Allan Carvalho Cardoso ◽  
Isaque Guerreiro Lima ◽  
Maurício de Pina Ferreira ◽  
Rafael Alves de Souza
Keyword(s):  
Shear Strength ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Experimental Tests ◽  
Recycled Concrete ◽  
Reinforced Concrete Beams ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Coarse Aggregates ◽  
Theoretical Results

ABSTRACT: This research evaluates the influence of the replacement of natural coarse aggregates (NCA) by recycled concrete aggregates (RCA) on the shear strength of reinforced concrete beams. Experimental tests on six reinforced concrete beams with RCA replacement ratios of 0%, 30%, and 100% are presented. Furthermore, a database with results of 170 tests on beams with RCA is used to discuss adjustments in the recommendations presented by ABNT NBR 6118 to estimate the shear strength of reinforced concrete beams. According to the Demerit Points Classification (DPC) proposed by Collins, 80% of the theoretical results obtained using models I and II from the Brazilian code fall in an appropriate safety condition range, showing that the substitution of NCA by RCA has a low impact on the shear strength reinforced concrete beams.

scholarly journals Statistical and Reliability Study on Shear Strength of Recycled Coarse Aggregate Reinforced Concrete Beams

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3321
Author(s):  
Hyunjin Ju ◽  
Meirzhan Yerzhanov ◽  
Alina Serik ◽  
Deuckhang Lee ◽  
Jong R. Kim
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Construction Material ◽  
Safety Margin ◽  
Shear Capacity ◽  
Reinforced Concrete Beams ◽  
Construction And Demolition Waste ◽  
Demolition Waste ◽  
Rc Structures ◽  
Coarse Aggregates

The consumption of structural concrete in the construction industry is rapidly growing, and concrete will remain the main construction material for increasing urbanization all over the world in the near future. Meanwhile, construction and demolition waste from concrete structures is also leading to a significant environmental problem. Therefore, a proper sustainable solution is needed to address this environmental concern. One of the solutions can be using recycled coarse aggregates (RCA) in reinforced concrete (RC) structures. Extensive research has been conducted in this area in recent years. However, the usage of RCA concrete in the industry is still limited due to the absence of structural regulations appropriate to the RCA concrete. This study addresses a safety margin of RCA concrete beams in terms of shear capacity which is comparable to natural coarse aggregates (NCA) concrete beams. To this end, a database for reinforced concrete beams made of recycled coarse aggregates with and without shear reinforcement was established, collecting the shear specimens available from various works in the existing literature. The database was used to statistically identify the strength margin between RCA and NCA concrete beams and to calculate its safety margin based on reliability analysis. Moreover, a comparability study of RCA beams was conducted with its control specimens and with a database for conventional RC beams.

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