scholarly journals Bond to Bar Reinforcement of PET-Modified Concrete Containing Natural or Recycled Coarse Aggregates

Environments ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 8
Author(s):  
Joseph J. Assaad ◽  
Jamal M. Khatib ◽  
Rawan Ghanem
Keyword(s):  
Steel Fibers ◽  
Recycled Aggregates ◽  
Test Results ◽  
Coarse Aggregates ◽  
Water To Cement Ratio ◽  
Concrete Production ◽  
Steel Bars ◽  
The Matrix ◽  
Concrete Mechanical Properties ◽  
Mixing Water

The use of post-consumer plastics in concrete production is an ideal alternative to dispose of such wastes while reducing the environmental impacts in terms of pollution and consumption of natural resources and energy. This paper investigates different approaches (i.e., reducing water-to-cement ratio and incorporating steel fibers or polymeric latexes) that compensate for the detrimental effect of waste plastics on the drop in concrete mechanical properties including the bond to embedded steel bars. The polyethylene terephthalate (PET) wastes used in this study were derived from plastic bottles that were shredded into small pieces and added during concrete batching at 1.5% to 4.5%, by total volume. Test results showed that the concrete properties are degraded with PET additions, given their lightweight nature and poor characteristic strength compared to aggregate particles. The threshold PET volumetric rates are 4.5% and 3% for concrete made using natural or recycled aggregates, respectively. The reduction of w/c from 0.55 to 0.46 proved efficient to refine the matrix porosity and reinstate the concrete performance. The incorporation of 0.8% steel fibers (by volume) or 15% polymers (by mixing water) were appropriate to enhance the bridging phenomena and reduce the propagation of cracks during the pullout loading of steel bars.

scholarly journals Evaluation of the Effects of Coarse Aggregate Sizes on Concrete Quality

2017 ◽  
Vol 2 (10) ◽  
pp. 1 ◽  
Author(s):  
Lawrence Echefulechukwu Obi
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Aggregate Size ◽  
Test Results ◽  
Construction Sites ◽  
Coarse Aggregates ◽  
Appreciable Increase ◽  
Concrete Production ◽  
Concrete Quality

This work was necessitated by the observations made at construction sites where artisans and craftsmen were left alone in concrete production. It was discovered that they used inadequate quantity and size of coarse aggregates due to difficulty associated in the mixing as if the coarse aggregates were not needed in concrete production. The research has established that the coarse aggregates and their sizes play critical roles in the development of adequate strength in concrete. It was observed that with proper mixing, the slump test results did not witness shear or collapse type of slump rather there were true slump in all cases of the test. The workability decreased with slight differences when the coarse aggregate size was increased. The increase in the coarse aggregates yielded appreciable increase in the compressive strength. It can therefore be inferred that the quality of concrete in terms of strength can be enhanced through an increase in the coarse aggregate size when proper mix ratio, batching, mixing, transporting, placing and finishings are employed in concrete productions.

INVESTIGATION OF EFFECTS OF RECYCLED AGGREGATES AND BLAST FURNACE SLAG ON PROPERTIES OF SELF-COMPACTING CONCRETE

2020 ◽  
Vol XVII (3) ◽  
pp. 1-14
Author(s):  
Leila Shahryari ◽  
Maryam Nafisinia ◽  
Mohammad Hadi Fattahi
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Blast Furnace Slag ◽  
Recycled Aggregates ◽  
Test Results ◽  
Self Compacting Concrete ◽  
Coarse Aggregates ◽  
Fine Aggregates ◽  
Negative Effect ◽  
Furnace Slag

The effects of simultaneous use of recycled aggregates and ground blast furnace slag as a percentage of cement-constituting materials on different properties of fresh self-compacting concrete (SCC) are investigated in this study. To this end, three series of SCC mixtures with a fixed volume of cement paste equalling 380 ltr/m3 (2.36 gal/ft3) and the replacement ratio of coarse aggregates (fifty percent and one hundred percent) and total aggregates (zero percent, fifty percent and one hundred percent) were prepared. The water content ratios in the first, second and third series were 0.4, 0.45, and 0.5, respectively. The results of the compressive strength tests for 7-day, 14-day and 28-day cubic specimens and compressive strength and Brazilian test results for 28-day cylindrical specimens were used as control parameters governing the SCC resistive quality. The results of fresh SCC tests (including slump-flow and T50 tests, V-funnel test, and L-box test) showed that the negative effect of recycled fine aggregates on fresh SCC properties is significantly more than that of recycled coarse aggregate. However, recycled SCC with acceptable properties can be obtained with a slight increase in the amount of superplasticisers used in the presence of slag.

Study on Losses of Self-Stress Created by Steel Fiber Reinforced Self-Stressing Concrete

2013 ◽  
Vol 438-439 ◽  
pp. 300-303 ◽  
Author(s):  
Bo Xin Wang ◽  
He Nan Jin ◽  
Teng Man
Keyword(s):  
Steel Fiber ◽  
Theoretical Models ◽  
Steel Fibers ◽  
Fiber Reinforced ◽  
Steel Bars ◽  
The Matrix ◽  
The Stability

Based on the 9-year-experiment of self-stressing concrete (SSC for short), the stability of self-stress caused by steel bars and steel fibers is investigated. The results show that the losses of self-stress are only from 0.6 MPa to 1.2 MPa during 2.5 years. Meanwhile the matrix of steel fiber reinforced self-stressing concrete (SFRSSC for short) has the characteristic of secondary expansion. Finally, according to the existing theoretical models, formulas of the losses of self-stress created by SFRSSC are obtained.

scholarly journals A Modular Approach for Steel Reinforcing of 3D Printed Concrete—Preliminary Study

2020 ◽  
Vol 12 (10) ◽  
pp. 4062
Author(s):  
Joseph J. Assaad ◽  
Abdallah Abou Yassin ◽  
Fatima Alsakka ◽  
Farook Hamzeh
Keyword(s):  
High Strength ◽  
Modular Approach ◽  
Test Results ◽  
Moment Capacity ◽  
Structural Applications ◽  
Steel Bars ◽  
The Matrix ◽  
3D Printed ◽  
Compressive And Flexural Strengths ◽  
Transverse Steel

3D concrete printing technology has considerably progressed in terms of material proportioning and properties; however, it still suffers from the difficulty of incorporating steel reinforcement for structural applications. This paper aims at developing a modular approach capable of manufacturing 3D printed beam and column members reinforced with conventional steel bars. The cubic-shaped printed modules had 240 mm sides, possessing four holes on the corners for subsequent insertion of flexural steel and grouting operations. The transverse steel (i.e., stirrups) was manually incorporated during the printing process. The reinforced 3D printed beams were built by joining the various modules using high-strength epoxy resins. Test results showed that the compressive and flexural strengths of plain (i.e., unreinforced) 3D printed specimens are higher than traditionally cast-in-place (CIP) ones, which was mostly attributed to the injected high-strength grout that densifies the matrix and hinders the ease of crack propagation during loading. The flexural moment capacity of 3D reinforced printed beams were fairly close to the ACI 318-19 code provisions; however, about 22% lower than companion CIP members. The reduction in peak loads was attributed to the modular approach used to construct the 3D members, which might alter the fundamentals and concepts of reinforced concrete design, including the transfer and redistribution of stresses at ultimate loading conditions.

A Study on the Use of Construction Wastes as Coarse Aggregates on High Performance Concrete

2010 ◽  
Vol 163-167 ◽  
pp. 1525-1531
Author(s):  
Chung Ming Ho ◽  
Wei Tsung Tsai
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Mechanical And Thermal Properties ◽  
Loss On Ignition ◽  
Coarse Aggregates ◽  
Flow Test ◽  
Water To Cement Ratio

In recent years, because of rising consciousness on environmental protection and the lacking of construction waste dumping yards, recycling of construction wastes has been promoted extensively. The purpose of this study is to ascertain the effect on properties of the fresh and harden concrete replacing coarse aggregates by construction wastes under ambient and enhanced temperatures exposure. This research mainly concentrates on high performance recycled concrete (HPRC); by adding different amount of superplasticizer into the HPRC and to test and compare its mechanical and thermal properties with general high performance concrete (HPC). Thereafter, tests are carried out determine its compressive strength, residual strength after high temperature and the loss on ignition of the HPRC mixed with two water-to-cement ratios and different replacement proportions of recycled aggregates. Similar tests, such as the slump test and slump flow test, are carried out both on the HPRC and HPC. When the water-to-cement ratio is 0.3 and the amount of superplasticizer added is 1.2%, HPRC has the best performance. The specimens with 100% recycled aggregates were 31% below the control concrete sample in compressive strength at age of 28 days. By the way of adding admixture, the recycled concrete could reach the demand strength of the HPC. The results show that it is feasible to allow a higher replacement percentage of construction wastes for producing concrete products.

scholarly journals Influence of hydraulic jigging of construction and demolition waste recycled aggregate on hardened concrete properties

2021 ◽  
Vol 14 (3) ◽  
Author(s):  
Iago Lopes dos Santos ◽  
Luciana Vanni Frantz ◽  
Angela Borges Masuero
Keyword(s):  
Recycled Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Demolition Waste ◽  
Coarse Aggregates ◽  
Concrete Properties ◽  
Concrete Production ◽  
Wide Scale

abstract: Concern with the maintenance of natural resources has increased research about recycled aggregates for concrete production. However, the heterogeneity of recycled aggregates is one of the main constraints for their use in practice, because it can generate variability in concrete properties, hence reducing their final quality. Then, the jigging has been seen as a promising way of improving recycled aggregate quality. This paper aimed to evaluate its use for better application in concrete. A modified jig was used to sort recycled coarse aggregates. Concrete were produced with water/cement ratio from 0.5 and 100% of recycled coarse aggregate. The recycled aggregate properties upgrade were achieved and the results of compressive strength and modulus of elasticity of recycled concrete made with aggregate which were submitted to jigging were increased, indicating a potential application in wide scale.

scholarly journals Mechanical characteristics of concrete containing basalt fiber and recycled aggregate

2021 ◽  
Vol 889 (1) ◽  
pp. 012044
Author(s):  
Hemant ◽  
Rachit Sharma ◽  
Ankush Thakur ◽  
Tiwary Kumar Aditya
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Mechanical Characteristics ◽  
Basalt Fiber ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Split Tensile Strength ◽  
Coarse Aggregates ◽  
Concrete Production ◽  
Negative Effect

Abstract The potential of construction waste as an alternative to the constituents of concrete has been generally examined to demonstrate their utility and ensure the climate and/or environment of its otherwise ill effects. The mechanical characteristics of concrete are investigated to comprehend its behaviour under compressive, tensile, and flexural loads. This experimental study investigates the effect of supplanting proportions of river aggregates with waste coarse aggregates in addition to the effect of basalt fiber additions on concrete mixes with (25 and 50%) substitutions of recycled waste coarse aggregates (RWCA). The workability of concrete mixes was negatively affected with recycled aggregates and/or basalt fiber inclusions. Using recycled aggregates with 25 and 50% replacements decreases the strength of concrete. On utilizing discrete proportions of basalt fiber with natural coarse aggregates, the strength was higher as compared to control mix however increasing the percentage of basalt fiber from 1% to 3% the compressive strength was reduced. On incorporating additions of basalt fiber with different proportions of RWCA, the strength of concrete was deteriorated as the percentage of fiber was increasing. For natural aggregates, the inclusion of fibers has negative effect on compressive strength however the tensile strength was increased with higher percentage of fibers. The inclusions of fibers to 25% recycled aggregate mixes, split tensile strength was much higher as compared to control mix. It was concluded that addition of basalt fibers provides a viable option to recycle recycled aggregate in concrete production.

On axial compressive behavior of steel fiber reinforced concrete confined by FRP

2021 ◽  
pp. 136943322098165
Author(s):  
Hossein Saberi ◽  
Farzad Hatami ◽  
Alireza Rahai
Keyword(s):  
Reinforced Concrete ◽  
Experimental Test ◽  
Steel Fiber ◽  
Experimental Tests ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Test Results ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Frp Confinement

In this study, the co-effects of steel fibers and FRP confinement on the concrete behavior under the axial compression load are investigated. Thus, the experimental tests were conducted on 18 steel fiber-reinforced concrete (SFRC) specimens confined by FRP. Moreover, 24 existing experimental test results of FRP-confined specimens tested under axial compression are gathered to compile a reliable database for developing a mathematical model. In the conducted experimental tests, the concrete strength was varied as 26 MPa and 32.5 MPa and the steel fiber content was varied as 0.0%, 1.5%, and 3%. The specimens were confined with one and two layers of glass fiber reinforced polymer (GFRP) sheet. The experimental test results show that simultaneously using the steel fibers and FRP confinement in concrete not only significantly increases the peak strength and ultimate strain of concrete but also solves the issue of sudden failure in the FRP-confined concrete. The simulations confirm that the results of the proposed model are in good agreement with those of experimental tests.

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