scholarly journals Mechanical Properties of Concrete with Recycled Concrete Aggregate and Fly Ash

Recycling ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 23
Author(s):  
Ihab Katar ◽  
Yasser Ibrahim ◽  
Mohammad Abdul Malik ◽  
Shabir Hussain Khahro
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Tensile Tests ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Hardened Concrete ◽  
Recycled Concrete Aggregate ◽  
Replacement Level ◽  
Split Tensile Strength ◽  
Hardened State

Recycled concrete aggregate (RCA) collected from the demolition of old reinforced concrete structures can be reused to prepare structural and non-structural concrete, thereby protecting the environment by preserving natural resources. This study explores RCA’s use, collected from the crushed concrete of different building projects in Riyadh, to manufacture fresh self-compacting concrete (SCC) and investigate its properties in the fresh and hardened state. Four SCC mixes were prepared by replacing natural aggregate (NA) with RCA at 0%, 25%, 50%, and 75% replacement levels. The water-cement (w/c) ratio was maintained constant at 0.38 for all the mixes. Slump Flow, J-ring, and V-funnel tests were performed on the SCC mixes in the fresh state, and the compressive strength of hardened concrete was determined after seven, 14, and 28 days. Water absorption and split tensile tests were also carried out for all the mixes. The findings revealed that it is possible to reach compressive strengths higher than 40 MPa at 28 days for RCA replacement level of 75% by using a superplasticizer and low w/c ratio. The decrease in compressive strength concerning the SCC-NA mix was 25% for 75% replacement level. The highest split tensile strength at 28 days was around 3.3 MPa for a 50% replacement level. The lowest water absorption was 3.2% for SCC-NA, which was gradually increased and was highest at 5.6% for 75% replacement level.

EFFECT OF RECYCLED CONCRETE AGGREGATE QUALITY ON PROPERTIES OF CONCRETE

2020 ◽  
Vol 15 (2) ◽  
pp. 57-69
Author(s):  
Daniel Hatungimana ◽  
Şemsi Yazıcı ◽  
Ali Mardani-Aghabaglou
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Water Absorption ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Hardened Concrete ◽  
Recycled Concrete Aggregate ◽  
Waste Concrete ◽  
Concrete Production

ABSTRACT The possibility of the use of recycled aggregates from the construction industry in green concrete production is of increasing importance to reduce the negative environmental impact associated with construction and demolition wastes. The objective of this study is to investigate the effect of recycled concrete aggregate (RCA) quality on the properties of hardened concrete properties such as compressive strength, splitting tensile strength, density, water absorption capacity and porosity accessible to water. The RCA used in this study was obtained from the crushing of waste concrete with two different compressive strengths (LRCA obtained from the crushing of waste concrete having compressive strengths below 30 MPa and HRCA obtained from the crushing of waste concrete having compressive strengths above 30 MPa). The natural coarse limestone aggregate was 100% replaced with coarse LRCA and HRCA. As a result of the study, the use of 100% HRCA and %100 LRCA instead of limestone coarse aggregate in the concrete adversely affected its mechanical and physical properties. In addition, HRCA showed better performance in terms of compressive strength, tensile strength, water absorption and porosity compared to the use of LRCA. Furthermore, the percentage of adhered mortar on the surface of LRCA and HRCA was analyzed using a computerized micro tomography device, and it was found that the percentages of attached mortar and aggregates are 61% and 35.5% for LRCA, whilst the attached mortar and aggregate contents for HRCA are 45.9% and 53.7%, respectively.

Effect of Recycled Concrete Aggregate Properties on Mixture Proportions of Structural Concrete

2012 ◽  
Vol 2290 (1) ◽  
pp. 105-114 ◽  
Author(s):  
Liam Butler ◽  
Jeffrey S. West ◽  
Susan L. Tighe
Keyword(s):  
Compressive Strength ◽  
Water Demand ◽  
Coarse Aggregate ◽  
Cement Content ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Hardened Concrete ◽  
Recycled Concrete Aggregate ◽  
Aggregate Properties ◽  
Equivalent Control

This study focuses on characterizing several recycled concrete aggregate (RCA) sources, developing concrete mixture proportions that incorporate RCA as coarse aggregate, and investigating the effect of coarse aggregate properties on the main mixture proportion parameters [i.e., cement content, water demand, and water–cement (w/c) ratio]. Four aggregate types were investigated: one control virgin aggregate source and three RCAs produced from the crushing of hardened concrete. Numerous aggregate tests, including density, absorption, abrasion resistance, adhered mortar content, and crushing value, were performed. Fourteen mixture proportions were developed with the use of three mixture proportion scenarios (control, direct replacement, and strength based) and two compressive strength levels (40 and 60 MPa). The effect of RCA on compressive strength and workability was evaluated by replacement of natural coarse aggregate with RCA. Contrary to numerous studies, one of the RCA concretes (RCA-1) had compressive strengths up to 12% higher than the equivalent control mixture. Mixture proportions (water, cement, and w/c ratio) were later adjusted to ensure that the RCA concretes had compressive strength and slump values similar to the control concretes. Variations in water demand, cement content, and w/c ratio could then be directly attributed to the properties of the RCA source. RCA-1 concrete required less cement (and a higher w/c ratio) to achieve strengths and slumps similar to the control concrete. The findings and recommendations of this research will assist concrete producers, engineers, and field technicians involved in the selection of RCA sources in developing mixture proportions for structural-grade RCA concrete.

scholarly journals Properties of Concrete with Recycled Concrete Aggregate Containing Metallurgical Sludge Waste

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1448 ◽  
Author(s):  
Jan Pizoń ◽  
Jacek Gołaszewski ◽  
Mohamed Alwaeli ◽  
Patryk Szwan
Keyword(s):  
Compressive Strength ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Hardened Concrete ◽  
Recycled Concrete Aggregate ◽  
Metallurgical Waste ◽  
Illegal Mining ◽  
Marine Sand ◽  
Sludge Waste ◽  
Natural Aggregates

Sand has been considered to be something of an immeasurable quantity. There are many indications that this view is no longer valid and that the limiting of natural aggregates usage is doubly justified. Firstly, the extraction of natural aggregates is expensive and has a huge impact on the environment. The main issues in sand and gravel mining are the large areas that are affected, ground water level changes, illegal mining, unsuitability of desert and marine sand, and costs of transport. Secondly, metallurgical waste can be used as a substitute for natural aggregates. This is doubly beneficial—the waste is recycled and the use of natural aggregates is reduced. Waste is stored in landfills that take up large areas and there is also the possibility of ground and groundwater pollution by hazardous compounds. The research presented in this article focuses on the technological conditions of using metallurgical waste in its original form and as a component of recycled concrete aggregate (RCA). The use of metallurgical sludge waste or crushed or round RCA to produce concrete deteriorates the consistency and does not significantly affect the air content and density of the concrete mix. RCA lowers the density of hardened concrete. Metallurgical sludge waste or RCA usage adversely affect the absorbability and permeability of concrete. Concrete containing metallurgical sludge waste is of higher compressive strength after 7 and 28 days, with up to 60% of waste as a sand replacement. RCA concrete achieved higher compressive strength also.

scholarly journals The Influence of Discharge Time, Kind of Additive, and Kind of Aggregate on the Properties of Three-Stage Mixed Concrete

2018 ◽  
Vol 10 (11) ◽  
pp. 3862 ◽  
Author(s):  
Alena Sicakova ◽  
Karol Urban
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Discharge Time ◽  
Concrete Mixtures ◽  
Concrete Properties ◽  
Concrete Production ◽  
The Impact

Application of recycled aggregates (RA) for concrete production is limited due to their poor quality. While the environmental benefits of using the RA are well accepted, some unsolved problems prevent this type of material from wide application in structural concrete. The research and development of techniques which can minimize the adverse effect of RA on the concrete properties are highly requested. A specific mixing approach can also be helpful; here, mineral additives play a significant role for improvement of RA performance within the mixing process. However, delivery process can influence the homogeneity and uniformity of the concrete mixtures, resulting in negative effect on technical parameters. In this study, the impact of delivery time (0 min, 45 min, and 90 min) on the set of hardened concrete properties is presented while the three-stage mixing is used. Two kinds of additives—fly ash (FA) and recycled concrete powder (RCP)—were tested to coat the coarse fraction of recycled concrete aggregate (RCA) in the first step of mixing. For comparison, cement as coating material and natural aggregate instead the RCA were also used. The following parameters were tested after 28 days of setting and hardening: density, compressive strength, splitting tensile strength, water absorption capacity, and depth of penetration of water under pressure. Generally, 90 min of working with concrete mixtures left no significantly negative influence on tested characteristics. Based on ANOVA results, with prolonged discharge time, the changes in composition of the mixtures become less important for compressive strength, density, and water absorption.

scholarly journals Evaluation of the Feasibility of Recycled Concrete Aggregate for Producing Structural Concrete

2020 ◽  
Vol 220 ◽  
pp. 01098
Author(s):  
Mohammad Tabrez Ali ◽  
Ibadur Rahman ◽  
Nirendra Dev ◽  
Priyanka Singh
Keyword(s):  
Compressive Strength ◽  
Construction Materials ◽  
Recycled Concrete ◽  
Environmental Benefits ◽  
Mix Design ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Structural Concrete ◽  
Average Value ◽  
Maximum Compressive Strength

When sustainability has become a primary measure of the selection of the building materials in the construction industry over the past decades, researchers all around the world have been looking upon for alternatives to reduce the overall environmental impact of the construction materials while not compromising the strength and durability. The factors like manufacturing, reusability, recyclability, disposal etc, are the criteria of utmost attention affecting the overall life cycle impact of the construction materials. In this prospect the Recycled Concrete Aggregate (RCA) has shown up as an exceptionally viable contender for the manufacturing of concrete with several environmental benefits over the Natural Aggregate (NA) and has already been identified by industry and several government agencies across the globe. The efficient material use of RCA can potentially deliver an inferior though competent concrete in comparison to the NA while averring the criteria of sustenance. The present study delves into the calculation of the proportion of the RCA in a mix design for achieving maximum compressive strength. The experimental setup constituted the casting of concrete cubes of control mix design of M40 grade with proportions of RCA varying from 0-100 percent spread over a space of 10% with NA which were later put to tests. The thorough investigation on the casted concrete cubes lead to the conclusion that the mix design with 50% proportion of RCA in addition to 50% proportion of NA delivered the maximum compressive strength, an average value of 8.23% higher than that of the normal concrete and the highest Rebound Number, an average value of 53.92 for the M40 grade concrete thereby showcasing the feasibility of producing structural concrete with RCA. The results are asserted to be governed by the better bonding between the RCA and NA and due to the significant increase in the water retention capacity by the provision of RCA in the mix.

scholarly journals The influence of recycled concrete aggregate on the properties of concrete

2018 ◽  
Vol 162 ◽  
pp. 02020 ◽  
Author(s):  
Nisreen Mohammed ◽  
Kaiss Sarsam ◽  
Mazin Hussien
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Modulus Of Rupture ◽  
Concrete Aggregate ◽  
Hardened Concrete ◽  
Recycled Coarse Aggregate ◽  
Natural Aggregates

Use of Recycled Coarse Aggregate (RCA) in concrete can be described in terms of environmental protection and economy. This paper deals with the mechanical properties of concrete compressive strength, splitting tensile strength, modulus of elasticity, and modulus of rupture. Three kinds of concrete mixtures were tested, concrete made with Natural Coarse Aggregate (NCA) as a control concrete and two types of concrete made with recycled coarse aggregate (50% and 100% replacement level of coarse recycled aggregate). These kinds of concrete were made with different targets of compressive strength of concrete f ’c (35MPa) and (70 MPa). Fifty specimens were tested of the fresh and hardened properties of concrete. The waste concrete from laboratory test cubes was crushed to produce the Recycled Coarse Aggregate used in recycled concrete. A comparative between the experimental results of the properties for fresh and hardened concrete is presented in the paper. Recycled aggregate concrete (RCA) had a satisfactory performance despite the replacement ratios. It was found using the size of Recycled Coarse Aggregate (RCA) of (5-14) mm has quite similar in performance with the same size of Natural Coarse Aggregate (NCA), it is necessary to use high quality of recycled concrete (with low levels of impurities). Recycled aggregate as an alternative to natural aggregates -seems quite successful.

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