New Concrete with Recycled Aggregates from Leftover Concrete

2015 ◽  
Vol 754-755 ◽  
pp. 389-394
Author(s):  
Ofelia Corbu ◽  
Attila Puskás ◽  
Andrei Victor Sandu ◽  
Adrian M. Ioani ◽  
Kamarudin Hussin ◽  
...  
Keyword(s):  
Concrete Strength ◽  
Ecological Impact ◽  
Experimental Tests ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
River Sand ◽  
Coarse Aggregates ◽  
Concrete Type ◽  
Natural Aggregates

We live in an era where people should be more aware of pollution and its consequences. The present paper reveals a way protecting the environment while producing high quality concrete. What make this type of concrete environmentally friendly are the recycled aggregates in the concrete composition amongst with eliminating the ecological impact by saving large amounts of natural aggregates resources. Recycling concrete comes with many other advantages that lead to waste reduction, economy in waste transportation and storage taxes, which are becoming increasingly expensive. This research is based on mix design and experimental tests carried out on C20/25 strength class concrete with uncontaminated leftover concrete aggregates (LCAgg). It reveals favorable results in order to militate for recycled concrete aggregate uses in regular concrete strength classes respectively for common structural elements, mainly for slabs. River sand (0/4 mm) and coarse aggregates (4/8 mm and 8/16 mm): natural sources or recycled concrete type-alternatively used in several mixes-were utilized in concrete mixes.

scholarly journals Natural aggregate totally replacement by mechanically treated concrete waste

2015 ◽  
Vol 10 (1) ◽  
pp. 83-90
Author(s):  
Jozef Junak ◽  
Nadezda Stevulova
Keyword(s):  
Compressive Strength ◽  
Concrete Strength ◽  
Reference Sample ◽  
Average Density ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates ◽  
Recycled Material

Abstract This paper presents the results obtained from the research focused on the utilization of crushed concrete waste aggregates as a partial or full replacement of 4/8 and 8/16 mm natural aggregates fraction in concrete strength class C 16/20. Main concrete characteristics such as workability, density and compressive strength were studied. Compressive strength testing intervals for samples with recycled concrete aggregates were 2, 7, 14 and 28 days. The amount of water in the mixtures was indicative. For mixture resulting consistency required slump grade S3 was followed. Average density of all samples is in the range of 2250 kg/m3 to 2350 kg/m3. The highest compressive strength after 28 days of curing, 34.68 MPa, reached sample, which contained 100% of recycled material in 4/8 mm fraction and 60% of recycled aggregates in 8/16 mm fraction. This achieved value was only slightly different from the compressive strength 34.41 MPa of the reference sample.

scholarly journals Concrete produced with recycled aggregates

2012 ◽  
Vol 5 (5) ◽  
pp. 692-701 ◽  
Author(s):  
J. J. L. Tenório ◽  
P. C. C. Gomes ◽  
C. C. Rodrigues ◽  
T. F. F. de Alencar
Keyword(s):  
Coarse Aggregate ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Specific Mass ◽  
River Sand ◽  
Recycled Coarse Aggregate ◽  
Coarse Aggregates ◽  
Natural Aggregates

This paper presents the analysis of the mechanical and durable properties of recycled aggregate concrete (RAC) for using in concrete. The porosity of recycled coarse aggregates is known to influence the fresh and hardened concrete properties and these properties are related to the specific mass of the recycled coarse aggregates, which directly influences the mechanical properties of the concrete. The recycled aggregates were obtained from construction and demolition wastes (CDW), which were divided into recycled sand (fine) and coarse aggregates. Besides this, a recycled coarse aggregate of a specific mass with a greater density was obtained by mixing the recycled aggregates of the CDW with the recycled aggregates of concrete wastes (CW). The concrete was produced in laboratory by combining three water-cement ratios, the ratios were used in agreement with NBR 6118 for structural concretes, with each recycled coarse aggregates and recycled sand or river sand, and the reference concrete was produced with natural aggregates. It was observed that recycled aggregates can be used in concrete with properties for structural concrete. In general, the use of recycled coarse aggregate in combination with recycled sand did not provide good results; but when the less porous was used, or the recycled coarse aggregate of a specific mass with a greater density, the properties of the concrete showed better results. Some RAC reached bigger strengths than the reference concrete.

scholarly journals Bricks and Concrete Wastes as Coarse and Fine Aggregates in Sustainable Mortars

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Alessandra Mobili ◽  
Chiara Giosuè ◽  
Valeria Corinaldesi ◽  
Francesca Tittarelli
Keyword(s):  
Crack Formation ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Capillary Absorption ◽  
Recycled Concrete Aggregate ◽  
Environment Friendly ◽  
Fine Aggregates ◽  
Natural Aggregates ◽  
Coarse Recycled Concrete Aggregate

The total substitution by volume of natural coarse calcareous aggregate by coarse recycled brick aggregate (RBA) and coarse recycled concrete aggregate (RCA) has been investigated to produce more sustainable and environment-friendly mortars. Aggregates were also partially substituted by their fines at 12.5% by volume. Mortars have been tested in terms of mechanical, microstructural, and durability properties. Results show that it is feasible to replace a natural calcareous aggregate entirely by recycled aggregates. In particular, the obtained mortars, even if more porous and more prone to the water capillary absorption than that manufactured with natural aggregates, result in less stiffness and thus are less subjected to crack formation, more permeable to water vapour, and less susceptible to sulphate attack.

scholarly journals VERIFICATION OF THE BASIC PROPERTIES OF RECYCLED AND NATURAL AGGREGATES

2019 ◽  
Vol 22 ◽  
pp. 67-71
Author(s):  
Karel Mikulica ◽  
Iveta Hájková
Keyword(s):  
Recycled Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Building Structures ◽  
Recycled Concrete Aggregate ◽  
Apartment Building ◽  
Demolition Waste ◽  
Concrete Mixtures ◽  
Natural Aggregates

In the future, it is planned to use up to 50% of construction and demolition waste (C&DW) for the production of new building structures. This leads us to think about how we can use recycled concrete aggregate (RCA) as a substitute for natural aggregate (NA) in concrete mixtures. This is why we compare the two typical representatives of recycled aggregates with a representative of natural aggregates. As a representative of recycled aggregates, we chose pure concrete recycled from the cutting of concrete and mixed recyclate from the demolition of the apartment building. As a representative of natural stone, we chose the extracted aggregate.

scholarly journals The Influence of Fly Ash on the Compressive Strength of Recycled Concrete Utilizing Coarse Aggregates from Demolition Works

2021 ◽  
Vol 11 (3) ◽  
pp. 7107-7110
Author(s):  
V. T. Phan ◽  
T. H. Nguyen
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Recycled Concrete ◽  
Experimental Results ◽  
Strength Development ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Coarse Aggregates ◽  
Natural Aggregates

The compressive strength of recycled concrete with coarse aggregates with and without fly ash was studied in this paper. The recycled concrete was designed to have a compressive strength of Rn=15Mpa. The ratio of conventional aggregates and recycled coarse aggregates was 50-50. Fifteen samples for each recycled concrete aggregate had been cast and were tested 7, 14, and 28 days after curing. The experimental results indicate that the strength development of the two recycled concrete mixes is relatively uniform. Fly ash increased the compressive strength of recycled concrete by 11% for 7-day aged samples. The recycled concrete with fly ash had 7% less compressive strength than the concrete consisting of natural aggregates.

Possibilities of Recycled Concrete Aggregate in Cement-Based Flowscreed

2014 ◽  
Vol 897 ◽  
pp. 247-251
Author(s):  
Adam Hubáček ◽  
Luc Boehme ◽  
Iveta Nováková
Keyword(s):  
Mechanical Properties ◽  
Recycled Concrete ◽  
Experimental Results ◽  
Recycled Aggregates ◽  
Partial Replacement ◽  
Concrete Aggregate ◽  
Rheological Characteristics ◽  
Test Results ◽  
Recycled Concrete Aggregate ◽  
Natural Aggregates

This paper presents some test-results of using fine recycled concrete as a partial replacement of natural aggregates in cement-based flowscreed. Special attention is given to describing and studying rheological characteristics and mechanical properties of cement-based flowscreed. Experimental results indicate that it is possible to prepare flowscreed with partial replacement of natural aggregates by recycled aggregates and obtain a quality that meets the requirements. This study was partially connected to the research-project RecyFlowscreed [1].

scholarly journals Investigations of the structural characteristics of concrete produced from recycled aggregates at varying water/cement ratios

2020 ◽  
Vol 39 (3) ◽  
pp. 640-646
Author(s):  
A.W. Otunyo ◽  
B.G. Jephter
Keyword(s):  
Compressive Strength ◽  
Structural Characteristics ◽  
Absorption Capacity ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Natural Aggregate ◽  
Natural Aggregates

The paper tried to investigate the structural characteristics of concrete produced by partially replacing natural aggregates with recycled aggregates at varying water/cement ratios. The study is basically a laboratory experimental study. Water/cement ratio component of the concrete were varied at 0.40, 0.45, 0.50, 0.55, 0.60; while the natural aggregate was partially replaced with RCA of 0%, 15%, 30%, 45%, 60%, 75% and 90% for concrete productions for 7, 14 and 28 days structural characteristics. The densities, water absorption capacity and Compressive Strength of these concretes were determined. The results were presented in graphs and Tables. Results of the study indicate an increased compressive strength at low percentage of RCA and water /cement ratio values. There is a marginal difference between compressive strength of normal concrete and concrete produced by partial RCA of 15% replacement at 0.4 w/c ratio. Keywords: recycled concrete aggregate, natural aggregate, compressive strength, water/ cement ratio and natural aggregate concrete.

scholarly journals MECHANICAL AND PHYSICAL PROPERTIES OF RECYCLED AGGREGATES CONCRETE

2020 ◽  
Vol 29 (1) ◽  
pp. 259-274
Author(s):  
Mayara Turi Gerin ◽  
Almir Sales ◽  
Silvana De Nardin
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Water Absorption ◽  
Experimental Tests ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Recycled Concrete Aggregates ◽  
Additional Water ◽  
Mixing Method ◽  
Natural Aggregates

Aggregate type - natural or recycled - governs a range of concrete properties (e.g. water absorption and workability). Knowing this, there are many recommended mixing methods for maintaining concrete workability. However, they may be not economic feasible or they may depreciate mechanical properties. In this work, four concrete mixtures were produced replacing 0, 30, 50 and 100% of natural aggregates by recycled concrete aggregates without any pre-wetting method or additional water. Instead of, the “Two-Stage Mixing Approach” mixing method was used. From the experimental tests it was possible to observe the influence of the substitution content on the workability, water absorption ability, density, voids index, compressive strength, tensile strength and modulus of elasticity.  In addition, the tensile strength and elastic modulus values of recycled concrete were also compared to those obtained in the equations recommended by ABNT NBR 6118:2014 for concrete with natural aggregates. The results showed that it is possible to maintain the workability of concrete without depreciating its mechanical properties.

scholarly journals Towards Better Understanding of Concrete Containing Recycled Concrete Aggregate

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Hisham Qasrawi ◽  
Iqbal Marie
Keyword(s):  
Concrete Strength ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Normal Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Air Content ◽  
Significant Difference

The effect of using recycled concrete aggregates (RCA) on the basic properties of normal concrete is studied. First, recycled aggregate properties have been determined and compared to those of normal aggregates. Except for absorption, there was not a significant difference between the two. Later, recycled aggregates were introduced in concrete mixes. In these mixes, natural coarse aggregate was partly or totally replaced by recycled aggregates. Results show that the use of recycled aggregates has an adverse effect on the workability and air content of fresh concrete. Depending on the water/cement ratio and on the percent of the normal aggregate replaced by RCA, the concrete strength is reduced by 5% to 25%, while the tensile strength is reduced by 4% to 14%. All results are compared with previous research. As new in this research, the paper introduces a simple formula for the prediction of the modulus of elasticity of RCA concrete. Furthermore, the paper shows the variation of the air content of RAC.

scholarly journals Physical, Deformation, and Stiffness Properties of Recycled Concrete Aggregate

2021 ◽  
Vol 13 (8) ◽  
pp. 4245
Author(s):  
Katarzyna Gabryś ◽  
Emil Soból ◽  
Wojciech Sas
Keyword(s):  
Recycled Concrete ◽  
Experimental Program ◽  
Concrete Aggregate ◽  
Test Results ◽  
Recycled Concrete Aggregate ◽  
Granulometric Analysis ◽  
Stiffness Properties ◽  
Grain Distribution ◽  
Natural Aggregates ◽  
Critical Reduction

The construction sector is currently struggling with the reuse of waste originating from the demolition and modernization of buildings and roads. Furthermore, old buildings are gradually being replaced by new structures. This brings a significant increase of concrete debris to waste landfills. To prevent this, many studies on the possibilities of recycling concrete, known as recycled concrete aggregate (RCA), have been done. To broaden the applicability of reused concrete, an understanding of its properties and engineering behavior is required. A difficulty in sustainable, proper management of RCA is the shortage of appropriate test results necessary to assess its utility. For this reason, in the present study, the physical, deformation, and stiffness properties of RCA with gravely grain distribution were analyzed carefully in the geotechnical laboratory. To examine the mentioned properties, an extensive experimental program was planned, which included the following studies: granulometric analysis, Proctor and oedometer tests, as well as resonant column tests. The obtained research results show that RCA has lower values of deformation and stiffness parameters than natural aggregates. However, after applying in oedometer apparatus repetitive cycles of loading/unloading/reloading, some significant improvement in the values of the parameters studied was noticed, most likely due to susceptibility to static compaction. Moreover, some critical reduction in the range of linear response of RCA to dynamic loading was observed.

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