scholarly journals Evaluation of Eco-Efficient Concretes Produced with Fly Ash and Uncarbonated Recycled Aggregates

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7499
Author(s):  
Miren Etxeberria
Keyword(s):  
Fly Ash ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Conventional Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Carbonation Resistance ◽  
Chloride Resistance ◽  
Natural Aggregates

The fabrication of conventional concrete, as well as remains from demolition, has a high environmental impact. This paper assessed the eco-efficiency of concrete made with uncarbonated recycled concrete aggregates (RCA) and fly ash (FA). Two concrete series were produced with an effective water/cement ratio of 0.50 (Series 1) and 0.40 (Series 2). In both series, concretes were produced using 0% and 50% of RCA with 0%, 25% and 50% FA. After analysing the compressive strength, and carbonation and chloride resistance of those concretes, their eco-efficiency based on the binder intensity and CO2-eq intensity was assessed. We found that the use of 50% uncarbonated RCA improved the properties of concretes produced with FA with respect to using natural aggregates. The concrete made of 25% FA plus RCA was considered the most eco-efficient based on the tests of compressive, carbonation and chloride properties with the values of 4.1 kg CO2 m−3 MPa−1, 76.3 kg CO2 m−3 mm−1 year0.5 and 0.079 kg CO2 m−3 C−1, respectively. The uncarbonated RCA improved carbonation resistance, and FA improved chloride resistance. It can be concluded that the use of 50% un-carbonated RCA combined with FA considerably enhanced the properties of hardened concrete and their eco-efficiency with respect to concretes produced with natural aggregates.

scholarly journals Modulus and Strength of Concretes with Alternative Materials

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4378
Author(s):  
Ana Elisabete Paganelli Guimarães de Avila Jacintho ◽  
Ivanny Soares Gomes Cavaliere ◽  
Lia Lorena Pimentel ◽  
Nádia Cazarim Silva Forti
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Model Code ◽  
Alternative Materials ◽  
Model Code 2010 ◽  
The Difference ◽  
Natural Aggregates ◽  
Predicted Values

This paper presents a study with concretes produced with natural aggregates, recycled concrete aggregates (RCA) and waste porcelain aggregates (WPA). The study analyzed the influence of recycled aggregates in the mechanical properties of conventional concretes and evaluated the difference between measured and predicted values of elasticity modulus. The incorporation of WPA in concrete showed better mechanical results compared to the concretes produced with RCA. Measured elasticity moduli were lower than moduli predicted by NBR 6118:2014 and fib Model Code 2010, while measured results were greater than values predicted by Eurocode 2:2004 and ACI 318:2014, as expected, which indicated the safety of the latter two standards.

scholarly journals Investigation of the Use of Recycled Concrete Aggregates Originating from a Single Ready-Mix Concrete Plant

2018 ◽  
Vol 8 (11) ◽  
pp. 2149 ◽  
Author(s):  
Eleftherios Anastasiou ◽  
Michail Papachristoforou ◽  
Dimitrios Anesiadis ◽  
Konstantinos Zafeiridis ◽  
Eirini-Chrysanthi Tsardaka
Keyword(s):  
Soil Stabilization ◽  
Coarse Fraction ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Fine Aggregate ◽  
Waste Products ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Concrete Mixtures

The waste produced from ready-mixed concrete (RMC) industries poses an environmental challenge regarding recycling. Three different waste products form RMC plants were investigated for use as recycled aggregates in construction applications. Crushed hardened concrete from test specimens of at least 40 MPa compressive strength (HR) and crushed hardened concrete from returned concrete (CR) were tested for their suitability as concrete aggregates and then used as fine and coarse aggregate in new concrete mixtures. In addition, cement sludge fines (CSF) originating from the washing of concrete trucks were tested for their properties as filler for construction applications. Then, CSF was used at 10% and 20% replacement rates as a cement replacement for mortar production and as an additive for soil stabilization. The results show that, although there is some reduction in the properties of the resulting concrete, both HR and CR can be considered good-quality recycled aggregates, especially when the coarse fraction is used. Furthermore, HR performs considerably better than CR both as coarse and as fine aggregate. CSF seems to be a fine material with good properties as a filler, provided that it is properly crushed and sieved through a 75 μm sieve.

scholarly journals Evaluation of the Ecotoxicological Potential of Fly Ash and Recycled Concrete Aggregates Use in Concrete

2020 ◽  
Vol 10 (1) ◽  
pp. 351 ◽  
Author(s):  
Patrícia Rodrigues ◽  
José D. Silvestre ◽  
Inês Flores-Colen ◽  
Cristina A. Viegas ◽  
Hawreen H. Ahmed ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Daphnia Magna ◽  
Raw Materials ◽  
Construction Materials ◽  
Recycled Concrete ◽  
Experimental Program ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates

This study applies a methodology to evaluate the ecotoxicological potential of raw materials and cement-based construction materials. In this study, natural aggregates and Portland cement were replaced with non-conventional recycled concrete aggregates (RA) and fly ash (FA), respectively, in the production of two concrete products alternative to conventional concrete (used as reference). The experimental program involved assessing both the chemical properties (non-metallic and metallic parameters) and ecotoxicity data (battery of tests with the luminescent bacterium Vibrio fischeri, the freshwater crustacean Daphnia magna, and the yeast Saccharomyces cerevisiae) of eluates obtained from leaching tests of RA, FA, and the three concrete mixes. Even though the results indicated that RA and FA have the ability to release some chemicals into the water and induce its alkalinisation, the respective eluate samples presented no or low levels of potential ecotoxicity. However, eluates from concrete mixes produced with a replacement ratio of Portland cement with 60% of FA and 100% of natural aggregates and produced with 60% of FA and 100% of RA were classified as clearly ecotoxic mainly towards Daphnia magna mobility. Therefore, raw materials with weak evidences of ecotoxicity could lead to the production of concrete products with high ecotoxicological potential. Overall, the results obtained highlight the importance of integrating data from the chemical and ecotoxicological characterization of materials’ eluate samples aiming to assess the possible environmental risk of the construction materials, namely of incorporating non-conventional raw materials in concrete, and contributing to achieve construction sustainability.

Influence of the Crushing Process of Recycled Aggregates on Concrete Properties

2014 ◽  
Vol 634 ◽  
pp. 151-162 ◽  
Author(s):  
Diogo Pedro ◽  
Jorge de Brito ◽  
Luís Evangelista
Keyword(s):  
Water Absorption ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Efficient Production ◽  
Capillary Water ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Carbonation Resistance ◽  
Chloride Penetration Resistance ◽  
Durability Performance

This work intends to evaluate the (mechanical and durability) performance of concrete made with coarse recycled concrete aggregates (CRCA) obtained using two crushing processes: primary crushing (PC) and primary plus secondary crushing (PSC). This analysis intends to select the most efficient production process of recycled aggregates (RA). The RA used here resulted from precast products (P), with strength classes of 20 MPa, 45 MPa and 65 MPa, and from laboratory-made concrete (L) with the same compressive strengths. The evaluation of concrete was made with the following tests: compressive strength; splitting tensile strength; modulus of elasticity; carbonation resistance; chloride penetration resistance; capillary water absorption; and water absorption by immersion. These findings contribute to a solid and innovative basis that allows the precasting industry to use without restrictions the waste it generates.

Polymer Based Treatments Applied on Recycled Concrete Aggregates

2013 ◽  
Vol 687 ◽  
pp. 514-519 ◽  
Author(s):  
Valerie Spaeth ◽  
Assia Djerbi Tegguer
Keyword(s):  
Material Flow ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Sustainable Material ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates

The recycling of concrete, bricks and masonry rubble as concrete aggregates is an important way to contribute to a sustainable material flow. However, there are still various uncertainties limiting the widespread use of recycled concrete aggregates (RCA). The fluctuations in the composition of grade recycled aggregates and their influence on the properties of fresh and hardened concrete are of particular concern regarding the use of RCA. So, the reuse of RCA is still limited. That’s why an efficient polymer based treatment is proposed in order to reuse RCA easier.

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.

Overcoming the limitations of recycled concrete aggregates in Belgium

2021 ◽  
Author(s):  
Talina Zeidan ◽  
Xavier Farina
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Structural Concrete ◽  
Environmental Aspect ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates ◽  
Walloon Region ◽  
Ready Mix Concrete

<p>In Belgium, the presence of numerous quarries in the Walloon region makes recycled concrete aggregates (RCA) less attractive for structural concrete applications: since the natural aggregates are at reach, it is unprofitable from both a financial and an environmental aspect to use RCA. In addition, the supply of recycled aggregates on the Belgian market is lacking. Only a few recyclers produce type A+ RCA, which could be used in ready-mix concrete, but tend to keep them for their own productions. Furthermore, although the revised Belgian national concrete standard (NBN B 15- 001) allows cast-in-situ concrete to contain higher fractions of recycled aggregates, there is presently no concrete supplier yet certified to produce concrete with recycled aggregates. One should finally note the lack of stimulation or even mandatory incentives by the Authorities to promote the use of RCA. The aim of this paper is to identify the various reasons behind RCA limitations in Belgium and to suggest solutions to overcome them.</p>

Effect of Recycled Concrete Aggregates and Natural Pozzolana on Rheology of Self-Compacting Concrete

2014 ◽  
Vol 600 ◽  
pp. 256-263 ◽  
Author(s):  
Said Kenai ◽  
Belkacem Menadi ◽  
Amina Debbih ◽  
El Hadj Kadri
Keyword(s):  
Rheological Properties ◽  
High Volume ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Fresh Properties ◽  
Self Compacting Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Pozzolana ◽  
Natural Aggregates

Self-compacting concrete (SCC) is a very fluid concrete in which its compaction can take place under the effect of its own weight, without vibration. SCC is characterized by its high volume of paste, and the use of superplasticizers. Very little work is reported in the literature on the use of recycled aggregates in SCC. The main objective of this paper is to study the effect of coarse and fine recycled concrete aggregates on the fresh properties of SCC, by substitution of either 100% or 50% of natural aggregates by recycled aggregates. The effect of substitution of 15% by weight of cement of natural pozzolana on the fresh properties of SCC is also studied. The results have shown that the substitution of 50% or 100% of natural aggregates by recycled concrete aggregates gives SCC with very comparable rheological properties to that of the reference SCC. However, SCC with recycled aggregates are less stable against bleeding. The addition of natural pozzolana decreases workability for both SCC with natural aggregates or with recycled aggregates.

scholarly journals Study Concerning Characterization of Some Recycled Concrete Aggregates

2016 ◽  
Vol 12 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Ion Robu ◽  
Claudiu Mazilu ◽  
Radu Deju
Keyword(s):  
Los Angeles ◽  
Road Construction ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Mechanical Resistance ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Los Angeles Test ◽  
Water Behavior ◽  
Natural Aggregates

Abstract Using recycled concrete aggregates (RCA) is a matter of high priority in the construction industry worldwide. In countries like the Netherlands, Denmark, Germany, USA, Japan, France recycled concrete aggregates obtained from demolition are valorized up to 90%, mainly for road construction and less in the manufacture of new concrete. Recycled concrete aggregates (RCA) generally result from a two-stage crushing of the concrete obtained from demolition followed by the screening and removal of contaminants (wood, plastic, metal, ceramics etc.). The literature review showed that the recycled aggregates concrete (RAC) are less resistant, with 15 to 40% versus concrete obtained using natural aggregates. The factors that play a role in the reducing of mechanical resistance are presented and analyzed in this study. This paper presents a study on the use of recycled aggregates, from a concrete of specified class, to acquire new cement concrete with different percentages of recycled aggregates. In order to evaluate the influence upon the properties of the new concrete obtained, recycled aggregates have been characterized in terms of the granulosity, the granule shape, the absorption of water, behavior to the Los Angeles test, the content of attached mortar etc.

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