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 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 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.

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>

scholarly journals Effect of Different Types of Recycled Concrete Aggregates on Equivalent Concrete Strength and Drying Shrinkage Properties

2018 ◽  
Vol 8 (11) ◽  
pp. 2190 ◽  
Author(s):  
Sungchul Yang
Keyword(s):  
Compressive Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Concrete Strength ◽  
Drying Shrinkage ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Test Results ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates

Residual mortar attached to recycled concrete aggregate (RCA) always leads to a decrease in Young’s modulus and an increase in the drying shrinkage of RCA concrete, mainly due to an increase of total mortar volume. To overcome this inherent problem, the modified and equivalent mortar volume (EMV) methods were proposed by researchers. Despite the comparable test results, both models are still subject to the slump loss problem. Thus, under the same W/C (water to cement ratio) ratio and slump condition, this study assessed the influence of the modified EMV mix method on RCA concrete properties. A total of six mixes were proportioned using the modified EMV method with three different RCAs. Test results show that the concrete mixed with RCA produced from old PC concrete sleepers exhibited compressive strength, Young’s modulus, and flexural strength values within 2% variation, equivalent to those values of the companion natural aggregate concrete. In other mixes, compressive strength was found to decrease to 11–20%. It was observed that for 100% replacement of RCA mix, Young’s modulus increased to 10% and drying shrinkage increased to 8% only, while for 50% replacement of RCA mix, Young’s modulus decreased to 8% and drying shrinkage dropped to 4%.

scholarly journals Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength Concretes

Buildings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 167
Author(s):  
Mohammed Seddik Meddah ◽  
Ali Al-Harthy ◽  
Mohamed A. Ismail
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
Recycled Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Materials ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates ◽  
Normal Strength

Recycled materials are now widely used in various industrial sectors to enhance sustainability and reduce environmental charges. Using recycled aggregates in concrete production significantly lowers demand for natural aggregates and the amount of solid waste sent to landfills. This paper summarizes the main results of a study undertaken to design low and normal strength concrete with various replacement ratios of coarse recycled concrete aggregates (RCA). To persuade the concrete industry to use recycled materials as one of the main components of concrete produced, the overall mechanical and durability performances of the RCA-concrete should be close or even similar to the concrete made with natural ingredients. The present research adopted an approach that consists of designing a series of low and normal strength with RCA having an equal target 28-day design strength to the corresponding natural aggregates concrete but while varying the water–cement ratios (w/c). Coarse recycled concrete aggregates, obtained by crushing waste concrete debris collected from different construction and demolition waste sources, were used in three different proportions of 30%, 50% and 100% (by weight) to produce new concrete with various w/c ratios and different compressive strength grades. Concrete mixes produced with general use Portland cement and various RCA contents were investigated in terms of their key mechanical and durability performances. The mechanical properties (crushing value) of the used RCA were visibly lower than the natural coarse aggregates (NCA). Thus, RCA-concrete showed lower performance than the NCA-concrete. It was found that by using up to 30% coarse RCA, the mechanical properties of concrete were not significantly affected. Beyond 30% of partial replacement of NCA by the coarse RCA, a continuing decrease in the mechanical performance with an increase in RCA amount was found. However, reducing the w/c ratio of concrete designed with the coarse RCA resulted in a compressive strength improvement, a better resistance to sulphate attack, carbonation, and chloride ion penetrations. Additionally, a proper design of Portland cement concrete produced with various proportions of RCA could also contribute to promoting sustainability in the construction industry and lowering its environmental impact.

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.

Influence of Waste Concrete Aggregates on the Performance and Durability of OPC Concrete

2005 ◽  
Vol 2 (2) ◽  
pp. 49
Author(s):  
Ahmad Ruslan Mohd Ridzuan ◽  
Azmi Ibrahim ◽  
Abdul Manaff Mohd Ismail
Keyword(s):  
Compressive Strength ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Moisture Condition ◽  
Aggregate Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Waste Concrete

The effects of using crushed waste concrete as course aggregates upon compressive strength and carbonation were investigated. Waste concrete cubes, which had been tested for compressive strength in compliance with construction specification, were crushed and utilized as coarse recycled aggregates in new concrete. It is important to mention that, in order to simulate the real life conditions, waste concrete with very minimal information about its originality was used in its natural moisture condition. Tests on the aggregates showed that the recycled concrete aggregates have lower specific gravity and bulk density but have higher water absorption capacity than the natural aggregates. The resistance to mechanical actions such as impact and crushing for recycled concrete aggregates is also lower. Concrete mixes with design strength of 30 N/mm2, 35 N/mm2 and 40 N/mm2 were prepared using this recycled aggregates as coarse aggregates and tested. From the strength point of view the recycled aggregate concrete compared well with natural aggregate concrete. Therefore, it could be considered for various potential applications. With respect to resistance to carbonation the recycled aggregate concrete shows comparable performance.

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.

scholarly journals Effect of Recycled Concrete Aggregates on Compressive Strength and Water Permeability of Concrete

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Compressive Strength ◽  
Negative Impact ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Coarse Aggregates ◽  
Natural Aggregates

This paper discusses the effects of recycled concrete aggregates (RCA) on compressive strength and permeability of recycled aggregate concrete (RAC) by using recycled concrete aggregates as a replacement of natural coarse aggregates (NCA). Four replacement percentages were used to study the effect of replacement. Replacement percentages used were 30%, 50%, 70% and 100% with 0% replacement was used as control. Mix design of 1:1.24:2.6 was used in the study with water to cement ratio of 0.43. Influence of RCA on compressive strength was determined for all the mixes as per ASTM C39 standard. The permeability of all the mixes was determined by measuring absorption, sorptivity and Darcy’s coefficient. Results of compressive strength indicated that concrete with 30% replacement of NCA can be successfully used in structural concrete without compromising too much on strength. Whereas, the replacement of natural aggregates with RCA has a negative impact on the permeability of concrete at all replacement levels. Absorption, sorptivity and permeability of natural aggregate concrete is lower as compared to RAC with 30% replacement showing the better performance as compared to other replacement ratios.

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.

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