Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength Concretes
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...
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| Format: | Article |
| Language: | English |
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MDPI AG
2020-09-01
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| Series: | Buildings |
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| Online Access: | https://www.mdpi.com/2075-5309/10/9/167 |
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| author | Mohammed Seddik Meddah Ali Al-Harthy Mohamed A. Ismail |
| author_facet | Mohammed Seddik Meddah Ali Al-Harthy Mohamed A. Ismail |
| author_sort | Mohammed Seddik Meddah |
| collection | DOAJ |
| description | 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 (<i>w</i>/<i>c</i>). 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 <i>w</i>/<i>c</i> 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 <i>w</i>/<i>c</i> 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. |
| first_indexed | 2024-03-10T16:13:03Z |
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| institution | Directory Open Access Journal |
| issn | 2075-5309 |
| language | English |
| last_indexed | 2024-03-10T16:13:03Z |
| publishDate | 2020-09-01 |
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| series | Buildings |
| spelling | doaj.art-d58ca31ac0bf41c3869e4849df1b3dde2023-11-20T14:21:56ZengMDPI AGBuildings2075-53092020-09-0110916710.3390/buildings10090167Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength ConcretesMohammed Seddik Meddah0Ali Al-Harthy1Mohamed A. Ismail2Department of Civil & Architectural Engineering, Sultan Qaboos University, Al-Khod 123, OmanDepartment of Civil & Architectural Engineering, Sultan Qaboos University, Al-Khod 123, OmanDepartment of Civil Engineering, Miami College of Henan University, Kaifeng 475004, ChinaRecycled 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 (<i>w</i>/<i>c</i>). 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 <i>w</i>/<i>c</i> 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 <i>w</i>/<i>c</i> 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.https://www.mdpi.com/2075-5309/10/9/167carbonationchloride ingressdurabilitymechanical propertiesrecycled concrete coarse aggregatessulphate attack |
| spellingShingle | Mohammed Seddik Meddah Ali Al-Harthy Mohamed A. Ismail Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength Concretes Buildings carbonation chloride ingress durability mechanical properties recycled concrete coarse aggregates sulphate attack |
| title | Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength Concretes |
| title_full | Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength Concretes |
| title_fullStr | Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength Concretes |
| title_full_unstemmed | Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength Concretes |
| title_short | Recycled Concrete Aggregates and Their Influences on Performances of Low and Normal Strength Concretes |
| title_sort | recycled concrete aggregates and their influences on performances of low and normal strength concretes |
| topic | carbonation chloride ingress durability mechanical properties recycled concrete coarse aggregates sulphate attack |
| url | https://www.mdpi.com/2075-5309/10/9/167 |
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