Investigations on carbon-sequestration optimization of recycled coarse-aggregate and its effects on concrete performances - Details

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Abstract：

Recycled　coarse-aggregate　(RCA)　derived　from　waste　concrete　can　be　re-used　for　concrete　preparation,　which　is　now　limited　due　to　its　drawbacks　such　as　micro-cracks,　high-porosity,　and　reduced　concrete　strengths.　To　remedy　these　deficiencies,　carbon-sequestration　was　employed　to　enhance　RCA　and　the　conditions　were　optimized,　including　the　temperature　(20　°C–40　°C),　pressure　(0.1　MPa–0.3　MPa),　time　(5　h–24　h)　and　initial　water　content　(25%–75　%).　There　parameters　were　optimized　based　on　the　orthogonal　test　with　scheme　L9(34),　which　was　evaluated　based　on　RCA　carbon-sequestration　amount　as　well　as　its　properties.　With　the　optimized　parameters,　RCA　was　enhanced　as　CRCA.　Both　RCA　and　CRCA　were　utilized　to　fully　replace　natural　coarse-aggregate　(NCA)　in　concrete　and　concrete　basic　performances　were　investigated　systematically,　including　strengths,　shrinkage　and　medium　transport　properties.　The　results　show　that　the　effects　of　carbon-sequestration　time　and　initial　water-content　of　aggregate　on　the　carbon-sequestration　efficiency　of　RCA　are　the　most　significant.　The　optimized　parameters　were　30　°C　temperature,　0.3　MPa　pressure,　24　h　time　and　25　%　initial　water　content　with　the　maximum　amount　of　carbon-sequestration　at　8.42　%.　The　carbon-sequestration　reduced　the　width　of　the　recycled　aggregate　interfacial　transition　zone　(ITZ)　in　concrete,　increased　the　microhardness　of　ITZ　and　mortar,　and　decreased　the　porosity　of　CRCA.　The　CRCA　elevated　the　compressive　strength,　splitting　tensile　strength　and　flexural　strength　of　the　concrete　(28d)　by　13.5　%,　8.5　%　and　7.4　%,　respectively.　The　drying　shrinkage　at　28d　of　RCA-concrete　was　decreased　by　12.0　%　when　RCA　was　replaced　with　CRCA,　however　with　the　CRCA　value　still　16.2　%　higher　than　that　of　NCA-concrete.　Moreover,　CRCA　can　decrease　the　medium　transport　coefficients　of　water,　chloride,　and　gas　in　concrete　when　compared　with　the　RCA-concrete　while　they　are　still　greater　than　those　of　NCA-concrete.　©　2024　Elsevier　Ltd

Keyword：

Carbon Chlorine compounds Compressive strength Concrete aggregates Durability Porosity Recycling Shrinkage Tensile strength

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[ 1 ] [Qian, Rusheng]Zhejiang Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology, Zhejiang University of Technology, Hangzhou; 310023, China
[ 2 ] [Qian, Rusheng]College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou; 310023, China
[ 3 ] [Lin, Wan-Wendner]Department of Civil Engineering, KU Leuven, Sint-Katelijne-Waver; 2860, Belgium
[ 4 ] [Yang, Chengqi]Zhejiang Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology, Zhejiang University of Technology, Hangzhou; 310023, China
[ 5 ] [Yang, Chengqi]College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou; 310023, China
[ 6 ] [Zhao, Ruze]Zhejiang Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology, Zhejiang University of Technology, Hangzhou; 310023, China
[ 7 ] [Zhao, Ruze]College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou; 310023, China
[ 8 ] [Ye, Zhibo]Zhejiang Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology, Zhejiang University of Technology, Hangzhou; 310023, China
[ 9 ] [Ye, Zhibo]College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou; 310023, China
[ 10 ] [Kong, Deyu]Zhejiang Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology, Zhejiang University of Technology, Hangzhou; 310023, China
[ 11 ] [Kong, Deyu]College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou; 310023, China
[ 12 ] [Zhang, Yong]College of Civil Engineering, Fuzhou University, Fuzhou; 350116, China