Optimization of gas-solid carbonation conditions of recycled aggregates using a linear weighted sum method. (July 2021)

• Record Type: Journal Article
• Authors: Sojobi, Adebayo Olatunbsoun; Xuan, Dongxing; Li, Long; Liu, Songhui; Poon, Chi Sun
• Is Part Of: Developments in the built environment. Volume 7(2021)
• Publication Date: 2021-07
• Subjects: Recycled concrete aggregates -- Gas-solid carbonation -- Pretreatment -- Temperature -- Optimization -- Wastewater -- Durability; RCA Recycled coarse aggregates -- RAC Concrete prepared with recycled coarse aggregates -- CDW Construction and demolition wastes -- NA Natural aggregates -- NAC Concrete prepared with natural aggregates -- RMA Regular mortar aggregates -- CS Compressive strength -- PC Pressurized carbonation -- FCSE Optimized conventional carbonation -- FC Conventional carbonation -- RAC-FC Concrete prepared with 24-h carbonated recycled coarse aggregates (RCA) -- RAC-PC Concrete prepared with pressurized carbonated RCA -- RAC-FCSE Concrete prepared with optimized carbonated RCA -- NSC24-25 Regular mortar aggregates non-sprayed and carbonated for 24 h @ 25 °C -- SC24-40 Regular mortar aggregates wastewater-sprayed, non-dried and carbonated for 24 h @ 40 °C -- SC12-60 Regular mortar aggregates wastewater-sprayed, non-dried and carbonated for 12 h @ 60 °C -- SA12C6-60 Regular mortar aggregates wastewater sprayed 12-h air dried and carbonated for 6 h @ 60 °C -- SE6C6-60 Regular mortar aggregates wastewater sprayed, 6 h dried in environmental chamber and carbonated for 6 h @ 60 °C -- MHnew mortar Microhardness of new mortar surrounding the regular mortar aggregate -- MHRMA Microhardness of the carbonated and uncarbonated regular mortar aggregate -- BD Bulk density -- WA Water absorption -- BEC Bulk electrical conductivity; Civil engineering -- Periodicals; Sustainable construction -- Periodicals; 624.05
• DOI: 10.1016/j.dibe.2021.100053
• Languages: English
• ISSNs: 2666-1659

Abstract

Abstract: Optimization of pretreatment and various gas-solid interaction conditions is necessary for effective carbonation of recycled coarse aggregates derived from concrete wastes (RCA). This study demonstrated the use of linear weighted sum method to simultaneously optimize the pretreatment and carbonation test conditions. The optimization of the test conditions produced simplified, and eco-friendly pretreatments and drastically reduced the carbonation duration of RCA from 72 h to 3 weeks in previous studies to 18 h in this study. In addition, the optimum experimental conditions were validated by casting concrete using the carbonated RCAs. The optimized pretreatment and carbonation conditions were spraying Ca 2+ -rich wastewater at a level of 60% of the 24 h water absorption of RCA, 12 h air drying and 6 h carbonation at 60 °C. This study also demonstrated that wastewater derived from ready-mix concrete batching plants can be utilized for spraying the RCAs to improve carbonation efficiency. Also, the mechanical and durability properties of concrete prepared with RCAs produced from the optimized conventional carbonation and pressurized carbonation were similar. Therefore, optimized conventional carbonation can be utilized as an alternative to pressurized carbonation. The improved mechanical and durability properties of concrete prepared with carbonated RCAs were attributed to the improved physical properties of carbonated RCAs and improved microhardness of the interfacial transition zone of the new mortar. The simplified, faster, ecofriendly, optimized pretreatment and carbonation conditions opens a new vista for industrial carbonation applications and optimization of gas-solid interactions. Highlights: Pretreatment of recycled concrete aggregates by carbonation improved mechanical properties and durability of concrete with recycled concrete aggregates. Optimized carbonation conditions: Spray wastewater at a level of 60% water absorption of RCA, 12 h air drying, carbonation at 60 °C for 6 h. Optimization benefits: Improved microhardness, reduced water absorption of RCA and reduced processing time. Pressurized and optimized conventional carbonation achieved similar mechanical and durability properties. Wastewater from concrete batching plants enhances quality of recycled aggregates through carbonation treatment.