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A platform for research: civil engineering, architecture and urbanism
Resource recycling and carbon sequestration by carbonizing concrete washing wastewater of ready-mix concrete plant
Highlights Carbonated wastewater had uniform particles distribution and stable composition. Cement mixed with carbonated wastewater showed desired fresh and hardened properties. Calcite in the carbonated wastewater filled the pores of the hardened cement blocks. Using carbonated wastewater to produce concrete can reduce CO2 emissions by half.
Abstract Recycling the concrete washing wastewater (CWW) of ready-mix concrete plants is significantly important for saving hundreds of millions of tons of water and avoiding water and soil pollution. However, to directly recycle CWW to mix fresh concrete is particularly difficult due to its high alkalinity and high solid content with unstable compositions. To respond these challenges, a feasible approach involving carbonation treatment of CWW and subsequent recycling of the carbonized CWW (CCWW) for concrete mixing is proposed in this paper. To this end, the CWW carbonation test was firstly carried out and the compositional analysis showed that the CCWW became a stable suspension with uniform distribution of fine CaCO3 particles, stable ions contents and neural pH value. The effects of CWW, CCWW and the tap water on the fresh cement pastes hydration and the mechanical and deformation properties of hardened cement pastes were then comparatively analyzed. The results supported that CCWW contributed to the improvement of workability of fresh paste, the increase of strength, the decrease of dry shrinkage and the pore refinement of harden paste. Approximate 16.6 million tons of CO2 per year was estimated to be captured by this approach wemix concrete plants. Benefiting from the improved mechanical properties and extraordinary CO2 sequestration capability, recycling CCWW for concrete mixing resulted in nearly half reduction in CO2 emission.
Resource recycling and carbon sequestration by carbonizing concrete washing wastewater of ready-mix concrete plant
Highlights Carbonated wastewater had uniform particles distribution and stable composition. Cement mixed with carbonated wastewater showed desired fresh and hardened properties. Calcite in the carbonated wastewater filled the pores of the hardened cement blocks. Using carbonated wastewater to produce concrete can reduce CO2 emissions by half.
Abstract Recycling the concrete washing wastewater (CWW) of ready-mix concrete plants is significantly important for saving hundreds of millions of tons of water and avoiding water and soil pollution. However, to directly recycle CWW to mix fresh concrete is particularly difficult due to its high alkalinity and high solid content with unstable compositions. To respond these challenges, a feasible approach involving carbonation treatment of CWW and subsequent recycling of the carbonized CWW (CCWW) for concrete mixing is proposed in this paper. To this end, the CWW carbonation test was firstly carried out and the compositional analysis showed that the CCWW became a stable suspension with uniform distribution of fine CaCO3 particles, stable ions contents and neural pH value. The effects of CWW, CCWW and the tap water on the fresh cement pastes hydration and the mechanical and deformation properties of hardened cement pastes were then comparatively analyzed. The results supported that CCWW contributed to the improvement of workability of fresh paste, the increase of strength, the decrease of dry shrinkage and the pore refinement of harden paste. Approximate 16.6 million tons of CO2 per year was estimated to be captured by this approach wemix concrete plants. Benefiting from the improved mechanical properties and extraordinary CO2 sequestration capability, recycling CCWW for concrete mixing resulted in nearly half reduction in CO2 emission.
Resource recycling and carbon sequestration by carbonizing concrete washing wastewater of ready-mix concrete plant
Zhu, Jiahui (author) / Kang, Jiamin (author) / Liu, Zanqun (author)
2023-05-20
Article (Journal)
Electronic Resource
English
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