Valorising industrial limestone-slurry waste into low-carbon Portland-limestone cement based aircrete: packing density, thermo-mechanical performance and microstructural insights

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🔬研究者:The dual valorisation methodology and packing density analysis provide a framework for optimizing waste incorporation in low-carbon cement systems.

🏢実務担当者:The results show that thermally processed limestone slurry can be used as a clinker substitute, and unprocessed slurry can replace sand in foamed concrete, offering a cost-effective waste management solution.

🏛政策担当者:This study supports policies promoting industrial symbiosis and circular economy in construction, as it reduces both waste and carbon emissions.

This study develops a dual valorisation route for Kota stone slurry limestone waste (KSSLW) in low-carbon Portland limestone cement (PLC)-based cellular foamed concrete (CFC). In the first stage, thermally processed KSSLW was used as a 20% replacement of OPC-43 to synthesise a PLC binder. The optimised binder showed initial and final setting times of 116 min and 7.5 h, and compressive strengths of 35.8 and 45.7 MPa at 7 and 28 days, respectively. A preliminary energy-carbon balance showed that, after accounting for thermal processing energy and possible carbonate decomposition, the system still provided a net saving of about 72.2 kg CO₂-eq/t PLC, corresponding to an 8.2% reduction relative to OPC. In the second stage, unprocessed microfine KSSLW was used to replace fine river sand from 0% to 100% in CFC mixes with target dry densities of 1000 and 800 kg/m³. The optimum response was obtained at 50% KSSLW replacement, where microfine particles improved particle packing, reduced voids, and enhanced the strength performance factors. The compressive strength performance factors (PFc,28d) reached 329 and 299 for the 1000 and 800 kg/m³ CFC series, respectively. Packing density analysis showed maximum values of 0.63 in binary mixes and 0.67 in ternary mixes, while the void ratio decreased to 0.59 and 0.49, respectively. The optimised CFC also showed low thermal conductivity, with k values of 0.351 and 0.311 W/m.K for the 1000 and 800 kg/m³ series, respectively. Isothermal calorimetry, optical microscopy, Field Emission Scanning Electron Microscopy (FESEM) and National Institute of Standards and Technology (NIST)-based modelling confirmed that processed KSSLW promoted hydration, whereas unprocessed KSSLW acted mainly as an inert micro filler. The proposed PLC-CFC system offers a practical route for clinker reduction, river-sand conservation, slurry waste utilisation and lightweight thermal-insulating walling applications. From an applied perspective, the results demonstrated a dual valorisation route for Indian Kota stone slurry limestone waste i.e. the thermally processed fraction can be used as a 20% clinker-saving PLC component, while the unprocessed microfine fraction can replace up to 50% natural river sand in CFC blocks for non-load-bearing masonry, partition or infill wall units, and thermal-insulating building components. Thus, the proposed PLC-CFC system directly addresses slurry disposal, river-sand conservation, clinker-factor reduction, and the production of lightweight energy-efficient construction units.

• openalex https://doi.org/10.6084/m9.figshare.32587517first seen 2026-06-07 04:59:33 · last seen 2026-06-16 04:51:59