Enhancing mechanical properties and CO2 capture in mortar using calcium lime waste through dry pre-conditioning and accelerated CO2 curing

Abstract

This research explores the efficacy of dry pre-conditioning treatment coupled with accelerated CO₂ curing for mortar incorporating unreactive Calcium Lime Waste (CLW), with a specific focus on enhancing mechanical properties and CO₂ capture. The investigation was initiated by characterizing the CLW material through various microstructural examinations and toxicity tests using the Toxicity Characteristic Leaching Procedure (TCLP). Different proportions of CLW (0–40%) were blended into Ordinary Portland Cement (OPC) mortar, and their performance was systematically compared with that of control samples. The assessment parameters encompassed physical properties (workability and density), mechanical properties (compressive strength), and CO₂ capturing properties (carbonation depth) over the initial 24 h, scrutinized under both atmospheric air and accelerated CO₂ carbonation curing conditions. Thermogravimetric analysis (TGA), X-ray diffraction, and Mercury Intrusion Porosimetry (MIP) tests were conducted on the identified optimum CLW mortar, which was cured under accelerated CO2 carbonation conditions. The results exhibited that CLW is extremely rich in calcium and demonstrates the behavior of Ca(OH)₂, making it an excellent material for capturing CO₂. Despite exhibiting higher porosity than cement mortars, the optimum CLW mortar combination met the standard’s strength requirements for non-loadbearing structural applications. Additionally, the Advanced Neural Networks (ANN) model was designed to predict mortar properties—namely, compressive strength and carbonation depth—by learning from input features, including cement content, CLW content, and curing conditions. It was revealed that an increase of 1% in cement content enhanced the compressive strength by approximately 0.2406 MPa, while curing conditions such as CO2 exposure and dry pre-conditioning significantly impacted the carbonation depth, with adjustments up to 2.7692 mm under specific conditions. By absorbing CO₂ and incorporating it into mortars, CLW enhances durability and strength, making it a key step toward developing sustainable materials.