Toward net negative carbon for bricks using mechano-alkaline activated carbonated recycled concrete fines

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S0950061824040893

Authors

Peiyuan Chen, Xinliang Qian, Hu Fang, Jiankai Xie, Yonghui Wang, Rui Liang, Jialai Wang

30 October 2024

https://doi.org/10.1016/j.conbuildmat.2024.138947

Highlights

•MAM method was proposed for CRCF based on its silica gel-rich components.

•More sub-micrometer particles and Ca2+-modified aluminosilicates formed during MAM.

•The 3d strength of B-M/Ca-CRCF reaches 28.6 MPa, a 55.8 % increase over the control.

•60.38 kg CO2 can be sequestered with the production of 1 ton CRCF bricks.

Abstract

Utilizing the high-calcium and high-alkali contents of recycled concrete fine (RCF) for CO2 sequestration has emerged as a promising approach; nevertheless, the application of the carbonated RCF (CRCF) becomes a novel challenge due to its high water-absorption value and lower reactivity. This paper proposes a method for producing unfired bricks using CRCF through pressure and high-temperature steam curing. In this work, CRCFs were firstly treated with mechano-alkaline activated (MAM) and then the treated CRCF was used to prepare unfired brick. The MAW process refers to CRCF being milled with Ca(OH)2 at a ratio of 10:1. Experimental results showed that the MAW treatment can significantly reduce the particle size of CRCF and decrease its porosity. More importantly, MAW treatment of CRCF enables the formation of Ca2+-modified aluminosilicates (e.g., calcium silicate and calcium aluminosilicate) and increases the tendency toward framework disordering, leading to the promoting the formation of hydration products and refining the pore structure of unfired CRCF bricks. The 3 d compressive strength of unfired bricks with CRCF can be increased by 55.8 % by the MAW treatment. In addition, the net-CO2 balance for producing 1 t B-M-Ca/CRCF brick is −48.83 kg, making it a carbon-negative product.

Source: ScienceDirect