# Developing Mineral Foam Blocks from Oil Shale Byproducts through Accelerated Carbonation

## TL;DR

This paper investigates using accelerated carbonation to make sustainable wall blocks from oil shale byproducts, improving strength and CO2 capture.

## Contribution

The study introduces a novel method for producing mineral foam blocks using oil shale ash and accelerated carbonation to enhance performance and CO2 sequestration.

## Key findings

- Carbonated samples showed higher compressive strength (2.5–5.7 MPa) compared to uncarbonated ones (1.1–3.4 MPa).
- ACC treatment maximized CO2 sequestration (∼140 kg/ton) while maintaining structural integrity.
- Carbonation-induced densification reduced porosity and improved microstructure through CaCO3 formation.

## Abstract

This study explores the impact of accelerated carbonation
curing
(ACC) on the production of sustainable mineral foam blocks (MFBs)
for wall applications. MFBs were prepared with varying proportions
of cement (CEM-I 42.5R) and oil shale ash (OSA), achieving 70–85%
residual resource integration. Aluminum powder acted as a pore-forming
agent to create the foamed structure. ACC conditions (100% CO2, 1 bar, ∼65% RH) enhanced performance metrics, which
were evaluated by compressive strength, density, porosity, and CO2 uptake values. OSA incorporation can offer advantages in
thermal properties of MFBs, yet without ACC treatment, the strength
development of MFBs was primarily governed by cement hydration. Carbonated
samples exhibited higher compressive strength (2.5–5.7 MPa)
than uncarbonated ones (1.1–3.4 MPa). The analyses revealed
partial carbonation of certain hydrated calcium-silicate and ettringite
phases, while portlandite formed during hydration reactions was nearly
fully converted to calcite. This conversion maximized CO2 sequestration (∼140 kg/ton), while maintaining a balanced
strength. The role of anhydrite was found to be primarily pH dependent, participating in secondary reactions that
enhanced the microstructure and integrity in conjunction with calcium
silicate hydrates (C–S–H), calcium–silicate­(aluminum)-hydrate
(C–S­(A)–H), ettringite, and gypsum. Mineralogical and
microstructural analyses confirmed the formation of CaCO3 in various morphologies. Carbonation-induced densification, primarily
driven by CaCO3 precipitation and transformation of amorphous
phases, resulted in a more compact microstructure with reduced porosity.
These findings demonstrate that ACC treatment improves MFB performance,
optimizing high-volume OSA use while achieving significant CO2 mineralization, advancing sustainable construction.