Diversified Application of Alkali-activated Lightweight Materials in the Construction Field

Abstract

Foam concrete is a lightweight construction material with excellent thermal and acoustic insulation properties. It is widely used in building envelopes, partitioning walls, sandwich components, etc. However, the foam concrete most commonly applied is made with Portland cement, which consumes a lot of energy and emits a large amount of carbon dioxide during its production process. As a green binding material without clinker, alkali-activated materials fully utilize fly ash, slag, and other industrial solid wastes or by-products, which largely reduces carbon dioxide emissions.

After preparing alkali-activated foam concrete using fly ash and slag, we discovered that the alkali-activated lightweight concrete with a density range of 200 kg/m³–1200 kg/m³ exhibited exceptional mechanical properties (the compressive strength of the developed foam concrete ranged from 0.50 MPa to 44.98 MPa, while the flexural strength ranged from 0.22 MPa to 13.86 MPa) and possessed a stable structure with a high volume of pores. This highly porous structure suggests that the material could serve as a high-performance adsorbent for heavy metal recovery from wastewater. However, during the wastewater treatment process, we observed that low-density alkali-activated material tends to deform in wet environments. To address this, expanded polystyrene particles were explored as lightweight aggregates to support the production of foam concrete. However, because expanded polystyrene particle lacks adhesive properties, the bonding effectiveness between expanded polystyrene particle and the alkali-activated matrix became a key focus. Various modification methods were applied to expanded polystyrene particle, and the one that best enhanced the overall stability of the material was selected.

In addition to the aforementioned challenges, to further contribute to the reduction of carbon dioxide emissions, we also utilized carbon dioxide as a filling gas in the production of alkali-activated lightweight material. This study plays a significant role in energy conservation and emission reduction.

Date of Award	8 Sept 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Denvid LAU (Supervisor) & Cheuk Lun CHOW (Co-supervisor)