Date of Award

12-25-2025

Thesis Type

PhD

Document Type

Thesis

Divisions

Faculty of Engineering

Department

Department of Civil Engineering

Institution

Universiti Malaya

Abstract

The construction industry plays a crucial role in global development but faces significant environmental challenges, particularly CO2 emissions from cement production. Gypsum blocks provide a sustainable alternative to traditional cement concrete blocks. However, the low mechanical strength and water resistance of gypsum materials limit the widespread adoption of gypsum-based materials in the construction industry. This study initially produced gypsum-based blocks using compression forming, adding supplementary cementitious materials (SCMs), and subjecting accelerated carbonation curing (ACC). It was found that compression forming addressed the shortcomings of traditional block manufacturing (high energy consumption and long production time), and the addition of SCMs generated secondary hydration products (AFt and C-S-H) within the gypsum-based materials, improving mechanical strength and water resistance. In addition, Basic oxygen furnace slag (BOFS), an industrial by-product, has shown potential as a SCMs. By gradually replacing ground granulated blast funace slag (GGBS) with BOFS in gypsum-based blocks, the results indicated that increasing the BOFS content enhanced the alkalinity and water content of the reaction system, promoting hydration reactions. Additionally, the morphology of C-S-H transitioned from an amorphous form to a fibrous structure with superior mechanical properties. Although BOFS, when entirely replacing GGBS, effectively enhanced the 28-day compressive strength of gypsum-based blocks by up to 28.2 %, its low reactivity and porous nature meant that high BOFS dosages reduced early-age compressive strength and water resistance. Compared with specimens incorporating GGBS as an SCMs, early-age and water-saturated compressive strengths decreased by up to 22.2 % and 54.8 %, respectively. Therefore, this study further explored ACC to improve the early strength and water resistance of gypsum-based blocks containing BOFS and provide permanent CO2 sequestration. By adjusting the forming parameters (compaction pressure (CP) and waterto- binder (w/b) ratio) and carbonation curing conditions (carbonation time and CO2 concentration), a balance between carbonation and hydration reactions was achieved, which enhanced the block’s applicability and ensured effective carbonation. The results showed that gypsum-based blocks containing 20 % BOFS, cured for 2 days under 20 % CO2 concentration with 20 MPa CP and a 0.20 w/b ratio, generated sufficient carbonation products (CaCO3 and SiO2-rich gel), which effectively filled the internal pores of the samples and triggered subsequent hydration reactions, further improving both early and later-stage compressive strength and water resistance. Compared with the corresponding non-carbonated specimens, the 2-day, 28-day, and water-saturated strengths increased by 37.6 %, 16.4 %, and 30.8 %, respectively. Additionally, each ton of these specimens could sequester approximately 40 kg of CO2, and the generated carbonates effectively immobilized heavy metals in the samples. The final life cycle assessment showed that the gypsum-based blocks subjected to ACC achieved reductions of 96.1 % in global warming potential and 87.7 % in energy consumption compared with cement-based products, demonstrating clear advantages in lowering carbon emissions and advancing more sustainable construction practices. Meanwhile, they also attained desirable mechanical strength and water resistance, confirming their sustainability efficiency.

Comments

Thesis (PhD) - Faculty of Engineering, Universiti Malaya, 2025.

Note

sms

Download

Share

COinS