The construction industry, integral to national infrastructure development, faces environmental challenges attributed to Portland cement’s high energy consumption and carbon dioxide emissions during production. To address this challenge, this study integrated waste fly ash and polystyrene into geopolymers to enhance environmental sustainability and economic feasibility. The objectives included developing low-density geopolymers using polystyrene inclusion, optimizing component mixing ratios, assessing activator concentration effects, determining the optimal curing conditions, and characterizing the resulting geopolymers. Through experimental investigation, low-density geopolymers were developed with optimized component ratios and curing conditions. The experimental procedure began with the classification of fly ash to determine its suitability for various applications, revealing it to be type F. Geopolymers were fabricated using a mixture of fly ash, water, sodium hydroxide activator, and polystyrene. Varied concentrations of sodium hydroxide and polystyrene were employed. Two curing temperatures, 60 °C and 100 °C, were explored. The results showed that greater sodium hydroxide concentrations improved the structure and compressive strength of the geopolymers. The results also demonstrated a significant correlation between the curing conditions and the mechanical properties of the produced geopolymers. The goal of reducing the density of the geopolymers for lightweight thermal-resistant applications was achieved through polystyrene incorporation. However, polystyrene incorporation negatively impacted the compressive strength. The optimum production conditions for the sodium hydroxide-varied samples were 8 g sodium hydroxide/g sample cured at 100 °C, while the optimum production conditions for polystyrene-varied samples were 1 g polystyrene/g sample cured at 60 °C. The findings confirmed the viability of utilizing fly ash and polystyrene wastes to produce sustainable, low-density, thermal-resistant construction materials. Overall, increasing activator concentration enhances the strength and durability of geopolymers, while polystyrene contributes to the development of lightweight geopolymers, provided the appropriate amount is utilized. To ensure replicability, the formulation procedure and input quantities must be tailored according to the intended geopolymer application. These insights offer practical guidance for optimizing geopolymer manufacturing processes towards enhanced sustainability and performance.

Prior to this study, the thermal stability of fly ash-based geopolymer (FAG) construction materials as a function of cellulose nanocrystal (CNC) concentration and the optimal CNC dosage leading to thermal stability have not been investigated. This study investigates the influence of CNC reinforcement and curing duration on the thermal stability of FAG geopolymer. A series of samples incorporating CNC dosages ranging from 0 to 1.86 wt.% were prepared and subjected to 24- and 48-h curing regimes to evaluate their thermal degradation behaviors. Thermogravimetric analysis (TGA) revealed that 24-h-cured samples exhibited steeper weight losses compared to 48-h-cured ones, particularly in the 100–600 ℃ range. This trend was attributed to incomplete stabilization of organics in shorter curing times. Among all dosages, the 48-h-cured 1.7 wt.% CNC sample demonstrated the lowest total weight loss (~ 9.6% lower than the control), indicating enhanced thermal resistance. Derivative weight analysis further confirmed this, showing the lowest peak weight change rate (0.105%/℃) for the 1.7 wt.% CNC sample cured for 48 h, compared to 0.304%/℃ for the unreinforced control. Additionally, differential scanning calorimetry (DSC) indicated reduced exothermic heat flow in 48-h-cured samples, especially in the 1.7 wt.% CNC formulation, suggesting minimal phase transitions and improved thermal reliability. The novelty of this work lies in demonstrating the synergistic enhancement of thermal resistance through CNC addition and extended curing. Unlike prior studies that primarily focused on mechanical reinforcement, this research establishes an optimal CNC dosage (1.7 wt%) that minimizes thermal degradation, offering critical insights for thermally stable, bio-reinforced geopolymer development. These findings support the application of CNC–geopolymer composites in fire-resistant, sustainable construction materials. Graphical Abstract

This book brings together scholarly contributions that explore the evolving nature of Postgraduate Diplomas in Higher Education offered across varied higher education contexts. Through fourteen chapters, the book provides rich insights into the complexities of academic staff development and the professional learning of university educators.