DEVELOPMENT OF GRAPHENE BASED MATERIAL AND AN INDUSTRIAL WASTE BASED HARDENING ACCELERATOR FOR EARLY STRENGTH GAIN IN CONCRETE

Abstract

Cement is distinguished as the most extensively manufactured material worldwide, with an annual production reaching approximately 2 billion tonnes. The process is primarily responsible for carbon emissions largely from construction industries. Thus the researchers are looking for new ways to replace cement with greener materials. The strategy to enhance concrete performance involves to utilize nanoengineered materials. During cement hydration, approximately 75% of the weight of the final hydrated product is composed of calcium silicate hydrate (C-S-H). Such products exist in a poorly crystalline state with a varying chemical composition. Consequently, there has been significant research emphasis on investigating the behavior of C-S-H, encompassing macroscopic and microstructural levels, in recent decades. In this thesis, graphene-based material is being developed using a low-cost synthesis method. The synthesis process initially starts with the oxidation of commercially available graphite powder and subsequently exfoliates the obtained graphite oxide in an aqueous solution using a high-frequency ultrasonication process. The synthesized graphene were characterized using different characterization techniques to authenticate their formation. The synthesized material in the aqueous solution form were added to cement concrete system as a strength-enhancing additive. The development of mechanical strength and durability performances of concrete containing graphene were measured and findings were documented. Furthermore, a C-S-H hardening accelerator was synthesized to promote early strength development in cement concrete. This was achieved by utilizing ground granulated blastfurnace slag (GGBS) as a industrial waste. The C-S-H was synthesized by extracting amorphous silica particles from a sodium silicate solution. Initially, the sodium silicate was oxidized using the sulphuric acid solution and then mixed with the calcium-oxide source GGBS , a residue of iron making industry. The C-S-H was further verified using different characterization techniques and then added to a cement concrete system for early strength gain. The efficiency and optimum dosage of C-S-H seeds in promoting early age strength development has been validated through heat of hydration, setting time, and early age compressive strength test. The study emphasizes the importance of finding sustainable solutions for waste disposal and the potential for turning waste into a valuable resource. In the context of industrial applications, the developed synthesis methods are utilized for making chemical admixtures that counteract the limitations of concrete. As it is commonly understood, concrete is widely employed in civil engineering construction because of its strong compressive strength, ease of molding, water resistance, and production efficiency. Nevertheless, it also possesses some unfavorable traits, such as low tensile properties, limited strain capabilities, and a tendency to form cracks due to its quasi-brittle nature. When faced with complex loads in building construction, the quasi-brittle nature of concrete is a significant drawback. In order to address these constraints, it is crucial to incorporate reinforcing materials into concrete to improve its overall performance. Another potential limitation of conventional concrete during the early stage is comparatively lower strength which reduces the progress of construction activities. In contrast, high early-strength concrete achieves strength more quickly than conventional concrete, making it suitable for construction in colder regions, accelerated the pavement construction process, and increases the precast concrete elements production rate. The research outcomes offer valuable insights regarding the capabilities of using graphene-based materials and waste material-based additives for improving the properties of concrete and promoting sustainable construction practices.