Geopolymers based from rice husk ash: A polymer modified and water activated one-part mix with self-healing properties for possible construction and coating applications

• Main Author: Lira, Brandon Cyril S
• Format: text
• Language: English
• Published: Animo Repository 2021
• Subjects: Polycondensation; Rice hull ash; Polymers; Chemistry; Polymer Chemistry
• Online Access: https://animorepository.dlsu.edu.ph/etdm_chem/2; https://animorepository.dlsu.edu.ph/cgi/viewcontent.cgi?article=1001&context=etdm_chem
• Institution: De La Salle University

Geopolymers are polycondensation polymers made from alumina and silica molecules forming an amorphous structure and synthesized under an alkaline medium. However, usual geopolymer formulations involve more than two components and would require special handling. If this kind of system is intended to be commercialized, it will not attract consumers due to storage, handling, and ease of preparation concerns. Thus, creating a one-part system where only water is added to a prepared mix containing dry components is more practical and somewhat similar to how an ordinary Portland cement is prepared. In this study, a geopolymer made from rice husk ash was prepared by just adding water. These geopolymers are applied as a coating material on a metal substrate. The amount of water added to the geopolymer mix was optimized, and that the water-to-solids ratio of 1.50 has produced the highest adhesion strength of 1.04 MPa among the trials performed. To further improve the adhesion strength and improve its workability, adding a 5 % vinyl acetate-ethylene redispersible dry polymer significantly increased the geopolymer's adhesion strength by 152 %, resulting in 2.63 MPa. Also, self-healing agents were incorporated into the geopolymer mix to allow end-users to save on minor repairs and cracks. These self-healing agents were synthesized using sodium silicate and aluminate solutions, encapsulating them in a polyurea shell. Incorporating these self-healing agents allowed the cured and then intentionally damaged geopolymer to repair itself for 24 hours through a water curing method. Observations of the microstructure of these materials were done using SEM. Also, the thermal properties of the geopolymers were analyzed using TGA. Finally, after conducting these optimizations, a final formulation that incorporates all the components were provided, and end-users can have this as a starting guide for a one-part RHA-based self-healing geopolymer.