Observations of Thermal Cracking Propagation in Geopolymer Curing

Abstract

Geopolymers are a growing potential alternative of study to traditional Portland cement applications. With this increase in interest of the material, additional scrutiny of the material is needed to verify applicability in more environmentally challenging applications. It is the goal of this work to further the understanding of previously identified surface cracking of geopolymer samples cured under high-heat conditions. To capture the full nature of the apparent sample cracking of high curing temperature geopolymers, new sample cubes are generated at high temperatures and pulled from curing at set times. As well as temperature variation, samples will also be cured in both a wet and dry environment. Unlike traditional cement testing, where the intervals of curing grow larger, for this test samples will be pulled from the heating environment every day for 14 days. This allows for the highest level of insight on the nature of the propagation of the cracks. The samples will undergo controlled, high-resolution photography in order to best catalogue the nature of the cracks. Additionally, all samples will be subjected to uniaxial UCS testing, biased to the direction of the apparent crack, to see if the failure plane is that of the crack. This generates insight into the depth of the crack, as they are typically too small to measure from the surface. The images collected as a result of this experiment are compared in both temperature and timeline conditions. It is expected that the cracking will onset, expand, and fail the sample faster in higher heat environments. These images will be paired with the corresponding UCS test values and trendlines for the UCS will be adopted. It is expected that if the propagation of thermal cracking is significant to the mechanical strength of the sample, there will be a notable point at which the UCS meaningfully deviates from the time trend, and optimistically this occurs before sample failures begin to occur in the curing environment. Details into the surface integrity, as well as the general thermal integrity, of geopolymers are relatively sparce at the time of this experiment. It is the hope that this work can serve as a foundation for the establishment of more detailed experiments which better characterize the nature of the cracking phenomenon.