The research objective of this BRIGE award is to investigate the viability of bombarding concrete with dry ice as a means of preparing the substrate to receive coatings and composite overlay. The specific goals are to (a) examine the effectiveness of removing corrosion byproduct from substrate, (b) identify whether dry ice bombardment induces damage within the substrate, and (c) explain how the fresh and hardened properties of concrete contribute to these behaviors. Diversity, education, family, and science will be united by creating parent-student teams to carry out a portion of the research activities. Close involvement of faculty, parents, and students in research will allow families from underrepresented groups to embrace the technology being investigated.
If successful, the results of this research will explain the fundamental relationships between basic substrate properties and their influence on cleaning efficacy and potential to cause substrate damage from dry ice bombardment. Significant achievement also prevails by adapting well-established, scientific protocol to investigate this unusual, yet unexplored blasting technique. Among such protocol include non-destructive inspection (NDI) using ultrasonic resonance, and Laser Scanning Confocal Microscopy (LSCM). From an environmental perspective, dry ice blasting could reduce the time and cost of surface preparation as well as lessen the negative impact on the surrounding environment and personnel carrying out the construction. Moreover, the dry ice supply is derived from reclamation of CO2 gas byproduct from existing manufacturing processes, thus, contributing to its sustainability. Potential energy-related implications could lead to an important research thrust in academia and industry in the future. Furthermore, the results generated from this research could be applied to other topical areas and material systems such as corrosion and lead-based paint removal from steel bridges, mold remediation in urban housing, and biofilm removal from timber piles or bridge piers located in thriving, yet delicate, marine ecosystems.
The overall goal of the research was to investigate the effects of bombarding (blasting) concrete with dry ice pellets (frozen carbon dioxide, CO2) to prepare concrete surfaces for restoration and repair. The effects were measured in terms of (i) environmental pollution and sustainability, (ii) damage to the concrete, and (iii) surface properties including roughness and cleaning effectiveness. The results were compared to those from sand blasting, which is the most common approach used to prepare concrete surfaces in the construction industry. Dry ice blasting is far safer than sand blasting since solid dry ice particles convert directly into a gas on impact (sublimate). As a result, dry ice blasting does not produce a cloud of sand particulate, which poses a significant health hazard to construction personnel. Sublimation of the dry ice pellets also permits cleaning in complicated cavities and structural joints that would typically trap grit blast media like sand. The results demonstrate that the environmental effects of dry ice blasting are comparable to those of sand blasting, despite the additional release of CO2 from the dry ice pellets. For a typical construction project, such as a highway bridge rehabilitation, the overall project duration may be shortened if using dry ice since dust containment tents (like those associated with sand blasting) are no longer essential unless environmental conditions warrant them. As a result, vehicular traffic delays (and fuel consumption) near the construction site can be reduced. In addition, the dry ice supply is derived from the reclamation of CO2 gas from existing manufacturing processes, thus, improving its sustainability. Measuring damage to the concrete was accomplished by measuring the distortion of sound waves passed through the concrete. The results indicate that the overall integrity of the concrete remained unchanged after blasting with dry ice or sand. Measurement tools including laser scanning confocal microscopy (LSCM) and 3-D optical profilometry were applied to measure the surface properties, such as roughness and texture. These instruments, primarily used in the biological sciences and manufacturing industries, were successfully applied to image and measure the surface properties of concrete. The results show that the roughness increases in a predictable manner for both types of blasting media (dry ice and sand). The relative amounts of water, cement, sand, and stone in a given concrete mix will determine the change in roughness that can be expected. To quantify the cleaning effectiveness, digital photographs and computer algorithms were developed to measure the amount of paint removed from the surface. The air content of the concrete was the most critical factor in predicting the cleaning effectiveness when using dry ice blasting. The primary educational/outreach endeavor was the creation of parent-student teams to carry out a portion of the experimental research activities. This program was a unique approach to unite families with science education and engage them in engineering research. Each team was formed by pairing an undergraduate student with at least one parent or guardian of their choice. After receiving formal training in laboratory safety and research ethics, the participants carried out some of the experimental research. The interaction and rapport between parents and students was overwhelmingly positive and rewarding for all participants. This program demonstrated that parents do possess a strong interest to work together with their sons/daughters to achieve a common goal. In addition, it reiterated the fact that there is no age limit to one's ability to learn, to educate, or to contribute to the scientific and engineering knowledge bases.
