The use of expansive chemical agents for concrete demolition: Example of practical design and application

Abstract

Numerical and experimental investigations for effective application of soundless chemical demolition agents (SCDAs) to dismantle large-scale concrete blocks were conducted. The expansive pressure from SCDAs was measured using a half-height water-submerged steel pipe. A numerical framework of the finite element method (FEM) with damage plasticity and a hard contact option in Abaqus was established and verified through several concrete block dismantling tests using SCDAs. The crack path and minimum required pressure for generating cracks in a concrete body were compared for verification. Further investigation was conducted to see the effect of heat from SCDAs on the minimum required pressure during chemical reaction. Then the effects of the parameters, such as the concrete compressive strength, tensile strength, distance between SCDAs (k-factor), and offset distance from the free end to the SCDA, on the minimum required pressure for vertically or horizontally forming cracks was studied in the FEM framework. This study found that the minimum required pressure for forming cracks was linearly proportional to the k-factor and the offset distance, while the minimum required pressure was considered either linearly or non-linearly proportional to the concrete strength. A significant interaction effect between the concrete strength and k-factor was also found using full factorial design of experiment. Based on the conducted parametric study with the various models, two simplified practical equations for horizontal and vertical formations of concrete cracks using SCDAs were proposed, which can conservatively predict the minimum required pressure up to 18.0% for the simulation data in this study. The two equations were then used in a field application, which revealed that concrete cracks using SCDAs could be formed as intended.