A modified, hydrophobic soundless cracking demolition agent for non-explosive demolition and fracturing applications

Abstract

Abstract Soundless Cracking Demolition Agents (SCDAs) are an alternative to the current practices of environmentally detrimental conventional demolition and rock fragmentation methods Although having the potential to produce a dense network of fractures when injected into a borehole, the applicability of SCDA is limited by its susceptibility to dilution in water-saturated conditions and delayed onset of expansive pressure. Such limitations can be eliminated by introducing a Viscousity Enhancing Agent (VEA) to modify the SCDA system. Even though adding a VEA enhances the wash out resistance in the SCDA system, the associated delay in the onset of expansive pressure limits the application of this new technology in the industry. Therefore, this study aims to recover the delayed onset of expansive pressure in modified SCDA by utilising a chemical accelerator (CaCl2) through a comprehensive experimental study. The developed new material was fully characterised by performing mechanical tests (uniaxial compressive strength tests, flowability tests, washout resistance tests), microstructural analysis (scanning electron microscopy) and mineralogical analysis (X-ray diffraction). According to the results, simply increasing the dose of CaCl2 in unmodified SCDA was found to be ineffective to attain an increased rate of expansive pressure generation and the peak expansive pressure development. The increased dose of CaCl2 resulted in an accelerated expansive pressure generation, but also a lower peak expansive pressure. The approach of combining the accelerator and VEA was found to be an effective means to increase the washout resistance and the rate of expansive pressure development of modified SCDA while retaining a reasonable flowability of SCDA. Finally, the study proposes an optimum combination of VEA (welan gum, 0.1%) and the accelerator (CaCl2, 2%) by weight of SCDA to produce an SCDA with enhanced expansive pressure generation in submerged conditions, which can be effectively and safely applied for demolition and rock fragmentation.