Condensed summary of current R&D on cementitious sealants for deep boreholes with HLW

Abstract

7Cement-based materials for use as sealants in underground waste storages must be erosion-resistant 8 and chemically stable. Placement of highly radioactive waste (HLW) in boreholes may require that the 9 rock is cement-grouted and stabilized by constructing concrete plugs. Where smectitic clay seals are in 10 contact with concrete there is mutual degradation, and low-pH cement with inorganic 11 superplasticizers, like talc, are recommended for preparing the concrete. This paper reviews our 12 current state-of-knowledge concerning the grout and concrete sealing very deep boreholes (DBD) for 13 purpose of high-level radioactive waste disposal. In this concept, the lower 2 km section of 4 km deep 14 holes bored in crystalline rock could host waste-containers while the upper parts are sealed by dense 15 clay and concrete 1 . The parts of such a hole that intersect fracture-poor rock are sealed with dense 16 expandable clay while concrete is cast where fracture zones are intersected. The paper summarizes the 17 available experimental results concerning the performance of grouts and concrete with talc as 18 superplasticizer in contact with smectitic clay. 19Keywords: Boreholes, Clay, Concrete, DBD, Radioactive waste, Talc, VDH, 20 Scope 21The basic idea of disposal of high-level radioactive waste (HLW) according to concepts termed DBD 22 is to locate the waste deep in rock with very heavy, saline, stagnant formational waters that are 23 1 At present, continued R&D will show if the holes can be only 2.5 km deep with HLW in the lower 2 km parts

A cement paste–tail sealant interface modified with a silane coupling agent for enhancing waterproofing performance in a concrete lining system

“…The waterproong of underground or underwater concrete structures is of great signicance to ensure desired performance and durability, which oen relies on hydrophobic surface coatings that consist of organic ingredients, such as rubber, asphalt binder or other organic materials. [1][2][3] For example, asphalt membranes and polyurethane waterproong paint have been used as coating materials for underground garages and tunnels for decades. 4,5 However, the origin of the hydrophobicity of most surface coatings lies in their own hydrophobic characteristics or simply physical adsorption with the concrete surface.…”