Experimental Investigation of CO2-Induced Silica Gel as the Water Blocking Grout Effect of Aquifer Ions

Ichhuy Ngo; Liqiang Ma; Jiangtao Zhai; Yangyang Wang; Tianxiang Wei; Yanxiao Ni

doi:10.1021/acsomega.2c00019

Experimental Investigation of CO₂-Induced Silica Gel as the Water Blocking Grout Effect of Aquifer Ions

ACS Omega. 2022 Jul 30;7(31):27090-27101. doi: 10.1021/acsomega.2c00019. eCollection 2022 Aug 9.

Authors

Ichhuy Ngo¹, Liqiang Ma¹, Jiangtao Zhai¹, Yangyang Wang¹, Tianxiang Wei¹, Yanxiao Ni²

Affiliations

¹ Key Laboratory of Deep Coal Resource Mining, China University of Mining & Technology, Ministry of Education, Xuzhou 221116, China.
² School of Foreign Studies, China University of Mining & Technology, Ministry of Education, Xuzhou 221116, China.

Abstract

This study aimed to prevent water flow in microcracks and simultaneously achieve CO₂ capture during grouting (CCG). Using sodium silicate (SS) as the primary material, the microcracks were grouted by a two-step approach. The low-initial-viscosity (5 mPa s) SS was first saturated within the microcracks followed by CO₂ injection at 2 MPa. Through CO₂ dissolution, silica gel was developed and tolerated a hydraulic pressure of up to 5.5 MPa. The effects of aquifer ions (Na⁺, Ca²⁺, Mg²⁺, HCO₃ ^-, and SO₄ ^2-) were equally evaluated at harsh conditions, and it was found that the strength of the silica gel was reduced, which was caused by salting out, low CO₂ solubility, and precipitation. As a result, the hydraulic pressure was reduced to as low as 3 MPa. After 210 days, 16% of the silica gels (without ion inclusion) were reversible to the liquid phase, where a similar effect was found in the cases of Na⁺ and Mg²⁺ ions. The degradation increased with more Ca²⁺ ions (up to 55%) and decreased with more HCO₃ ^- and SO₄ ^2- ions. Microcracks grouted with CCG extended the CO₂ utilization in grouting application. Combined with the effect of dissolved ions, the proposed approach is feasible in the field implementation for underground engineering under water bodies.