Investigation on the pore size characteristics and mechanical properties of grouting materials scoured by flow water

Investigating the pore size characteristics and mechanical properties of the stone bodies formed by residual grout is crucial for understanding the authentic permeability and load-bearing capacity of grouting materials after being scoured by water flow. In this study, the pore size distribution, porosity, uniaxial compressive strength (UCS), and elastic modulus (E) of stone bodies formed by residual grout from polyacrylate latex-modified cement grouting material (PLMC) were systematically investigated, and pure cement grout (PC) as a control group. First, scouring tests were conducted on grouting materials with various water-to-cement ratios (w/c, 0.6–0.8) and polymer-cement ratios (p/c, 0–0.2) under different flow velocities (0–1 m/s). Subsequently, the pore size characteristics of stone bodies formed by residual grout under various conditions were studied via nuclear magnetic resonance test. Finally, the uniaxial compression tests were conducted to investigate the impact of water scouring on the mechanical properties of grouting materials, and the relationship between pore size characteristics and macro mechanical responses was analyzed. Results show that the stone bodies formed by residual grout compared to the non-scoured state develop mesopores and macropores, and the number of micropores also increased significantly. This porosity escalation results in a reduction in UCS and E. When the flow velocity reaches 1 m/s, the porosity of PLMC with w/c = 0.8 increases by 2.95 %, while UCS decreases by 14.6 % and E decreases by 37.4 %. PC demonstrates more pronounced changes, with a porosity increase of 7.01 %, UCS decreases by 32.9 %, and E decreases by 41.5 %. With the rise in w/c, the deterioration of pore structure and mechanical properties of the stone bodies formed by residual grout is more significant compared to the non-scoured state. Increasing p/c can mitigate the deterioration of the pore structure and mechanical properties. The findings provide meaningful guidance for the grouting reinforcement under dynamic water conditions.