Experimental research into the injectability of cement grouts in reef limestone

Reef limestone has special pore structures, which makes its seepage characteristics remarkably different from those of conventional terrestrial tight rocks. In this article, the microscopic structure of reef limestone and the water–cement ratio (WCR), cement fineness, and an admixture on flocculated cement particles were studied. Meanwhile, the probability analysis was adopted to evaluate the injectability for reef limestone cement grouts. The results indicate that the pore size gradually diminishes and the thickness of the wall for cemented walls increases little by little as the density of reef limestone increases. Generally, reef limestone has many seepage channels, indicating strong grout injectivity; when the WCR is larger and the cement fineness is smaller, the number and the size of flocculated cement particles is smaller, so the injectivity of cement grout is improved; this may be enhanced further after use of an admixture. In summary, the volume fraction of flocculated cement particles in cement grouts, as well as the relative sizes of pores and flocculated cement particles, can affect the degree of grout injectability. Injectability results calculated using the theoretical formula based on these influencing factors are found to match those arising from cement-grouting experiments, verifying the practicability and reliability of the injectability probability formula.