Cementing loose coral sand to reduce the permeability of island reef formations is one of the key approaches to enhancing freshwater retention in ecological islands. To this end

a permeability test was conducted on zinc sulfate-bonded coral sand

analyzing the effects of varying immersion durations

zinc sulfate solution concentrations

and initial dry densities on its permeability. The durability was verified through dry-wet cycling tests

while the microscopic cementation mechanism was investigated using XRD(X-ray diffraction)

SEM(scanning electron microscope)

EDS(energy dispersive spectrometer) and CT(computed tomography) scanning. The test results show that: (1) the permeability coefficient of coral sand is reduced by 70.17% to 95.79% after cementation with zinc sulfate. (2) After undergoing 16 dry-wet cycles and 36 hours of cementation

the mass loss rate of the cemented coral sand samples does not exceed 4%

and the variation of permeability coefficient is less than 1.0×10 cm/s

indicating excellent durability of the samples. (3) Additionally

the reaction between coral sand and zinc sulfate produces dihydrate gypsum and smithsonite

filling the pores of the samples

resulting in a decrease in the average pore-throat radius and coordination number

and a significant reduction in pore connectivity. This technology holds significant engineering application value

as it can be applied to sand fixation and erosion prevention in the initial stage of island reef reclamation

improving foundation bearing capacity and reducing permeability to promote groundwater conservation and eco-island construction.