Water-adaptive cement self-healing system, preparation method and application thereof

A method for preparing a water-adaptive cement self-healing system, comprising the following steps:

• step 1, preparation of a self-healing capsule, comprising the following steps:
• step A1, preparation of an aqueous phase, comprising:
• adding a pH-triggered shell curing agent, an inorganic nano-emulsifier, and a polysaccharide shell material into deionized water, and then uniformly stirring to obtain the aqueous phase;
• wherein a mass fraction of the pH-triggered shell curing agent in the aqueous phase is 18.7%-37.4%, a mass fraction of the inorganic nano-emulsifier in the aqueous phase is 2.0%-8.0%, and a mass fraction of the polysaccharide shell material in the aqueous phase is 0.5%-2.0%;
• and the pH-triggered shell curing agent is a disodium calcium ethylenediaminetetraacetate, a calcium carbonate, or an aluminum hydroxide;
• step A2, preparation of a first oil phase, comprising:
• adding an active diluent to an epoxy, and then uniformly stirring to obtain the first oil phase;
• wherein a mass fraction of the active diluent in the first oil phase is 10%-20%;
• step A3, preparation of an oil/water emulsion, comprising:
• mixing the aqueous phase obtained in the step A1 and the first oil phase obtained in the step A2 according to a volume ratio of 80-50:20-50 to obtain a first mixture, and stirring the first mixture at 10,000-12,000 revolutions per minute (rpm) to obtain the oil/water emulsion;
• step A4, preparation of a second oil phase, comprising:
• adding a surfactant into paraffin oil, and then uniformly stirring to obtain the second oil phase;
• wherein a mass fraction of the surfactant in the second oil phase is 50%-62.5%;
• step A5, preparation of an oil/water/oil emulsion, comprising:
• mixing the second oil phase obtained in the step A4 and the oil/water emulsion obtained in the step A3 according to a volume ratio of 80-75:20-25 to obtain a second mixture, and stirring the second mixture at 600-800 rpm to obtain the oil/water/oil emulsion;
• and
• step A6, preparing the self-healing capsule, comprising:
• dropwise adding an acidic liquid into the oil/water/oil emulsion obtained in the step A5 to obtain a mixed solution, stirring the mixed solution until the mixed solution is shaped to obtain a solid, centrifuging the solid, and then washing the centrifuged solid with deionized water, followed by freeze-drying the washed solid to obtain the self-healing capsule;
• wherein the self-healing capsule is of a core-shell structure, a shell material of the core-shell structure is the aqueous phase prepared in the step A1, and a core material of the core-shell structure is the first oil phase prepared in the step A2;
• and
• step 2, mixing an epoxy curing agent with the self-healing capsule prepared in the step 1 according to a mass ratio of 0.5-1:1 to obtain the water-adaptive cement self-healing system based on an oil/water/oil double-emulsion template.