Provide is a cement ink for a cement ink for 3D printing (which also includes additive manufacturing) of 3D cement structures and materials. The cement ink includes an American Petroleum Institute (API) Class G cement, a nano-clay, a superplasticizer, a hydroxyethyl cellulose, and a defoamer. The nano-clay may be hydrophilic bentonite. The superplasticizer may be a polycarboxylate ether. The defoamer may be 2-ethyl-1-hexanol. Processes for forming the cement ink and printing 3D cement structures using the cement ink are also provided.