The use of up to 20 % clinoptilolite-Ca zeolite replacement of portland cement was investigated. The as-received Ca zeolite exhibited reduced monosulfate associated heat of hydration. Blended samples had a higher initial chemical dissolution of calcium and aluminate; but subsequently, the consumption of both were higher compared to the neat cement control. Clinoptilolite-Ca zeolite exhibited a transformation into clinoptilolite-Na zeolite in NaOH and NaCl solutions and showed a distinct monosulfate formation heat flow. Micro-chemical analysis suggests a different hydration reaction mechanism for both calcium and sodium-based zeolite along with the possibility of reduction in the formation of C-S-H, ettringite, and monosulfate due to the formation of new hydration products. The clinoptilolite-Ca zeolite consumed higher aluminate forming amorphous calcium-aluminum-silicate-hydrate (C-A-S-H) gels. In contrast, the clinoptilolite-Na zeolite released sodium ions and produced sodium aluminosilicate hydrate (N-A-S-H), and did not interfere with the monosulfate formation reaction.