This study explores the calcium leaching resistance of cement composite with liquid-crystal display glass powder (LCDGP). Authors compare LCDGP with other pozzolanic materials, fly ash and soda-lime glass powder, replacing 20% of the cement. Results show that LCDGP reduces the leaching rate by 47.2% and hardness degradation depth by 28.6%, compared to the fly ash-blended mixture. High pozzolanic reactivity of LCDGP lowers the initial calcium hydroxide and total porosity including a decreased volume of pores exceeding the capillary pore size, resulting in a dense microstructure. Consequently, these effectively delay calcium hydroxide dissolution and calcium-silicate-hydrate decalcification. LCDGP-blended mixture shows the decreased C-S-H gel decalcification depth by 21.4% and exhibits 28.6% less hardness reduction depth compared with fly ash-blended mixture. Based on these findings, authors advocate the potential application of LCDGP as an admixture for concrete structures that are exposed to water.