The authors present preliminary study results on concrete mixtures for structural applications containing high volumes of natural pozzolan (50% by total cementitious material mass). In high-volume natural pozzolan (HVNP) concrete mixture preparation, three different natural pozzolans were used from Turkish deposits. For purposes of comparison, two additional mixtures were also prepared with a high volume of low-calcium fly ash and granulated blast-furnace slag. Additionally, as a reference, a conventional portland cement concrete mixture was prepared. High-range water-reducing admixture dosage was determined for resistance to chloride-ion penetration, splitting-tensile strength, compressive strength, setting time, air content, and given slump. The suitability of studied high-volume natural pozzolan concrete mixtures for structural concrete applications were indicated by preliminary results with compressive strengths of 1.74 to 2.03 ksi (12 to 14 MPa) and 4.21 to 5.51 (29 to 38 MPa) at 3 and 28 days, respectively.