In this study, natural zeolite (clinoptilolite) was used as an aggregate and bubble-generating agent in autoclaved aerated concrete (AAC) production. The crushed and grinded samples were classified into two different particle sizes: 100 mu m (fine-ZF) and 0.5-1 torn (coarse-ZC) before using in AAC mixtures. The effects of particle size, replacement amount (25%, 50%, 75% and 100% against quartz) and curing time on the AAC properties were experimentally investigated. it was found that usage of natural zeolite, especially with a coarser particle size, has beneficial effect on the physical and mechanical properties of AAC. The optimum replacement amount was determined as 50% and at this rate the compressive strength, unit weight and thermal conductivity of AAC were measured as 3.25 MPa, 0.553 kg/dm(3) and 0.1913 W/mK, respectively. Scanning electron microscopy analysis also confirmed the above findings. Denser C-S-H structures were obtained up to a replacement amount of 50%. Finally, the test results demonstrated that calcined zeolite acts as both an aggregate and a bubble-generating agent, and that AAC with a compressive strength of 4.6 MPa and unit weight of 0.930 kg/dm(3) can be produced without aluminum powder usage. (C) 2009 Elsevier Ltd. All rights reserved.