The characteristics and engineering properties of dry-mix/steam-injection concrete

This study aims to investigate the characteristics and engineering properti es of the dry-mix/steam-injection method (DMSIM) which was developed to ove rcome difficulties involved in vacuum conditions of the lunar environment. A comparison was made to examine the differences in the hydration process, mechanical properties and the composition of hydration products between DMS IM and the normal-temperature wet-mix method (NTWMM). In DMSIM. when dry ce ment particles come in contact with steam, heal immediately transfers from the steam to the cement, with part of the steam being forced into the inner regions of the cement particles via the micropores. As cement particles ga in activation energy and moisture condensed from steam? they undergo rapid and complete hydration. Test results showed that the optimal steaming tempe rature for dry-mix samples of cement and standard sand is 180-200 degreesC and the optimal steaming scenario for 10 cm(3) samples of concrete is at 20 0 degreesC for 18 h. The present DMSIM has advantages of lower cement conte nt, shorter hardening time and higher concrete strengths, as compared to NT WMM. (C) 2001 Elsevier Science Ltd. Ail rights reserved.