Abstract
Houses of usual people in developing countries are very vulnerable against earthquakes. Authors have been working on this issue and conducting a series of experiments. We faced a big difference between structures of construction practice on sites and specimens for laboratory experiments. We assume that strength of cement mortar is one of the key issues which cause the difference. Therefore we implement comparative study on several specimens of cement from several countries with different circulation/storage conditions. We also implemented strength tests of specimens made under similar conditions of actual construction sites in developing countries. We find quality of different counties/manufacturer is not so significant. On the other hand, cement/sand ration, remixing and curing affects the strength significantly for increasing the strength on sites.
