A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 2001

Until now, in Thailand, there has been no record on slipform construction technique of large concrete head tank. Hence, the purpose of this study is to investigate the construction techniques and related problems of a large head tank located in Chachoengsao province, Thailand. Visual inspection and data collections at site were made with the emphasis on concrete properties, slipforming technique, post-tensioning system, and related problems. From the results obtained in this study, it is found that slump loss and settings times of concrete are two important factors to be considered for construction using slipform technique. But the changing of ambient temperature and time for casting concrete can vary those prope1ties. Therefore, retarding admixtures are used to adjust those concrete cracking, low speed for rate of sliding, discontinuity of concrete casting, honeycomb and bleeding properties. The major problems encountered in head tank construction are cold joints, of concrete. Finally, in order to successfully constrnct a large head tank using slipforming technique, the following should be carefully look into. (1) Properties of fresh and hardened concrete should be prior dete1mined. (2) Capacity of equipment used to supply materials such as concrete must be investigated. (3) Standby of the equipment must be prepared in case of breakdown. (4) Time for concrete pouring must be carefully checked before starting. (5) Capacity of batching plant to supply concrete must be sufficient. (6) Checking the vertical alignment of the strncture must be made during the process. (7) Manpower must be sufficient. (8) Good co-operation among construction workers must be maintained.