Page - 1177 - in Book of Full Papers - Symposium Hydro Engineering

Non-Dispersible Underwater Concrete was first realized by the development of cellulose ethers in Germany. Non-Dispersible Underwater Concrete technology has been employed in other countries in Europe, Japan and USA soon. This technology was adopted in the projects of Access bridge of Kansai International Airport, Akashi strait bridge, Rehabilitation of Copenhagen Port, Breakwater along west coast in Scotland and so on. In 1993, the publish of a Chinese translation of “Design and construction guideline to Non-Dispersible Underwater Concrete” by Research Center of Coastal Developing Technology in Japan, has a positive role in promoting underwater concrete technology in China [2]. Now, polymer flocculants with long polymer chain structures are widely used in Non-Dispersible Underwater Concrete. The cement particles absorbed by active functional groups on long carbon chains can be bridged to form stable floc structures. At the same time, the hydrogen bonds between the hydroxyl on the functional group in flocculant and water molecules will form to increase the affinity of water molecules. The long molecular chains of flocculants attract each other and the mesh structures form by these chains. Particles of cement are covered by the meshes and difficult to be dispersed by the washing of external water molecules. However, flocculant will affect the workability of concrete mixture, and also cannot totally avoid the washing effect of water on concrete mixture. The price of non-dispersible underwater concrete is relatively high. In early 2010s，an innovative technology for underwater concrete has been developed and authorized patent in China. It was named Self-Protected Underwater Concrete (SPUC) [3] later. 2. WORKING PRINCIPLE AND IMPLEMENTATION OF SPUC 2.1. WORKING PRINCIPLE The working principle of SPUC is different from that of Non-Dispersible Underwater Concrete. A soluble polymer, called Underwater Protective Agents (UPA) will be poured into the water body prior to the pouring of underwater concrete. Then the water body will be transformed into a solution of UPA, usually the concentration of UPA will be about 100 ppm. The structures of UPA molecules chains will prevent the dispensation of cement particles into the water body, so as to avoid segregation. The employment of self-compacting concrete makes the vibration-free cast of concrete. 2.2. DEMO COMPARISON BETWEEN DIFFERENT TECHNOLOGY To demonstrate the difference among ordinary concrete, non-dispersible underwater concrete and SPUC，a demo test was conducted, as shown in Fig. 1. In the demo test, three type of fresh self-compacting mortar were poured via a 1177