Investigation on Middle Flow Tunnel Lining Concrete Using Thickener-Containing Fluidizing Agent
Japanese national expressway company known as NEXCO (Nippon Expressway Company ltd.) has developed mid-flow concrete to improve the workability and overall quality of secondary tunnel lining. This new concrete was standardized in July 2013. In recent years, it has become more popular to use mid-flow concrete with increased viscosity, which often is produced by utilizing thickenercontaining air-entraining (AE) super plasticizer during batching at ready-mix concrete plant. However, this kind of concrete occasionally is faced with production limitation as some plants may not be equipped with required facilities and apparatus. To overcome this problem, we have developed a new type of mid-flow secondary tunnel lining concrete which can be manufactured on site by dosing fluidizer which contains thickening agent. These two types of concrete with varying manufacturing methods were tested indoors for fresh properties and casting performance using simulated molds. This paper reports the results of the conducted tests and illustrates the on-site construction management methods of this new type of concrete.