지열시스템을 위한 광미 혼입 고유동 충전재

Abstract

The construction industry in Korea is being advance more than ever demanding a durable, lightweight, multipurpose and at the same time specialized and products while keeping the cost at a minimum range. Excavation and underground tunneling works in large cities are becoming major tasks to meet the evergrowing population demand of convenient infrastructure. In this study, industrial by products like pondash and mine tailing where used to investigate the mixing characteristics and the thermal conductivity of CLSM. In addition, a raw, microwaved and microwaved plus magnetic separated mine tailings were used to evaluate the performance. However, pretreatment of mine tailings does not affect the flowability, settlement and strength of the CLSM, significantly.

On the other hand, the standard settled by ACI 229R standard indicates that the flowability should be above 200 mm and the settlement being less than 1 % by volume of the mix. In addition, the standard recommends the strength to be in between 0.3 MPa or more and 2.1 MPa or less. Furthermore, the use of mine tailing by blending minimizes the effect on the environmental and also satisfies the environmental impact criteria based on the TCLP test. However, while using pond ash it is difficult to achieve the environment impact criteria. This might affect the pH of the ground water through time, but since the geothermal system itself does not use CLSM in large quantities the amount of CLSM itself is about 1/3 to 1/4 that of the total concrete so the long term pH disturbance problem is less dangerous than mortar grouts.

As a result of designing based on the thermal conductivity, the required pipe length is reduced compared to conventional bentonite-silica grout and the depth of perforation is reduced. Therefore, considering the same level of thermal efficiency, it is expected that the construction cost to be reduced by at least 20 % from the existing bentonite-silica grout by at least 9 %.