A Study on the Shrinkage Cracking Properties of Concrete by Using Blast Furnace Slag Cement and Frost-Resistant Accelerator

고로슬래그시멘트 및 내한촉진제를 사용한 콘크리트의 수축균열특성에 관한 연구

Abstract

As a cold-weather-concrete construction technique for enhancing the sustainability and improving efficiency of cold-weather construction, the cracking timing, the starting point of deterioration for concrete, due to the shrinkage of the blast furnace slag cement concrete including accelerator was evaluated. As a result, by using blast furnace slag and accelerator, the cracking was developed faster with higher cracking potential under the restrained conditions at constant age and free-shrinkage strain. It can be considered that the results of decreased stress relaxation by creep or increased restraint with increased free-shrinkage strain causes the increased cracking development speed. Hence, it should be considered the necessary of cracking due to the shrinkage when blast furnace slag or accelerator was used for cold-weather construction.

환경부하저감 및 동절기 시공의 효율을 위해 환경부하저감형 한중콘크리트 시공기술로서 고로슬래그시멘트와 내한촉진제를 병용한 콘크리트에 있어 열화의 기점이 되는 수축균열에 관해 검토했다. 그 결과, 고로슬래그시멘트 및 내한촉진제를 첨가함으로서 자유수축변형량 및 동일재령에 있어서 균열포텐셜은 증가하는 경향으로 구속조건하에서의 균열의 발생도 빠른 것을 확인할 수 있었다. 이것은, 자유수축변형량의 증가와 함께 크리프에 의한 응력 이완량의 감소나 구속도의 증가 등이 원인으로서 생각할 수 있으며, 동절기 시공에 있어서 고로슬래그 및 내한촉진제를 적용할 때는 수축에 의한 균열발생에 대해 검토할 필요가 있다고 판단된다.

Figure 1. Overview of ring test

Figure 2. Free shrinkage

Figure 3. Restraint shrinkage

Figure 4. Restraint stresses

Figure 5. Tensile strength

Figure 6. Cracking potential

Figure 7. Conceptual diagram of the stress on the concrete generated by restrained shrinkage[14]

Figure 8. Elastic stress, residual stress and stress relaxation (OPC-0)

Figure 9. Elastic stress, residual stress and stress relaxation (OPC-4)

Figure 10. Elastic stress, residual stress and stress relaxation (BB-0)

Figure 11. Elastic stress, residual stress and stress relaxation (BB-4)

Figure 12. Degree of restraint

Table 1. Experimental program

Table 2. Materials used

Table 4. Fresh Properties and compressive strength

Table 5. Crack configuration and cracking days

Table 3. Mix designs

Table 6. Stress relaxation