An Experimental Study on the Curing Method and PP Fiber Mixing Ratio on Spalling Resistance of High Strength Concrete

This study is to investigate the fundamental and fireproof qualities of high strength concrete corresponding to changes in the curing factors and the PP fiber ratio. The results were as follows. For the fundamental characteristics of concrete, the fluidity was reduced in proportion to the increase in the PP fiber ratio. The compressive strength was somewhat reduced according to an increase in the PP fiber ratio. However, it had the high strength scope of more than 60 MPa at 7 days and of more than 90 MPa at 28 days. On the spalling mechanism followed by changes of the water content ratio, spalling was prevented in all combinations, except the specimen without PP fiber and subjected to 3.0% of moisture contents. When spalling was prevented at that time, the residual compressive strength ratio was 22%~41% and the mass reduction ratio was 5%~7%, which was relatively favorable. As the spalling mechanism corresponds to changes in the curing method, spalling was prevented in concrete with a PP fiber mixing ratio of more than 0.05% in the event of standard curing, and in concrete with a PP fiber mixing ratio of more than 0.10% in the case of steam curing and autoclave curing. In these cases, when spalling was prevented, the residual compressive strength ratio was 23~42% and the mass reduction ratio was 7~11%. In these results, the ease of spalling prevention in high strength concrete was inversely proportional to the water content ratio. Depending on the curing method, spalling was prevented in concrete with over 0.05% PP fiber with standard curing and in concrete with over 0.1% PP fiber with steam curing and autoclave curing.

양생요인 및 PP 섬유 혼입율 변화에 따른 고강도 콘크리트의 폭렬특성

본 연구는 양생요인 및 PP 섬유 혼입율 변화에 따른 고강도 콘크리트의 기초적 특성 및 내화특성을 분석하였는데, 그 결과를 요약하면 다음과 같다. 콘크리트의 기초적 특성으로 유동성은 PP 섬유 혼입율이 증가 할수록 감소하는 경향을 나타내었고, 압축강도는 PP 섬유 혼입율 증가에 따라 약간 감소하였으나 재령 7일에서 모두 60 MPa 이상 재령 28일에서 90 MPa이상으로 고강도 범위를 나타내었다. 함수율 변화에 따른 폭렬성상으로 함수율 3.0 %에서 PP 섬유를 혼입하지 않은 플레인을 제외한 모든 배합에서 폭렬이 방지되는 것으로 나타났다. 이때 폭렬이 방지된 경우 잔존압축강도율은 22~41%, 질량감소율 5~7 %로 비교적 양호한 것으로 분석되었다. 양생방법 변화에 따른 폭렬성상으로 표준양생의 경우 PP 섬유 혼입율 0.05 % 이상, 증기 양생 및 오토클레이브의 경우 PP 섬유 혼입율 0.10 %에서 폭렬이 방지되는 것으로 나타났다. 이때 폭렬이 방지된 경우 잔존압축강도율은 23~42 %, 질량감소율은 7~11 % 전후로 나타났다. 이상을 종합하여 볼때 고강도 콘크리트는 함수율이 작을수록 폭렬방지가 용이하고, 양생방법에 따라서는 표준양생이 PP섬유 0.05 % 이상, 증기양생 및 오토클레이브의 경우 PP 섬유 혼입율 0.1 %이상을 혼입해 주어야 폭렬이 방지됨을 알수 있었다.