콘크리트 포장의 적정줄눈절단시기 예측

Abstract

줄눈콘크리트포장의 시공과정에서 적정줄눈절단시기의 결정은 포장 전체 공용성에 큰 영향을 끼친다. 초기강도가 충분히 발현되지 않았을 때 줄눈절단을 실시하면 라벨링이 발생하고, 줄눈절단이 너무 늦으면 랜덤균열이 발생하는 등 콘크리트포장의 품질에 악영향을 끼치게 되기 때문이다. 적정줄눈절단시기는 콘크리트 절단 후 라벨링이 발생하지 않는 시점에서부터 랜덤균열이 발생하기 직전의 종점으로 결정된다. 본 연구에서는 줄눈콘크리트포장의 적정줄눈절단시기를 제시하기 위하여 담양·고창 간 고속도로 3공구에서 2006년 5월 23일 1차 시험시공, 현재 신설중인 평택·음성 간 고속도로(안성·음성 간) 5공구에서 2007년 6월 8일 2차 시험시공, 2007년 6월 11일 3차 시험시공, 7공구에서 2007년 10월 18일 4차 시험시공을 실시하였다. 적정줄눈절단시기 시점의 기준값을 제시하기위하여 스크래치시험, 압축강도시험, 성숙도 산정 및 줄눈절단시험을 실시하였으며 적정줄눈절단시기의 종점 확인을 위해 줄눈부 균열유도 시간을 수집하고 HIPERPAV(High PERformence PAVinsoftware)의 초기 균열발생 시간과 비교하였다. 실험결과 줄눈절단이 가능한 시점은 실험의 범위내에서 콘크리트포장의 포설 후 9～19시간, 성숙도는 333～537℃·HR, 압축강도는 17.3～29.5kg/㎠이며 줄눈부 균열유도시간으로 알아본 종점은 11～35시간이었다. 동일 날짜의 시공구간이라 하더라도 시공시각에 따라 절단가능한 시간대는 크게 달라짐을 알 수 있었다. 여름철 줄눈절단 가능시간대(Sawcutting Window)는 매우 짧을 수 있으므로 절단시기를 놓치지 않도록 유의해야 하며 가을시공의 경우 줄눈절단시간대는 비교적 여유가 있었다.; The determination of optimum saw-cutting time affects the overall performance of the pavement greatly among the construction process of joint concrete pavement for the following bad effects on the quality of the concrete pavement. When the saw-cutting is carried out while the early strength of the concrete is not adequately manifested, ravelling occurs. If the saw-cutting is carried out too late, random cracking takes place. The optimum saw-cutting time is thus determined by the time window between the point of no ravelling after the joint concrete cutting and the time point just prior to the occurrence of random cracking. This study carried out four test constructions in order to propose the optimum saw-cutting window for joint concrete pavement at the following locations. The first, second, third, and fourth test constructions were conducted at the third construction zone of Damyang-Gochang Highway on May 23, 2006, at the fifth construction zone of (Ansung-Eumsung) currently under construction Pyungteak-Eumsung Highway on June 8, 2007 and again on June 11, 2007, and at the seventh construction zone of Pyungteak-Eumsung Highway on October 18, 2007, respectively. Such tests as scratch test, compressive strength test, maturity computation, and saw-cutting test were carried out to propose a standard value for the optimum saw-cutting time window. The time to derive cracks at the joint area was measured to determine the end point of the optimum saw-cutting time window, and it was compared with the time for the initial cracking as computed by HIPERPAV (High PERformence PAVinsoftware). The result of the experiment reveled that the optimal saw-cutting time window, maturity, and the compressive strength were 9~19 hours after the placement of the concrete pavement, 333~537℃·HR, and 17.3~29.5kg/㎠ within the scope of this experiment. Additionally, the end point of optimum saw-cutting time was determined to be 11~35 hours based on the experiment of deriving cracks at the joint area. Further more, it was found that the optimum saw-cutting time differs greatly depending on the time of the hour even if the pavement was the same and the saw-cutting was conducted on the same date. Because the optimum saw-cutting time window can be very brief during the summer, extra-care is required during the summer season. On the other hand, the optimum saw-cutting window was rather longer during the fall season.