摘要 目前各國對於鹼-骨材反應的判斷規範，多以量測試體外部的膨脹量作為骨材是否具有反應潛能的依據，如砂漿棒（ASTM C227）或混凝土角柱（ASTM C1293），最後獲得的僅為試體的長度變化；對於反應造成的裂縫行為及發展過程並無有效的記錄。本文採用台東宜灣安山岩及花蓮和平溪骨材製作混凝土試體，在不同齡期以平台式掃描器來擷取混凝土板表面影像以記錄裂縫生長的過程，並配合影像軟體分析，建立膨脹量與裂縫的關係。 經觀測後發現裂縫呈現不規則地圖狀，與發生鹼-骨材反應的現地混凝土結構物表面類似。裂縫大多先由砂漿開始並沿著骨材周圍生長，部分裂縫甚至貫穿骨材。而在膨脹量的量測上，使用影像分析與多點式應變規得到的數據雖然有些微的差異，不過趨勢大致相同，顯示經由記錄影像的方式來量測膨脹量是可行的。並由裂縫分析結果發現，膨脹量與裂縫面積可以迴歸出良好的線性關係。 ABSTRACT Generally, standard test methods for potential alkali activity is to measure the expansion of specimens, mortar bars(ASTM C227) or concrete prisms(ASTM C1293), for instance. It just shows the change in total length of the specimen, but the behavior and development of cracks can not be investigated. In this article, the relationship between expansion and crack of the specimens is established with image measurement. So scanner is used to record the surface image of concrete plates which are made of andesite and aggregate from Heping river. The image is analyzed with software, Simple PCITM, to give the quantitative description of the cracks and expansion. The results indicate that the surface crack is map-like, similar to those observed from in-situ concrete structures and development of cracks almost start from mortar part and then extended to aggregate part in concrete specimens, even cut over the aggregate. From the analysis of image, the crack area contributes the most in the total expansion after the first crack. The expansion threshold for cracking to exist on concrete specimen is 0.15%.
