水泥砂漿受壓之聲射訊號特性

Abstract

鑑於非破壞性檢測技術（Nondestructive Testing Method，NDT）在土 木工程上之應用日益受到各先進國家之重視，本研究乃針對聲射（ Acoustic Emission，AE）檢測技術在混凝土材料方面之應用進行基本特 性之探討。由於水泥砂漿（Cement Mortar）為混凝土之基本組成材料， 故本研究乃針對水泥砂漿試體在單軸抗壓試驗下的聲射訊號進行探討。此 外，由於飛灰混凝土之使用正逐漸增加，故本研究亦探討飛灰水泥砂漿（ Fly-Ash Cement Mortar，FACM）試體在單軸抗壓試驗下的聲射訊號特性 。本研究探討之主題主要包含以下四個項目： (1) 水泥砂漿各主要參數 （水灰比、抗壓強度、齡期、應變、孔隙率及水化程度等）與聲射訊號間 之關係。 (2) 飛灰水泥砂漿各主要參數（飛灰取代水泥量、抗壓強度、 齡期及應變等）與聲射訊號間之關係。 (3) 水泥砂漿及飛灰水泥砂漿之 聲射凱撒效應（Kaiser Effect)。 (4) 試體受壓應變與聲射訊號間關係 之探討。 由本研究之 312 個水泥砂漿試體及 210 個飛灰水泥砂漿試體 的實驗結果中可發現，水泥砂漿及飛灰水泥砂漿各主要參數與聲射訊號之 總事件數（Total Event）、計數率（Count Rate）、尖峰振幅（Peak Amplitude）、高振幅事件比率（High Amplitude Event Ratio）等均存 在著良好之關係。同時，實驗結果亦顯示在持續的載重狀況下，聲射總事 件數的突然急速增加將可作為結構物瀕臨破壞之警訊。另一方面，在聲射 凱撒效應的研究方面，實驗結果顯示在載重不超過 80 % 試體極限抗壓強 度時，聲射凱撒效應均存在於水泥砂漿及飛灰水泥砂漿試體中；而在探討 環境變數對聲 射凱撒效應的研究方面，由實驗結果中可以發現，在本研 究的環境變數（包括加載速率、加載方式、加載方向、養護齡期及不同時 間再壓效應等）下聲射凱撒效應仍然存在於水泥砂漿及飛灰水泥砂漿試體 中；此結果顯示聲射凱撒效應對於混凝土材料荷載歷史之檢測將深具潛力 。此外，由試體受壓應變與聲射訊號間關係之推導中可發現，聲射總事件 數與試體應變間約呈一線性之正比關係，而此一發現對於未來應用聲射檢 測技術在混凝土材料之研究發展上將頗有助益。 The application of nondestructive testing (NDT) methods has become increasingly significant in the field of civil engineering. This study is devoted to the investigation of the characteristics of acoustic emission (AE) signals detected from concrete materials under uniaxial compression. Due to the fact that cement mortar is the basic component of concrete materials, it is believed that an investigation focusing on the AE characteristics of cement mortar and fly-ash cement mortar (FACM) should be studied first. The following topics are studied in this research: (1) Correlation between AE signals and the major parameters of cement mortar such as water-cement ratio, compressive strength, age, strain, porosity ratio and hydration level; (2) Correlation between AE signals and the major parameters of FACM such as the amount of cement replaced by fly- ash, compressive strength, age and strain; (3) The characteristics of AE Kaiser effect of cement mortar and FACM; (4) Correlation between AE signals and the compressive strains. From the experimental results of 312 specimens of cement mortar and 210 specimens of FACM, good correlations between the major parameters of the specimens and the AE signals (such as total event, count rate, peak amplitude and high amplitude event ratio) were observed. For the study of the AE Kaiser effect, the test results showed that the AE Kaiser effect existed in specimen up to 80% of its ultimate strength. In addition, the experimental results also showed that the existence of the AE Kaiser effect will not be affected by the variations of the test conditions (including loading rate, loading pattern, loading direction and curing time, etc.) given in this study. Furthermore, a linearly correlation was observed and established between the compressive strain of the specimens and the AE total event. This observation shows that the AE technology has good potential to be used as a useful tool to monitor the integrity of concrete materials.