高強度混凝土受高溫後之性質

Abstract

高強度混凝土之使用日廣，其火害後之性質則廣受關切。因此針對火 害後高強度混凝土之物理性質變化、力學性質變化、受高溫時之熱膨脹及 火害後之非破壞檢測作探討。 混凝土受高溫後微裂縫增加、骨材破裂 、水化物分解，造成強度及彈性係數的降低。而其冷卻後卻因重行水化作 用而使強度及彈性係數回復。本文即針對火害冷卻後之高強度混凝土試體 於空氣及水中養護，依不同齡期進行抗壓、靜彈性係數及超音波、動彈性 係數等實驗，以量測其強度與彈性係數之變化情形，並求出超音波－強度 ，動彈性係數－強度間之經驗公式。 為瞭解高強度混凝土熱膨脹性質 ，進行水泥漿、水泥砂漿及混凝土之熱膨脹實驗，以比較其間之異同。 High strength concrete is widely used today. Its mechanical propertiesat high temperatures is concerned by the citizens. This research is to investigate not only the physical, mechanical changes and the thermal expansion of high strength concrete, but also the nondestructive tests onthe specimens when exposed to extreme temperatures. The compressive strength and modulus of elasticity of concrete decreaseswith the increasing temperatures. It is believed that the changes in bothstrength and modulus of elasticity may be attributed to a combination of decomposition of the hydrated pastes, deterioration of the aggregates, andthe increase of microcrackings. When specimens were cooled back to room temperature before testing, the strength and elastic modulus will recoverdue to rehydration. The specimens after heating were respectively cured inair and water in this study. The strength, static & dynamic modulus of elasticity, and pulse velocity of concrete after cooling were determinatedat different ages. The correlations between dynamic modulus of elasticityand the strength, the pulse velocity and the strength are presented. To understand the thermal expansion of high strength concrete, the testsalso compare the differences among the cement paste, mortar and concrete.