VERIFICATION OF COMBINATION USE OF EXPANSIVE AGENT AND LIGHTWEIGHT AGGREGATE ON FATIGUE RESISTANCE OF RC SLAB AND THERMAL STRESS RESTRANT AND ITS UTILIZATION

研究表明，水泥混凝土中同时使用膨胀剂和人工轻骨料可以抑制高温下混凝土板的温度应力，延长混凝土板的疲劳寿命。本研究借由量测试件之热膨胀系数及观察轻集料周围之微观形貌，以了解其复杂的作用机制。通过实验研究，提出了两个重要的影响因素。一是混凝土的热膨胀系数随时间的变化。混凝土早期的抗压强度高于普通混凝土，但随着龄期的延长，抗压强度逐渐减小。二是轻集料的热膨胀系数约为普通集料的一半。未观察到由于膨胀作用而在轻骨料周围产生的差距空间处沉淀出额外的水化产物，尽管这被认为是该机制的可能原因。

It was reported that simultaneous use between expansive agent and artificial lightweight aggregate in cement concrete could restrain thermal stress induced under elevated temperature, and it could also prolong fatigue life of RC slab. In this study measurements of thermal expansion coefficient of specimens and microscopic visual observation around lightweight aggregate were conducted to understand its complicated mechanism. By the experimental investigations two tendencies were suggested as important factors. One is time dependent change of thermal expansion coefficient of this concrete. It is higher than normal concrete at the early age but it becomes small in the longer time. The other is that thermal expansion coefficient of lightweight aggregate is almost half of normal aggregate. Precipitation of additional hydration product at the gap space created around lightweight aggregate due to expansive action was not observed though it was suggested as a possible cause of that mechanism.