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

据报道，水泥混凝土中同时使用膨胀剂和人造轻骨料可以抑制高温下产生的热应力，并可以延长RC板的疲劳寿命。在本研究中，对样本的热膨胀系数进行了测量，并对轻骨料周围进行了显微镜目视观察，以了解其复杂的机制。通过实验研究，两种趋势被认为是重要因素。一是该混凝土的热膨胀系数随时间变化。早期它比普通混凝土高，但随着时间的推移它变小。二是轻骨料的热膨胀系数几乎是普通骨料的一半。由于膨胀作用，在轻质骨料周围产生的间隙空间中没有观察到额外水化产物的沉淀，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.