Kang Sung-Hoon, Lee Ji-Hyung, Hong Sung-Gul, Moon Juhyuk
Department of Architecture & Architectural Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea.
Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore 117576, Singapore.
Materials (Basel). 2017 Sep 20;10(9):1106. doi: 10.3390/ma10091106.
For optimum production of ultra-high performance concrete (UHPC), the material and microstructural properties of UHPC cured under various heat treatment (HT) conditions are studied. The effects of HT temperature and duration on the hydration reaction, microstructure, and mechanical properties of UHPC are investigated. Increasing HT temperature accelerates both cement hydration and pozzolanic reaction, but the latter is more significantly affected. This accelerated pozzolanic reaction in UHPC clearly enhances compressive strength. However, strength after the HT becomes stable as most of the hydration finishes during the HT period. Particularly, it was concluded that the mechanical benefit of the increased temperature and duration on the 28 day-strength is not noticeable when the HT temperature is above 60 °C (with a 48 h duration) or the HT duration is longer than 12 h (with 90 °C temperature). On the other hand, even with a minimal HT condition such as 1 day at 60 °C or 12 h at 90 °C, outstanding compressive strength of 179 MPa and flexural tensile strength of 49 MPa are achieved at 28 days. Microstructural investigation conducted herein suggests that portlandite content can be a good indicator for the mechanical performance of UHPC regardless of its HT curing conditions. These findings can contribute to reducing manufacturing energy consumption, cost, and environmental impact in the production of UHPC and be helpful for practitioners to better understand the effect of HT on UHPC and optimize its production.
为了实现超高性能混凝土（UHPC）的最佳生产，研究了在各种热处理（HT）条件下养护的UHPC的材料和微观结构性能。研究了HT温度和持续时间对UHPC水化反应、微观结构和力学性能的影响。提高HT温度会加速水泥水化和火山灰反应，但后者受到的影响更为显著。UHPC中这种加速的火山灰反应明显提高了抗压强度。然而，由于大部分水化在HT期间完成，HT后的强度变得稳定。特别是，得出的结论是，当HT温度高于60°C（持续48小时）或HT持续时间超过12小时（温度90°C）时，温度和持续时间增加对28天强度的力学益处并不明显。另一方面，即使在最小的HT条件下，如60°C养护1天或90°C养护12小时，28天时仍能获得179MPa的出色抗压强度和49MPa的抗弯抗拉强度。本文进行的微观结构研究表明，无论其HT养护条件如何，氢氧化钙含量都可以作为UHPC力学性能的良好指标。这些发现有助于降低UHPC生产中的制造能耗、成本和环境影响，并有助于从业者更好地理解HT对UHPC的影响并优化其生产。
