Fine limestone additions to regulate setting in high volume fly ash mixtures
Fine limestone additions to regulate setting in high volume fly ash mixtures
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DOI：
10.1016/j.cemconcomp.2011.09.004
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发表时间：
2012-01-01
影响因子：
10.5
通讯作者：
Weiss, W. Jason
中科院分区：
文献类型：
--
作者：
Bentz, Dale P.;Sato, Taijiro;Weiss, W. Jason
大掺量粉煤灰(HVFA)混凝土因其成本和可持续性优势而被越来越多地考虑。虽然这些HVFA混凝土的长期性能通常达到或超过传统混凝土，但它们的早期性能通常具有水化反应过度延迟、凝结时间延迟和强度低的特点。将HVFA混合物扩展到含有细石灰石粉的三元混合物中，可能会为这些缺陷提供可行的解决方案，特别是水化延迟和凝结问题。本文研究了一种纳米石灰石粉和另外两种中值粒径(4.4微米和16.4微米)增大的石灰石填料在C级粉煤灰/水泥混合料中加速早期反应和缩短凝结时间的倾向。石灰石的细度对其加速水化和缩短凝结时间的效果有显著影响。用细小的硅粉制备的伴生样品表明，细小的石灰岩可能通过物理和化学机制起到有利的作用。等温量热法和维卡针在浆体上的渗透测量伴随着砂浆上的强度测量，以验证石灰石粉的替代不会对强度发展产生负面影响。用等温量热法测定砂浆的1d和7d抗压强度与其相应的累积放热量之间存在着线性关系，并具有合理的相关性。爱思唯尔有限公司出版。
High volume fly ash (HVFA) concrete mixtures are being considered more frequently due to their cost and sustainability advantages. While the long term performance of these HVFA concretes typically meets or exceeds that of conventional concretes, their early age performance is often characterized by excessive retardation of the hydration reactions, delayed setting times, and low strengths. Extending an HVFA mixture to a ternary blend that incorporates a fine limestone powder may provide a viable solution to these deficiencies, particularly the hydration retardation and setting issues. In this paper, a nano-limestone powder and two other limestone fillers of increasing median particle size (4.4 mu m and 16.4 mu m) are investigated for their propensity to accelerate early age reactions and reduce setting times in a Class C fly ash/cement blend. The fineness of the limestone has measurable effects on its efficacy in accelerating hydration and decreasing setting times. Companion specimens prepared with a fine silica powder suggest that the fine limestone may act favorably through both a physical and a chemical mechanism. Isothermal calorimetry and Vicat needle penetration measurements on pastes are accompanied by strength measurements on mortars, to verify that the limestone powder substitutions are not negatively impacting strength development. A linear relationship with a reasonable correlation is found to exist between 1 d and 7 d compressive strengths of mortars and their accompanying cumulative heat release values as determined using isothermal calorimetry. Published by Elsevier Ltd.