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首页> 外文期刊>Magazine of Concrete Research >Assessment Of Methods For Optimising Ternary Blended Concrete Containing Metakaolin
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Assessment Of Methods For Optimising Ternary Blended Concrete Containing Metakaolin

机译：含偏高岭土的三元混合混凝土优化方法的评价

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The relative effectiveness of three approaches-isothermal calorimetry, trial batching and particle packing models-for optimising mix proportions in Portland cement/metakaolin (MK)/fly ash (FA) ternary blended concretes was compared through measurements of workability and compressive strength, in consideration of economy. Mixtures were prepared using single cement and class C FA and two MKs of varying fineness. The finer MK showed a higher rate of reaction, but the isothermal calorimetry also suggested that MK replacements of 5% or higher are needed to overcome the hydration delay resulting from the use of 25% by mass FA. Trial batches at three water-to-cementitious materials ratios (w/cm)-0·30, 0·40 and 0·50-were designed based on the calorimetry results. While workability decreased with increasing MK content, similar or better workability than the control mixes was achieved in the ternary blends. The compressive strength significantly increased with increasing MK content, as compared to the ordinary concrete and the FA binary blends, and especially at low w/cm (i.e. w/cm = 0·30). The trial batch strength results confirmed that the hydration rates (measured by isothermal calorimetry) could be used to optimise binder composition for early concrete strength. However, in the third approach, the particle packing model was found to be insufficiently related to measured 1-day strength or to strength in higher w/cm concrete; the closest relationship between the primary model parameter (q) and strength was found at lower w/cm and at later ages (i.e. 28 days). It is proposed that the lack of consideration of the constituent's chemical reactivity of highly reactive materials, such as MK, makes this approach unreliable at early ages and at higher w/cm. Finally, despite the lack of correlation between q and strength, results show q values of 0·26-0·29 are optimal for workability.
机译：通过测量可加工性和抗压强度，比较了三种方法的相对有效性-等温量热法，试验分批法和颗粒堆积模型-用于优化波特兰水泥/偏高岭土（MK）/粉煤灰（FA）三元混合混凝土中的配合比经济。使用单一水泥和C级FA和两种不同细度的MK制备混合物。较细的MK显示出更高的反应速率，但等温量热法还表明，需要使用5％或更高的MK替代品来克服因使用25质量％的FA而导致的水合延迟。根据量热法设计了三种水胶结材料比率（w / cm）-0·30、0·40和0·50的试验批次。尽管可加工性随着MK含量的增加而降低，但在三元共混物中却获得了与对照混合物相似或更好的可加工性。与普通混凝土和FA二元共混物相比，抗压强度随着MK含量的增加而显着增加，尤其是在低w / cm（即w / cm = 0·30）的情况下。批强度试验结果证实，水合速率（通过等温量热法测量）可用于优化粘结剂成分，以提高混凝土的早期强度。但是，在第三种方法中，发现颗粒堆积模型与测得的1天强度或较高w / cm混凝土中的强度没有足够的关系。在较低的w / cm和较高的年龄（即28天）发现了主要模型参数（q）与强度之间的最密切关系。有人提出，由于缺乏对高反应性材料（例如MK）的化学反应性的考虑，使得这种方法在早期和更高的w / cm下不可靠。最后，尽管q和强度之间缺乏相关性，结果显示q值0·26-0·29对于可加工性是最佳的。

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