New Admixtures for Eliminating Steam Curing and its Negative Effects on Durability

R. Khurana, I. Torresan
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引用次数: 8

Abstract

Heat curing is the most common method used for accelerating the strength development in concrete. Accelerated curing finds large applications in the precast industry for quick turnaround of forms and casting beds. The increase in the initial strengths is simply a result of increased rate of hydration caused by higher temperature. However, later strengths are often lower than those of the same concrete cured at 20C. The causes of the strength loss are of physical and chemical nature. The physical cause results in increased porosity and cracking because the concrete constituents have different thermal expansion, (air has the highest). The chemical causes are the differences in the hydration products, microstructure and degree of hydration. Generally, physical causes are the dominating factors for strength loss in hear cured concrete. Results of extensive laboratory and field tests are presented showing that equivalent compressive strengths at 18 hours are obtained with concrete containing the new generation superplasticizers and heat cured concretes at 60C. The 28 day strengths of concretes with admixtures are substantially higher. Thus, with the use of these new generation superplasticizers it's possible to overcome the negative effects of steam curing such as strength loss, permeability, shrinkage, creep and frost resistance.
消除蒸汽固化及其对耐久性的负面影响的新型外加剂
热养护是促进混凝土强度发展最常用的方法。加速固化在预制工业中发现了大量的应用,用于快速周转形式和铸造床。初始强度的增加仅仅是温度升高引起的水化速率增加的结果。然而,后期强度往往低于相同混凝土在20℃下养护的强度。强度损失的原因有物理和化学性质。物理原因导致孔隙率和裂缝增加,因为混凝土成分具有不同的热膨胀(空气具有最高的热膨胀)。化学原因是水化产物、微观结构和水化程度的不同。一般来说,物理原因是造成固化混凝土强度损失的主要因素。大量的室内和现场试验结果表明,含有新一代高效减水剂的混凝土和60℃的热固化混凝土在18小时的等效抗压强度。掺合料混凝土的28天强度显著提高。因此,使用这些新一代高效减水剂可以克服蒸汽固化的负面影响,如强度损失、渗透性、收缩、蠕变和抗冻性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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