Role of Fine Mineral Powders to Produce High-Performance Concrete

近年来，人们指出混凝土结构容易因超载和环境恶化而遭受攻击，要求其具有各种功能和性能。在此背景下，高强度、高耐久性、自密实的高性能混凝土应运而生。细矿粉被认为是生产高性能混凝土的重要关键因素。本研究的目的是探讨细矿粉的保水性对混凝土高质量的作用，如高耐久性。试验结果总结如下：评价了细矿粉的比表面积、粒径分布、形状因子和孔隙率等特性。考察了细矿粉的保水能力，并通过流动试验、出血试验和粉膏离心试验确定了保水系数。我们不仅研究了保水性因素之间的相互关系，还研究了保水性因素与粉体物理性能之间的相互关系。研究了用九种细矿粉代替部分体积的砂石，提高混凝土泌水量和泌水速率的效果。混凝土粉的减凝效果与其保水能力密切相关。细矿粉掺入对混凝土减凝效果的影响可通过粉膏试验中确定的保水系数来估计。在肉质混凝土中有空气空洞的水将被移动到表面。当渗水过多时，会对粗集料下部形成水渠、水袋等缺陷的产生产生有害影响，靠近混凝土表层的间距系数增大。混凝土的渗漏对混凝土中粗集料的界面区有广泛的影响。特别是在离混凝土浇筑面20mm ~ 40mm处，粗集料周围的软弱区增大。薄弱区将导致混凝土的抗冻性降低。矿物细粉的应用对于形成合适的气孔系统、形成细孔结构和控制粗集料周围的薄弱区非常有效，对制备高耐久性混凝土具有重要意义。少

In recent years, it has been pointed out that concrete structures are likely suffer the attacks due to excess load and aggravated environment, and various function and performance for them are required. Given this background, High-performance concrete with high strength, high durability and self-compacting has been developed. Fine mineral powder is considered to play an important key factor to produce these high-performance concretes. The purpose of this study is to investigate the role of water retentivity of fine mineral powder to make the concrete with high quality such as high durability. Test results are summarized as follows ;1. Characters of fine mineral powders, such as specific surface area by BET, particle size distribution, shape factor and percentage of void, are evaluated.2. The capability to retain water by the fine mineral powders is examined to estimate water retaining factors which were definea from flow test, bleeding test and centrifugation test using powder paste. M … More utual relationships are investigated not only among the water retaining factors but also between these factors and physical properties of the powders.3. The effect for improving amount and rate of concrete bleeding is studied using nine fine mineral powders which are replaced some the volume of sand. The effect to reduce the bleeding of concrete by the powder is closely related to its capability to retain water. Effect of fine mineral powder incorporated on reduction of concrete bleeding could be estimated by water retaining factor defined in these powder paste tests.4. Water with air voids in fleshly placed concrete will be moved toward the surface. When the bleeding is excessive, harmful effects will arise on production of defects such as the formation of water channels and water pockets beneath the coarse aggregates, and the spacing factor was increased near the surface layer of concrete.5. The bleeding of concrete broadly influences interfacial zone of coarse aggregates in concrete. Especially, at the 20mm〜40mm from placed side of concrete, the weakness zone around coarse aggregates is increased. The weakness zone will result in less frost resistance of concrete.6. The application of mineral fine powders is very effective to make proper air-void system, to form the fine pore structures and to control the weakness zone around coarse aggregates, and it was very important for make the high durable concrete. Less