Role of Fine Mineral Powders to Produce High-Performance Concrete

近年来，人们指出混凝土结构容易受到超载和恶劣环境的侵袭，对其功能和性能提出了更高的要求。在此背景下，高强、高耐久、自密实的高性能混凝土应运而生。细矿物微粉被认为是生产这些高性能混凝土的重要关键因素。本研究的目的是探讨矿物细粉的保水作用，使混凝土具有高耐久性等高品质。试验结果总结如下：1.评价了矿物微粉的比表面积、粒度分布、形状因子和孔隙率等性能。考察了矿物微粉的保水性能，并通过流动试验、渗水试验和粉浆离心试验确定了保水系数。M…不仅考察了保水因素之间的关系，而且还研究了这些因素与粉末物理性质之间的关系。研究了9种矿物微粉替代部分砂量对提高混凝土出水量和出水率的效果。微粉对混凝土的减渗效果与其保水性能密切相关。掺入矿粉的细粉对混凝土的减渗效果可以通过粉浆试验中确定的保水系数来评价。在肉质混凝土中有气孔的水将被移向表面。当掺量过大时，会对粗骨料下的水槽、水囊等缺陷的产生产生不利影响，混凝土表层附近的间距系数增大。混凝土的渗漏对混凝土中粗骨料的界面区有广泛的影响。尤其是在距混凝土浇筑侧20 mm~40 mm处，粗骨料周围的弱化区增大。软弱区将导致混凝土抗冻性降低。矿物微粉的应用对于形成合适的气孔体系、形成细小的孔结构、控制粗集料周围的薄弱区域是非常有效的，对配制高耐久混凝土具有重要意义。较少

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