Development of Mortar for Structures

结构用砂浆是为了改善混凝土存在离析危险的缺陷而研制的。本研究基于混凝土抗离析性能随骨料最大粒径越小而增大的现象。也就是说，砂浆应用于结构的关键是减少干缩和防止裂缝，因此通过调整级配，砂浆中的骨料体积与混凝土中的骨料体积一样增加是很重要的。为了研制上述结构用砂浆，本研究首先进行了细骨料级配与固相体积百分比关系、砂浆流动性、离析阻力与细骨料级配关系的实验研究，并根据实验结果，找出了砂浆中骨料与混凝土中骨料含量相当，且能保证所需流动性和抗离析性能的细骨料级配。其次，研究了砂浆的干燥收缩率与细骨料体积的关系，确定了砂浆的干燥收缩率随细骨料体积的增大而减小。然后，根据这些结果制作了结构用砂浆的原型，并确定其干燥收缩率与混凝土相同。在此基础上，提出了结构砂浆配合比设计方法。最后，在实际预拌混凝土厂生产结构用砂浆，并浇筑成墙体形式，确定结构用砂浆的填充能力和和易性均高于混凝土。

The mortar for applying to structures (mortar for structures) was developed in order to improve the defect that concrete constantly involves the risk of segregation. This study was based on the phenomenon that segregation resistance of concrete becomes higher as the maximum size of aggregate is smaller. That is to say, the key matter to apply mortar to structures is the reduction of drying shrinkage and the prevention of crack, therefore it is important that the aggregate volume in mortar increase as much as that in concrete by adjustment of grading.In order to develop the above mortar for structures, in this study, first, the experiments to investigate the relationship between grading of fine aggregate and percentage of solid volume, the relationship between fluidity, segregation resistance of mortar and grading of fine aggregate were carried out, and from the results of these experiments, the grading of fine aggregate that mortar can contain aggregate as much as that in concrete and can assure required fluidity and segregation resistance was found out. Next, the relationship between drying shrinkage of mortar and fine aggregate volume was investigated and it was determined that drying shrinkage decreases as fine aggregate volume increases. Then, the prototype of mortar for structures was made based on these results, and it was determined that its drying shrinkage is as much as that of concrete. Furthermore, the mix design method of mortar for structures was developed. Finally, mortar for structures was manufactured at actual ready-mixed concrete plant, then it was cast into wall form and it was determined that filling ability and workability of mortar for structures are higher than these of concrete.