Development of Mortar for Structures

为了改善混凝土经常存在离析风险的缺陷，开发了应用于结构的砂浆（结构用砂浆）。本研究是基于混凝土的抗离析性随骨料最大粒径的减小而增大的现象。也就是说，在建筑物中使用砂浆的关键是减少干燥收缩和防止裂缝，因此，通过调整级配，使砂浆中的骨料体积与混凝土中的骨料体积一样多地增加是很重要的。为了开发上述结构用砂浆，本研究首先进行了细骨料级配与固体体积百分比之间关系的试验，研究了砂浆的流动性、抗离析性与细集料级配的关系，并根据试验结果，找出了砂浆能与混凝土中的集料一样多，又能保证所需流动性和抗离析性的细集料级配。接着，研究了砂浆的干燥收缩与细骨料体积之间的关系，并且确定了干燥收缩随着细骨料体积的增加而减小。在此基础上制作了结构用砂浆的原型，并确定了其干燥收缩与混凝土的干燥收缩相当。在此基础上，提出了结构用砂浆配合比设计方法。最后，在实际预拌混凝土厂配制结构用砂浆，并将其浇注成墙体模板，确定结构用砂浆的填充能力和工作性均高于混凝土。

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.