人工軽量骨材の粒度配列について

抄録

It is the aim of this report to present the result of experiments in the effect of grading of two available artificial lightweight aggregates on the properties of mortar and concrete. The tests were divided into three classes.
In experiment 1, specific character of aggregate at an interval of size and the effects of grading of lightweight sand were investigated. Consequently, we obtained a tendency that the larger the size of the aggregate, the smaller the specific gravity of the grain became and the larger water absorption grew. But the gradings of the sand which were composed of grains, gave a slight variety to the specific gravity, coefficient of water absorption and solid volume percentage of sand, even if the gradings were widely chosen. So the gradings had an inconsiderable effect on the properties of the mortar.
In experiment 2, we investigated how the grading of fine sand, the grading of gravel and fine aggregate ratio affected the properties of concrete. As the result of the test, the aggregate ratio and the grading of sand had comparatively large effects on various kinds of strengths, but the grading of gravel affected only little. The quantity of surface water over the sand at the time of mixing had a large effect on the slump of fresh concrete, and the influence of grading was relatively small compared with it.
In experiment 3, to study the fundamental effects of aggregates such as size, surface area, specific gravity and strength of aggregate on the properties of concrete, test was carried out using the cubic model aggregate made from paper vacancy, rubber, mortar and steel. In consequence, the characteristic of the aggregate including the grading had a great effect on compressive strength, tensile strength, static modulus of elasticity and specific gravity of concrete. It exceeded the effect of water cement ratio. As for the paper vacancy aggregate which was compared to lightweight aggregate, the effect of size on the properties of concrete became marked.
Through the above mentioned three tests, it was indicated fundamentally that various kinds of strengths, specific gravity and static modulus of elasticity of concrete were affected by strength, specific gravity and the grading of lightweight aggregate. On the other hand, as for the artificial lightweight aggregate concrete actually used, the effect of grading on the properties of concrete was found to some extent but factors except grading such as the quantity of surface water over the sand effected it much more.