시멘트기와의 품질개선(品質改善)에 관(關)한 연구(硏究) = Studies for the improvement of qualities of cement mortar roofing tiles

다국어 초록 (Multilingual Abstract)

The experiment was carried out to investigate the qualities of cement mortar roofing tiles which were produced at ordinary roofing tile manufacturing plants and to show some criteria for making better qualities of roofing tiles by experiment results.
The results obtained in this experiment are summarized as follows;
1. Two different tiles in their qualities such as special and common have been produced at some roofing tile factories. In order to investigate their qualities they were sampled at random in 12 roofing tile plants located at the city of Suwon.
In this experiment, three different ratios of cement to sand by volume such as 1:3，1:6 and 1:12, were also prepared as samples to find out some criteria for the improvement of qualities of roofing tiles. The tests on them were carried out according to the standard testing methods which are specified in the Japanese Industrial Standard (J.I.S). A simplified testing tool for bending was also specially designed and used it for bending test.
2. According to the experimental results on the samples taken from the ordinary different plants, the percentages of the number of tiles satisfied the criteria in J.I.S, were 80 percents for specials and 90 percents for commons on their absorption tests, and about 60 percents for specials and almost zero percent for commons on their bending strength test. It could be said that the results of the absorption rates were much better for both special and common than those of the bending strength. However, as the latter is usually considered to be more important in their qualities, one must pay attention for selecting tiles produced at ordinary roofing tile manufacturing plants.
3. The relation between different ratios of mortar and their optimum ratios of water to cement controlling the absorption rates, can be expressed by the following regression equation;
Y=0.1+1/15X
where Y: ratio of water to cement X：ratio of mortar
4. The relation between different ratios of mortar at their optimum ratio of water to cement, and bending strengthes are shown in Fig. 7
5. The relation between different ratios of mortar at their optimum ratios of water to cement, and numbers of roofing tiles produced per sack of cement can also expressed by the following regression equation;
Y=12.2X
where Y: numbers of tiles X: ratio of mortar
9. In accordance with the results obtained in this experiment, it is estimated that the ratios of cement to sand by volume for roofing tiles produced at ordinary roofing plants, would be 1:8 for special ones, and between 1:10 and 1:12 for common ones, respectively, and that their numbers of tiles per sack of cement would also be 95 for the formers, and between 110 and 120 for the latters, respectively.
7. Concerning with the improvement of qualitise of roofing tiles, it is proposed that the least mixing ratio of mortar should be 1:7, the ratio of water to cement being 0.55. In addition, the number of produced per sack of cement should be restricted to less than 85 tiles, and tiles must be cured under water at lease 7 days after removing their molds.