185 (57)
The foregoing table gives results of experiments with various limes and standard red earth and sand.
None of these results show development of hydraulic properties in the lime tested, whether air slaked, or unslaked, in the time available, vis. :-14 days. The strength of the dry mortar is considerably reduced by the immersion of the briquette in water for one day only. Vide 40, 42, 44, 46, &c.
Red earth alone and time alone give same results. Vide 47, 48. Lime alone, and red earth alone, immersed immediately after making and kept in water 14 days, remain soft. Vide 48 & 55.
A mixture of lime and sand is not suitable for mortar.
Vide 63/67.
A mixture of 1 part lime to 2 parts red earth makes the best mortar, but it requires protection from wet; as far as we can tell from 14 day experiments, even mortar which takes a strain of 114 lbs. to break it, vide 43, is reduced to 43 lbs. by one day's immersion, vide 44, and would if kept in water finally disintegrate.
I am disappointed in the results obtained from unslaked stone lime, vide 54/68, as this was used hot.
Generally, I am of opinion the briquettes should be kept at least 3 months before test- ing, as previous experiments with similar materials have shown distinct hydraulic properties in the local mortar; but these experiments were not conducted in such short tiine as 14 days.
ARTHUR H. OUGH,
A. M. Inst. C. E., A.RI.B.A,,
January 3rd, 1907.