Abstract
As a preparatory study on the theory of the hardening of mixed portland cement, experiments have been made on the wet reaction between “white earths” or volcanic ashes and slaked lime by the aid of optical observation, X-ray analysis, thermal analysis, and the determination of free lime. 2 “white earths” and 3 volcanic ashes, both raw and calcined for 2hr. at 800°C., have been employed. Among them, “white earth” of Beppu contained 12.20% of insoluble matter and 78.45 and 2.16% of soluble silica and soluble alumina resp., while volcanic ash of Karatsu had 28.82, 25.68, and 13.42% of insoluble matter, soluble silica and soluble alumina resp. The results of the experiments may be condensed as follows:
(1) On the addition of water, calcium hydroxide is first adsorbed on the surface of minute grains of the stuffs and then reacts slowly with them, producing hydrates in gelstate.
(2) The mixing stuffs rich in soluble constituents and especially those containing much soluble alumina react actively. Thus the reaction of the Karatsu volcanic ash is most remarkable.
(3) The stuffs calcined at 800°C. are more active than the natural ones.
(4) The chemical reactions in the system calcium hydroxide-mixing stuff-water can be observed by a microscope at their early periods. However the reactions in later periods must be computed also by thermal analysis and the determination of free lime.
