Abstract
The authors continued their previous studies I-XIV on various mixed Portland cements and here reported the further results of comparative studies on various mixed Portland cements comparing common Portland cements and the main points of the present communication are abstracted from the original Japanese paper, as follows:
(1) The strengths for longer curing ages 13, 26 or 52 weeks of dry or non-plastic mortars and wet or plastic mortars of common and mixed Portland cement samples, which were already reported in the previous reports, are tested and discussed for the characteristic points of mixed Portland cements. The mixed cements have generally smaller strengths at shorter curing ages 3 days, 1, or 4 weeks, but larger strengths at longer curing ages, 8, 13, 26, or 52 weeks than ordinary common Portland cements, owing to the larger increment of strength by the combination between lime set free from the hydration of. clinker part and soluble sillica of high siliceous admixture.
(2) Common Portland cement, obtained from clinkers containing large amount 5-10% of uncombined or free lime, are very unstable for setting and also gave unstable mortars. But it is successfully able to obtain very stable mixed Portland cements, by mixing and grinding these clinkers with high siliceous admixtures, which are obtained plentifully as “Kayohakudo”, “Yokeihakudo”, “Keisanhakudo”, etc as shown in the previous reports.
(3) Iron or ore cements of high iron oxide special Portland cement, which already reported by the present authors in the other paper (The Journal of Chemical Industry, Japan, 1935, 38, 109, 215, 726, 1457, 1592), were prepared from clinkers containing uncombined free lime 3-6%, and their mixed cements were prepared from these clinkers and high siliceous admixtures. These cements were compared on their soundness of neat cement paste by the Le Chatelier's calliper method or Bauschinger's prismatic test pieces, and their strengths by plastic mortars as before. The mixed iron cement were very stable and completely sound, owing to the combination between the free lime in the clinkers and soluble silica in the siliceous admixtures.
