As allophane has a high moisture content of 100-250%, it is necessary to decrease the moisture content by some means so that plasticity index (PI) of the stabililized allophane decreases and that the trafficability is improved in early stage of earthwork. The treatment of such clay soil with quick lime is quite effective for this purpose. On the other hand, new minerals produced by the reaction of allophane with hydrated lime were appreciated by the forwer reports, but the strength of allophane could not be satisfactorily improved by hydrated lime.
Studies were made on the characteristics of strength of allophane stabililized with quick lime as compared with hydrated halloysite and a typical clay soil of Kanto loam which consists of 75% hydrated halloysite and 25% allophane.
From test results the following was obtained.
(1) In allophane stabililized with quick lime, the increase in plastic limit (PL) is accomparied by a decrease in liquid limit (LL). Consequently the plasticity index (PI=LL-PL) is greatly reduced.
(2) The unconfined compressive strength of hydrated halloysite and that of Kanto loam increase by means of treatment with quick lime of under 20% content by weight of dried soil, but that of allophane does not increase with the same content of quick lime.
(3) The stabilization with quick lime of above 30% content can make it possible to develop the strength of allophane.
(4) The unconfined conpressive strength of dried allophane treated with quick lime increases as compared with that of undried allophane with the same content of quick lime.
(5) The generating rate of reaction products of allophane with quick lime can be accelerated by drying the clay soil.

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In this study, both insoluble anhydrite resulted from calcining of phosphogypsum and flyash were used as the shrinkage reducing mixes. These mixes were added to mortar or concrete so as to contain the total SO₃ content of 3 to 4 % in ordinary Portland cement base.
The strength and shrinkage of mortar and concrete added or no added these mixes were examined.
The results obtained are shown as follows :
1) The shrinkage of mortar specimens added these mixes decreases to about 50% of that of original cement no added, while the shrinkage of plain concrete or air entrained concrete specimens added these mixes decreases to 70% of that of original one.
2) Anhydrite accelerates the initial stage of hydration and in later stage, flyash plays the part of strength development by pozzolanic reaction, so the presence of these mixes induces a good strength development through full stage of curing. Especially, the 91 days compressive strength of mortar specimens increases to above 110% of that of original cement no added.

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