Reported herein are the results of study on properties of intrusion mortar for prepacked concrete and on relationships between properties of intrusion mortar and those of prepacked concrete. The study was carried out as a part of the research project on the mothods of underwater-concreting in Materials Laboratory during
the period from April 1957 to March 1964.
　To obtain prepacked concrete of reliable quality, the intrusion mortar is required to have such properties as medium flowability, proper expansibility, the minimum　tendency of segregation and proper time of setting before hardening and required strengths, high durability and the minimum volume change after hardened. As well known, these properties are affected more or less by the type and quality of　materials to be employed, mix proportion, mixing and curing conditions, and other factors, however, the relationships among the mortar properties and these factors as mentioned above have not necessarily been made clear although some have been already proved. In this study, therefore, investigated were the influences of type and quality of mortar making materials as cement, flyash, sand, cement dispersing agents, and powdered aluminum, mix proportions and mixing conditions of intrusion mortar. Also, proportions and properties of intrusion mortar upon properties of prepacked concrete were investigated and discussed.
　At first, the effects of mix proportions upon the properties of intrusion mortar were studied. Investigated were the relations between each of ratios as water c
ement ratio W/(C+F), flyash content F/(C+F), sand cement ratio S/(C+F), dosage of cement dispersing agent CDA/(C+F), and dosage of powdered aluminum A1/(C+f) and each of mortar properties as flowability, expansibility, bleeding, water retentivity, time of setting, flexural and compressive strengths, and drying shrinkage of mortar. Based on these relations proved, the conditions to be taken into consideration in proportioning intrusion mortar were then discussed. Next, effects of type and quality of mortar making meterials upon the properties of mortar were investigated and then the influences of temperature, mxing speed and mixing time were tested and the requirements for the field mixing of mortar were discussed. Finally the interreltions among the properties of intrusion mortar and those of prepacked concrete were brought to light.
　In analyzing the relationships between the mix proportions and the properties of　mortar, the concept of movable water factor was brought in as a fundamental qua
ntity proper to a certain mix proportion and the author showed that the variation of flowability, bleeding and water retentivity of intrusion mortar due to a change in mix proportion are basically attributed to the variation of the movable water factor of the mix. This concept of movable water factor was contrived from the following hypothesis.
　It has been proved by T.C. Powers and H.H.Steinour in their theory on bleeding of cement paste that a part of the unit water content of the paste is adsorbed chemically or physically to the surface of fine cement particles and is ineffective to the flowability of the paste, i.e., only the rest of water deducted the adsorbed water from the unit water content is effective to flowability and bleeding of the paste. K.Yamazaki has proved the theory to be applicable to the paste of cement blended with flyash or mineral fines. Assuming the theory is also applicable to intrusion mortar and the amount of water adsorved to mineral fines in the mortar is known, the change in flowability, bleeding and water retentivity of mortar due to a change in mix proportion can be analyzed in terms of the amount of water, only which is considered effective to these properties of mortar. Immobile water factor is known as an index of the amount of water adsorbed to the mineral fines, which is considered proper to the type of the mineral fines, and the rest of water deducted the amount equivalent to the immobile water factor from the unit water content has been named as movable water content by T.C. Powers. Since the immobile water factor, however, is neither a factor per unit volume nor unit weight of paste, the definition of this movable water content is not so clear and it seems no further efforts have been made to express it quantitatively. The author defined the movable water factor by the amount of water deducted unit immobile water content from the unit water content of mortar, assuming the immobile water content is proportional to the immobile water factor and to the solid volume of cement, flyash and sand, which can be easily justified. The unit immobile water content is the amount of water which is adsorbed on the surface of fine particles as cement, flyash and sand in unit volume of mortar, and it can be reduced from the immobile water factors of cement, flyash and sand and solid volumes of these particles providing they are known through tests, mix proportion and their specific gravites.
　From the study on the properties of intrusion mortar as stated above, the author concludes as follows.