Bulletin Volume 3-29 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 edition. Excerpt: ...problem was to determine whether or not the same qualities which make a cement strong or weak at the end of the 7-day period make it strong or weak at the end of the 28-day period. As a high degree of relationship was found to exist between the strengths at the two periods, it was concluded that some of the same qualities must control the strength at both ages. In this paper a beginning of the study of the specific qualities which might influence the 7-day and 28-day strengths will be made. The cement quality chosen for study is that of the times of initial and final sets (Gilmore Needle Method) and their relation to tensile strengths at the 7-day or 28-day period. Stated otherwise do the ingredients in cement which tend to hasten or retard the times of initial and final sets, have a tendency to weaken or strengthen the cement at the ordinary test ages? Data The data included in this discussion include 687 cements tested at the University of Maine Testing Laboratory upon which complete information is available on the time of set, and the 7day and 28-day tensile strengths. These cement samples represent approximately 159,000 bbls. of cement of a varied number of brands in common use in New England. The strength tests were carried out in the usual manner according to A.S.T.M. specifications. The times of sets were determined by the Gilmore Needles. The time of set is taken as the time interval in hours. between the time of adding the water to form the neat cement paste and the time when the pat will just support the smaller needle in the case of the initial set and the larger needle in the case of the final set. It should be noted that both from the nature of the apparatus and from the nature of the test this time cannot be exact and very...