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This paper presents a study conducted on the effects of mixing within a batch plant operation for 'building industry' type concretes containing mineral admixtures (fly ash, limestone filler or blast-furnace slag). The primary objective of this study was to evaluate the technical bases of French standard XP P 18-305, which stipulates that the mixing time of these concretes is to be increased whenever a mineral admixture is introduced, as opposed to the admixture being mixed with Portland cement to create a blended cement. Testing was carried out in a semi-industrial plant at a 1:1 scale; various techniques were employed both to evaluate the homogeneity of the batches and to characterise the performance of the materials produced. Results suggest a slight advantage in homogeneity in favour of the blended cements, yet this advantage at the scale of the completed structure is not necessarily significant. Moreover, the feasibility of concretes with a binder consisting of at least two-thirds blast-furnace slag, added into the mixer under typical batch plant operations, has been confirmed. The paper concludes with a few research directions in the area of concrete mixing.

A study of Québec penitentiary population trends from 1972 to 1991 (for sentences of 2 years and more), shows a marked ageing in individuals being admitted. After having presented the most pertinent data concerning age at admission, the remaining analysis focuses on some possible explanations for the incurred transformations: (a) the demographic hypothesis, (b) the relative reduction in young adults being admitted, and (c) the increase in older individuals. Although we should not ignore possible changes in delinquent behaviour, it would seem that the incurred transformations are foremost the result of societal reactions and modifications brought to penal policies and practices. Where the changes in the ratios of imprisonment and in the structure of the penitentiary population are concerned, the amendments to legislation, the decisions of those charged with devising the penal practices and those who have to apply them, such as the judges, must be considered as having as much importance as the alleged transformation of «criminality ».

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