Paper by TABAILLON BLASZCZYK BLASZCZYK CHARONNAT from ISCR 8th 1998 Lisbon Portugal
Since 1975, the year in which the first continuous concrete plant was introduced for a road construction project, the use of a continuous production process has become more widespread, and even generalized, in France. Applications in other European countries have started to appear, yet do remain in the nascent stages. Over the course of the past twenty-plus years, considerable improvement has been made to the plant's various components. This progress reflects an increasing level of knowledge acquired in the field thanks primarily to the observations being recorded on the work site as well as to the results of joint research efforts on the part of construction firms and Public Works design offices. With respect to the quantity determination of constituents used, trends have most often demonstrated a better control over flow rates. While not leading to a complete resolution of this problem (chimney, vault, etc.), the research undertaken has provided greater understanding of the reasons behind flow irregularities in the constituents, whether these be sands or dry / wet powders, and has helped give rise to a more rational design of batchers. As far as the mixing stage is concerned, progress has once again been chiefly driven by advances stemming from research. Among these, the adaptation of rotation speeds and the positioning of blades both warrant recognition. Other results from this work have produced some original developments, such as the possibility of inclining the mixer. In addition to these advances as well as other, exclusively technical ones, improvements have also been apparent in the mobility of the production plant and its operating conditions. The most valuable of these, from the vantage point of maintenance personnel, pertain to the accessibility of vital components (especially batchers) and to the positions that enable a very quick clean-up at the end of the day, for the mixer in particular. These rather meticulous operations are often neglected, despite the importance they do represent for the subsequent stages in the production process. The consistency in the quality obtained along with the potential they currently offer serve to make the continuous production facility a well-adapted tool for large-scale concrete production requiring a high rate of instantaneous output, as exemplified by the construction of concrete pavements.