Utilisation de granulats tendres dans les chaussees

By soft materials we mean those which do not conform to existing standards in respect of mechanical strength, and materials of heterogeneous strength derived from calcareous rocks and containing soft elements; the strength of these materials often conforms to specifications in force in the USSR. Chippings from these rocks have a wide range of mechanical strengths and frost resistances; their strength does not often exceed 20 MPa. Studies carried out in the framework of cooperation between the Sojuzdornii and the Laboratoire Central des Ponts et Chaussées have revealed the possibility of using chippings derived from soft rocks, and in particular calcareous rocks, in pavement courses. Soft materials of heterogeneous strength can behave well in the pavement, because the soft particles in the dense mixes are not greatly destroyed during compaction or under traffic, or they tend towards a stable state. Specifications have been drawn up concerning particle size distribution, the content of impurities, and other properties in the light of working conditions in the USSR and in France.     

Utilisation de la photographie de moire pour mesurer l'usure des granulats dans les couches superficielles de chaussees

The author describes a rapid and non-destructive method of following and measuring the evolution of the shape of aggregates used in wearing courses of roads. The method is based on the moiré phenomenon which, in the present example, allows us to draw graphic curves, with a precision up to a few tenths of millimeters on a vertical cut. The article describes:

- the method and equipment necessary to obtain a workable moiré on a photograph,

- a computer-programmed chain which, during a series of topographical cross-cuts, measures and studies the distribution of spacings of contour lines. The spacings vary according to the rounded nature of the aggregates which are classified according to their shape.

The road studied is then characterized by drawing graphs of the distribution of the lengths of cuts of the road, occupied by the different shapes of the selected aggregates. The author gives a few examples of the uses of the method in studying the evolution of surface dressings and embedded stone on concrete. The author also shows that his method can be used in other fields than civil engineering.     

Classification des granulats pour les couches de roulement des chaussees

Resistance to polishing mainly depends on microroughness of stone elements, which is considered more or less as a natural quality of the rock and is in connection with its mineralogical composition. On the contrary mechanical resistance depends also on exploitation methods and on the technology of production. We must point out that the knowledge of resistance to polishing of aggregates can be improved if more precise relations between laboratory tests, real behaviour in road courses under the traffic and the proposed classification can be found. This classification depends on two laboratory tests: polished stone value and Los Angeles.     

Possibilites d'emploid des calcaires de durete moyenne a faible dans les betons hydrauliques

The crushed limestone aggregates with medium to weak hardness present two difficulties concerning first the influence of the variations of the thin elements (0/500 μm) content, (these thin elements are produced between the production of the aggregates 5/20 mm and their utilization) and second the hardness of these materials which is lower than for traditionnaly employed silico-calcareous aggregates. The results of the research described in the paper do no confirm this fear; on the contrary, it is obvious that the limestones allow to elaborate concretes presenting quite satisfactory characteristics; the technology of use does not introduce any particular problem except the necessity of employing wet aggregates. In return, the durability of these concretes, tested through the freezing test, shows that it is better, especially for concretes with a medium cement content, to use an air entraining-agent.     

Influence de la petrographie sur les caracteristiques physiques et mecaniques de granulats calcaires de lorraine

Limestones with different textures and petrographic composition were chosen for study: polyparies limestones, oolitic limestone and micritic limestone. These rocks are characterized by the study of their porosity and their texture with a Scanning Electron Microscope, by the measurement of the longitudinal elastic waves and of quality index. Uniaxal compression tests were performed, with a servo-controlled testing machine. Aggregates produced from these rocks were tested with Los Angeles and Microdeval machines. The experimental reslts were compared with S.E.M. observations. We compare also surface aspects of the aggregates before and after mechanical test, so fracture pattern of grains.     

Gonflement de la chaux dans les briques

Le problème de l'éclatement des briques dû à l'action de la chaux devient grave dans la fabrication des briques en différents endroits de l'lnde et d'ailleurs. Des briques cuites tombent en poussière lorsqu'elles sont exposées à l'air libre, du fait de la présence de particules de chaux. L'Institut central de recherche de la construction de Roorkee s'est attachée à l'étude du mécanisme par lequel les chlorures peuvent prévenir cet inconvénient.     

Metaux lourds dans les sediments de l'estuaire de la loire

Estuaries, being interfaces between fluviatile and marine environments, are the scene of considerable physico-chemical and biological gradients which can have an effect on the distribution of metallic elements between the solid and dissolved phases. The purpose of the present study was to determine the relative influence of each parameter in this distribution.The study included two series of samples (ICOLO 26 and ICOLO 32) taken by means of the Schipeck grab at 19 selected points of the estuary as indicated in Fig. 1.Within the framework of this study we first investigated and were able to determine the origin and evolution of the metallic elements in the Loire estuary.Pollution levelTable 1 and Fig. 2 summarize the results: firstly, the metallic element contents are relatively low, indicating that pollution is not very strong. Secondly, the contents measured in the different samples vary considerably due to the great heterogeneity of sample composition and particle-size distribution.Upstream-downstream evolutionFigure 2 shows that the longitudinal profiles for metals are very similar to those obtained for the different characteristics of the sediments. Such an observation has already been made by various authors. Owing to the existence of these relationships, we believe, as do Boust et al. (1981), that it is preferable to interpret the results relative to metals obtained on a given site in terms of the various characteristics of the sediment. In Fig. 3, the metallic element contents (ICOLO 26 samples) is thus plotted against organic carbon. As shown in the figure, there is a very good relationship between the two parameters. Figures 2 and 3 indicate that the contents are uniform throughout the estuary with no evidence of further significant sedimentation this uniformity being due to tidal action. Owing to this uniformity, the impact of significant discharges is highly localized except for the wastewater from the city of Nantes as a whole, whose impact which is felt along the entire estuary.The relationship between copper and volatile matter for the ICOLO 32 samples, as represented in Fig. 4, shows that the points fall into two groups, which are the same whatever the explanatory parameter involved. Though the results are more uniform for the ICOLO 26 than for the ICOLO 32 samples, Fig. 6 clearly shows that the “marine” points stand out in both series of samples. This is indicative of a reduction in contents in the downstream direction, especially noticeable beyond point B (Zn, Cr, Ni) or even M (Cd, Cu, Pb).The seasonal evolution is clearly shown on the “metal-characteristic of sediment” graphs by the comparison of the slopes of the lines linking the same point sampled during the two sampling campaigns. The example of copper is shown in Fig. 7.On the whole, analysis of the results derived from the study of one characteristics of the sediment, indicates that only limited enrichment or depletion occurs at a point over a period of time. This probably reflects a good constancy over time of the metallic flux in the estuary. There is little doubt that changes in the composition of the sediment, will cause changes in the trapping of the metallic flux. In this case, variations in contents do not reflect alterations in the metallic flux over the sediment, but the varying capacity of the sediment under investigation to trap the same polluting flux according to is own composition.This study was also productive in the investigation of the various phenomena responsible for the reduction in metal contents during estuarial transit, which phenomenon can be expected to occur in a large number of estuaries.The impact depends on the chemical properties of the element under investigation.Solubilization of metallic elements due to to increased salinity occurs but plays only a secondary role in the upstream-downstream reductions. This is presumably because of the low percentages of metal absorbed in relation to the total amount of metals associated with the sediments.The reduction in metal contents related to the degradation of organic matter also occurs but it is of little significance compared with the overall phenomenon. The disappearance of metals associated with organic matter could well be related to salinity.The considerable reduction of contents in the lower estuary markedly occurs downstream of the salinity front and precisely where the first sediments characteristic of the marine environment are encountered. Consequently, the most obvious parameter responsible for the reduction in the metallic element contents is the mixing of relatively laden fluviatile sediment with “clean” marine sediments.     

Prise en compte de l'environnement dans les inventaires de gisements

Conflicts and difficulties encountered in the opening of quarries in spite of the setting up of impact studies and regulations regarding the obligation of restoring the site after quarrying operations, led to the undertaking of environmental studies carried out before the impact study itself. The first experiments taking the surroundings and environment into account had been carried out without any consultation concerning the method. Recent experiments made in “Departements” (=subdivisions) were subject to a more theoretical approach and allowed the setting of a new french methodology. This new methodology includes both the environmental approach itself, and its close relation to the survey of aggregate deposits, as well as the economical survey of the aggregate requirements. The approach is based on an analysis and a mapping of all environmental factors for the whole territory considered. It includes the analysis of quarry effects on the surroundings involved, as well as the emergency of the consequent obligations. For each quarry the nature and importance of the particular obligations are appreciated, followed by the evaluation of the environment obligation as a whole. The latter may vary according to the economical interest of the deposit and the alternatives (location, lessening of effects, restoration of the site, transportation of aggregates). It is thus possible to draw up a quarry classification showing optimal potentialities of workability compatible with the protection of the environment. The approach allows the development of a process of great concertation necessary for setting up a true quarry policy. Previouly to the impact study, it is advisable to carry on two successive studies (at two different levels). Results from such studies can be easily combined with planning and national development.     

Les relations karst-rivière dans les calcaires barrémo-bédouliens du Diois (Drôme – France) Exemple de la Gervanne

The karst in the Gervanne river is a well-developed system found in a limestone formation from the Barremian-Bedoulian that is about 400?m thick. Although its limits are not known to any great precision, they are very similar to those of the geographical area of the Gervanne watershed. Explorations have brought to light a dense system of cavities and one main outlet: Les Fontaigneux spring, a permanent spring. The relationships between the river and the karst are complex. They can be analysed by studying the hydrological data and tracer information. During low waters, seepage from the river often reduces river flow to nothing. Tracer tests were carried out to check the conditions in which water circulates in the karst. The rate between the first arrivals of the tracer and the peak velocity shows that the flow takes place in a channel pattern with very low longitudinal dispersal during low waters. Dispersion was only seen to occur during high waters, when the karst feeds water back into the river in a flow that takes into account the fissuring and joints between the rock. The seepage discharge in the Gervanne therefore depends on the amount of water in the karst. In fact, it does not seem possible to conduct artificial maintenance of the water level in order to avoid losses from the river into the karst. If artificial measures were to be taken to maintain a minimum water level in the river, for instance, by building a dam, watertightness could not be guaranteed because the basin is much too permeable.     

Evaluation de la charge virale dans les eaux d''une station d''epuration biologique au moyen de deux methodes de concentration de virus par adsorption-elution sur poudre de verre ou sur microfibre de verre

Two methods of adsorption-elution on glass powder or on glass microfibre have allowed to determine the virus quantity at the entrance and at the exit of a biologic sewage farm. Almost the same results are obtained by comparing the two techniques. The frequency of virus isolation is very important both in the affluent and in the effluent. The rate of reducing the quantity of virus in the effluent is in the region of 78%. The identification of the virus has shown the systematic existence of Enterovirus. If one has to choose between the two techniques, the method of adsorption-elution on glass powder is more advisable, because there is no problem of blockage.     

Emploi des calcaires en limite de specification

Building a motorway involves to deal with enormous quantities of materials which, if not available near the site, will have an incidence on the transportation cost. This may considerably modify the economic balance of a project. A double mission was committed to the “Laboratoire Régional de Nancy” in the building of Lorraine-Bourgogne motorway:

-to detect all available resources near the project;

-to adapt, if necessary, production and building practise to the distinctive features of the encountered limestones.

This led to the opening of Harmonville quarry and the valorization of Bajocian oolitic limestones which had not yet been used in road construction. This quarry produces:

-materials for high quality embankments,

-up to one million tons of subgrade materials,

-materials for gravel-slag mixture for foundation layer and sand for gravel-bitumen mixture and bituminous mixes, in spite of geotechnical characteristics which were at first considered to be too weak.

Unusual or “risky” materials are not adapted to conventional production or building techniques, hence the research of new technologies leading to an increase of the price of the materials, which is widely compensated by the savings on transportation. It is also an economy in the field of traditional resources, because the production of this quarry is equivalent to 10 years of work for a medium size gravel-pit exploitation. Harmonville quarry exploitation can be considered as a regional first experience, because it represents on a large scale the importance of “near specification limits limestones” in road construction.     

Essai au bleu et nocivité des montmorillonites dans les matériaux composites

The behaviour in wet conditions of materials (aggregates, soils, rocks...) containing clay particles depends on both the latter content and its mineralogical nature. According to the technique involved (cement-treated soils, bituminous mixes, concrete...), only external surface area or both external and internal surface areas of the clays are dominantly relevant. In this paper, we describe two simple ways of using the Methylen Blue test which allow the swelling nature of the clays, through the ratio of the external to the internal surface areas as well as their amount to assessed for The operating procedures are given; potential applications are also discussed.