Sous-produits industriels comme granulats routiers

Relation between the characteristics of the aggregates and the properties of some materials—Experimental research works (laboratory or site). Industrial by-products used are as follows:

- as an aggregate:

? stone and gravel pit refuse

? crushed blast furnace slag

? incenerator waste slag

- as a binder:

? hydraulic and non-hydraulic fly ash

? granulated blast furnace slag

? hydrated and carbide lime refuse.

Pavement layers applied are as follows:

- unbound base courses: mechanical stabilisation using stone pit refuse, crushed blast furnace slag, waste incinerator slag

- with hydraulic binder: (cement, fly-ash, granulated slag):

? lean concrete with crushed blast furnace slag and stone pit refuse

? hydraulically bound crushed blast furnace slag, waste incinerator slag, and sand obtained as refuse at sieving

- with hydrocarbon binder:

? bituminous stone pit refuse, bituminous crushed blast furnace slag, and bituminous mixture of gravel and sand and waste incinerator slag

? rolled asphalt with crushed blast furnace slag.

     

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.     

Recherches sur les argiles Egyptiennes pour la production de granulats legers

In some countries, serious problems will have to be faced, due to the absence of natural gravels and the development of building construction from lightweight concrete may be an interesting solution. From this point of view we approach, in this work, the procedure of lighweight aggregate production of four Egyptian clay deposits, which could provide valuable stocks. In this way, this paper presents:

-chemical, mineralogical and thermal characterization of clays;

-correlation between characterization and bloating;

-physical and mechanical properties of produced lightweight aggregates;

-evolution of physical characteristics of aggregates as a function of firing conditons.

     

Recherche de developpement d'emploi des sables issus de roches massives siliceuses et silicatees dans les betons hydrauliques

Because of the depletion in some parts of France of the alluvial sands normally used for hydraulic concretes, consideration has been given to using sands produced by crushing massive rocks as a substitute. Rocks of twelve different mineralogical types, representing most of the types of rock found in France, have been investigated. Attempts were made:

- to determine the maximum acceptable filler content of the sands, in terms of the properties of the mortars and concretes in both the fresh and hardened conditions;

- to assess the risks of alkali-aggregate reactions;

- and to work out the best techniques for the industrial production of these sands, so that the filler content and particle size distribution are compatible with the results of the research on mortars and concretes.

     

Etudes prealables a l'etablissement de zones d'exploitation et de reamenagement coordonnes en Alsace,France.

Problems related to gravel-pits, their exploitation (26 Mt/year) and the disorderly spreading of the sites in the Rhine alluvial plain are a matter of regional concern. The establishment of a regional master plan for the gravel pits (referring to article 109–1 of the Mining Code) has become compelling. This operation started in its working stage with the setting up of a “gravel-pits technical group” within the D.R.I.R., which secured the backing of several regional technical departments, among those the SGAL which has been instructed to supply the required data for:

- defining 16 workable areas as planed for the 30 coming years,

- working out analytical summaries, specifying for each area, the main features of the gravel beds, the technical aspects of their working, and the impact on ground-water,

- drafting the specifications governing the working of gravels in these areas,

- specific research on technical problems tied to the deepening of some gravel-pits coming up against day or conglomerate layers.

This work is part of a broad action concerning 7 Z.E.R.C. (Zones where Exploitation and Recovering of aggregates sites are Coordinated) which cover the whole valley of Alsace, in order to follow the goals defined at a regional level:

- to ensure a good management of the resource corresponding to the regional common good,

- to locate the future working sites, in order to respect at best the economical, geological, agricultural and environmental limitations.

     

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.     

Hungarian experiences gained with the aggregate abrasion test

Since 1979 the Institute for Transport Sciences /KTI/ in Hungary has dealt with abrasion tests. This testing method is an adaptation of British Standard BS 812:P.3.9:1975. The results obtained are as follows:

-The Hungarian testing method is based on oven-dried chippings

-The Hungarian method considers the actual chipping volume.

-The actual abrasion value can be determined with ±5% accuracy, on 90% probability level from test results on eight samples.

-The KTI standard gives limits for the abrasion value.

     

L'essai au bleu de methylene turbidimetrique

The use of the conventional methylene blue test for assessing the cleanliness of aggregates is now wide spread. It appears in most of the recent french specifications on aggregates. However, this test is not convenient in the case of relatively clean materials such as sands for concrete, pebbles,...

- First, turbidity, which measures approximately the surface area of the particles, suspended in the water. Hence the name of the new test.

- Secondly, changes in the light absorption spectra of the methylene blue molecules when passing from the free state to the adsorbed state. It is an easy means of measuring the amount adsorbed which a given quantity of methylene blue undergoes when it is allowed to meet a mineral surface. Hence we can assess the activity of this mineral surface.

The equipment and the operating procedure are described and the results compared to those obtained with the conventional blue test.     

Synthese des etudes de ressources en materiaux pour usages routiers

At the C.C.I.R. request (Comité Conseil à l'Innovation Routière) the C.E.T.E. (Centres d'Etudes Techniques de l'Equipement) carried out in 1981 and 1982 a synthesis on the aggregates resources for road-uses. The objects were:

-analysis of the various constraints lying on the supply in traditional materials (synthesis including the studies already realized, a balance-sheet for each department and area of the present market, and future prospects),

-working out of a list of the materials eventually utilizable, taking into account their natures, qualities and quantities, especially for “new materials”,

-to point out the main centers of interest and to propose future orientations and actions.

The investigation of the different reports allows to define:

-some particularly sensitive areas in which aggregates supplies are already difficult or are going to be short in the near future leading to promote the utilization of “new materials”. Examples: Aquitaine, Midi Pyrénées, Champagne-Ardennes, Centre, Charentes, Région Parisienne.

-some regions or districts where difficulties of supply exist in limited areas or some other districts where difficulties will only come out at several years date. Examples: Provence, Alpes, Côte d'Azur, Corse, Auvergne, Bourgogne, Franche-Comté, Rhône Alpes, Haute Normandie, Nord, Picardie, Lorraine,

-some regions where there are no problems of supply in the foreseeable future. Examples: Limousin, Bretagne, Pays de Loire, Basse Normandie, Languedoc, Poitou, Alsace.

     

Les matieres en suspension dans les estuaires

This paper, devoted to the behaviour of suspended matters in estuaries, deals successively with:

- the nature and origin of sediments suspended in some estuaries

- the behaviour of suspended materials: flocculation, falling rate of flakes, shrinkage, rheology, picking up by currents, slides inside the deposits

- the sedimentary movements of floating materials in the estuaries: transport under the influence of the tides, sedimentary materials available in the estuary, influence of the river discharge and of the salinity, ejection of suspended matters out of the estuary,

- volume of the deposits in some estuaries.

     

Etudes Françaises de materiaux de substitution

The authors examine the substitution materials studies realized in France during the last 10 years with the “Tax on Aggregates” financial support. The different types of substitution are first looked into:

-substitution of crushed hard rocks to fluviatile sands and gravels, whose reserves are becoming exhausted or sterilized by environmental constraints;

-materials not respecting standard specifications of aggregates: 1) soft rocks; 2) soils (fine sands, clayey sands, moraines, superficial deposits); 3) quarries, mines and industrial wastes.

Technical possibilities of uses for these “out of standards” materials are examined for natural or treated materials.     

Application de la teledetection a la recherche de sites d'exploitation de granulats et a l'etude de leur impact sur l'environnement

A statistic sampling of publications concerning “aggregates” prospecting and environment impact studies shows that remote sensing is not so often used, contrarily to what heppens generally in the geological field. Which can be the reasons of that under-use?

- pecularities and traditions in prospecting?

- redundency of the results of remote sensing studies with the result of other methods?

- inadequation or underperforming of remote sensing in the peculiar field of “aggregates” prospecting.

In a first part, that note defines what seems to be the most common wishes of the users concerning remote sensing. In a second part, the various tools of remote sensing are described and their performances evaluated. In a third part, a comparison between the tools and the needs of the users try to evaluate the adequation of remote sensing. After some considerations about environmental impact studies the conclusion shows that Remote Sensing, even if not able to solve all the problems, offers to the users a great variety of usefull tools which, combined with other methods, give valuable results in efficiency and cost-effectiveness.     

Granulats elabores par concassage de betons de demolition

Because of the limitation of the extraction of gravels in some alluvial districts and because of the increase of the transportation costs, the French Administration decided, to encourage and to promote the utilization of materials which would be able to replace the traditional materials, the basic principle being to use at the best, all the regional materials. These materials may be from natural or artificial origin. It's in that context, that in 1982 a road contractor, proposed on his own initiative to use the materials produced from the crushing of reinforced concrete issued from the pulling down of buildings so as to supply aggregates for road-building around Paris. This experience proved to be roughly positive, in spite of the problems concerning particularly:

-the crushing and screening plant for the production of aggregates. Though the quality and homogeneity of the reinforced concrete were rather fair (principal origin: pulling down of the “La Villette” slaughter-houses), the crushing and screening plant needed particular engines which were not yet correctly tested to eliminate the undesirable components (iron, plastics, wood...);

-the rate of production;

-the required characteristics concerning aggregates, taking into account the important traffic on this road and of the techniques which were used; the addition of hard aggregates was considered as necessary.

In spite of these difficulties, this experiment deserves certainly to be renewed; Important quantities of such materials are available in all important urban districts.     

Sable-cendre volante: Influence de la nature du granulat

The evolution, at 20°C and 40°C, of unconfined compressive strength (R'_c) and of splitting tensile strength (S_t) has been studied for five “sand-lime-fly ash” mixtures. Those mixtures are very similar with respect to grading, volumic mix design (aggregate, binder, water) and state of compaction, but they differ in the nature of the 0/2 mm sand: natural or crushed silica, limestone, porphyry and LD-slag. According to the aggregate treated, strengths and cohesion at the same age vary in a ratio from one to about two, even at long term. This difference in behaviour has been assigned principally to three factors which are in decreasing weight:

- surface texture of particles: strengths increase with micro-roughness owing to better adhesion between sand and binder mixture (fly ash + lime),

- chemical nature of aggregate (“acid-base”, character): at 40°C and 20°C till about 50 days of age, its influence seems to be of minor importance in comparison with that of micro-roughness. Later on, at 20°C, its effects appear clearly by a much slower strength increase when the aggregate has a rather “acid” character (silica and porphyry),

- angularity of particle: the influence of crushing is rather of little weight.

The estimation of the angle of internal friction from the S_t/R'_c ratio must be regarded more as an evaluation of the particle-binder adhesion for bound granular material than as one of the angle itself.     

Caractéristiques des masses et marnes du gypse et de leurs faciès d'altération dans la région parisienne méthodologie des études géotechniques

The author presents the principal results of a research project concerning a geological formation widely represented in the natural region of Parisis, North of Paris, which is dreaded by geotechnicians: masses and interstratified marls of ludian gypsum. The impossibility of making ground observations essential to a thorough study of the phenomena of weathering of the gypsum, and notably its substitution, led to the work being undertaken along the following lines:

-Modelling of the geological infractructure of the gypseous slopes.

-The quest for indicators of the lithology and distribution of the residual masses and interstratified marls of gypsum, and the valuable role of diagraphs of natural radioactivity.

-The incidence of the weathering of the gypsum on the mechanical (pressiometric) characteristics of the gypseous areas.

-A methodology of geotechnical surveys on gypseous sites.

A progressive approach is proposed, beginning with a feasibility study, followed by a detailed study of the evolutive nature of the site, essential to the establishment of a suitably adapted project, and concluding with a mechanical characterisation necessary for the structural design of foundations.     

Utilisation d'arènes granitiques pour la fabrication de béton en terre

Completely weathered granites are abundant materials and, as a first approximation, their composition is such that treatment with lime should be quite satisfactory, whether they are used for road-building or to produce stabilized blocks for low-cost housing. Three types of completely weathered granite were selected. Their mineralogical and geotechnical properties, and the rocks from which they originate, are described. The completely weathered granites studied differ:

- in the particle size distribution;

- in the mineralogy of their clayey fraction;

- in the degree of weathering affecting them.

The aim of the treatment was to obtain a material having sufficient mechanical strength and insensitivity to water. The results reveal differences among the materials. On dry test specimens, the best results are obtained with the completely weathered granites having the highest clay content, while in saturated test specimens, we find that the mineralogy of the clayey fraction is a factor: the test specimen that performed best had the highest clay content, but its clayey fraction contained no smectites. It is shown, however, that the harmful effects appear only above a threshold that varies with the percentage of lime, and the performance of one of the specimens, artificially enriched with its own fines, which contained smectites, was improved. We propose a relation between the saturated strength values and the quantity of binding agents formed, as assessed on the basis of a mild acid attack. To conclude, on the whole, completely weathered granites can benefit from treatment with lime, whether the purpose is road-building or the production of stabilized blocks. But optimization of the treatment product-performance couple depends on a detailed knowledge of the materials.     

Gestion des risques et des crises liés à l'instabilité des carrières souterraines abandonnées

Instability of underground excavations and karsts generally leads to violent events that affect zones which are difficult to locate precisely. For this reason, monitoring and alarm systems are not very efficient and risk management must therefore be essentially focused on prevention. In France, the aim of such prevention is to find a balance. Although the French legal and regulatory framework is rational, it is deficient in certain respects, and particularly faces difficulties concerning implementation as revealed by the development of the Plans of Exposure to Risks (PER) having taken too long. The comments made during the symposium held at Nainville-les-Roches have lead to the proposal of a number of improvements for the present system:

-promote a global approach which integrates risk management into land-use planning, ensuring coherence between national, regional, departmental and local plans,

-develop an operational approach for each “basin” at risk,

-speed up hazard mapping by its separation from regulatory procedures,

-develop plans for crisis management at a municipal level; bring experts, technical services and emergency services closer together and involve populations at risk in the preparation process,

-launch an operational information policy on the risks and develop a true culture of risk prevention,

-set up a local public service responsible for risk management of underground excavations within areas of greatest risk.

     

Influence des argiles illitiques sur les graves ciment

This paper deals with the properties of 0–14 mm gravels stabilized with cement, with the addition of different clay contents (illite: 0–2–4–8%). The clay influence has been emphasized by replacing the clayey particles by calcareous fines. The quantitative and qualitative influence has been appreciated by the means of:

- cleanliness tests (methylen blue, S.E.);

- quality tests (R_t, E_t, I.Q.E.).

This work has been carried out with a 0–14 mm alluvial gravel from the river “Garonne”. This study reveals that the cleanliness tests are only influenced by the nature of the fine particles when the quality tests depend both on the nature and on the percentage of those fine particles.     

Determination des caracteristiques mecaniques des graves non traitees au triaxial a chargements repetes

Untreated gravels study was marked a long time by an empiricism mainly based on the global behaviour of these materials in pavements. For that reason, specifications in use may seem sometimes restrictive and lead to reject new and cheap materials. Repeated loading triaxial test chiefly developed for the last twenty years in Anglo-Saxon countries allows to solicit sample with stresses levels comparable to those induced by trafic in pavements. The paper presented describes an apparatus designed in the “Laboratoires des Ponts et Chaussées” network and meant more particularly to usual studies. The main relations between untreated gravels stresses and deformations (reversible and permanent) will be reminded. This new test method, very discriminant, allows to compare easily materials between themselves. The paper gives, by way of illustrations, examples:

- Behaviour of untreated gravels coming from crushed stones and alluvial untreated gravels corrected by fillerised sands.

- Attrition study for untreated gravels elaborated from aggregates having a high Los Angeles coefficient.

     

Spatial planning and housing policy: On the ties that bind

Spatial planning and housing policy in the Netherlands have supported each other for many years. In addition, spatial planning has played a stimulating role in carrying out spatial policy. Since the end of the 1980s, however, a new coalition has emerged between spatial planning and environmental policy, especially at the intraregional level. In the same period, housing policy has become strongly market-oriented. Thus, frictions have arisen in the relation between spatial planning and housing policy. This paper deals with a number of contradictions between housing policy and spatial planning:

-the artificial shortage of land for housing;

-the tension between urban density and consumer preferences;

-the rigid housing differentiation, which is at odds with the flexibility of housing markets;

-the danger of spatial segregation; and

-the tension between residential construction and environmental priorities.

It proves difficult to combine an ambitious central spatial planning policy with a market-oriented housing policy. A more promising solution would be to approach both fields as a combination of market and policy. This would entail more policy in housing and more market in environmental policy. More coordination between spatial planning and housing policy is both possible and desirable.