Aggregates for the Attica Basin (Greece). Utilization of wastes from bauxite mines of Parnassus-Giona-Elikon-region

About 12 million tons of crushed aggregates are used every year in the greater Athens area (Basin of Attica). These materials consist mainly of limestone and their production, at the beginning of 1980, was from 34 quarries. During recent years a situation of uncertainty has prevailed over the future of the quarries. This problem has been studied with the intention of establishing a definite and long-term solution, capable of securing the supply to the greater Athens area of the required quantities of aggregates. Among the solutions which were proposed for study and research, one was considered to have priority: utilization of waste rocks from the bauxite mines of the well known bauxitic zone of Parnassus-Giona-Elikon, situated 100–220 km W-NW of Athens. Large quantities of such waste (6–7 million tons/year) come from surface mining of bauxite deposits. They consist of limestones suitable for the production of aggregates. The results of the quantitative evaluation of the waste, the geographical distribution and the exploitation parameters are presented in this paper.     

Aggregate properties of Devonian limestones for use in concrete in Istanbul,Turkey

Limestones are the major source of crushed rocks for use in concrete in Istanbul. The existing quarries are located in a variety of limestone types. The study reported here was carried out in the Kartal Quarry in eastern Istanbul. The physico-mechanical properties of limestones of different compositions and textures were determined and the results were compared with those from standard aggregate tests. The relationships between all parameters were described by simple regression analyses. Kartal Quarry produces coarse aggregates, which are considered suitable for concrete. Laboratory testing of limestones with different compositions from Kartal Quarry indicates that fine-grained micritic limestones have superior mechanical and physical properties compared to other limestones.     

Development of a quantitative relationship between unconfined compressive strength and los angeles abrasion loss for carbonate rocks

Dry density, absorption, and uncofined compressive strength were determined for ten NX-size cores of each of the 15 carbonate rocks sampled from various quarries, strip mines, and road cuts. Three Los Angeles abrasion tests were performed on aggregate prepared from the same rock blocks from which the cores were cut. Regression analyses were performed to determine relationships that L.A. abrasion loss, dry density, and absorption may have with unconfined compressive strength. Results indicate that multiple linear regression, with unconfined compressive strength as a function of Los Angeles abrasion loss, dry density, and absorption, yields a useful predictive equation (adjusted R²=0.729) for the rocks studied. The equation was further validated by using test data from five additional samples.     

Evaluation of the mechanical degradation of carbonate aggregate by rock strength tests

Aggregate degradation (AD) is one of the major reasons accounting for failure of aggregate materials, and the mechanical degradation of aggregate materials can be determined by different test methods. This process basically requires many aggregate samples and special instruments, and thus is time-consuming. The main purpose of this research is to evaluate the possibility of estimating the AD characteristics using rock strength tests and to investigate the relationships between AD properties and rock strength tests. For understanding the relationships, two common rock strength tests are employed, i.e. unconfined compressive strength (UCS) and point load index (PLI) tests. In the tests, the AD properties of 40 kinds of carbonate aggregates sampled from Iran were studied. The AD properties were determined by Los Angeles abrasion value (LAAV), aggregate impact value (AIV) and aggregate crushing value (ACV). Also, the samples are classified according to the strength and rock types, and the effect of this classification is investigated based on the relationship between rock strengths and AD properties. The results indicate that the PLI is better than UCS for evaluation of AD properties. Among rock strength tests, PLI has a closer relationship with AIV (R² = 0.832). Also, UCS has relative larger effects on the ACV (R² = 0.812) under the same loading condition. The weakest correlation occurs between LAAV and UCS (R² = 0.679). In view of the rational AD properties in the predictive procedure, it is possible to predict AD properties based on the strength tests and rock types. The results also show that the prediction of AD properties using rock strength test based on rock types yields better correlations than that using unclassified samples. The classification based on rock types can extrapolate the different relationships of AD prediction from rock strength tests. The results in this context could be used for preliminarily selecting proper rock aggregates with a limit of allowable AD tests for practical applications by PLI.     

Comparison of properties of steel slag and crushed limestone aggregate concretes

Steel slag is produced as a by-product during the oxidation of steel pellets in an electric arc furnace. This by-product that mainly consists of calcium carbonate is broken down to smaller sizes to be used as aggregates in asphalt and concrete. They are particularly useful in areas where good-quality aggregate is scarce. This research study was conducted to evaluate the mechanical properties and durability characteristics of steel slag aggregate concrete in comparison with the crushed limestone stone aggregate concrete. The durability performance of both steel slag and crushed limestone aggregate concretes was evaluated by assessing water permeability, pulse velocity, dimensional stability and reinforcement corrosion. The results indicated that the durability characteristics of steel slag cement concretes were better than those of crushed limestone aggregate concrete. Similarly, some of the physical properties of steel slag aggregate concrete were better than those of crushed limestone aggregate concrete, though the unit weight of the former was more than that of the latter.     

General report,session I: Engineering properties of carbonate rocks

After reviewing the geological classification of carbonate rocks, a method of describing carbonate rocks for engineering purposes is developed following the recommendations set out by the I.A.E.G. Mapping Commission. Particular attention is paid to the details of the weathering profile developed on carbonate rocks. The engineering classification of carbonate rocks is based on both the engineering behaviour of the rock as a material and in the mass. Physical properties, including strength and deformation characteristics, are used to determine a modulus ratio for a wide range of limestones including the English chalk. In addition to rock material properties, and engineering classification of the rock mass has to take account of structure, discontinuities, and details of the weathering profile. Assessment of rock mass properties requiresin situ testing to determine deformation characteristics. If the usually limited amount of data on such quantitativein situ properties is related to other measures of rock quality, then engineering geological mapping can be used to extend the applicability of the limitedin situ data to a whole site. RQD has been related to the compressibility of the rock mass, and a rock mass factor has been proposed that links the deformability of the rock material to that of the rock mass. Rock mass classifications for large underground openings may be used with limestones. Engineering problems associated with carbonate rocks are briefly reviewed, as are the properties of limestones as a building stone and as aggregate.     

An integration of aeromagnetic and electrical resistivity methods in dam site investigation

Aeromagnetic map (Katsina-Ala sheet 272 S.E.) and the electrical resistivity sounding data obtained along eight traverses, from two sites, across the Katsina-Ala river were examined with the principal aim of defining depths to the bedrock, bedrock relief, geologic structures and the nature of the superficial deposit. The purpose of this exercise was the selection of probable axis for a hydroelectric power dam. The aeomagnetic map shows the basement rocks trending roughly NE-SW. This trend correlates with the 40°–45° strike of foliation measurements made on the rock outcrops along the river channel. A network of cross cutting lineaments suspected to be fault/fractures trending approximately NE/SW and NW/SE was delineated from the magnetic map. The depths to the bedrock estimated from depth sounding data at site I generally vary from 1–53.1 m. Depths to the bedrock estimated at site II range from 1.9–19.5 m. The superficial deposit varies from clay to sandy clay. clayey sand (with boulders in places), sand and laterite. The bedrock relief is relatively flat and gently undulating along most of the traverses with an overall dip towards the river channel. Except for the relatively high overburden thicknesses, two traverses at site I and one traverse at site II are probable, axes for a major and minor dam respectively.     

Quality assessment of a geologically heterogeneous rock quarry in Pirkanmaa county,southern Finland

The geological features and mechanical properties of metamorphosed volcanic and sedimentary rocks from a quarry in southern Finland were studied. Resistance to wear (from the studded tyres test and Los Angeles test) and petrography were used as quality indicators. The study reported was undertaken some 5 years after the opening of Pirkanmaa rock quarry in order to optimise the environmental and economic benefits. The study draws attention to the importance of the assessment of geologically heterogeneous rock quarries which makes it possible to produce a wider range of aggregates from the same quarry for various construction purposes, maximise the crushing process and minimise changes in aggregate quality.      

Influence of the quality of fine fractions on engineering-geological properties of crushed aggregate

Fine fractions of aggregate crushed from Finnish Precambrian crystalline bedrock were studied by determinining the particle size distribution with a Sedigraph particle size analyzer, specific surface area using the nitrogen adsorption method and porosity with a mercury porosimeter. According to abrasion resistance (Los Angeles) and brittleness (Swedish impact) values, all the materials studied were suitable as road aggregate. Roads where material with high specific surface area were used however soon proved to suffer from frost damage. No correlation between specific surface area and values of abrasion and brittleness were found. The specific surface area also proved to depend on the quality rather than the quantity of the fine fractions. Presence of clay minerals tends to increase the sp.s.a. Thus, in addition to the quantity also the quality of fine fractions must be analysed in road aggregate material.     

Aggregate resources inventory in Ontario,Canada

Ontario has an abundance of aggregate resources; however, their location is fixed by nature and they are not always found in the areas of greatest demand. Over 120 million tonnes are produced yearly. Much of this production is in urban fringe areas. Comprehensive planning and resource management strategies, based on an appropriate planning framework and a sound knowledge of the total mineral aggregate resource base, are required to make the best use of available resources. To achieve this, Ontario's Mineral Aggregate Resource Policy requires 1) the Ontario Ministry of Natural Resources to prepare a detailed inventory of the aggregate resources, including location, quality, quantity and extractive activity, and 2) the recognition of aggregate resources in municipal official plans.     

Characteristics and the environmental acceptability of the natural stone quarrying waste rocks

The paper summarises the results of a study by the Geological Survey of Finland on the potential use of waste rocks from natural stone quarry production. Petrographic, chemical, mechanical and physical tests were undertaken on granite, rapakivi granite, migmatite, syenite, diorite, gabbro, anorthosite gabbro, schist and soapstone from 33 dimension stone quarries in Finland. The results indicate the waste rocks of Finnish natural stone quarries can generally be considered environmentally sound with potential uses in other industries.     

Evaluation of the technological level and productivity of the aggregate quarries of Piemonte (Italy)

The results of an inquiry at the aggregate quarries of Piemonte, the Region ranking second in Italy as aggregate producer (about 20 million cu.m per year), are analysed in the paper. Data have been collected from a representative sample of both the alluvial and massive rock exploitations, on excavation, washing, crushing and classifying machinery, on their efficiency, on manpower productivity. The sample has been divided into classes according to the yearly output levels and the features of the deposit, in order to calculate for each class average index values of the characteristic parameters of the production process; among them, the man shift productivity, the installed power per worker, the energy consumption per unit production, the installed power per unit production. A comparison can be so made between the different classes and types of production units, and the weak points in the production system can be pinpointed. In the concluding remarks, some suggestions are made on the evolutive trend of the aggregate production technology.     

A field index to determine the strength characteristics of crushed aggregate

The suitability of a simple technique to determine the strength characteristics of aggregates is reviewed. The results indicate that the strength characteristics of aggregates – in terms of crushing, impact and abrasion values – can be estimated and predicted from simple and quick tests for rock strength such as the Schmidt hammer and point load. The rocks and aggregates used in this work were of igneous, sedimentary and metamorphic origin and of different types, ages and degrees of weathering. More than 110 rocks and aggregate samples were tested according to British Standard and ASTM. The laboratory tests included the Schmidt hammer and point load for rock material while the crushing impact and Los Angeles abrasion test were undertaken on the aggregates. Regression analyses were performed and empirical relationships between the strength of rocks (in terms of their compressive strength and point load indices) and aggregates (in terms of their crushing, impact and abrasion values) were developed. Relatively strong relationships were obtained between the compressive strength of the rock and the crushing and impact value of the aggregate, while moderately strong relationships were obtained for the Los Angeles abrasion values. Electronic Publication     

Inventory of aggregates in an expanding urban area

Faced with a potential shortage of aggregate, the Minnesota Department of Transportation funded a study to inventory the aggregates in four pilot areas of the state and compare it with the estimated requirements in these areas. Based on the results of the study, several methods were suggested to enhance the aggregate supply in these areas. The aggregate resources in the four pilot areas were determined by analyzing the geology of the deposits, both natural aggregate and crushed rock. In addition, reserves in permitted properties were determined using a questionnaire that was given to each quarry operator in these areas. Permitted properties were defined as those for which permits have been issued by the government unit having jurisdiction. Analysis of the questionnaire date was supplemented with interviews of county and state highway department personnel and local planning agencies. Aggregate demand in the four areas was determined from national and county models of demand. Computer-aided multiple regression models defined the relationships between aggregate demand and construction of public and private facilities, ratio of non-metal to metal construction products, and the price of aggregate. Four methods were suggested for enhancing the aggregate supply. These included the definition of quantity and quality of aggregate in the vicinity of urban areas, improvement in beneficiation techniques to maximize the utilization of mined material, development of end-use specifications to permit maximum use of lower grade reserves and of recycled pavements, and revision of land use regulations to prevent the loss of aggregate reserves to urban sprawl.     

Resistivity mapping as a tool for identification and characterisation of weakness zones in crystalline bedrock: definition and testing of an interpretational model

In recent years, the focus on feasibility studies for tunnels has increased in Norway. Traditionally, the refraction seismic method and the very low-frequency electromagnetic method (VLF-EM) have been used. The Geological Survey of Norway introduced the electrical resistivity traversing method (ERT) in feasibility studies for tunnel construction purposes. Resistivity modelling shows that the method has the potential to characterise fracture zones geometrically; i.e., the thickness, dip, and depth extent. Based on previous studies, a model for mineralogical characterisation is proposed. This model, and the possibility for geometrical characterisation, is critically tested with success on three tunnel projects. The results of the comparison study, with regards to weakness zones, show that VLF-EM is a method that is capable of locating fracture zones, while refraction seismic is capable of locating and indicating the width of the zone, and can be used to imply the thickness of the soil cover above bedrock. The 2D resistivity method is able to locate the weakness zone, indicate the width, depth extent, and the dip of the zone, and in addition, characterise the zone with respect to stability or water problems. The crystalline bedrock characterisation is divided into three groups: resistivity values above 3,000 Ω m indicating good rock quality, values between 3,000 and 500 Ω m indicating bedrock with mainly water problems, while values <500 Ω m indicate clay-bearing, unstable rock with fewer water problems. From our investigations, we conclude that the 2D resistivity method is a very good supplement to traditional methods for feasibility studies on tunnelling purposes in crystalline rock.     

Fines characterization through the methylene blue and sand equivalent test: comparison with other experimental techniques and application of criteria to the aggregate quality assessment

In road construction the general term fines is used to describe particles passing the 0.063, 0.074 or 0.08 mm sieve. Some types of fines are considered to be relatively inert and have almost no effect on pavement performance, whilst the presence of even small amounts of others can significantly affect the stiffness and freezing–thawing behaviour of unbound and hydraulically bound layers. This paper presents the results of research on 12 Slovenian aggregates produced from limestone and dolomite bedrock, and naturally occurring river alluvium gravel. At each production site three different materials were sampled and tested: the actual aggregate for unbound base layers, the clayey soils, which presented the most potentially harmful component at the specific location, and the stony dust, which presented the finest size of crushed aggregate and is typically found as coatings on the crushed grains. Six different methods were used to identify the nature of the fines: X-ray diffractometry, carbonate content determination, methylene blue, sand equivalent, Enslin–Neff water absorption, Atterberg limits test, soil suction measurements and soil water characteristic curves. Based on the results, the relationship between the properties of the different fines was determined and included in draft Slovenian national criteria for sand equivalent and methylene blue values currently being trialed.     

A comparison of particle shape characteristics of crushed basalt and granite rocks

There is an opinion that the shape of comminuted particles first of all depends on: a) natural properties of the rock, and b) manner of rock crushing. The paper presents results of investigation relating to the first of above questions. The samples both granite and basalt rocks, taken from different deposits, were crushed in the same way. The rocks to be crushed were characterized by structure of mineral composition and some physical properties. Particles produced by crushing were characterized by three shape coefficients. These characteristics were analysed comparatively in the context of rock properties and particle diameter. From the analysis there is no evident relation between shape of particles and rock characteristics.     

Use of TBM muck as construction material

Tunnel boring machines (TBMís) are widely used in tunnel construction in rock. The rock chips (muck) produced are rarely used for construction applications, however, because the suitability of the material is not well understood. Yet the cuttings appear to be of approximately the correct average size for some applications. If they are suitable in other respects, cost savings can be realized in tunnel construction, where aggregate is a common requirement. A review of standard construction aggregate specifications indicates that hardrock TBM much would be suitable for several construction applications with a minimum of processing: road pavement and structural concrete. Processing options also are discussed for cases where the raw TBM muck is nearly, but not quite, suitable. A 0.65 metric ton (1420 lb) cutting sample generated by a laboratory tunnel boring machine operating in a welded tuff is analyzed for suitability for different construction applications. In addition, numerous tunneling projects that use or have studied TBM waste for construction purposes are described.     

Blast-induced rock damage control in Fangchenggang nuclear power station,China

In the process of blasting excavation, stress wave propagation and gas expansion can basically induce damage to surrounding rocks, which is detrimental to rock mass integrity and engineering safety. In this case, evaluation and control of blast-induced effects are essential to the safety of nearby buildings and integrity of bedrock in blasting field. In Fangchenggang nuclear power station of China, the drill-and-blast method was employed for bedrock excavation. In order to reduce the blast-induced damage zone, the wave propagation and associated damage to rock mass should be carefully investigated. In this paper, the wave propagation regressively obtained from field monitoring data was presented based on empirical formula (e.g. Sadovsky formula). The relationship between the peak particle velocity (PPV) at a distance of 30 m away from the charge hole and charge per delay in blast design was derived. Meanwhile, the acoustic tests before and after blasting were conducted to determine the damage depth of rock mass. The charge per delay in blast design was then calibrated based on the blast-induced wave propagation regularity. The results showed that a satisfactory effect was achieved on blast-induced damage control of rock mass. This could be helpful to rock damage control in similar blasting projects.     

片麻岩骨架密实型水泥稳定碎石的研究与应用

利用武英高速公路沿线片麻岩进行水泥稳定碎石基层试验,研究不同级配和不同击实、成型方法对片麻岩水泥稳定碎石混合料的性能影响规律,试验结果表明:片麻岩骨架密实型水泥稳定碎石具有较高的抗压强度和间接抗拉强度,较低的干缩系数和温缩系数。武英高速公路路面基层上基层水泥掺量选用4.5%,下基层水泥掺量选用3.5%,水泥掺量均比悬浮型密实型级配设计低0.5%。武英高速公路路面基层检测结果表明,片麻岩骨架密实型水泥稳定碎石能够满足基层强度设计要求,改善基层抗裂性能。