Crushed Rock Aggregates Research Articles

BOOK REVIEW / CRITIQUE DE LIVREAggregates: sand, gravel and crushed rock aggregates for construction purposes (3rd ed.)

BOOK REVIEW / CRITIQUE DE LIVREAggregates: sand, gravel and crushed rock aggregates for construction purposes (3rd ed.)

Permanent Deformation Behavior of Granular Materials and the Shakedown Concept

The shakedown concept has been used to describe the behavior of conventional engineering structures under repeated cyclic loading. The possibility has been raised that a critical stress level exists between stable and unstable conditions in pavement. According to the “shakedown” concept, this level is termed the “shakedown limit.” Several repeated load triaxial tests were performed on crushed rock aggregates at different stress levels. The resulting permanent deformation, which accumulated with the repeated loading, was described and compared with the types of responses usually described by the shakedown approach. The existing shakedown approach can describe some, but not all, of the observed responses. Thus, a modified set of possible responses was defined in shakedown terms. The method of description could provide a powerful material assessment and pavement design tool for engineering unbound pavement bases. A design chart derived from the data illustrates a possible design approach.

1. Introduction

Aggregates are defined here as particles of rock which, when brought together in a bound or unbound condition, form part or the whole of an engineering or building structure. Natural sand, gravel and crushed rock aggregates are fundamental to the man-made environment and represent a large proportion of the materials used in the construction industry. Re-use of aggregates has become a more common practice and the substitution of natural aggregates by artificial aggregates made from waste products of other industries is a small part of the industry. Production of aggregates for civil engineering and building construction is one of the world’s major industries. Quarrying is the largest industry in terms of tonnage of output (but not value) in the United Kingdom and even in 1985, production was two and a half times that of coal. With the closure of so many deep coal mines in 1999 this figure was nearly seven times larger. Consumption of aggregates has more than doubled over forty years from 100 million tonnes in 1959 to between 200 and 300 million tonnes per annum throughout the last decade (see Fig. 1.1). Sand and gravel production in 1959 was 67% of the total with crushed rock providing the balance of 33%. By 1998 this situation had changed significantly with crushed rock production increasing substantially to 132 million tonnes (60%) and sand and gravel only to 86 million tonnes (40%). In 1989, growth in demand was strong and a compound growth rate of 3% was forecast leading to

Kiessande für sekundäre Strassen | Aggregates for Low Volume Roads

Gravel is the most important material for road construction. In most countries the quality of gravel for sub-base and base is standardised. The Association of Swiss Road and Traffic Engineers recently revised the Swiss SN standard 670 120d for subbase gravel. Quality requirements concerning the admissible content of fine particles and the limits of particle size distribution were intensified, for no obvious reason. Former studies and experiences proved that these stricter specifications are neither necessary, from a soil-mechanical point of view, nor economical. For low volume roads, such as forest and rural roads, it is therefore suggested to use the limits of particle size distribution for gravel II (except for crushed rock aggregates),but a clearly higher amount of fine particles can be accepted.

Blending of marginally suitable tropical sub-base materials for use in base course construction

In some parts of Ghana, road construction costs can be very high because of the limited opportunity of locating suitable base material within economic haul distances. Due to extensive infrastructural development in areas where suitable road base materials occur, the city of Kumasi is experiencing a general paucity of such materials within 10 km of project sites. Three marginally suitable but abundant sub-base materials, typical of the soils within the Kumasi metropolis of Ghana, have been blended with varying proportions of readily available crushed rock aggregates and alluvial gravel for road construction. All the soils were improved by these stabilizers for use in base course construction. This study revealed that it would be uneconomical to haul borrow gravel beyond 13 km for road construction in the metropolis. Rather, these abundant but inferior naturally-occurring materials within the corridors of proposed roads, should be blended with both stabilizers but preferably alluvial gravel due to its relative cheapness, to construct the base course.

The use of low-grade and unsound crushed rock aggregates in Ghana for construction : D. O. K. Kuma, Geotechnical & Geological Engineering, 13(4), 1995, pp 217–225

The use of low-grade and unsound crushed rock aggregates in Ghana for construction : D. O. K. Kuma, Geotechnical & Geological Engineering, 13(4), 1995, pp 217–225

The use of low-grade and unsound crushed rock aggregates in Ghana for construction

Ghana and many developing countries have relied heavily, in the past, on hard granites and granitic gneisses for the production of rock aggregates and rock products for civil engineering works including the construction of roads and buildings. Experience in Ghana has shown however, that the quantity of crushed rock aggregates produced from hard rocks have proved insufficient for the needs of the country. This situation has called for engineering geological studies into the use of rock types and rock formations previously designated as low grade and unsound for the production of aggregates. The major objective of this study was to review the occurrences of non-conventional hard rocks and gravels such as quartzites, silicified sandstones, metagreywackes, dolomitic limestones and quartz gravels. This was followed by the application of appropriate standard specification tests to establish criteria for the selection and recommendation for the use of low grade and unsound rocks and gravels for various civil engineering projects in Ghana and other developing countries, especially those of the subregion with similar geological formations.

Intelligent optomechatronic instrumentation for on-line inspection of crushed rock aggregates

Improved inspection of crushed rock aggregates will reduce the production of unsaleable material, enhance site quality control and boost sales revenue through premium quality aggregate mixtures. A low cost optomechatronic system is described which aims to provide a rapid breakdown of particle size distribution, along with descriptions of constituent product shape. A material sampling system directs aggregate into a novel optical inspection chamber, where particle geometry is digitised in real time by a dual beam laser scanning system. Classical image processing algorithms obtain dimensional triaxial information from the digitised data, and allow fractal or fourier features to be extracted if required. Soft computing techniques implement a neurofuzzy pattern classifier which assigns linguistic shape descriptors - rounded, irregular, flaky etc. to the particle data. These methods combine to allow a detailed and meaningful interpretation of the sampled crusher product.

Evaluation of crushed granitic rock aggregates in Ghana : Tsidzi, K E N Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6–10 August 1990V4, P3013–3021. Publ Rotterdam: A A Balkema, 1990

Evaluation of crushed granitic rock aggregates in Ghana : Tsidzi, K E N Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6–10 August 1990V4, P3013–3021. Publ Rotterdam: A A Balkema, 1990

Predicting the performance of crushed rock aggregates in highway wearing courses : Cawsey, D C Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6–10 August 1990 V4, P3045–3053. Publ Rotterdam: A A Balkema, 1990

Predicting the performance of crushed rock aggregates in highway wearing courses : Cawsey, D C Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6–10 August 1990 V4, P3045–3053. Publ Rotterdam: A A Balkema, 1990

Properties of concretionary laterite gravel concrete

The compressive strength and the expansion of conrete made with both highly and slightly/moderately indurated concretionary laterite gravels were studied. The compressive strength (19–42 MPa) of most of the laterite concrete is comparable with the average strength (45 MPa) of concrete made with the usual granite crushed rock aggregates from the region. The strength of the laterite concrete is mainly dependent on the aggregate-cement bond whereas the physical properties of the aggregates are only of secondary importance.

J. C. B ullas replies:

J. C. B ullas replies: I confirm that all the aggregates tested in my Technical Note were crushed rock aggregates, and with hindsight this fact should have been stated in the Note. Because of this, Dr Gribble is correct in his supposition that my proposed new value for K of 2800 applies to crushed rock aggregates only. It would seem that the value for K of 4000 currently in use was derived from a combination of test results from both crushed rock and natural gravel aggregates. I would like to thank Dr Gribble for pointing out this omission from my Technical Note.

Discussion on ‘Modification of the formula used in the determination of the ten per cent fines value of aggregate’

C. D. G ribble writes: I read the technical note by J. C. Bullas with interest. He discusses the value of K used to estimate the value of force (in kN) which must be applied to a sample of aggregate to obtain ten per cent fines in the expression: Force (kN) = K /AIV. The reduction he suggests in the value of K from 4000 to 2800 is based upon samples of crushed rock aggregates, i.e. all the samples were obtained from aggregates produced by crushing various types of hard rock. I and other workers have found that the previous value of K = 4000 works quite well when testing aggregate from sand and gravel sources. I plotted the 10 0.000000ines values and AIV data from samples of gravel, given in various Mineral Assessment Reports (1981-1986), in a graph similar to the one used by Mr Bullas. On to this graph ( Fig. 1 ) I superimposed a nest of hyperbolic curves with K = 2000, 3000, 4000 and 5000. From this graph the best fit curve is one with K = 4250. I would therefore suggest that two values of K are needed: (i) K = 2800 for aggregate from crushed rock sources which is the one proposed by Mr Bullas in his paper; (ii) K = 4000 for aggregate from sand and gravel sources, which is the value of K previously used in this type of calculation

The future of aggregate extraction and evaluation in Europe

Introduction The construction industry in Europe has been extremely buoyant in the past four to five years, particularly in the UK, Spanish, French and Dutch markets. Even in West Germany the difficulties experienced until 1987 appear to have been overcome and demand for aggregates is likely to be more than the 516 Mtonnes of 1988. Thus, with some 12 0rowth in the European construction industry predicted for 1989, there would appear to be great potential for the future. Table 1 gives production figures for some EEC countries. In the UK aggregate production rose to 270 Mtonnes in 1988, surpassing the previous record of 256 Mtonnes set in 1973. Crushed rock aggregate production at 154 Mtonnes now exceeds sand and gravel production by approximately 40 Mtonnes and seems likely to be the major source of UK aggregates for the future. Planning control on extraction The major Constraints on the development of any new aggregate source are those related to agriculture, landscape and ecology, with both nationally and locally based policies influencing the allowed extraction. Such constraints may restrict mineral working but are rarely an absolute bar to the granting of planning permission. However, despite a 40 0ncrease in production of aggregates in the 1980s there are few signs that local planning authorities are prepared to accept that the demand for aggregates should be provided for within their county and it is difficult to see how the increasing demand should be met. Marine aggregates supply some of the needs of coastal markets

Towards understanding the behaviour of naturally-occurring road construction materials

Naturally-occurring road construction materials generally contain a greater amount of fines, and the fines have a higher plasticity than traditional materials such as a crushed rock aggregates. This makes their behaviour more difficult to understand and predict since soil suction and fabric become important controlling factors. The concepts of suction and fabric are outlined, and their role in controlling the behaviour of road construction materials is illustrated by a fundamental laboratory study of a lateritic gravel and two calcrete gravels. These materials have successfully been used as road base construction materials in low-volume bituminous-surfaced roads in Kenya and Botswana. It is concluded that the presence of fines can be an advantage, since they allow significant suctions to develop and also reduce the permeability.

Aggregates: sand, gravel, and crushed rock aggregates for construction purposes

Aggregates: sand, gravel, and crushed rock aggregates for construction purposes

Sand, gravel and crushed rock aggregates for construction purposes : Sims, I Q J Engng Geol V19, N3, 1986, P325–338

Sand, gravel and crushed rock aggregates for construction purposes : Sims, I Q J Engng Geol V19, N3, 1986, P325–338

Sand, gravel and crushed rock aggregates for construction purposes

1. Introduction Engineering geology has traditionally been concerned more with interaction between the engineering structure and its geological environment than with the performance of rock aggregates in the structure itself. In recognition of this imbalance, the Engineering Group of the Geological Society established a Working Party in 1978 to compile a reasonably comprehensive document covering the most important aspects of natural and crushed rock aggregates used for construction purposes. The objectives of the Working Party are set out in detail in Section 1 of the Working Party Report, which is being published by the Geological Society in separate book form. The membership of the Working Party, under the Chairmanship of Professor Peter Fookes, reflected a broad range of expertise and consisted of experienced individuals involved with construction materials, including producers, specifiers, users and researchers. The Working Party members are listed at the end of this summary. The first complete draft of the Report was submitted for open discussion at a one-day session of the 17th Annual Regional Meeting of the Engineering Group in 1981 at Bangor. A great number of suggestions arising from the open discussion have been considered in the preparation of the final Working Party Report; additional advice has been obtained from a considerable body of corresponding members and professional organizations. The Working Party Report contains a full list of acknowledgments. The Report was written for a wide audience and is intended to provide basic information on subjects that are new to the reader as well as serving

Crushed aggregate—bentonite mixtures as backfill material for repositories of low- and intermediate level radioactive wastes

The candidate backfill materials for the repositories of low- and intermediate-level radioactive wastes consist of three components: crushed rock aggregate, finely ground rock aggregate and bentonite. The hydraulic conductivity of mixtures with 15% of sodium bentonite is approximately 5 · 10 -9 m/s based on the laboratory tests. The sweling potential for the same material varies between 20 and 60 kPa depending mainly on the salinity of the groundwater.

Influence of geological factors on soundness and abrasion resistance of road surface aggregates: A case study

A study has been carried out on soudness and abrasion resistance of crushed-rock aggregates used in heavily trafficked road surfacings in Gauhati, a city situated in the State of Assam, India. The crushed-rock aggregates under study were obtained from Precambrian acid igneous rock outcrops in and around Gauhati. The grain, size and the volume of pore spaces were found to be the significant geological factors influencing soundness and abrasion resistance. The durability, in terms of resistance to weathering and resistance to wear, of the acid igneous rocks was found to increase with decrreasing grain size and decreasing volume of pore spaces.