Elena Kuznetsova

Resource management and a Best Available Concept for aggregate sustainability

Abstract Aggregates are major constituents in construction, the global demand for which approaches some 22 billion tonnes per year. Some major challenges follow: firstly, the dependency on geological conditions and the availability of resources; secondly, the traffic, emissions and energy use connected with transportation; thirdly, the technology of utilizing resources with a variety of properties to meet user requirements; and finally, the need for increased awareness, particularly over issues like land-use conflicts, environmental impact of the aggregate and quarrying industry, and the need to make these activities sustainable. Aggregate standards have primarily been written by engineers, and engineers are first of all concerned with technical requirements. However, in the future, there will be a greater focus on environmental impact and sustainability. Geological resources are non-renewable, which, for example, can be seen in the rapid depletion of natural sand/gravel deposits. This causes increasing awareness along with environmental impact, conflicts of interest concerning land use, sustainability in mass balance and – not least – increasing transport distances required to get the materials to the places of use. The principle of a Best Available Concept (BAC) for aggregate production and use is introduced, working with four essential phases: inventory and planning; quarrying and production; use of aggregates; and reclamation of mined-out areas. In order to compare alternatives and calculate environmental and economic consequences of decisions, it is recommended that new LCC (Life Cycle Cost) and LCA (Life Cycle Assessment) tools are worked with, which have been recently developed in two EU (European Union) funded research projects.

Weathering of volcanic ash in the cryogenic zone of Kamchatka, eastern Russia

Abstract The nature of the alteration of basaltic, andesitic and rhyolitic glass of Holocene and Pleistocene age and their physical and chemical environments have been investigated in the ash layers within the cryogenic soils associated with the volcanoes in the central depression of Kamchatka. One of the main factors controlling the alteration of the volcanic glass is their initial chemistry with those of andesitic (SiO2 = 53-65 wt.%) and basaltic (SiO2 < 53 wt.%) compositions being characterized by the presence of allophane, whereas volcanic glass of rhyolitic composition (SiO2> 65 wt.%) are characterized by opal. Variations in the age of eruption of individual ashes, the amount and nature of the soil water, the depth of the active annual freeze-thawing layer, the thermal conductivity of the weathering soils, do not play a controlling role in the type of weathering products of the ashes but may affect their rates of alteration.

Behaviour of crushed rock aggregates used in asphalt surface layer exposed to cold climate conditions

AbstractGeological factors (mineralogy, structure, degree of weathering), processing method (crushing, sieving, washing, storing) and user technology for a specific area of use (e.g. asphalt pavements) should be the selecting criteria for crushed rocks used in the construction industry. While the last two criteria have been widely studied, the geological origin of the material has been less considered. Mechanical properties, shape, gradation of the stone material and affinity with the binder are considered the main discriminating factors in road construction. Although those properties are extremely relevant to avoid or milden difficult challenges for pavement surface layers, a deeper knowledge of the geological properties of materials exploited could lead to a general improvement of the overall resistance and durability of the road surface, especially in extreme weathering conditions. The purpose of this work is to investigate the influence of the rock materials properties (mineralogy, texture and porosity expressed by water absorption coefficient) in asphalt pavements. Different samples of aggregates and asphalt mixtures used in Norwegian and Spanish roads were tested with the Cantabro test after conditioning in sodium chloride and freeze–thaw cycles. Mineralogy, grain size, grains bonding, orientation and porosity (expressed by water absorption coefficient) could be related to the mechanical resistance of the aggregates and asphalt mixture behaviour. Even if just a qualitative analysis, the petrographic analysis of the rocks appeared to be a relevant tool to estimate the quality and the long-term durability of aggregates and asphalt mixtures already during the design phase.

Environmental Impact and Sustainability in Aggregate Production and Use

For aggregates as for most engineering materials, standards have been written by engineers. And engineers are first of all concerned with technical requirements. However, in the future, probably the environmentalists will take over much of the standardisation work. And they will focus on environmental impact and sustainability. Already we see an increasing awareness from society when it comes to the exploration, quarrying, production and use of mineral resources: The non-renewable character of the resources; the environmental impact on neighbourhood and nature; the conflicts of interest versus preservation, groundwater, agriculture and building areas; sustainability concerning mass balance and deposition of surplus sizes; and not least—the increasing transport lengths required to get the materials to the places of use. Actions should be taken to meet these challenges by following up the principles of a Best Available Concept (BAC), as suggested in the EU project EcoServe. This concept works with four essential phases: (1) Inventory and planning, (2) Quarrying and production, (3) Use of aggregates in construction, and finally (4) Reclamation of mined-out areas. LCC (Life Cycle Cost) and LCA (Life Cycle Assessment) tools should be used to compare alternatives and calculate/foresee the environmental as well as economic consequences of choices and decisions.

THERMAL CONDUCTIVITY AND THE UNFROZEN WATER CONTENTS OF VOLCANIC ASH DEPOSITS IN COLD CLIMATE CONDITIONS: A REVIEW

Layers of volcanic ash and Andosol soils derived from the ash may play an important role in preserving snow and ice as well as in the development of permafrost conditions in (a) the immediate vicinity of volcanoes at high elevations or at high latitudes and (b) land areas that are often distant from volcanic activity and are either prone to permafrost or covered by snow and ice, but have been affected by subaerial ash deposition. The special properties of volcanic ash are critically reviewed, particularly in relation to recent research in Kamchatka in the Far East of Russia. Of special importance are the thermal properties, the unfrozen water contents of ash layers, and the rate of volcanic glass weathering.Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite), but occurs at a much slower rate under cold compared to warm climate conditions. Existing data reveal (1) a strong correlation between the thermal conductivity, the water/ice content, and the mineralogy of the weathered part of the volcanic ash, (2) that an increase in the amounts of amorphous clay minerals (allophane, palagonite) increases the proportion of unfrozen water and decreases the thermal conductivity, and (3) that amorphous silica does not alter to halloysite or other clay minerals, even in the Early Pleistocene age (Kamchatka) volcanic ashes or in the Miocene and Pliocene deposits of Antarctica due to the cold temperatures. The significance of these findings are discussed in relation to past climate reconstruction and the influence of volcanic ash on permafrost aggradation and degradation, snow and ice ablation, and the development of glaciers.