Janez Turk

Environmental evaluation of green concretes versus conventional concrete by means of LCA.

A number of green concrete mixes having similar basic properties were evaluated from the environmental point of view by means of the Life Cycle Assessment method, and compared with a corresponding conventional concrete mix. The investigated green concrete mixes were prepared from three different types of industrial by-products, i.e. (1) foundry sand, and (2) steel slag, both of which were used as manufactured aggregates, and (3) fly ash, which was used as a mineral admixture. Some green concrete mixes were also prepared from a recycled aggregate, which was obtained from reinforced concrete waste. In some of the green concrete mixes the recycled aggregate was used in combination with the above-mentioned types of manufactured aggregate and fly ash. All of these materials are able, to some extent, to replace natural aggregate or Portland cement in concrete mixes, thus providing an environmental benefit from the point of view of the saving of natural resources. Taking into account consequential modelling, the credit related to the avoidance of the need to dispose of the waste materials is considered as a benefit. In case of the recycling of waste concrete into aggregate, credit is attributed to the recovery of scrap iron from the steel reinforcement. In the case of the use of steel slag, credit is attributed to the recovery of metals, which are extracted from the slag before being used as an alternative material. The disadvantage of using alternative materials and recycled aggregates can sometimes be their relatively long delivery distance. For this reason, a transport sensitivity analysis was carried out. The results indicate that the use of the discussed alternative and recycled materials is beneficial in the concrete production industry. Preference is given to the fly ash and foundry sand scenarios, and especially to those scenarios which are based on the combined use of recycled aggregate with these two alternative materials. It was found that longer delivery distances of the alternative materials do not necessarily affect the results significantly. However, variable delivery distances may have a greater effect when choosing between different alternative scenarios.

Hair imprints in Pleistocene cave sediments and the use of X-ray micro-computed tomography for their reconstruction

Detailed studies of cave sediments in the Divje babe I cave, in western Slovenia, have revealed both fossil hairs and the imprints of such hairs present within phosphate aggregates in the clastic sediments. These aggregates consist of fine rock and bone fragments, as well as hairs cemented by phosphate precipitated from pore water. The hairs and their imprints were discovered by means of scanning electron microscopy and are likely to have belonged to cave bears, which were the most frequent inhabitants of this cave. From X-ray micro-computed tomography showing the spatial distribution of the hair imprints, and their number, it appears that the hairs did not belong to one particular animal which died at the location where the samples were collected, rather the hairs probably accumulated on the floor of the cave not only from cadavers, but also because hairs were shed during the hibernation of bears and their visits to the cave.

Life Cycle Assessment of Natural Fibre Reinforced Cementitious Composites

Three cementitious composites containing different natural fibres (flax, hemp and sea-grass) were evaluated from an environmental perspective by means of Life Cycle Assessment (LCA) method applying the cradle-to-gate approach. The environmental impact of these composites was compared to that of cementitious composites reinforced with conventional synthetic polyacrilonitrile (PAN) fibres. The functional unit was the production of one cubic meter of cementitious composites ready-for-use. The results show that generally the environmental footprint of composite with synthetic fibres is bigger than the footprint of the composites with added natural fibres. Exceptions may only be the impacts on eutrophication and freshwater aquatic ecotoxicity, which are significantly affected by cultivation of crops. Flax and hemp cultivation is associated with emissions to soil and water. For this reason, the composite mixture with flax fibres has a significantly greater impact on eutrophication and freshwater aquatic ecotoxicity than the composite mixture with synthetic fibres. A cementitious composite mixture with sea-grass shows the lowest impacts in all impact categories. The entire life cycle of the studied composites was not included in this research since the life cycle of natural fibre composites is not straightforward and is highly dependent on the durability of the fibres within the matrix.

Comparative Life Cycle Assessment of possible methods for the treatment of contaminated soil at an environmentally degraded site

This study reports on the assessment of the environmental sustainability of different management practices for an environmentally degraded site in Slovenia: the Old Zinc-Works in the town of Celje. Life Cycle Assessments (LCAs) were applied in order to evaluate possible trade-offs by comparing a proposed in situ remediation scenario with two other reclamation scenarios (scenario 2: incineration, metal extraction, underground disposal and reclamation of the site by refilling it with replacement material, and scenario 3: underground disposal and reclamation of the site by refilling it with replacement material) and with a no-action scenario. The results of the comparisons performed show that in the case of the in situ remediation scenario, the consumption of resources is smaller by a factor of 51 compared to that in the second scenario and by a factor of 7 compared to that in the third scenario. The impacts on human health and ecosystem quality are approximately 30 and 3.5 times less in the first scenario than in the second and third scenarios, respectively. Compared to the impact of the no-action scenario, the impact on human health of the in situ soil remediation scenario is approximately 6 times less, whereas its impact on the ecosystem is approximately 4 times less. The results confirmed that the in situ soil remediation scenario is the most sustainable practice from an environmental point of view. Its main advantage lies in the achieved conservation of natural resources. Despite the recovery of valuable metals (Zn, Pb, Cu, and Ni) from the bottom ash, the second scenario is significantly more environmentally burdensome compared to both the first and third scenarios. This outcome is due to the significantly high impacts related to the consumption of fuels needed to support the incineration of low-calorific contaminated soil and to electricity consumption. The present study demonstrates that the results of LCA studies, in addition to technological, economic and social indicators, yield important information about the sustainability of different management practices and therefore should be an important part of decision-making when approaching the reclamation of environmentally degraded sites.