@incollection{ThielStengelGehlen, author = {Thiel, Charlotte and Stengel, T. and Gehlen, Christoph}, title = {Life cycle assessment (LCA) of road pavement materials}, series = {Eco-efficient Construction and Building Materials}, booktitle = {Eco-efficient Construction and Building Materials}, publisher = {Woodhead Publishing}, doi = {10.1533/9780857097729.2.368}, pages = {368 -- 403}, abstract = {At present the choice of materials and techniques in road construction is dictated by structural requirements and economic aspects. However, ecological factors have gained in importance due to environmental considerations in politics and society. To evaluate the environmental impact of motorways, a life cycle assessment (LCA) according to ISO 14040 was carried out for different pavement types. By investigating different case scenarios, the reduction potential of environmental impact was quantified. The biggest reduction in air pollution can be achieved by improving pavement properties (e.g., texture, stiffness and flatness) which would significantly reduce the fuel consumption of vehicles.}, language = {en} } @inproceedings{ThielBeddoeLowkeetal., author = {Thiel, Charlotte and Beddoe, Robin E. and Lowke, Dirk and Gehlen, Christoph}, title = {Accelerated carbonation: changes in water transport, porosity and phases of mortar due to different CO 2 pressures}, series = {Proceedings of the 10th fib International PhD Symposium in Civil Engineering, July 21 to 23, 2014, Qu{\´e}bec, Canada}, booktitle = {Proceedings of the 10th fib International PhD Symposium in Civil Engineering, July 21 to 23, 2014, Qu{\´e}bec, Canada}, organization = {F{\´e}d{\´e}ration International du B{\´e}ton (fib)}, pages = {217 -- 221}, abstract = {Currently, the carbonation resistance of concrete is assessed on the basis of accelerated tests performed with high (unrealistic) CO2 concentrations. It remains unclear whether these high concentrations reflect the processes occurring under natural conditions and enable the accurate prediction of field behaviour. To develop future test procedures with higher reliability, it is necessary to deepen the knowledge on the mechanisms of carbonation. Thin slices of mortar were stored in a gaseous mixture of 2 \% CO2 and 98 \% N2 at atmospheric pressure or 5 bar. IH-NMR equipment was used to detennine moisture profiles with aresolution of 0.2 mm. At 5 bar a drying front at the near-surface region of the mortar discs severely inhibited the progression of the carbonation reactions. This effect was prevented by exposure to altemating cycles of pressure and storage at atmospheric pressure (65\%RH) which significantly increased the rate of carbonation, but was too severe to resolve the effect of cement type on carbonation resistance. Furthermore , the evolution of water beyond the carbonation front of mortar sampies under accelerated concentration and at atmospheric pressure was clearly visible. This may lead to an overestimation of carbonation resistance of sampies tested under accelerated conditions at the optimal relative humidity for natural carbonation (50-70\% RH).}, language = {en} } @inproceedings{FrankeThielDuranetal., author = {Franke, Wolfram and Thiel, Charlotte and Duran, F. and Gehlen, Christoph}, title = {Effect of Calcium Nitrate on the freeze-thaw-resistance of concrete}, series = {Proceedings of the 2nd International Congress on Concrete Durability, 2, 2014, New Delhi}, booktitle = {Proceedings of the 2nd International Congress on Concrete Durability, 2, 2014, New Delhi}, abstract = {Concrete in cold climates is not only exposed to cold weather while concreting but also to freeze-thaw cycles during its lifetime. Thus not only the concrete production needs to be adjusted to the environmental conditions but also the mixture has to be durable and resist the environmental impacts. Commonly an air entraining agent is used to interrupt the capillary pore system and to provide further space for the freezing water to expand. The downside of this approach is a loss in compressive strength. Within this paper the effect of simultaneous use of air entraining agent and calcium nitrate is discussed. It is shown that calcium nitrate can counteract strength loss due to the air entraining agent without reducing the durability gain in the same extent. A certain combination of calcium nitrate and air entraining agent can also be used to increase the freeze-thaw-resistance.}, language = {en} }