Comparative environmental footprint analysis of ultra-high-performance concrete using Portland cement and alkali-activated materials

Considering the ambitious greenhouse gas emission reduction and efficient use of resource targets set by the Sustainable Development Goals and the importance of concrete structures to achieve these goals, there is an increasing need to study the environmental performance of different concrete production alternatives. Cement is one of the main building materials that contribute significantly to global warming; therefore, studying the environmental performance of innovative binders that can substitute the use of cement is highly recommended. This article investigates the climate, material, energy, and water footprints of four innovative mixtures of ultra-high-performance concrete (UHPC) with a binder made of alkali-activated materials in comparison with the one made of Portland cement. Footprint analysis is carried out within cradle-to-grave life cycle assessment boundaries. Within the life cycle assessment, the functional unit defines the quantification of the final product or service. The functional units of the UHPC were adapted for the comparability of concrete mixtures with different compressive strengths. The results show that UHPC made with an alkali-activated material has 32%–45% better performance in terms of a climate footprint and 19%–33% better performance in terms of material footprints, whereas a trade-off can be seen regarding 44%–83% higher energy footprints and 75%–146% higher water footprints. The disadvantages in energy and water footprints are caused by waterglass. When allocation is considered, mixtures with high silica fume content have higher environmental footprints

High Resolution Spectral Domain Optical Coherence Tomography (SD-OCT) in Multiple Sclerosis: The First Follow Up Study over Two Years

“Non-invasive, faster and less expensive than MRI” and “the eye is a window to the brain” are recent slogans promoting optical coherence tomography (OCT) as a new surrogate marker in multiple sclerosis (MS). Indeed, OCT allows for the first time a non-invasive visualization of axons of the central nervous system (CNS). Reduction of retina nerve fibre layer (RNFL) thickness was suggested to correlate with disease activity and duration. However, several issues are unclear: Do a few million axons, which build up both optic nerves, really resemble billions of CNS neurons? Does global CNS damage really result in global RNFL reduction? And if so, does global RNFL reduction really exist in all MS patients, and follow a slowly but steadily ongoing pattern? How can these (hypothesized) subtle global RNFL changes be reliably measured and separated from the rather gross RNFL changes caused by optic neuritis? Before generally being accepted, this interpretation needs further critical and objective validation.We prospectively studied 37 MS patients with relapsing remitting (n = 27) and secondary progressive (n = 10) course on two occasions with a median interval of 22.4±0.5 months [range 19–27]. We used the high resolution spectral domain (SD-)OCT with the Spectralis 3.5 mm circle scan protocol with locked reference images and eye tracking mode. Patients with an attack of optic neuritis within 12 months prior to the onset of the study were excluded.Although the disease was highly active over the observation period in more than half of the included relapsing remitting MS patients (19 patients/32 relapses) and the initial RNFL pattern showed a broad range, from normal to markedly reduced thickness, no significant changes between baseline and follow-up examinations could be detected.These results show that caution is required when using OCT for monitoring disease activity and global axonal injury in MS

Environmental Assessment of Carbon Concrete Based on Life-Cycle Wide Climate, Material, Energy and Water Footprints

The construction industry contributes a major share to global warming and resource consumption. Steel-reinforced concrete (SC) is the world’s most important building material, with over 100 million cubic meters used per year in Germany. In order to achieve a resource-efficient and climate-friendly construction sector, innovative technologies and the substitution of materials are required. Carbon concrete (CC) is a composite material made of concrete and a reinforcement of carbon fibers. Due to the non-rusting and high-strength carbon reinforcement, a much longer life-time can be expected than with today’s designs. In addition, the tensile strength of carbon fibers is about six times higher than that of steel, so CC can be designed with a relatively lower concrete content, thus saving cement and aggregates. This research analyzes and compares SC with CC over its entire life-cycle with regard to its climate, material, energy, and water footprints. The assessment is done on material and building level. The results show that the production phase contributes majorly to the environmental impacts. The reinforcements made from rebar steel or carbon fibers make a significant contribution, in particular to the climate, energy, and water footprint. The material footprint is mainly determined by cement and aggregates production. The comparison on the building level, using a pedestrian bridge as an example, shows that the footprints of the CC bridge are lower compared to the SC bridge. The highest saving of 64% is in the material footprint. The water footprint is reduced by 46% and the energy and climate footprint by 26 to 27%. The production of carbon fibers makes a significant contribution of 37% to the climate footprint

Biotic Part of the Product Material Footprint: Comparison of Indicators Regarding Their Interpretation and Applicability

The product material footprint (PMF) represents a central instrument to assess the potential environmental impacts of products and services based on their life-cycle-wide material use. Within the life cycle impact assessment framework, the indicators raw material input (RMI) and total material requirement (TMR) have been used for its calculation, but so far, only abiotic materials have been considered. This research analyses the requirements and indicators for the assessment of the biotic part of the PMF. The central question is whether the indicators RMI biotic and TMR biotic are suitable for this purpose or if they need to be adapted. For comparison, the indicator cumulative raw material demand (CRD) is applied. The indicator concepts of RMI, TMR, and CRD are compared by defining the system boundaries for determining the biotic parts of the footprint. To test the applicability, the production of wheat bread is assessed as a case study. The characterization factors of wheat grains are determined and each of the three indicators is implemented in the software openLCA for use with the ecoinvent database. The results show that RMI biotic and TMR biotic are suitable indicators for the quantification and assessment of the biotic part of the PMF. While CRD abiotic provides the same information as RMI abiotic, both indicators differ regarding the biotic part. The CRD per definition does not consider biotic inputs from agriculture and forestry and thus conveys insufficient information on the used and unused biomass extraction for the product LCA. The ratio of RMI biotic to the net annual increment and TMR biotic to the net primary production could be used for absolute sustainability assessment

Biotic Part of the Product Material Footprint: Comparison of Indicators Regarding Their Interpretation and Applicability

The product material footprint (PMF) represents a central instrument to assess the potential environmental impacts of products and services based on their life-cycle-wide material use. Within the life cycle impact assessment framework, the indicators raw material input (RMI) and total material requirement (TMR) have been used for its calculation, but so far, only abiotic materials have been considered. This research analyses the requirements and indicators for the assessment of the biotic part of the PMF. The central question is whether the indicators RMI biotic and TMR biotic are suitable for this purpose or if they need to be adapted. For comparison, the indicator cumulative raw material demand (CRD) is applied. The indicator concepts of RMI, TMR, and CRD are compared by defining the system boundaries for determining the biotic parts of the footprint. To test the applicability, the production of wheat bread is assessed as a case study. The characterization factors of wheat grains are determined and each of the three indicators is implemented in the software openLCA for use with the ecoinvent database. The results show that RMI biotic and TMR biotic are suitable indicators for the quantification and assessment of the biotic part of the PMF. While CRD abiotic provides the same information as RMI abiotic, both indicators differ regarding the biotic part. The CRD per definition does not consider biotic inputs from agriculture and forestry and thus conveys insufficient information on the used and unused biomass extraction for the product LCA. The ratio of RMI biotic to the net annual increment and TMR biotic to the net primary production could be used for absolute sustainability assessment

Measuring Product Material Footprint as New Life Cycle Impact Assessment Method: Indicators and Abiotic Characterization Factors

The global economy is using growing amounts of natural resources such as raw materials, water, and land by making and using goods, services, and infrastructure. Aspirations on international, regional, and national levels e.g., the Sustainable Development Goals, the EU flagship initiative Roadmap to a Resource Efficient Europe or the German Program for Resource Efficiency are showing an urgent need to bring the global raw material use down to sustainable levels. An essential prerequisite to identify resource efficient options and to implement resource efficiency measures and solutions is the ability to compare different products or services regarding their raw material use. Until today, there is no internationally standardized approach defined and no software supported calculation method including the necessary data basis available to measure the raw material intensity of products. A new life cycle impact assessment (LCIA) method Product Material Footprint PMF is described. Two indicators are used to quantify the PMF: the Raw Material Input RMI and the Total Material Requirement TMR. The calculation of global median values for the characterization factors CFRMI and CFTMR of abiotic materials was done based on different databases. This article presents the methodological approach of the PMF, the calculation results for CFRMI of 42 abiotic materials and CFTMR of 36 abiotic materials, and the implementation of the LCIA method into the software openLCA for use with the ecoinvent database

Modelling and Simulation of Building Material Flows: Assessing the Potential for Concrete Recycling in the German Construction Sector

Gefördert durch den Publikationsfonds der Universität Kasse

Modelling and Simulation of Building Material Flows: Assessing the Potential for Concrete Recycling in the German Construction Sector

The reuse and recycling of materials can make an important contribution to the conservation of natural resources in the sense of a circular economy. This applies in particular to high quality recycling, supporting the material use of waste and closing product cycles. The construction sector is the most important sector in terms of available volume of materials for recycling. However, the largest share of recycling (RC) materials goes predominantly into road construction and underground engineering. This research developed a dynamic model and used a simulation tool to calculate future building material flows in the German construction sector of residential buildings to explore the medium- and long-term potential for RC concrete. The results show that, by increasing the RC rate of concrete to produce recycled aggregates for concrete (RAC) from currently 1.5% to 48%, up to 179 million tons of sand and gravel could be saved until 2060. If the current maximum secondary input rate of RAC of 45% is increased to 70%, the savings could rise over another 66 million tons. If a secondary input rate of 100% is applied, RAC could completely fulfill the demand for sand and gravel for new residential building in Germany from 2045 onwards. The approval of RC concrete for more concrete strength and exposure classes is required to avoid a surplus of RAC and a rapid exhaustion of landfill capacities in the future

Environmental Assessment of Carbon Concrete Based on Life-Cycle Wide Climate, Material, Energy and Water Footprints

Gefördert durch den Publikationsfonds der Universität Kasse

Comparative Analysis of Resource and Climate Footprints for Different Heating Systems in Building Information Modeling

Buildings play an important role to meet Sustainable Development Goals, especially regarding the use of resources and greenhouse gas emissions. They are increasingly designed with energy-efficient solutions regarding their operations, while the related use of natural resources is still insufficiently considered. In this article, a methodology in Building Information Modeling is proposed to measure the resource and climate footprints of buildings’ heating systems. The methodology is applied to a case study building in Germany. The studied heating systems include a gas condensing boiler, ground-source heat pump, ground-source heat pump with a photo-voltaic system and air-source heat pump backed up with a gas boiler. Next to the operational energy, the production and transport of the heating systems were also studied. Results show that heating system operations have the largest impact and that the variant of ground-source heat pump combined with photovoltaics (GSHP + PV) has the lowest impact. In comparison with the gas boiler (GB), savings of 75%, 47%, 80%, and 84% are addressed to climate, material, energy, and land footprints, respectively, while the water footprint of GSHP + PV is 73% higher than that of GB