Secondary raw material markets in the C&D sector: Study on user acceptance in southwest Germany

In industrialized countries, regulations demand increasingly higher recycling (RC) rates and many efforts are undertaken to recycle construction and demolition (C&D) waste fractions. The C&D sector has indisputable relevance due to the highest mineral waste fraction, high numbers of employees and turnovers. High-quality RC construction products can be produced to substitute primary resources and reduce land use. This empirical study analyses the acceptance of RC materials in Germany particularly of private awarding authorities in their private construction project(s). In 41 structured interviews, data is collected and evaluated based on hypotheses. Qualitative and quantitative analyses show that acceptance problems cannot be stated. How-ever, medium knowledge and low experience with RC construction materials as well as communication problems are identified. The respondents have no concerns and tend to trust in RC construction materials, but this is decreasing with the increased structural importance of the materials. Surprisingly, quality is the most frequently mentioned decision criteria in private construction projects, followed by cost. Private awarding authorities see no increase of their property value by using RC construction materials. And, the majority is unwilling to pay a premium for RC construction materials. Higher material quality standards, regular government reviews and financial support are seen conducive

On the integration of diverging material flows into resource‐constrained project scheduling

This study deals with an extension of the resource-constrained project scheduling problem (RCPSP) by constraints on material flows released during the execution of project activities. These constraints arise from limited processing capacities for materials and maximum inventories of intermediate storage facilities. Production scheduling problems with converging material flows have been studied extensively. However, this is the first project scheduling problem integrating diverging material flows typically observed in dismantling projects, e.g., building deconstruction, power plant decommissioning, or battery/car decommissioning. Diverging material flows do not directly impact the project planning but only impose delays in the case of congestion. We model material flows by using operations that represent the processing of materials, and cumulative resources that represent storage facilities. As a method for efficiently generating starting solutions, we propose a schedule generation scheme tailored to the particular precedence structure of such problems. Furthermore, we extensively study the schedule generation scheme’s performance on generated test instances and compare it to the constraint programming solver IBM ILOG CP Optimizer. It turns out that the solution quality strongly depends on the employed model and that neither of the two solution methods is generally superior

Instance dataset for resource-constrained project scheduling with diverging material flows

This data article describes an instance dataset motivated by the problem of scheduling a project with diverging material flows. Such material flows are released during the execution of the project and are subject to limited processing and storage capacities. Typical examples are nuclear dismantling or other deconstruction/demolition projects, where large amounts of material must be classified, scanned for hazardousness, and processed accordingly. The problem setting is mathematically described as a resource-constrained project scheduling problem with cumulative resources (RCPSP/c). The RCPSP/c deals with finding a project schedule with minimal makespan that satisfies temporal, renewable resource, and cumulative resource constraints. In total, the dataset comprises 192 artificially generated instances that are suitable for testing models and solution methods. In addition, we provide our best found solution for each instance and different modeling variants (e.g., for two types of objective functions). These solutions were computed by heuristic solution methods. The dataset serves as a benchmark for researchers evaluating the performance of solution methods for the RCPSP/c or the more general problem class with resources that can be produced and consumed

Building Information Modeling (BIM) for existing buildings - literature review and future needs

Abstract not availableRebekka Volk, Julian Stengel, Frank Schultman

Post-Demolition Autoclaved Aerated Concrete: Recycling Options And Volume Prediction In Europe

Autoclaved aerated concrete (AAC) is an increasingly used building material due to its exceptional thermal properties. Post-demolition AAC is mainly disposed in landfills because of lacking established recycling processes. However, the growing demand for sustainable products, greenhouse gas reduction, decreasing landfill capacities and new legal frameworks require recycling options for post-demolition AAC. Current research includes using post-demolition AAC recycling in the production of lightweight aggregate concrete, lightweight mortar, no-fines concrete, and floor screed. Even closed-loop recycling could be achieved by adding finely ground post-demolition AAC in the AAC production process or by producing belite cement clinker from post-demolition AAC as a substitution for Portland cement. Predicting the generation of post-demolition AAC volumes is crucial for a recycling and circular management of AAC. But, post-demolition AAC volumes in Europe are currently neither recorded in statistics nor investigated in comprehensive studies. Therefore, a post-demolition AAC prediction model is presented that quantifies post-demolition AAC on a national and European level. Results show low volumes in South East, Western, and Southern Europe as well as Scandinavia due to small market sizes. In North West and Central Europe, especially the UK (700,000 m³) and Germany (1,200,000 m³) in 2020 drive post-demolition AAC volumes. The most significant post-demolition AAC volumes occur in Eastern Europe, especially in Poland (1,800,000 m³) and Russia (3,900,000 m³) in 2020. While relative volumes between the regions stay similar, the absolute post-demolition AAC volumes in Europe will nearly double in the next decade from 12.3 to 22.0 million m³

CO₂ -based assessment for sustainable production planning in the metal processing industry

By assessing the emissions of greenhouse gases of finished goods over their entire lifecycle, it can be seen that a significant part of the emissions is caused in production and related upstream processes. A strong focus on resource-efficient production techniques could provide possibilities for significant emission reduction in these processes. This causes the need of a quantitative comparison of different production techniques and processes by their total CO2-eq.-emissions. Especially small enterprises may not be able to provide information on energy and resource flows and resulting emissions on a level that is detailed enough to reveal emission reduction potentials. The assessment model introduced is applicable for every enterprise to quantify production-related emissions of their finished goods and to compare them with other possible production techniques and processes, in order to facilitate CO2-based production planning. The model is highly flexible, as calculations are based on a process database that can easily be modified. Moreover, the input of country-specific and manufacturer-specific data like country-specific electricity-mix or material-manufacturer-specific CO2-eq.-emissions enables a high customization level