Conference Agenda

Recycling secondary iron-bearing materials is an important step toward more sustainable metallurgical production. Agglomeration allows fine by-products to be converted into mechanically stable bodies for furnace charging. At the same time, replacing fossil carbon in self-reducing agglomerates requires renewable carbon sources, and biochar is of interest because of its biogenic origin, porous structure, and reactivity. The same pore network, however, can disturb the early mixing stage. Added water may be drawn into the biochar before the organic binder can be sufficiently hydrated and distributed between neighbouring particles. This can change the local moisture balance, hinder binder distribution, and reduce green strength and handling stability.

This study investigates how the moisture state of biochar before mixing and the binder-to-moisture balance affect the mechanical properties of the produced agglomerates. Biochar was wetted before mixing, and agglomerates were prepared with starch-based binders and one additional biomass-derived binder candidate. The formulations were varied by the dry binder-to-total moisture mass ratio, considering both the water retained in the pre-conditioned biochar and the water added during mixing. The produced agglomerates were tested by compressive strength measurements and drop tests to compare their resistance to loading and repeated handling. The results are intended to support binder and moisture selection for biochar-containing self-reducing agglomerates.

Metal artwork is among the most significant material remains of Pre-Columbian Costa Rica. Due to commonly absent contextual information and lack of field evidence for ore mining and processing in the country, stylistic groupings based on the typological characteristics of metal objects have traditionally been used to infer on their possible provenance and chronology. Analyses of metalwork by geoscientific approaches have been widely proven to yield useful insights into the technological practices and raw material procurement strategies of past societies, thereby allowing to complement, challenge or confirm conclusions derived from qualitative methodologies. So far, however, their application to Costa Rican metal objects remained limited, with early invasive studies in the 1950s and 1960s solely determining bulk major element compositions and more recent studies only employing surface analytical techniques.

Here, we present a pilot study on fragments sampled from 30 metal objects of the collection of the Museo Nacional de Costa Rica. One part of the samples was prepared as polished mounted blocks for metallographic and in-situ compositional analysis while the remaining material will be available for solution-based isotopic analysis. The sample suite is representative for Costa Rican metalwork in terms of object types, geographic origin (if known) and material. Based on metallographic identification and spatially-resolved compositional analysis of microstructures, e.g., the bulk metal matrix, inclusions, surface enrichment and corrosion phenomena, we will evaluate indications for technological choices and raw material source types, and discuss its relation with existing evidence from qualitative approaches.

In this study the transition of talc pigments (Mg₃[(OH)₂/Si₄O₁₀]) to proto-enstatite (Mg₂Si₂O₆) was investigated in the white painted areas of two Kamares shards (unpublished, Heidelberg University Museum) using SEM-EDS and XRD. The Kamares ware characterised by polychrome decoration emerged in the pottery production on the Mesara Plain in southern Central Crete in the Middle Minoan Period IB (1900 BCE). White and red pigments were applied to a black background, mostly in ornamental forms, prior to the three-phase ceramic firing. The conversion in the white paint took place temperatures above 950°C. Our results corroborated this transition confirming the results of a series of investigations over the last 50 years. In contrast in other Middle Minoan pottery – particularly from northern and eastern Crete – white paint applications were formed by a lime silicate white.

As a second goal we try to identify possible talc sources for the ceramic paint. Therefor talc samples from various sites in Crete, the Cyclades and Egypt were analysed by XRF. A comparison of the elemental composition and statistical analyses suggest that the probable origin of the talc used in the Kamares shards can be found in the Asterousia Massif (ophiolitic deposits) in the south or the Dikti Mountains in the north of Crete. Whilst the use of Cycladic talc sources appears unlikely, Egyptian talc resources cannot be entirely ruled out as a raw material for the ceramic talc white which have already been identified as sources for cold-processed white pigments in Late Bronze Age Egyptian fresco painting.

The present work focuses on identifying the original materials used in the Medusa mosaic from the Roman legionary camp Castra Bonnensia. Discovered in 1904. It remains the only known Roman mosaic from Bonn and has been archaeologically identified as part of a Roman military camp. Since 2020, the mosaic has been undergoing extensive restoration work and is being made accessible to the public. Previously, the restoration team in Bonn classified the material into eleven destinct material groups based on macroscopic characteristics. However, more detailed knowledge of the material composition is required to develop a scientifically based restoration strategy. The aim of this work is to evaluate whether the macroscopic classification aligns with the materials' mineralogical composition. Using the mineralogical analytical methods of thin-section microscopy and X-ray diffraction analysis, four different sedimentary rock types, dolomitic marble, trachyte, and four compositional ceramic groups were identified. Overall, the results confirm the material classification previously established by macroscopic observation; however, the mineralogical investigation provides greater compositional detail. The investigations are ongoing, and future studies are already considered necessary, focusing on the provenance of the stones and ceramics, as well as whether some of the materials were reused, e.g. from the legionary camp itself.

Underground Thermal Energy Storage (UTES) systems rely on the long-term thermal and mechanical stability of subsurface geological formations subjected to repeated heating and cooling cycles. This study investigates the thermo-mechanical and petrographic behaviour of marble formations from northwestern Pakistan to evaluate their response to elevated temperatures relevant to subsurface thermal energy applications.

Four marble varieties were characterized through petrographic, physical, and geotechnical analyses under ambient conditions and after thermal treatment at 100 °C, 200 °C, and 300 °C. Laboratory investigations included water absorption, porosity, bulk density, ultrasonic pulse velocity (UPV), compressive strength, tensile strength, and microscopic petrographic examination.

Results indicate that mineralogical composition and grain texture strongly influence thermal behaviour. Calcite-rich marbles with equigranular textures exhibited higher porosity and greater thermal fracturing, while quartz-bearing and dolomitic marbles showed comparatively improved thermal stability and mechanical performance. Thermal exposure produced progressive microcracking, reduction in UPV, and variations in strength properties associated with differential thermal expansion of mineral grains and grain-boundary deformation.

The findings contribute to understanding thermal-induced changes in carbonate rocks relevant to UTES, geothermal systems, and subsurface energy infrastructure. The study highlights the importance of petrographic characteristics in assessing the long-term integrity and thermal performance of geological materials used in sustainable underground energy storage applications.