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In this master thesis work calcination parameters' impact on the resulting quicklimes slaking reactivity is investigated. This is done by calcination of three different sedimentary limestones in an N2 atmosphere according to a design of experiment matrix. The limestones are from Wolica Poland, Slite Sweden and Jutjärn Sweden. The temperatures and residence times are varied between 1000ºC, 1050ºC, and 1100ºC for 5 min, 27.5 min, and 60 min. There were seven experiments per limestone sample. The calcination experiments were conducted in an electrical muffle furnace.When the limestone samples were calcined, the resulting quicklimes slaking reactivity was tested according to standard SS-EN 459-2:2010 Building lime - Part 2: Test methods. Four different parameters were used to determine the slaking reactivity, these were the maximum temperature, how much the temperature increases under the initial 30 s, the time it takes for the temperature to reach 60ºC, and the time for the slaking to become 80% finished.From the slaking reactivity experiments, the calcination parameters to produce the most reactive quicklime for the limestone from Wolica and Jutjärn are 1000ºC for 60 min, and for the limestone from Slite 1100ºC for 5 min. For all three limestones the least reactive quicklime was received by calcining at 1100ºC for 60 min. The most and least reactive quicklimes were analyzed in SEM, where it could be seen that the least reactive quicklime samples were coarser compared to the most reactive samples. Depending on what slaking reactivity parameter is of interest, the calcination settings should be different and can be an indication for operation parameters for industrial kilns. The statistical analysis on the experimental model showed that the experiment had a poor statistical fit for most of the experiment. This could be due to that the model possibly was too simple to describe the calcination parameters complex impact on the slaking reactivity.

According to the Mine Health and Safety Administration (MSHA), between 2006 and 2016, the underground stone mining industry had the highest fatality rate in 4 out of 10 years, compared to any other type of mining in the United States. Additionally, the National Institute for Occupational Safety and Health (NIOSH) stated that structurally controlled instability is a predominant failure mechanism in underground limestone mines. This type of instability occurs when the different discontinuity sets intercept with each other forming rock blocks that displace inwards the tunnel as the excavation takes place, posing a great hazard for miners and overall mine planning. In recent years, Terrestrial laser scanning (TLS) has been used for mapping and characterizing fractures present in a rock mass. TLS is a technology that allows to generate a three-dimensional multimillion point cloud of a scanned area. In addition to this, the advances in computing power throughout the past years, have allowed numerical modeling codes to represent more realistically the behavior of a fractured rock masses. This work presents and implements a methodology that integrates laser scanning technology along with Discrete Element Modeling as tools for characterizing, preventing, and managing structurally controlled instability that may affect large-opening underground mines. The stability of an underground limestone mine that extracts a dipping ore body with a room and pillar (and eventual stoping) mining method is analyzed with this approach. While this methodology is proposed based on a specific case study that does not meet the requirements to be designed with current NIOSH published guidelines, this process proposes a general methodology that can be applied in any mine experiencing similar failure mechanisms, considering site-specific conditions. The aim of this study is to ensure the safety of mine workers and to reduce accidents that arise from ground control issues. The results obtained from this methodology allowed us to generate Probability Density Functions to estimate the probability of rock fall in the excavations. These models were also validated by comparing the numerical model results with those obtained from the laser scans. / M.S. / According to the Mine Health and Safety Administration (MSHA), between 2006 and 2016, the underground stone mining industry had the highest fatality rate in 4 out of 10 years, compared to any other type of mining in the United States. Additionally, the National Institute for Occupational Safety and Health (NIOSH) stated that structurally controlled instability is one of the main causes of rock falls in underground limestone mines. This type of instability occurs when the fractures present in the rock mass intercept each other forming rock blocks that displace into the tunnel as the excavation takes place and poses a great hazard for miners. In recent years, Terrestrial laser scanning (TLS) has been used for mapping and characterizing fractures present in a rock mass. TLS is a technology that allows to generate a three-dimensional multimillion point cloud of a scanned area. In addition to this, the advances in computing power throughout the past years, have allowed simulation softwares such as the Discrete Element Model (DEM) to represent more realistically the behavior of a fractured rock mass under excavation. The aim of this work was to develop and evaluate a methodology that could complement already exisiting design guidelines that may not apply to all kind of underground mines. The presented methodology evaluates rock failure due to presence of discontinuites, through the integration of TLS with DEM and considers site specific conditions. An area of a case study mine was assessed with this methodology, where several laser scans were performed. Information extracted from this laser scans was used to simulate the response of the rock mass under excavation by running Discrete Element Numerical Models. Results from these models allowed us to estimate the probability of rock failure in the analized areas. These, rock block failure probability estimations provide engineers a tool for characterizing, preventing, and managing structurally controlled instability, and ultimately improving workers safety.

Within the EU's railway research program IN2TRACK3, a product known as the 3MB track system (Moulded Multi Modular Block slab track system) has been developed. The new innovative track system can be explained as a hybrid solution between traditional ballast tracks and slab track systems. The project has a primary objective for the 3MB system to reduce life cycle costs, improve reliability and punctuality, and increase capacity. The modular construction system allows for easier maintenance of railway tracks, as damaged parts can be replaced more quickly. In September 2022, a full-scale test was initiated on a 50-meter stretch in Gransjö, north of Boden, situated along the Iron Ore Line (Malmbana). Initially planned for a 2-year testing period, but the track system was dismantled and removed after approximately one year due to the emergence of a recurring severe crack pattern within the blocks. This degree project aims to conduct a thorough damage investigation, focusing on investigation the reasons behind the repeated crack patterns observed in the 3MB system. The analysis will particularly emphasise the design of the reinforcement and assesses whether the chosen concrete type is suitable for the specific conditions of the construction. Various laboratory tests, including compressive strength, tensile strength, and thin section analysis, are employed in this investigation. Additionally, a comprehensive literature study is conducted to ensure its credibility and quality. The results reveal that the aggregate in the sample is porous. This porosity increases the risk of frost damage and cracking in the concrete. The air content was measured at 7.1%, which is somewhat high, together with a high w/c equivalent between 0.50 and 0.55, which has a potentially negative impact on the strength. The study's in-depth analysis of the 3MB system blocks revealed two main problems: the choice of porous limestone as aggregate and insufficient coverage of the reinforcing steel. The porous nature of limestone led to water absorption and frost susceptibility, while inadequate coverage resulted in corrosion and frost cracking. Laboratory experiments also showed low tensile strength and uneven concrete quality. Calculations indicated the need for spalling reinforcement. Workmanship errors, including haphazard concrete pouring and suboptimal rail fastening solutions, exacerbated the situation. The study highlights the need for improvements in the concrete's waterproofing and fatigue strength to meet the system's requirements and avoid similar problems in the future. Despite the challenges, the project presents potential for success with the right adjustments and lessons learned from the initial testing phase. Despite challenges and identified obstacles in the project, the 3MB system can succeed. By fine-tuning the concrete recipe, and optimizing reinforcement and aggregate quality, the problems can be avoided. It is crucial to look beyond these obstacles and stick to the overall goal of the project: to establish the sustainable and efficient railways of the future. These challenges can be overcome through careful measures and ensure the project's positive contribution to the transport sector. / Inom EU:s järnvägsforskningsprogram IN2TRACK3 har en produkt känt som 3MB spårsystem (Moulded Multi Modular Block slab track system) utvecklats. Det nya innovativa spårsystemet kan förklaras som en hybridlösning mellan traditionella ballastbanor och ballastfria banor. Projektet har som primärt mål för 3MB-systemet att minska livscykelkostnaderna, förbättra tillförlitlighet och punktlighet, och öka kapaciteten. Det modulära byggsystemet möjliggör enklare underhåll av järnvägasspår, eftersom skadade delar kan bytas ut på ett snabbare sätt. I september 2022 inleddes ett fullskaleprov på en 50 meter lång sträcka i Gransjö, norr om Boden, belägen längs Malmbanan. Ursprungligen planerad för en 2-årig testperiod, men spårsystemet demonterades och togs bort efter cirka 1 år på grund av uppkomsten av ett återkommande allvarligt sprickmönster inom blocken. Målet med detta examensarbete är att genomföra en grundlig skadeutredning, med fokus på att undersöka orsakerna bakom de upprepade sprickmönster som observerats i 3MB-systemet. Analysen betonar särskilt dimensioneringen av armeringen och bedömning om den valda betongtypen är lämplig för konstruktionens specifika förutsättningar. Olika laboratorietester, inklusive tryckhållfasthet, draghållfasthet och tunnslipsanalys, används i undersökningen. Dessutom genomförs en omfattande litteraturstudie för att säkerställa studiens trovärdighet och kvalitet. Resultaten avslöjar att ballasten i provet är porös. Denna porositet ökar risken för frostskador och sprickbildning i betongen. Lufthalten uppmättes till 7,1%, Vilket är något högt, och tillsammans med ett högt vatten-cement-tal mellan 0,50 och 0,55, ger de en potentiellt negativ påverkan på hållfastheten. Studiens djupgående analys av 3MB-systemet block avslöjade två huvudproblem: valet av porös kalksten som aggregat och otillräcklig täckning av armeringsstålet. Kalkstenens porösa natur ledde till vattenabsorption och frostkänslighet, medan otillräcklig täckning resulterade i korrosion och frostsprickor. Laboratorieexperiment visade också på låg draghållfasthet och ojämn betongkvalitet. Beräkningar indikerade behovet av spjälkningsarmering. Utförandefel, inklusive ej fullgod betonggjutning och suboptimala rälbefästnings-lösningar, förvärrade situationen. Studien framhåller behovet av förbättringar i betongens vattentäthet och utmattninghållfasthet för att möta systemets krav och undvika liknande problem i framtiden. Trots dessa utmaningar har projektet en potential att bli framgångsrikt med rätt justeringar och lärdomar från den initiala testfasen. Trots utmaningar och identifierade hinder i projektet kan 3MB-systemet lyckas. Genom att finjustera betongreceptet, optimera armeringen och ballastkvaliteten bör uppkomna problemen undvikas. Det är avgörande att se bortom dessa hinder och hålla fast vid projektets övergripande mål: att etablera framtidens hållbara och effektiva järnvägar. Genom noggranna åtgärder kan dessa utmaningar övervinnas och säkerställa projektets positiva bidrag till transportsektorn.