This report aims to investigate why proven methods for recycling concrete waste as road construction material are not practiced in Sweden. An additional objective is to investigate how concrete is handled as a waste product and whether it would be environmentally friendly and financially beneficial to clients and contractors. Information has been extracted via interviews conducted with experts from various positions within the civil engineering industry. Additional information was obtained through literature studies and questionnaires sent and received via email. Results which were frequently mentioned by engineering professionals included the extra expense of transporting and processing crushed concrete, parties involved in the design and construction processtend to follow traditional methods of using tried and tested virgin materials, the assumption of responsibility for structural failure due to alternative materials and general lack of knowledge surrounding crushed concrete as a construction material. Conclusions are that crushed concrete is suitable for construction of subbases in roads and base courses of cycle/pedestrian paths. Traditionally used virgin materials are generally less expensive than crushed concrete. Existing legislation makes the use of recycled construction material difficult. Awareness and education regarding recycled concrete, as a construction material, should be increased.

The cement industry releases large quantities of CO₂ into the atmosphere during the manufacture of Portland Cement. The intrinsic property of the cement to reabsorb some of this CO₂ over its life time through a process called recarbonation has been investigated. This thesis reports on the development of an accelerated recarbonation apparatus for studying the recarbonation of crushed concrete under controlled conditions. The apparatus involved a series of airtight desiccators into which were placed the crushed concrete samples. The desiccators were then filled to ~50,000 ppm CO₂, which is significantly greater than the ~380 ppm by volume CO₂ available in the earth’s atmosphere. The CO₂ concentration was then monitored with respect to time inside the desiccator using CO₂ specific infrared probes. Two concrete design strengths of 20MPa and 40MPa with various crushed particle sizes were exposed to conditions of 50-60 % relative humidity, a temperature of 20 ± 1.5 °C, an exposure period of 21 days and a maximum CO₂ concentration of ~50,000 ppm by volume. The CO₂ uptake measured by the infrared probes was verified using other detection methods of FTIR, TGA, XRF, phenolphthalein indicator and the weight gain of the crushed concrete samples. The research found that a concrete of 20 MPa design strength and a water to cement ratio of 0.67 could absorb 12-83 % of the original calcination emissions for particle sizes <40, <20 and <10 mm in the 21 day time period. Similar behaviour was also exhibited by the 40 MPa design strength (w/c 0.49) but the extent of CO₂ uptake was not as pronounced. The 40 MPa (w/c 0.49) design mix absorbed 9-70 % of the original calcination emissions for the same particle sizes of <40, <20 and <10 mm. It was found that significant quantities of CO₂ could be absorbed by the smaller crushed sizes of <10 and <20 mm for both design mixes, owing to their much larger surface area. It was also found that about 80 % of the total CO₂ absorbed occurred within the first 10 days of exposure. It is envisaged that the results contained in this thesis will assist in future investigations into crushed concrete recarbonation.

Crushed or recycled concrete aggregates (CCA/RCA) is an increasingly popular material as a replacement for natural aggregates in concrete due to industry demands for more recycled, lower carbon and responsibly sourced materials. In the UK, the majority of CCA is utilised in non-structural applications such as: a general fill material, road base/subbase or in low-grade concrete. Recycled aggregate producers however, are seeking new ways to incorporate CCA into higher value applications such as structural concrete to increase profits. Opportunities to incorporate CCA into structural concrete may also arise because of project demands for sustainability or in situations where natural aggregates are in short supply. Limited research has been published regarding the effect of coarse CCA on the durability of structural concrete, particularly in respect to water and chloride ion ingress and possibility of corrosion initiation. The aim of this EngD research programme was to investigate the effect of coarse CCA and supplementary cementitious materials (SCMs) on the durability performance of structural concrete, with particular emphasis on the key liquid transport mechanisms within concrete, namely absorption by capillary action, diffusion and migration. This addressed an industry concern regarding the detrimental effect of coarse CCA which has resulted in a limit on replacement levels of coarse natural aggregates in structural concrete, as defined in Eurocodes and local national standards for concrete. In this study, structural concrete was produced with varying levels of coarse CCA replacement (up to 100%), from five different sources and/or structural elements across the UK, with various combinations of SCMs to replace in part the Portland cement. Petrographic analysis was used as an innovative technique to characterise the coarse CCA sources to determine suitability which yielded positive results. The durability performance of the resultant concrete was analysed by exposing the concrete to aggressive chloride environments. The results indicate that the inclusion of coarse CCA, even as low as 20%, had a detrimental effect on the durability performance of structural concrete, in relation to absorption by capillary action, diffusion and migration. This effect however, can be offset through the use of SCMs, which have been shown to outperform control Portland cement concrete with 100% natural aggregates in durability performance tests. The results also suggest that cementitious materials had a greater influence on durability performance than the type and source of coarse aggregates used. It is recommended that the replacement of natural aggregate with coarse CCA be limited to 30% in cases where compliance with the 28 day characteristic strength is of particular importance. If the criterion for compliance at 28 days can be relaxed and the compressive cube strength of concretes with SCMs tested at later ages for conformity (56 or 90 days), then higher quantities of coarse CCA may be incorporated up to 60% to produce a more sustainable structural concrete. It is recommended that Portland cement is partially replaced with 50% ground granulated blast-furnace slag (GGBS) to produce a CEM III/A concrete. This is a significant step towards the potential wider implementation of coarse CCA in structural concrete, provided a suitable quantity of SCM is adopted along with a reliable and consistent source of coarse CCA.

Strängbetong krossar kasserade håldäckselement som sedan används som ballast i nya gjutningar. Den krossad betong ligger i en hög utomhus innan den används. Det första materialet krossades under 2020 och det senaste vintern 2022. Betongen karbonatiserar, en process som tar upp koldioxid från luften. Arbetet går ut på att kvantifiera den mängd koldioxid som tas upp samt finna förbättringsåtgärder för att kunna öka karbonatiseringen.  För att förstå hur karbonatisering fungerar utfördes informationssökning genom att leta efter tidigare forskningsrapporter som behandlar ämnet. Då det är brist på information om karbonatisering av krossad betong har antaganden gjorts för att komma vidare i arbetet. Vilket innebär att beräkningarna behöver mer korrekt indata för att visa ett mer rimligt resultat.  Den krossade betongen analyserades med karbonatiseringsindikator för att se om ytan av materialet karbonatiserat beroende på hur länge materialet varit orört.  Teoretiska beräkningar utfördes utifrån två olika exponeringar, regn och skyddad från regn, samt olika exponeringstid, resultatet visar att koldioxidupptaget blir högre om högen är skyddad från regn. Att strukturerat plocka material runt högen medför en längre exponeringstid för materialet, därmed ett högre koldioxidupptag jämfört med hur materialet plockas idag där allt material plockas från samma sida. / Strangbetong crushes discarded hollow core slabs, which are used for filling materials in new castings. The crushed concrete is stored in a pile outside before it is used. The first material was crushed during 2020 and the latest material were crushed in the winter of 2022. The concrete carbonates, a process where the concrete absorbs carbon dioxide from the air. The point of this project is to quantify the carbon dioxide which is absorbed and find solutions to make the carbonation more efficient.  To understand how concrete carbonation works, information has been searched for by studying already existing research reports. As there is a lack of information about carbonation of crushed concrete assumptions have been made to move the project forward. Which means that the calculations need more specific data to show a more reasonable result.  The crushed concrete was analyzed with a carbonation indicator to see how far the material had carbonated, depending on how long the material had been untouched.  Theoretic calculations were made throughout two different exposures, rain and covered from rain and different exposure time, the carbon dioxide uptake increases if the pile is covered from rain. Structured picking of material around the pile results in a longer exposure time for the material, therefore a higher uptake of carbon dioxide compared to how the material is picked today where the material is picked from the same side all the time.

A Mechanically Stabilized Earth (MSE) wall is a vertical grade separation that uses earth reinforcement extending laterally from the wall to take advantage of earth pressure to reduce the required design strength of the wall. MSE wall systems are often prefabricated to reduce construction time, thus improving constructability when compared with conventionally cast-in-place reinforced wall systems. However, there is a lack of knowledge for predicting the service-life of MSE retaining wall systems when recycled backfill materials such as Recycled Asphalt Pavement (RAP) and Crushed Concrete (CC) are used instead of Conventional Fill Material (CFM). The specific knowledge missing is how these recycled materials, when used as backfill in MSE wall systems, affects the corrosion rate of the reinforcing strips. This work addresses this knowledge gap by providing recommendations for MSE wall systems backfilled with CC or RAP, and provides a guide to predict the service-life based on corrosion rate test data obtained from embedding steel and galvanized-steel earth reinforcing strips embedded in MSE wall systems backfilled with CC, RAP, and CFM. Experimental data from samples emulating MSE wall systems with steel and galvanized-steel reinforcing strips embedded in CC and RAP were compared to samples with strips embedded in CFM. The results of the testing provide data and methodologies that may, depending on the environmental exposure conditions, justify the use of RAP and CC for the construction of MSE walls. If these backfill materials are obtained from the construction site, this could provide a significant cost savings during construction.

Constitués de plusieurs composants (granulats naturels et pâte de ciment adhérente), les GBR ne sont à l’heure actuelle pas utilisés largement dans la formulation de nouveaux bétons. Les propriétés médiocres des GBR compliquent considérablement la détermination de la quantité d’eau efficace dans le béton frais. Tout d’abord, une étude bibliographique va mettre en évidence la grande dispersion des résultats des essais de caractérisation des GBR et des propriétés des bétons recyclés à l’état frais et durci. Ensuite, une étude vise à analyser l’hétérogénéité des GBR et des granulats de béton concassé (GBC) par rapport à différents paramètres : aux impuretés granulaires, à la densité et à la teneur en pâte de ciment, au malaxage du béton parent, et au niveau de la capacité d’absorption d’eau des GBC en fonction de leur état de pré-humidification. Enfin, une dernière partie est destinée à améliorer la maîtrise de l’eau efficace réelle dans la fabrication du béton recyclé. La cinétique d’absorption des GBC dans une pâte de ciment est tout d’abord étudiée. Ensuite, l’évolution de l’eau efficace durant le malaxage de bétons à base de GBC est investiguée au moyen d’une méthode originale basée sur le suivi des courbes de puissance du malaxeur. Finalement, l’effet d’un malaxage sous vide relatif sur les propriétés des bétons à base de granulats naturels et des bétons à base de GBC est étudié. / Composed of several components (natural aggregates and adherent cement paste), RCA are not widely recommended in new concrete formulations. Their poor properties considerably complicate the determination of the effective water in fresh concrete. In a first part, a bibliographic study will highlight the wide dispersion of the results of characterization tests of RCA and the properties of fresh and hardened recycled concrete. In a second part, the heterogeneity of RCA and crushed concrete aggregates (CCA) is studied according to different parameters: granular impurities, density, cement paste content, mixing of parent concrete, and water absorption capacity according to their pre-humidification. The third part consists of three experimental studies that intend to improve effective water control in the manufacture of recycled concrete. The absorption kinetics of CCA in a cement paste is first studied. Then, the evolution of effective water in fresh concrete during mixing is studied using an original method based on the power evolution of the mixer. Finally, the effect of vacuum mixing on the properties of ordinary and recycled concretes is investigated.