<abstract xmlns="http://www.w3.org/1999/xhtml">This study investigates the feasibility of using bauxite residue (BR) as supplementary cementitious material (SCM) for the cement and concrete industry. It is shown from pastes of BR and calcium hydroxide, that BR is highly pozzolanic in nature. The early hydration of cement pastes with BR is accelerated while long-term strength is reduced probably due to the alkaline nature of BR. To be used as cement replacement material in concrete, attempts have been made to reduce the alkali content of BR, in particular to reduce the chance of alkali-aggregate reactions. Co-calcination of BR with kaolin or washing and cooking of BR with calcium hydroxide or calcium hydroxide and gypsum resulted in considerable reduction of alkali content; up to 75%. At the same time the reactivity of the BR was reduced but still being higher compared to fly ash already used in the cement industry.</abstract>

Bauxite Residue as Supplementary Cementitious Material – Efforts to Reduce the Amount of Soluble Sodium

<abstract xmlns="http://www.w3.org/1999/xhtml">Despite the new Swedish client requirement to reduce the climate impact from the construction of roads, there has been relatively little research so far on how the optimization measures regarding the environmental impact of road pavements can be integrated in the traditional design. An increase in axle weights, changes of the traditional ways of travel, e.g. the use of automated and guided vehicles, and stricter customer requirements on reducing the climate impact require new approaches to steer the road and pavement industry towards more climate neutral solutions. This paper analyzes the latest standards for sustainability assessment of engineering works in an attempt to adjust these standards for assessing various road design options in a comparable and fair way, also when various materials are included.</abstract>

KTH Royal Institute of Technology, Division of Concrete Structures

Making Concrete Pavements Competitive by Using the Standardized Framework for Comparisons of Infrastructure Projects in Terms of Cost-Efficiency and Climate Impact

<abstract xmlns="http://www.w3.org/1999/xhtml">Several inspection methods can be used to assess the corrosion state of steel reinforcement in concrete. Especially for periodical field surveys and monitoring, non-destructive testing (NDT) methods are to be preferred as they do not cause any or very limited damage to the existing concrete. In this paper, the corrosion state of three reinforced concrete beams exposed to marine environment for 25 years was evaluated by measuring three parameters; electrochemical potential, concrete resistivity and corrosion rate. The measurements were performed with commercial devices. It was found that all devices are applicable for field inspections. Among the methods selected for the study, the electrochemical potential measured in a fine grid and analysed statistically offered the best possibility of evaluating the corrosion state; preferably in combination with selected excavations for determination of the level of corrosion.</abstract>

SINTEF Community, Department Architecture, Materials and Structures

Norwegian University of Science and Technology

Non-destructive Test Methods for Corrosion Detection in Reinforced Concrete Structures

<abstract xmlns="http://www.w3.org/1999/xhtml">Crack formation in concrete structures due to various load and non-load factors leading to degradation of service life is very common. Repair and maintenance operations are, therefore, necessary to prevent cracks propagating and reducing the service life of the structures. Accessibility to affected areas can, however, be difficult as the reconstruction and maintenance of concrete buildings are expensive in labour and capital. Autonomous healing by encapsulated bacteria-based self-healing agents is a possible solution. During this process, the bacteria are released from a broken capsule or triggered by water and oxygen access. However, its performance and reliability depend on continuous water supply, protection against the harsh environment, and densification of the cementitious matrix for the bacteria to act. There are vast methods of encapsulating bacteria and the most common carriers used are: encapsulation in polymeric materials, lightweight aggregates, cementitious materials, special minerals, nanomaterials, and waste-derived biomass. Self-healing efficiency of these encapsulated technologies can be assessed through many experimental methodologies according to the literature. These experimental evaluations are performed in terms of quantification of crackhealing, recovery of durability and mechanical properties (macro-level test) and characterization of precipitated crystals by healing agent (micro-level test). Until now, quantification of crack-healing by light microscopy revealed maximum crack width of 1.80mm healed. All research methods available for assesing self-healing efficiency of bacteria-based healing agents are worth reviewing in order to include a coherent, if not standardized framework testing system and a comparative evaluation for a novel incorporated bacteria-based healing agent.</abstract>

Department of Materials & Environment, Faculty of Civil, Engineering & Geosciences

TH Royal Institute of Technology, Division of Concrete Structures

Encapsulation Techniques and Test Methods of Evaluating the Bacteria-Based Self-Healing Efficiency of Concrete: A Literature Review

<abstract xmlns="http://www.w3.org/1999/xhtml">The article addresses the modelling of the maturity of concrete. The apparent activation energy is the backbone of the Arrhenius model, which is typically used to model the maturity of concrete. The maturity (or the equivalent age) is influenced by the curing temperature and it is applied when modelling the hydration process and the hardening of concrete for instance in order to forecast the early-age strength to determine the time for removal of formwork or the time for prestressing. Part 1 of the article describes the background for the maturity model and the test series carried out at the DTI concrete lab.Laboratory tests at different curing temperatures (from 5°C to 60°C) are presented and the compressive strength results are modelled according to the original Freiesleben Hansen and Pedersen maturity model that has been applied in the field for many years. The tests include five different concretes, using three different cement types and the addition of fly ash. There are significant differences especially when considering the later-age strength modelling at either low temperatures or at high temperature curing.</abstract>

Concrete Expert, Danish Technological Institute

Activation Energy for the Concrete Maturity Model – Part 1: Compressive Strength Tests at Different Curing Temperatures

<abstract xmlns="http://www.w3.org/1999/xhtml">The article addresses the modelling of the maturity of concrete. The apparent activation energy is the backbone of the Arrhenius model, which is typically used to model the maturity of concrete. The maturity (or the equivalent age) is influenced by the curing temperature and it is applied when modelling the hydration process and the hardening of concrete for instance in order to forecast the early-age strength to determine the time for removal of formwork or the time for prestressing. Part 1 of the article describes the background for the maturity model and the tests carried out as part of a large test programme at the DTI concrete lab. The tests were applying iso-thermal curing temperatures from 5°C to 60°C for various durations before measuring the compressive strength.Part 2 of the article presents a model for the activation energy based on these test results. An alternative formulation of the maturity model is suggested and compared with other similar concrete tests found in the literature for early-age strengths. The alternative model is shown to give better accuracy when modelling the early-age strengths of concrete. The tests include five different concretes, using three different cement types and the addition of fly ash.</abstract>

Activation Energy for the Concrete Maturity Model – Part 2: New Model for Temperature Dependent Ea

AHEAD OF PRINT

Volume 69 (2023): Issue 2 (December 2023)

Volume 68 (2023): Issue 1 (July 2023)

Volume 67 (2022): Issue 2 (December 2022)

Volume 66 (2022): Issue 1 (July 2022)

Volume 65 (2021): Issue 2 (December 2021)

Volume 64 (2021): Issue 1 (June 2021)

Volume 63 (2020): Issue 2 (December 2020)

Volume 62 (2020): Issue 1 (June 2020)

Volume 61 (2019): Issue 2 (December 2019)

Volume 60 (2019): Issue 1 (June 2019)

Volume 59 (2018): Issue 1 (December 2018)

Volume 58 (2018): Issue 1 (June 2018)

Nordic Concrete Research

 The aim is to publish reviewed papers on research, recent experiences, and education within the broad concrete field. The scope covers all aspects of concrete and other cementitious materials, e.g., materials, design, construction, assessment, maintenance, repair, strengthening, dismantling, and recycling. The scope is limited to papers that have a Nordic connection, e.g., through the environment conducting the investigation, affiliation of any of the authors, or if the subject of the paper is devoted to any specific Nordic circumstances such as geographical, geological, or organizational ones.The Nordic Concrete Federation (NCF) which is publishing the bi-annually publications Nordic Concrete Research (NCF), is a collaboration organization of the concrete associations in the five Nordic countries, Denmark, Finland, Iceland, Norway and Sweden. Read more about NCF on www.nordicconcrete.net.  "Nordic Concrete Research” has no article processing chargers (APCs) nor article submission charges.  Archiving  Sciendo archives the contents of this journal in Portico - digital long-term preservation service of scholarly books, journals and collections.  Plagiarism Policy  The editorial board is participating in a growing community of Similarity Check System's users in order to ensure that the content published is original and trustworthy. Similarity Check is a medium that allows for comprehensive manuscripts screening, aimed to eliminate plagiarism and provide a high standard and quality peer-review process. 