Dispersing Multi-Walled Carbon Nanotubes (MWCNTs) into concrete at low (<1 wt% in cement) concentrations may improve concrete performance and properties and provide enhanced functionalities. When MWCNT-enhanced concrete is fragmented during remodelling or demolition, the stiff, fibrous and carcinogenic MWCNTs will, however, also be part of the respirable particulate matter released in the process. Consequently, systematic aerosolizing of crushed MWCNT-enhanced concretes in a controlled environment and measuring the properties of this aerosol can give valuable insights into the characteristics of the emissions such as concentrations, size range and morphology. These properties impact to which extent the emissions can be inhaled as well as where they are expected to deposit in the lung, which is critical to assess whether these materials might constitute a future health risk for construction and demolition workers. In this work, the impact from MWCNTs on aerosol characteristics was assessed for samples of three concrete types with various amounts of MWCNT, using a novel methodology based on the continuous drop method. MWCNT-enhanced concretes were crushed, aerosolized and the emitted particles were characterized with online and offline techniques. For light-weight porous concrete, the addition of MWCNT significantly reduced the respirable mass fraction (RESP) and particle number concentrations (PNC) across all size ranges (7 nm – 20 μm), indicating that MWCNTs dampened the fragmentation process by possibly reinforcing the microstructure of brittle concrete. For normal concrete, the opposite could be seen, where MWCNTs resulted in drastic increases in RESP and PNC, suggesting that the MWCNTs may be acting as defects in the concrete matrix, thus enhancing the fragmentation process. For the high strength concrete, the fragmentation decreased at the lowest MWCNT concentration, but increased again for the highest MWCNT concentration. All tested concrete types emitted <100 nm particles, regardless of CNT content. SEM imaging displayed CNTs protruding from concrete fragments, but no free fibres were detected. 

Incorporation of additives into a reinforced concrete matrix to delay or even completely avoid the initiation of corrosion during the service-life of the construction is a widely pursued topic. One of the new promising technologies achieving increased interest is to incorporate corrosion inhibitors encapsulated in layered double hydroxide (LDH). LDH structures follow a controlled release of the inhibitor while chloride is efficiently trapped at the same time. Another type of nanostructure additive offering self-protection ability in concrete is polyhedral oligomeric silsesquioxanes (POSS) developed to exhibit water-repellent functionalities protecting the reinforcement from corrosive attack. In the present laboratory work, the enhanced performance of concrete infrastructures in a marine environment was studied using a SCC design. The addition of LDH (0.5, 1 and 2 % by mass of binder (bmb)) and POSS (2 and 4 % additive level) was explored. Migration and diffusion Cl transport tests have been performed towards corrosion protection of reinforcing bars. The results showed that Cl transport decreases with the concrete maturity, and this is even more effective for concretes with LDH and POSS. This delay effect is more pronounced in the unidirectional diffusional Cl transport. LDH is significantly retarding the initiation of rebar corrosion.

In Sweden, there are many assets for drinking water such as water towers, water treatment plants and pipes. Many of these structures are made of reinforced concrete and were built between 1950 – 1970. The normal design life of these structures is 50 years meaning that they are reaching their intended design lifespan. In addition, these structures face harsh environments that can lead to degradation. All these leads to the need of repair and renovation of these specifics assets. For that purpose, methodologies and tools for performing inspections, assessing the condition and the time to intervention are needed. Nowadays, in general the procedures for condition assessment are based on the judgement and expertise of engineers performing the inspection. In this project a compilation of best practices for performing the condition assessment for drinking water structures has been performed. This assessment should include an ocular inspection of the object, documentation, tests to ensure certain parameters and an overall analysis of the assessment of the object and finally provide a proposal for measures. The measures must be designed so that both the method and the time aspect are specified. In addition, in this project a methodology and a simplified tool has been developed to accommodate the condition assessment of reinforced concrete drinking water infrastructures and the time to intervention after the assessment. The tool also includes the uncertainty analysis of the condition assessment performed.

Cracking of prefab sandwich panels impact s not only the appearance of buildings aesthetically but has also consequences for the material durability, as well as the thermal and acoustic performance of the building envelope as a whole. The project investigates the possible causes of cracks from the design to the production stage, transport and final application and exposure. The study w ill focus on material related causes due to the different types of restrained shrinkage, considering also mitigation measures by shrinkage reducing/compensating admixtures, to design related factors and to environmental factors during transport and the service life of the elements. The actual study will focus on the drying shrinkage as well as shrinkage mitigating possibilities. Restraining and environmental factors wil l be investigated experimentally and by FEA. The results of the project will be evaluated and concluded in a list of recommendations for mitigating cracking in sandwich elements

Cracking of prefab sandwich panels impact s not only the appearance of buildings aesthetically but has also consequences for the material durability, as well as the thermal and acoustic performance of the building envelope as a whole. The project investigates the possible causes of cracks from the design to the production stage, transport and final application and exposure. The study w ill focus on material related causes due to the different types of restrained shrinkage, considering also mitigation measures by shrinkage reducing/compensating admixt ures, to design related factors and to environmental factors during transport and the service life of the elements. The actual study will focus o n the drying shrinkage as well as shrinkage mitigating possibilities. Restraining and environmental factors will be investigated experimentally and by FEA. The results of the project will be evaluated and concluded in a list of recommendations for mitigating cracking in sandwich elements.

Cracking of prefab sandwich panels impact s not only the appearance of buildings aesthetically but has also consequences for the material durability, as well as the thermal and acoustic performance of the building envelope as a whole . The project investigates the possible causes of cracks from the design to the production stage, transport and final application and exposure. The study w ill focus on material related causes due to the different types of restrained shrinkage, considering also mitigation measures by shrinkage reducing/compensating admixtures, to design related factors and to environmental factors during transport and the service life of the elements. The actual study will focus o n the drying shrinkage as well as shrinkage m itigating possibilities. Restraining and environmental factors will be investigated experimentally and by FEA. The results of the project will be evaluated and concluded in a list of recommendations for mitigating cracking in sandwich elements.

Cracking of prefab sandwich panels impact s not only the appearance of buildings aesthetically but has also consequences for the material durability, as well as the thermal and acoustic performance of the building envelope as a whole. The project investigates the possible causes of cracks from the design to the production stage, transport and final application and exposure. The study w ill focus on material related causes due to the different types of restrained shrinkage, considering also mitigation measures by shrinkage reducing/compensating admixt ures, to design related factors and to environmental factors during transport and the service life of the elements. The actual study will focus o n the drying shrinkage as well as shrinkage mitigating possibilities. Restraining and environmental factors will be investigated experimentally and by FEA. The results of the project will be evaluated and concluded in a list of recommendations for mitigating cracking in sandwich elements.

The aim of the present paper is to further validate a model proposed for assessing bond strength in corroded and non-corroded steel bars. The model was obtained by applying multiple linear regression analysis to an initial database obtained from literature containing over 650 bond tests: 372 with corroded steel bars. In this paper, a second stage for further validating the model has been conducted with new database consisting of 131 new tests of bond with corroded steel bars resulting in a final database of 500 tests of bond with corroded reinforcing steel bars. In this model, bond strength is considered as an average stress on the nominal surface of a straight length of a bar over the bond length. The corrosion effect is considered using the cross-section loss (% Cor) considered as uniform corrosion along the bonded length of the bar. In addition to the cross-section loss, corrosion effect in bond is additionally considered with an additional variable that implicitly includes the effect of cracking depending on the range of cross section loss, bond condition and presence of transverse reinforcement. In the paper, the former formulation proposed in is compared with the formulation adapted with rounded coefficients for the former database, the new database and the combined database with different statistical criteria to compare the accuracy of the bond strength predictions obtained with the model. Finally, the predictions of the model show a good fitting with the experimental results with the new database and also have a low scatter. This is showing its utility in the safety assessment of bond strength in reinforced concrete members.

The purpose of CF2T project is to develop a competitive foundation, immerse it as part of a precommercial project and validate the concept in a real sea environment. The innovative foundation will be designed to decrease construction costs, with modular interfaces to allow an installation in several packages (foundation parts, ballasts, turbine) in order to limit the installation vessel’s crane capacity requirement, which will also reduce installation costs. The different alternatives to reduce the structure construction costs and modularity will be evaluated including the design of a hybrid foundation combining concrete and steel. The new foundation should also have an adaptive interface with the seabed in order to avoid any seabed preparation. In addition, the project will develop a monitoring system to have a better understanding of loads applied to the structure for future foundations developments. This monitoring will allow to carry out a survey of the structural health for preventive maintenance which will contribute to improve reliability of the foundation. This report is the first deliverable in WP6 (Foundation Monitoring), namely D6.1 Sensor characteristics and implementation report. RISE led the work in collaboration with SAITEC and ALKIT. This report proposes sensor characteristics and implementation for the foundation of tidal turbine designed within the project. A literature review is firstly included on Structural Health Monitoring (SHM), relevant SHM techniques and SHM’s applicability to both concrete and offshore structures. Fibre optics, specifically Fibre Bragg Grating (FBG), were identified to be the most suitable solution for SHM of the concrete foundation. Critical measurement areas and performance indicators for the concrete foundation were identified and a detailed measurement scheme was proposed. Implementation on the laboratory scale was studied for both material and component levels, i.e., steel reinforcement and concrete surface. It was observed that the fibre optics were able to measure the distribution of strains coherently and accurately on steel reinforcement subjected to tensile loading, all while proving to be durable against high levels of corrosion. Detection of strain in the concrete surface which could indicate tilting and/or onset of cracking was also possible with the proposed fibre optic system.

The purpose of CF2T project is to develop a competitive foundation, immerse it as part of a precommercial project and validate the concept in a real sea environment. The innovative foundation will be designed to decrease construction costs, with modular interfaces to allow an installation in several packages (foundation parts, ballasts, turbine) in order to limit the installation vessel’s crane capacity requirement, which will also reduce installation costs. The different alternatives to reduce the structure construction costs and modularity will be evaluated including the design of a hybrid foundation combining concrete and steel. The new foundation should also have an adaptive interface with the seabed in order to avoid any seabed preparation. In addition, the project will develop a monitoring system to have a better understanding of loads applied to the structure for future foundations developments. This monitoring will allow to carry out a survey of the structural health for preventive maintenance which will contribute to improve reliability of the foundation. This report is the second deliverable in WP6 (Foundation Monitoring), namely D6.2 Sensor implemented and calibrated in proof-of-concept. RISE led the work with collaborative efforts from ALKIT. The proof-of-concept was proposed by RISE to enable the implementation of the proposed and developed monitoring system based on fibre optics in a representative reinforced concrete test object. This report covers the implementation in the proof-of-concept, the execution of experiment with mechanical loading on the test object, as well as the calibration of the given sensors and verification using secondary measuring techniques. The results show a complete characterization of the structure strain response along several loading cycles and the compatibility between the fibre optics-based sensors and the strain gauges validating the optical solution for structural monitoring. The system showed its capability for crack detection and also showed a good consistency of the measurements under repeated cycles. Lastly, a description of requirements and details for taking this proof-of-concept to the next phase of offshore monitoring of the concrete foundation is provided.