The role of eigen-stresses on apparent strength and stiffness of normal, high strength, and ultra-high performance fibre reinforced concrete

Concrete is characterized in terms of its engineering properties, mainly strength and stiffness, which are subsequently used in structural design. However, the apparent (i.e., measured) concrete properties are not intrinsic but dependent on the conditions under which the measurement is performed. Herein a combined experimental and numerical...

Scheurvorming in jong beton: Onderzoek biedt nieuwe inzichten in de spanningsrelaxatie bij jong beton

Beton is tijdens het verharden onderhevig aan thermische en autogene vervormingen. Wanneer deze worden verhinderd, resulteert dit in spanningen en het risico op scheurvorming, mede afhankelijk van relaxatie. Aan de TU Delft is onderzoek gedaan naar het effect van spanningsrelaxatie op scheurvorming in jong beton. In tegenstelling tot de...

Cementitious cellular composites with auxetic behavior

Auxetic behavior refers to material with negative Poisson's ratio. In this research, a new type of cementitious auxetic material is developed. A novel crack bridging auxetic mechanism is discovered which is in contrast with a local buckling mechanism commonly employed to trigger auxetic behavior. Taking advantage of 3D printing techniques,...

Tunable mechanical behavior of auxetic cementitious cellular composites (CCCs): Experiments and simulations

This research presents an investigation of the compressive behavior of auxetic cementitious cellular composites (CCCs) using a combination of experiments and finite element (FE) simulations. Typical auxetic centrosymmetric geometry was used as unit cells for the cellular structure and fiber reinforced cementitious mortar were used as...

Experimentally informed micromechanical modelling of cement paste: An approach coupling X-ray computed tomography and statistical nanoindentation

This work proposes a method for numerically investigating the fracture mechanism of cement paste at the microscale based on X-ray computed tomography and nanoindentation. For this purpose, greyscale level based digital microstructure was generated by X-ray microcomputed tomography with a resolution of 2 μm/voxel length. In addition,...

Development of ductile cementitious composites incorporating microencapsulated phase change materials

Abstract In the past two decades, much research has been devoted to overcoming the inherent brittleness of cementitious materials. To that end, several solutions have been proposed, mainly utilizing fibres. One of the most promising classes of materials is strain hardening cementitious composite (SHCC). It utilizes PVA fibres, and it is...

Failure Modes in Concrete Repair Systems due to Ongoing Corrosion

Corrosion of steel reinforcement is the main cause of deterioration in reinforced concrete structures. It can result in cracking and spalling of the concrete cover. After the damaged cover is repaired, reinforcement corrosion might continue and even accelerate. While the development of the corrosion cell is difficult to control, the damage can...

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical...

Cracking of SHCC due to reinforcement corrosion

Reinforcement corrosion is the most important deterioration mechanism affecting reinforced concrete infrastructures. After corrosion starts, expansive pressures are exerted onto the surrounding concrete, causing cracking and spalling of the cover concrete. The amount of cover cracking can possibly be reduced by using strain hardening...

Influence of Cracking on Moisture Uptake in Strain-Hardening Cementitious Composites

Strain-hardening cementitious composites (SHCCs) are a class of cement-based materials that show strain-hardening behavior in tension. This is achieved by multiple microcracking, which results in a tightly spaced crack pattern with relatively small crack widths (50–80 μm, in general) and high strain capacity (up to 4–5%). Because of their...

Microscale Testing and Modelling of Cement Paste as Basis for Multi-Scale Modelling

This work aims to provide a method for numerically and experimentally investigating the fracture mechanism of cement paste at the microscale. For this purpose, a new procedure was proposed to prepare micro cement paste cubes (100 × 100 × 100 µm3) and beams with a square cross section of 400 × 400 µm2. By loading the cubes to failure with a...