Fred Veer

Post-Tensioned Glass Beams

At Delft University, glass researchers have developed a revolutionary safety concept for glass beams. This safety concept shows some analogy with reinforced concrete; glass beams are reinforced and/or post-tensioned by adding (stainless) steel to the layout of the beam.

Crack Closure and Fatigue Threshold of AA5083 Alloy in Air and Seawater by Two Determination Methods

We study the subthreshold growth of cracks in specimens with central crack made of AA5083-H321 aluminum alloy in air and seawater for various positive values of the load ratio. To this end, we use two different methods. In the first case, according to the ASTM E-647 standard, we gradually decrease the value of ΔK for constant R. In the second case, we gradually decrease Kmin for constant Kmax and, hence, increasing R. The results of both studies are in relatively good agreement. The insignificant difference between the thresholds ΔKth in air and seawater is, most likely, explained by the deposits of corrosion products.

Feasibility of Using Low CO 2 Concrete Alternatives in Extrusion-Based 3D Concrete Printing

In conventional concrete, replacing high-volume (more than 45%) of ordinary Portland cement (OPC) by supplementary cementitious materials (SCMs) is not a novel CO2 reduction method, whereas rarely in 3D printable concrete. This study attempts to explore the feasibility of using SCMs in 3D printable concrete. Initially, the existing binder mixes, required fresh properties and a research method of 3D printable concrete are investigated by reviewing the relevant papers. Additionally, the constraints and opportunities of using SCMs in 3D printable concrete are illustrated and summarized. Finally, it has been found that up to 45% of cement can be replaced by a blend of fly ash and silica fume. The essential fresh properties of 3D printable concrete include extrudability, workability, open time, buildability and structural build-up, which are influenced by the binder mix, particle size distribution, water to binder ratio, binder to aggregate ratio, admixture addition, the dosage of reinforced-fibers, etc. On the other hand, there are many limitations to develop SCMs-based 3D printable concrete, such as few relevant studies, a lack of the certificated standard, massive related-parameters and the shortage of common SCMs. For the first three problems, it can be solved with the development of 3D printable concrete. For the last one, calcined clay is one potential alternative for developing sustainable 3D printable concrete in the areas where are in short supply of fly ash and silica fume.

Quality Control and the Strength of Glass

To determine the strength of glass is important to determine the dimensions of glass structures. Conventional materials have singular strength values that are quite reproducible and independent of size. The strength of glass is strongly dependent on the size of the glass and the quality of the edges.