Udo Antons

Measuring the Effectiveness of Hydrophobic Layers Using a Non-Destructive Method

The paper focuses on the relationship between the effective hydrophobic layer thickness and the durability of impregnated hydrophobic treatments using single-sided nuclear magnetic resonance measurements. Weathered and non-weathered specimens were compared to detect the influence of different exposures on the performance of hydrophobic layers. The results show that structural changes caused by carbonation of blast furnace cement based concrete have an effect on the hydrophobic layer thickness while the carbonation of Portland cement concrete has none.

Influences on the Hydrophobicity of Concrete Surfaces Treated with Alkyl Trialkoxysilanes

Abstract The paper focuses on how alkaline media, UV radiation, and carbonation as well as on-going cement hydration affects hydrophobic treatments of concrete and influences the properties of these water-repellent layers. Single-sided nuclear magnetic resonance measurements show that layers formed by impregnating samples with alkyl trialkoxysilanes are stable even under long-term exposure to alkaline solution and UV radiation, with the damage of the latter being limited to the topmost surface layers. Microstructural changes during accelerated carbonation of blast furnace slag cement based concrete have a major impact on the hydrophobic layer properties, while the carbonation of Portland cement concrete has no influence. On-going hydration additionally influences the hydrophobic layer properties.

Zerstörungsfreie Visualisierung von hydrophob wirksamen Schichten in Beton

This paper is based on the NMR investigations on hydrophobized concrete specimen carried out in the framework of the research project “Durability of hydrophobic treatments on concrete” founded by the German Research Foundation. Next to the penetration behavior of the hydrophobic agents and the resulting thickness of the hydrophobic layer by investigating two different concretes, the effects of temperature and carbonation on the hydrophobic layer thickness will be shown by using artificially weathered specimens. With the non-destructive NMR measuring technique a method is presented which will in future be used to measure the penetration depth of freshly applied hydrophobic agents directly at the structure.

Assessing the Performance of Hydrophobing Agents on Concrete Using Nondestructive Single-Sided Nuclear Magnetic Resonance

AbstractSingle-sided nuclear magnetic resonance is a nondestructive analytical technique by which the ingress behavior of hydrophobing agents as well as the properties and performance of the result...

Durability of Hydrophobic Treatments on Concrete

The paper deals with the durability of hydrophobic layers in concrete, investigated by using non-destructive single-sided nuclear magnetic resonance (NMR). With this measuring technology, the amount and distribution of water as well as of hydrophobing agents inside the concrete can be visualised. By comparing NMR measurements of single specimen over time, changes in the hydrophobic layer properties can be seen. Results after UV radiation, alkaline storage and carbonation show the different effects of each exposure. The investigated hydrophobing agents for application on concrete were stable during long term exposure in alkaline solution. The effect of UV radiation was limited to the roll-off behaviour of the concrete surface. The results after CO2 exposure show that structural changes caused by carbonation of blast furnace slag cement based concrete decrease the hydrophobic layer thickness, while carbonation of Portland cement concrete has no influence. In addition, efficacy tests show that water transport through the affected hydrophobic layers of blast furnace slag concrete is accelerated.

Einsatzmöglichkeiten der NMR-MOUSE® in der Bauforschung – aktueller Stand der Arbeiten am ibac / Potential Applications of the NMR MOUSE® in Building Research – Current State of the Art at the Institute of Building Materials Research Aachen

The NMR MOUSE®, a device using single-sided nuclear magnetic resonance, allows the non-destructive determination of static and dynamic near-surface (currently up to 25 mm depth) hydrogen-containing phases in objects of any size. The present article briefly describes the measuring principle and then highlights applications of single-sided NMR in building materials research using examples from current and former ibac projects. These are mainly the quantitative, depth-dependent measurement of the water content, monitoring the transport of water, hydrophobing agents, and reactive systems in concrete along with determining the layer thickness and ageing processes in polymer films. In addition, the article describes how the presence of steel reinforcements influences the measured values and presents initial results obtained at a real-life building.

Hard and Soft: Principles of Polyner-Impregnated Concrete Using Elastomers

The effect of incorporating elastomeric domains in concrete is described from the point of fracture mechanics. Concrete is subject to brittle failure, since cracks propagate at an enormous speed in the crystalline matrix. However, micro cracks are attracted to volume elements with lower elastic moduli such as elastomeric domains. Cracks that encounter the concrete-elastomer interface are stopped since energy is dissipated by plastic deformation of and/or crack deflection by the elastomer. The domain size and the distribution of the elastomer as well as, and properties of the elastomer-concrete interface are crucial parameters. Such a combination differs substantially from previously prepared polymer-impregnated concretes, in which only glassy polymers were used.