fib Task Group 8.9 – Aesthetics of concrete surfaces

Scope:

The notion of attractive concrete is subjective and varies according to the viewer. In order to have a basis for the work of TG 8.9, it is necessary to limit the requirements regarding the appearance of concrete surfaces. Because exposed concrete has been established in recent years by well-known architects as having a homogenous and smooth appearance, the work will be focused on this kind of visible concrete surfaces.

An attractive concrete surface is observed within the context of the surfaces of the whole building. The resulting impression depends considerably on the viewing distance and lighting conditions. Therefore the utilization of the building is important when evaluating a concrete surface. The realization of an exposed concrete surface is influenced by many different factors, including concrete technology, concrete formwork and formwork material, the application of a releasing agent, the method of operation on-site, logistical conditions during transportation of the concrete and concreting, as well as climatic influences and the coordination of all persons involved in the building process.

Objectives:

TG 8.9 will formulate a state of the art report how exposed concrete is defined and built. The final aim is to create a generally accepted recommendation or guideline for exposed concrete with a homogenous appearance. This generally accepted recommendation or guideline will be characterized by classifying exposed concrete in different categories. The limit of its objective performance will be considered as well as the consequences on the effort on-site and the planning of structural framework.

Work programme:

Phase 1: it will first be necessary to collect and evaluate test results and practical experience with exposed concrete. The influences on the appearance of a visible surface should be discussed and it should be assessed in how far they can be controlled in the planning process and during the execution.

The results will have to be summarized in a state of the art report.

Phase 2: Based on the results of phase 1 as well as on already existing national regulations and recommendations, categories for exposed concrete surfaces will be developed. These categories will result in a generally accepted recommendation or guideline for exposed concrete with a homogenous and smooth appearance. The kind of publication of this guideline has to be discussed, possibly as recommendations for the classification of attractive concrete surfaces.