Katrin Rübner

Use of municipal solid waste incinerator bottom ash as aggregate in concrete

As a result of their chemical and mineralogical characteristics, bottom ashes from municipal solid waste incinerators can, in principle, be used as aggregates in the production of normal strength concrete. However, because the ashes contain concrete-damaging components, such as chlorides, sulphates and organic compounds, or excessive quantities of fines, aluminium and waste glass, recycling becomes problematic. In particular, inclusions of aluminium in the ash particles and a glass content of about 15% cause considerable cracks and spalling in concrete specimens within a very short time. The harmful substances can be reduced or removed by additional treatments, such as upstream sieving and washing, waste glass separation, and lye treatment with sodium hydroxide solution. Tests on concretes with 2–32 mm bottom ash as coarse aggregates indicate that the quality of the ash is actually improved by the additional processing. Thus concretes with a compressive strength of C20/25 can easily be produced. Similar to concretes made with recycled aggregates, these concretes exhibit 15% lower compressive strength and E-modulus but twice the porosity of control specimens containing exclusively natural sand and gravel. However, only those concretes that were made with ash with a low aluminium content as a result of lye treatment remained free of damage.

GRAVIMETRIC MEASUREMENT OF WATER VAPOUR SORPTION, MOISTURE AND DRY MASS

The gravimetric measurement of the moisture content of solids is discussed in comparison to other usual methods. Results of measurements of silica gel are reported. Furthermore, we inform on standardisation work.

Components in concrete and their impact on quality: an overview

Abstract: This chapter provides a general background of the material aspects to be considered in typical testing problems. It gives an introduction and motivation for the essential issues to be discussed in more detail later in the book and in volume II, and some recommendations on how to proceed in practice. This includes a short outline of the different concrete constituents and their relation to microstructure, pointing out their relevance for the overall concrete properties.

Analysis of solid components and their ratios in reinforced concrete structures

Abstract: Methods common for the analysis and description of the solid components of hardened concrete are reviewed. The methods consist of both standard methods and well-established techniques, developed over the last 20 years.