Development of procedures for identifying indiviudal components, especially of bound and unbound cements in building material dusts, and differentiated evaluation thereof as a percentage of mine dusts

Ziel

The aims of the research are as follows:

- to analyse the mineral components of cements before and after specific time-related hydration stages by x-ray diffractometry and infrared spectroscopy and develop a computer-aided routine anlaysis procedure taking account of the influence of the mineral content of mine dusts on the identification of cement components (interference);
- to identify other possible hazardous substances in building materials used in mines, particularly heavy metals;
- to undertake an analytical differentiation between genuine mine dusts and dusts which are not mine-specific, in order to facilitate the medical assessment of workplaces and make it possible to show mine dusts separately in epidemiological surveys. Signficant here is the fact that the MAC commission is in the process of fixing an MAC value for cements, taking account of possible fibrogenity and damage to the entire respiratory system as a result of the high basicity of dusts.

More and more frequent use is being made in deep mines of building materials which cause considerable changes in the compositon of mine dusts. Whereas in the past building materials based on anhydrite and CaSO4 hemihydrates were predominant, cement is increasingly being added to materials, particularly as a result of rising rock temperatures, in order to improve construction and safety characteristics. More and more power station waste and other residues which may contain various harmful substances are also being used for building material production. As a result, all components used must henceforth be assessed separately.

Up to now there has been no possibility of analysing, in particular, the cement dust components in airborne dust samples. Such dusts have hitherto been assessed exclusively by taking account of quartz, a method which does not fully reflect the potential hazard. A differentiated assessment of the various harmful components thus seems to be a matter of some urgency.

Special difficulties arise because of the different hydration stages, which are time-related (minutes, hours, days), i.e. all calcium silicates take in humidity and are transformed into hydrates - a permanent change in composition. The fastest to react are tricalcium aluminates (C3A) and tricalcium silicates (C3S). In the final stage ettringite, a trisulphate, is even partly transformed into gypsum.

Hydration also leads to structural changes, for example long-fibre calcium silicate hydrate (CSH) is tranformed into the short-fibre type. These changes occur at a pH-vaue of more than 12, and it is necessary to establish whether there are any significant differences when the pH-value is down in the slightly acidic range, in order to know how material which has not yet gone through all hydration stages might react in the lung area.

The plan of work is as follows:

- Analysis of cement components at various hydration stages by x-ray diffractometry and infrared spectroscopy, selection of standard substances, determination of influence of particle size differences;
- Analysis of building materials used in mines by atomic absorption spectrometry in order to establish levels of toxic heavy metals;
- Study of the effect of changes in pH-value on the formation or transformation of individual cement components;
- Study of the influence of mineral mine dusts with regard to identifying cement components for a quatitative description of mixed dusts,
- Development of a computer-aided routine analysis;
- Drafting of evaluation criteria with a view to stipulating limit values

Programm/Programme

ECSC-MINEHYG 6C - Sixth research programme (ECSC) "Industrial Hygiene in Mines", 1990-1993

Thema/Themen

3 - Dust measurement and determination of dust properties

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

Data not available

Koordinator

Institut für Gefahrstoff-Forschung der Bergbau-Berufsgenossenschaft

EU-Beitrag

Keine Daten

Adresse

Waldring 97
44789 Bochum
Deutschland

Gesamtkosten