XVI Reunión Científica de la Sociedad Española de Arcillas - Libro ...

Galhano AC et al. / Comunicaciones SEA 2001 – Baeza (Jaén)
Although improving engineering properties of soil by heating has long been
appreciated theoretically, it has not been considered appropriate for engineering
application because of the high energy cost. In the USSR, heating has been found
to be as economical as prewetting or blasting for treatment of loess. Both these
methods are generally less expensive than using piles or caissons for treatment
depth up to 12 m (Lim 1981)
Heating fine-grained soils to moderate temperatures (higher than 100ºC) can
cause drying and strength increase if subsequent rewetting is prevented.
Depending upon the soil type, heating to temperatures in the range of 300ºC to
1000ºC can produce significant permanent property improvements such as a
decrease in water sensitivity, swelling, and compressibility, and increase in
strength.
As stated earlier, the primary reason for the limited application of thermal
stabilization by heating is the high energy cost associated with it. Hence, the
general intent of this study is to enhance the current state of knowledge by
offering a through understanding of the effect of heating on soil properties, namely
on clays with different mineral composition, stablishing a data base useful for
development of an effective and economical stabilization system.
For this intent we have used about ten clayey soils, of different sites of
Portugal and we have submit them to several temperature ranges, between
natural sample and a maximum temperature of 1000ºC. In each heating range
were determined some plasticity properties, expandability and mineral
composition with geochemical composition.
In general terms the liquid limit and plasticity index dropped slightly when
heated up to 100ºC, stayed almost constant between 100ºC and 300ºC, and then
dropped very rapidly when heated over 300ºC. The plastic limit increased slightly
when heated up to 200ºC, decrease slightly when heated between 200ºC and
300ºC, and then increased slightly again between 300ºC and 400ºC. In some