STUDY OF CONCRETE CONTAINING SAND COMPOSED OF A MIXTURE OF GRANULATED BLAST-FURNACE SLAG AND FLY-ASH FROM POWER STATIONS

A comparative study is presented of the mechanical properties of standard concrete and concrete which, instead of standard sand, contains an equal weight mixture of fly-ash and granulated blast-furnace slag. The water/cement ratio of the concrete tested was selected so that its workability could be compared to that of control samples. Seventeen types of concrete were studied: 9 containing Portland cement, 3 containing blast-furnace cement and 5 containing some fly-ash from the North and Pas-de-Calais Bassin instead of sand, materials from the Materials from the Seine, and crushed slag instead of gravel. The tests used applied to pavement concrete and foundation concrete. Results show that the most favourable proportioning from the point of view of workability was 20 to 30 per cent fly-ash and 70 to 80 per cent granulated slag. The water content had to be slightly increased in the laboratory in order that the workability of the tested concrete compare with that of central samples; this may not be necessary on the site. Mechanical strength was of the same order for test samples and control samples in spite of the increase in water content. It is not affected by a market under-proportioning of cement if the absolute volume of cement is replaced by the same absolute volume of slag-fly ash mixture.