Mix design of durable concrete with the additions of silica fume or fly ash

Abstract

The aim of the research is the laboratory study of a durable concrete, according to UNI-EN 206-1 and 11104, comparing four types of concrete by varying the type of binder to highlight some aspects of durability. For each type of concrete, to graph the correlations between: W/C ratio - resistance; cement dosage - strength; days of ripening-resistance; three mixes were packaged by varying the W/C ratio and the cement dosage. Three durable concretes were then designed, by way of example, with resistance class C30/37, exposure class XS1, workability class S5, maximum diameter 20 mm, by varying the type of binder to enhance some aspects of durability:

- Type 1) With Portland II-A-LL 32.5 R cement

- Type 2) With Portland II-A-LL 32.5 R cement + 11% silica fume

- Type 3) With Portland II-A-LL 32.5 R cement + 22% fly ash.

A cost analysis was then conducted for the concretes type 1), 2), 3), to highlight the incidence of additions in the concrete, and the benefits in terms of mechanical resistance to compression.