Page 207 - New Trends in Eco efficient and Recycled Concrete

178 New Trends in Eco-efficient and Recycled Concrete

Figure 7.9 Different aggregate shape for the same aggregate size.

Figure 7.10 Detail of a polished surface of a concrete with EAFS. EAFS, electric arc
furnace slag.

slag will occupy a smaller solid volume, so using this aggregate there will demand
more cement paste and mortar to obtain the same concrete volume. A higher
amount of cement paste results in larger amounts of cement per cubic metre to
maintain the properties of the matrix, compared to traditional concrete.
Fig. 7.10 shows detail of a polished surface of concrete with EAFS. The picture
shows that the mortar completely surrounds the EAFS. This volume of mortar guar-
antees the separation between the aggregates, preventing contact between them.
Reduced mortar volumes result in very few fluid concrete mixes when EAFS aggre-
gate is used.
Regarding the mechanical properties of concrete made with EAFS coarse aggre-
gate, the consulted literature report considerable values of compressive strength.
Some of the most important properties have been listed in Table 7.2. With
3
300 kg/m of cement and water/cement ratios of 0.5, 40 MPa are easily achieved.