The initial mixture was a mixture of a lightweight concrete with
vermiculite used commercially. This first mixture was adapted to
be used with additives. From this initial mixture, the mixtures
studied were established by varying two factors, the amount of
lightweight aggregate (percentage of volume of lightweight aggregate
in relation to the total concrete volume – VLA) and the quantity
of air-entraining agent (percentage weight relative to the
quantity of cement – AEA) (Table 1).
Table 2 shows the runs of the 22 full factorial design [22,23].
Eight different compositions determined by Statistica 8.0 statistical
software (StatSoft Inc., 2007) were evaluated, with one replication
for each level.
The concretes were manufactured in laboratory according to
NBR 5738 [24]. Four cylindrical specimens (200 100 mm) were
molded. It was necessary about 16.5 dm3 of concrete for each mixture.
From the starting mixture 1:4:4.67 – cement (mass):lightweight
aggregate (volume):sand (mass), and using the water to
cement ratios (w/c), were calculated the amounts of materials
using data from Table 3 and Eq. (1). The w/c ratios used were 0.5
(for V1 and V2), 0.6 (for V3 and V4), 0.76 (for E1 and E2) and 1.10
(for E3 and E4).