## 3 Results and Discussion
### Dry and Wet Bulk Densities  
Tables 6 and 7 present the analysis of variance for the dry and the saturated density, respectively. For these properties, all factors and the interaction between them had a significant influence (significance of 95% or more). Note that the amount of foam was the factor that most influenced the dry density. This is because the higher the amount of foam, the greater the number of voids and the lower the density of the material. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Factor**} & **Sum of** & **Degrees of** & **Mean of** & \multirow{2}{*}{_F-Value_} & \multirow{2}{*}{_p-Value_} & \multirow{2}{*}{\% Contribution_} \\  & **Squares** & **Freedom** & & & & \\ \hline Cement Type (CT) & 659,792 & 2 & 329,896 & 275.9 & 0.0000 & 19.4 \\ Foam Amount (FA) & 1,696,582 & 2 & 848,291 & 709.6 & 0.0000 & 50.0 \\ Additive Type (AT) & 40,996 & 3 & 13,665 & 11.4 & 0.0000 & 1.2 \\ CT*FA & 324,870 & 4 & 81,218 & 67.9 & 0.0000 & 9.6 \\ CT*AT & 50,929 & 6 & 8488 & 7.1 & 0.0000 & 1.5 \\ FA*AT & 314,349 & 6 & 52,392 & 43.8 & 0.0000 & 9.3 \\ CT*AT & 219,660 & 12 & 18,305 & 15.3 & 0.0000 & 6.5 \\ Error & 86,077 & 72 & 1196 & & 2.5 \\ Total & 3,393,255 & 107 & & & 100.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Analysis of variance for dry density (28 days of curing). Figure 4a shows the dry density and the saturated density in relation to the type of cement used. Note that the specimens made with CP II-F cement have a lower dry and saturated density than CP II-Z cement. Probably this occurs due to 6-10% limestone filler being added to the CP II-F cement, which decreases the capillarity of mortars and concretes, while pozzolanic material ranging from 6% to 14% in mass being added to CP II-Z cement lowers its permeability and increases its density [48; 49]. The CP V-ARI cement presented an intermediate value of dry and saturated density in relation to the other cements studied. Figure 4b shows the relationship between the density of the specimens and the amount of foam (% of total mass). The smallest amounts of foam are those with the highest densities, which is as expected [37]. When less foam is added, the air bubbles incorporated are grouped by dehydration, resulting in larger bubbles. Variations in density can also occur when bubbles collapse due to the hydrophilic film being reduced, thus making the bubbles less resistant, this being a consequence of using CCW instead of natural sand [58; 59]. Figure 4c plots the dry and the saturated density relative to the type of additive. The specimens with the highest densities (dry and saturated) were those to which superplasticizer was added [23]. The air additive had an average dry density of 1270 kg/m\({}^{3}\) and a mean saturated density of 1580 kg/m\({}^{3}\). The plasticizer additive presented an average dry density of 1290 kg/m\({}^{3}\) and an average saturated density of 1590 kg/m\({}^{3}\). The specimens that did not have additives added had an average dry density of 1285 kg/m\({}^{3}\) and a mean saturated density of 1605 kg/m\({}^{3}\). Although there are differences between the specimens with and without additives, this is very small, i.e., the additives have little influence on this property. High densities were obtained for foamed concrete compared with previous studies [22; 29; 60; 61]. However, the density results are within the acceptable range for lightweight concrete density [11].