## 3 Results and Discussion
### Air Void  
Table 9 presents the analysis of variance for air void. From this analysis it can be affirmed, with 95% reliability, that the type of cement, the amount of foam and the type of additive have a significant influence on the number of pores present in the blocks of foamed concrete produced in the study. The factor that had the greatest influence on the air void was the amount of foam, its contribution being 41%. Note that the type of cement and the type of additive acting individually made a low contribution (0.6% and 1.4%, respectively) to the number of pores, but the interaction between these factors made a high contribution of approximately 17%. It is known that additives act to reduce the surface tension of water or the deflocculation via a change in the electric charge of the particles of the cement [66]. Therefore, the additives reduce the consistency of the mortar, thereby increasing its fluidity, and making the mortar more fluid, which may offer less physical resistance to maintaining the structure of the air bubbles incorporated by the foam [26; 67]. Figure 6a shows the air void graph in accordance with the type of cement, where the mean values of the air voids were very close, these being 28.9% for CPII F, 27.8% for CPV-ARI, and 27.1% for CPII Z. Likewise, little variation was observed in the number of pores when the additive used changes, even if they perform different functions in the mixtures. The results observed in the present study are in agreement with the studies carried out by [PERSON] and [PERSON] [68], who evaluated the effect of superplasticizers on the properties of foamed concrete. The relationship between the air void and the additives tested can be seen in Figure 6c. In general, the additives have little influence on air being incorporated into the mortar. Note that the test specimens without and with additives had a very similar air void, with a mean that ranged from 26.3% to 29.3%. Figure 6b shows that the amount of foam is the factor that has the greatest influence on the air void, precisely because it accounts for how many pores form in the structure of the blocks. The blocks to which 9.5% foam was added had a mean air void of 33.5%; blocks to which 7.7% foam were added resulted in a mean air void of 30.4%; and, finally, adding 5.7% foam to blocks resulted in an average air void of 19.9%. Comparing with a previous work [22], the value for air voids found was lower. This is possibly because the water/cement (W/C) ratio used in this work was lower, that is, in the present work a W/C ratio of 0.48 was used and in the previous work a W/C ratio of 0.64 was used. The W/C ratio is a factor that significantly influences all responses [29]. Figure 7 presents macrographic and typical binary images (*) of transversal sections of the 36 specimens in sequence, following the order of Table 3. Average porosity values were: (1*) 13%, (2*) 20%, (3*) 28%, (4*) 15%, (5*) 29%, (6*) 28%, (7*) 34%, (8*) 29%, (9*) 31%, (10*) 31%, (11*) 47%, (12*) 33%, (13*) 29%, (14*) 29%, (15*) 20%, (16*) 19%, (17*) 34%, (18*) 33%, (19*) 45%, (20*) 34%, (21*) 33%, (22*) 32%, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Factor** & **Sum of Squares** & **Degrees of Freedom** & **Mean of Squares** & **_F-Value_** & **_p-Value_** & **\% Contribution** \\ \hline Cement Type (CT) & 57.18 & 2 & 28.59 & 4.85 & 0.0105 & 0.6 \\ Foam Amount (FA) & 3697.69 & 2 & 1848.84 & 313.80 & 0.0000 & 40.7 \\ Additive Type (AT) & 124.85 & 3 & 41.62 & 7.06 & 0.0003 & 1.4 \\ CT*FA & 987.53 & 4 & 246.88 & 41.90 & 0.0000 & 10.9 \\ CT*AT & 1578.10 & 6 & 263.02 & 44.64 & 0.0000 & 17.4 \\ FA*AT & 961.67 & 6 & 160.28 & 27.20 & 0.0000 & 10.6 \\ CT*FA*AT & 1243.12 & 12 & 103.59 & 17.58 & 0.0000 & 13.7 \\ Error & 424.20 & 72 & 5.89 & & 4.7 \\ Total & 9074.343 & 107 & & & 100.0 \\ \hline \hline \end{tabular}  
* Interaction between factors.  
\end{table} 
Table 9: Analysis of variance for air void (curing time of 28 days).