## 3 Presentation and Discussion of the Results
### Pull-Out Test  
Figure 19 illustrates the graph with the correlation obtained between the pull-out force (P) and the average concrete compressive strength (\(f_{\text{cm}}\)) for the studied SCC, as well as the corresponding equation for the straight line (continuous line) used to fit the results, with a correlation coefficient of about 0.98. Figure 20 illustrates the comparison between the correlation obtained in the present research work for SCC (Figure 19) and those obtained for NVC by [PERSON] and [PERSON] [4; 7] and by [PERSON] and [PERSON] [2]. For both SCC and NVC, the correlations in Figure 20 show the same tendency and high correlation coefficients. However, for the same concrete compressive strength, the pull-out force is higher for NVC when compared to SCC. This observation can be explained because of the higher amount of mortar and the existence of smaller aggregates in the surrounding area of the probe for SCC. For NVC, the existence of larger aggregates in the surrounding area provides higher resistance to failure in the zone of the compressive arm between the probe and the counterpressure ring.  
At the ending of the last century, many independent analytical and experimental studies have been developed to understand how failure mechanism works during the pull-out test. A consensus has been achieved regarding the existence of a triaxial state of stress highly non uniform on the concrete involving the insert during extraction [1; 3]. In spite of some divergence as far as the basic failure  
Figure 19: Pull-out force versus average concrete compressive strength.  
Figure 20: Comparison between correlations for SCC and NVC using pull-out test.  
mechanism is concerned, a consensus exists regarding the fact that the last pull-out load is influenced by the same properties which influence the concrete compressive strength [1; 3]. As previously mentioned, the pull-out test is assuming by the BS 1881-207:1992 [15] as being a very reliable test method, for which the use of general correlations is allowed with reasonable accuracy for a wide range of NVC mixes. However, the same standard points out that special correlations are required for lightweight concretes or other mixes with less common constituents. The different mix proportions of an SCC compared to NVC and the absence of vibration can justify the differences in the concrete hardness in the surface or near to the surface. Such differences were also detected when using the surface hardness test.  
Table 6 shows that for SCC the S\({}_{\mathrm{d}}\) varied from 1.13 to 4.27 kN with the average being 2.17 kN. These values are similar to those obtained in NVC of compressive strength up to 82 MPa [4; 7], the correlation of which is shown in Figure 20, presenting an S\({}_{\mathrm{d}}\) from 1.24 to 5.19 kN with the average being 2.53 kN. [PERSON] and [PERSON] [2] have reported as typical a S\({}_{\mathrm{d}}\) from 1.9 kN to 2.5 kN when using 150 mm cubes and nearly 2.8 kN for larger specimens. For SCC, the C\({}_{\mathrm{v}}\) varied from 3.0 to 8.0% with the average being 4.9% (Table 6), while for NVC [4; 7] of high strength the C\({}_{\mathrm{v}}\) varied from 2.9 to 7.0% with the average being 5.1%. [PERSON] and [PERSON] [2] reported as typical a C\({}_{\mathrm{v}}\) between 6.8% and 7.5% when using 150 mm cube specimens and nearly 9.9% for larger specimens. The BS 1881-207:1992 [15] indicates a typical C\({}_{\mathrm{v}}\) of 7%. Previous analysis on repeatability of pull-out test, undertaken by [PERSON] and [PERSON] [10], bringing together NVC and SCC reported results, have revealed that S\({}_{\mathrm{d}}\) is the statistical parameter which better represents the repeatability, which contradicts the [PERSON]'s report [3].