Issue 49

L. Restuccia, Frattura ed Integrità Strutturale, 49 (2019) 676-689; DOI: 10.3221/IGF-ESIS.49.61 684 Results of mechanical tests The mechanical experimental results showed very interesting indications, as sign that recycled washed sand RSw could be used as replacement of standard sand SS in mortar. The results of Series 1, Series 2 and Series 3 are reported in Tabs. 6-8. Each batch is composed of three specimens and the results correspond to the mean values ± standard deviation. ID Batch P MAX E K IC G F σ f σ c [N] [GPa] [MPa√m] [N/m] [MPa] [MPa] M-SS 871.48±33.59 5.72±0.71 3.53±0.73 5.62±8.91 6.67±0.26 59.16±0.79 M-RSw_25% 529.31±20.77 3.67±1.49 3.05±1.20 4.06±9.77 4.05±0.16 32.61±0.98 M-RSw_50% 685.54±24.99 4.43±1.53 3.90±1.31 5.70±11.16 5.25±0.19 40.10±0.29 M-RSw_75% 820.71±75.25 5.19±6.95 3.66±3.58 6.38±8.81 6.28±0.58 56.49±2.10 M-RSw_100% 871.41±13.33 4.70±2.55 4.05±3.97 7.46±11.05 6.67±0.10 56.20±1.37 Table 6 : Mechanical and fracture results, Series 1 (w/c = 0.5; 1.00 % SP1). ID Batch P MAX E K IC G F σ f σ c [N] [GPa] [MPa√m] [N/m] [MPa] [MPa] M-SS 871.48±33.59 5.72±0.73 3.53±0.73 5.62±8.91 6.67±0.26 59.16±0.79 M-RSw_25% 551.81±33.85 3.92±1.71 3.25±1.72 4.03±6.65 4.22±0.26 34.79±0.57 M-RSw_50% 611.54±15.72 4.10±2.94 3.54±7.57 4.83±4.81 4.68±0.12 38.50±0.19 M-RSw_75% 684.99±49.19 4.07±2.41 3.68±1.92 5.94±5.21 5.24±0.32 46.23±0.68 M-RSw_100% 816.37±22.20 4.13±2.91 4.06±1.22 7.03±2.02 6.25±0.17 50.20±1.39 Table 7 : Mechanical and fracture results, Series 2 (w/c = 0.5; 0.75 % SP1). ID Batch P MAX E K IC G F σ f σ c [N] [GPa] [MPa√m] [N/m] [MPa] [MPa] M-SS 895.79±50.21 6.46±2.08 3.77±1.59 7.32±3.05 6.86±0.38 55.00±2.19 M-RSw_25% 653 .00±15.98 4.52±1.63 3.73 ±1.31 5.02±2.69 5.00±0.12 38.14±0.43 M-RSw_50% 685.83±15.00 4.25±1.44 3.99±1.40 5.77±5.34 5.25±0.11 38.33±0.50 M-RSw_75% 881.68±62.57 5.02±1.86 4.31±3.41 7.12±1.23 6.75±0.48 55.98±0.88 M-RSw_100% 893.78±30.17 4.84±3.41 4.22±1.91 7.58±4.79 6.84±0.23 56.31±2.97 Table 8 : Mechanical and fracture results, Series 3 (w/c = 0.45; 1.00 % SP1). According to Tabs. 6-8, it is evident that the greater is the percentage of RSw in mortars, the greater are mechanical performances, with very similar values to those of traditional ones. This can be explained by the FESEM results: the particles of RSw appear highly irregular and indented, while those of standard sand by definition “are generally isometric and rounded in shape" [29]. Therefore, in compositions with higher percentages of RSw, it is possible to hypothesize more non-homogeneity grains, which surely increase the ability to create a strong bond with the matrix. Furthermore, the washing process allows removing the fine powders (< 0.08 mm) and