Issue 49

L. Restuccia, Frattura ed Integrità Strutturale, 49 (2019) 676-689; DOI: 10.3221/IGF-ESIS.49.61 679 Sand packets have been realized through remixing of each granular fraction of standard sand SS with the corresponding granular fraction of recycled washed sand RSw, using four different percentages (25%, 50%, 75% and 100%) of replacement. In Tab. 3, the four different mix compositions with the specific amounts of both of them are reported: Square mesh size [mm] Cumulative retained [%] Retained [%] Retained mass [g] 2.00 0 0 0 1.60 7 7 94.5 1.00 33 26 351 0.50 67 34 459 0.16 87 20 270 0.08 99 12 162 Filler 100 1 13.5 Table 2 : CEN Standard Sand – Granular fractions. Size 25% 50% 75% 100% SS RSw SS RSw SS RSw SS RSw [mm] [g] [g] [g] [g] [g] [g] [g] [g] 1.60 70.9 23.6 47.25 47.25 23.6 70.9 0 94.5 1.00 263.3 87.8 175.5 175.5 87.8 263.3 0 351 0.50 344.25 114.75 229.5 229.5 114.75 344.25 0 459 0.16 202.5 67.5 135 135 67.5 202.5 0 270 0.08 121.5 40.5 81 81 40.5 121.5 0 162 < 0.08 10.1 3.4 6.8 6.8 3.4 10.1 0 13.5 Table 3 : Mix compositions of sand packets with Recycled Washed Sand RSw. The specimens have been manufactured in accordance with UNI EN 196-1:2005 (standard procedure). After 24 hours from the moulding procedure, all the specimens have been cured in water for 7 days. In Tab. 4, the main characteristics of the specimen series produced are reported. It is important to underline that, after washing process, it was very hard to collect a sufficient quantity of < 0.08 mm fraction. For this reason, a calcium carbonate filler named VG1 has been used for replacing the filler fraction (in total 13.5 g as shown in Tab. 2); this substitution does not involve any substantial change, as it only accounts for 1% of the total amount of sand used. In order to achieve an optimal mix-design, two parameters have been modulated: the amount of superplasticizer (SP1, acrylic polymer of MAPEI Dynamon SP system) and water/cement ratio. In Tab. 4, the mix-design summary for each composition: the strategy adopted is to gradually decrease both the amount of superplasticizer and the water/cement ratio, in order to obtain mortars with better mechanical performances. It is important to specify that for only standard sand mortar (M-SS), the SP1 has been added with respect to the weight of cement, while for the other compositions it has been varied according to the quantity of recycled washed sand RSw.