PSI - Issue 29

Mario De Stefano et al. / Procedia Structural Integrity 29 (2020) 71–78 De Stefano and Cristofaro / Structural Integrity Procedia 00 (2019) 000 – 000

74 4

stones of various sizes (even very sma ll) immersed in mortar beds of varying thickness and completely misa ligned brick inserts. The lowest mechanica l parameters arose from the tests, on the ground floor, on the wa lls of the museum room, which develops a long one side of the “ Giardino delle Rose ” where the ca lcula ted E va lues do not exceed 1550 MPa. Here, in fact, the wa lls show a varied and uneven texture with irregular, doubled or converging rows.

Fig. 2. Typical datasheets of testing with double flat-jacks.

2.3. Penetrometer tests on the mortar To characterize the mortar that secures the joints of the wa ll panels, penetrometric tests were carried out. The results of the penetrometric tests have shown va lues of the compressive strength of the mortar that strongly vary from wa ll to wa ll. In particular, in no masonry there is a compressive strength va lue equa l to or grea ter than 2.5 MPa . Fig. 3b summarizes the results in terms of compressivestrength.

maximum values of the elastic modulus

compressive strength of mortars

Penetrometer tests code

Double flat jack code

(a)

(b)

Fig. 3. (a) Graph summarizing maximum values of the elastic modulus; (b) Graph summarizing compressive strength of the mortar.

Only in the case of the border wa ll between the “ Sale Fiorentine ” and the courtyard of the “ Opificio delle Pietre Dure ” , the resistance va lue ( f m = 2.22 MPa) was found to be close to the minimum va lue specified in the standard. A high number of tests, on as many mortar joints, has provided va lues of f m placed approximately at around 1 MPa . Most of the tested mortars provided extremely low resistance va lues, equa l to about 0.5 MPa . It should be noted that a lso to the touch, during the visua l inspection, the mortar in many cases was remarkably sandy and removable, with a slight manual rubbing. 2.4. Compression tests on specimens of natural andartificial stone taken in situ In some of the wa ll portions subjected to inspection, a sample of standard dimensions of natura l and artificia l elements was taken and subsequently tested in the laboratory. The test performed according to UNI EN 772-1: 2002 (2002), a llows to obta in the compressive strength of the specimen. The results, in terms of average va lues, of the monoaxia l compression tests performed on stone and brick specimens, are shown in Tab le 1. It can be observed that the average va lues, for each mechanica l parameter, are somewhat variable, both in the case of brick and stone specimens.