PSI - Issue 29

A. Boostani et al. / Procedia Structural Integrity 29 (2020) 79–86

84 6

Boostani et al./ Structural Integrity Procedia 00 (2019) 000 – 000

4. Experimental campaign aimed at the identification of compositematerials for wall stitching Preliminary tests were carried out on site in order to highlight the relevance of (i) the gypsum/water ratio in the implementation of composite bars, since a large amount of water is absorbed by earth; (ii) the shape of the bars (threading) to improve pull out strength. Based on this preliminary investigation, a through experimenta l campaign was carried out. Different mortars were manufactured, namely 12 types, with varying composition, e.g. gypsum, earth, wa ter andadditives forworkability-timeretarding (asphodel-basedglue), see Table 2.

Table 2. Composition of mortar types tested in Laboratory

Water to

Dry Phase

Mortar Type

Number

Asphodel to gypsum ratio

Gyps um

Ea

dry phase ratio

of specs.

rth

A1 A2 A3 G1 G2

3 3 3 3 3 3 3 3 3

1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.9

1.0 0.8 0.6 0.8 0.6 0.8 0.6 0.6 0.8

0.001 0.001 0.002 0.002 0.003 0.001

I1 I2

J

0.

K

1

0.

L

3

0.9

0.8

1

0.

M

3

0.8

0.8

2

0.

N

3

0.7

0.8

3

Three-point bending tests on mortar samples were carried according to UNI-EN 1015-11. The test was conducted under displacement control a t a speed of 0.5 mm/min. The two stumps obta ined from each bending test were subjected to a uniaxia l compression test with a load application surface of 40x40 mm 2 . The INSTRON Satectm 5592-315HVL-F2-G2 test machinewas used, equippedwith a 600kNstrain gauge loadcell.

Figure3. The three-point bending test on stitching rods comparison diagram Tests revea led that the effect on mortar strength of the amount of water is linear and the best gypsum/water ratio is 07-0.8 for grout injection. The use of asphodel additive, reducing too much the mortar strength, was discarded. Based on the conclusions mentioned above, the matrix mortar type A2 (9.56 MPa average compression strength, 0.72GPa average Youngmodulus and2.66MPa average tensile strength) was chosen for the stitching rods.