165 research outputs found
Determination of shear strength of historic masonries by moderately destructive testing of masonry cores
No full textTo determine masonry shear strength, which is a fundamental parameter for evaluating the seismic vulnerability of existing masonry buildings, several experimental techniques can be adopted. A promising method is subjecting cores, easily core-drilled from masonry buildings, to splitting test with mortar layer rotation, so that in the centre of the mortar joint a mixed compression-shear stress state is present. To investigate the actual suitability of testing cores for determining masonry shear strength, in this study a systematic comparison between reference masonry panels, subjected to shear-compression test, and cores, subjected to splitting test with different mortar layer inclinations, was performed. Ten masonry panels were constructed using fired-clay solid bricks and a mixed lime-cement mortar with poor mechanical properties, with the aim of resembling materials used in historic buildings. After curing for 28 days, nine masonry panels were tested, compression stress being kept constant at a fixed value and shear stress being increased until failure. By plotting shear stress against compression stress and performing linear regression, the initial shear strength and the angle of internal friction of the masonry were obtained. The tenth masonry panel was core-drilled to obtain cylindrical cores (10 cm diameter, 25 cm length) with a central diametric mortar joint. The cores were then subjected to splitting test with mortar layer inclinations of 0°, 15°, 30°, 40°, 45° and 50° with respect to the horizontal. While cores tested at 15° and 30° exhibited a splitting failure mode, cores tested at higher mortar layer inclinations exhibited a sliding failure mode, which was considered as the most representative one for evaluating masonry shear resistance. By plotting the shear stress against the compression stress for cores tested at 40°, 45° and 50° and then performing a linear regression, the initial shear strength and the angle of internal friction were derived. As results found for reference masonry panels and for cylindrical cores exhibit very good agreement, the proposed methodology seems like a very promising technique, which has the advantage of requiring only moderately destructive samples that can be easily core-drilled from existing buildings
Comparison between experimental methods for evaluating the compressive strength of existing masonry buildings
No full textIn this study, the suitability of determining masonry compressive strength by using the following two moderately destructive techniques was evaluated: (i) testing bricks and mortar, separately, and then using formulas available in literature for calculating masonry compressive strength; (ii) testing cylindrical cores, completed with cement mortar castings above and beneath the core, according to a procedure recently proposed by the authors. Two sets of masonry specimens were purposely constructed in laboratory conditions, using bricks and mortar with different mechanical characteristics. From the results of the study, an evaluation of the reliability of the two testing techniques was possible
The effect of CO2 and salinity on olivine dissolution kinetics at 120 {ring operator} C
No full textThis paper reports the results of an experimental study on the dissolution kinetics of olivine (Mg1.82 Fe0.18 SiO4) at operating conditions relevant to the mineral carbonation process for the permanent storage of CO2. In particular, we investigated the effects of CO2 fugacity (fCO2) and of salinity on the kinetics of olivine dissolution, which is assumed to be the rate-limiting step of the overall carbonation process. Dissolution experiments were carried out at 120 {ring operator} C in a stirred flow-through reactor. Different pH values (between 3 and 8) and solution compositions were investigated by varying fCO2 and by dosing LiOH (for pH control), NaCl, and NaNO3. The specific dissolution rate values, r, were estimated from the experimental data using a population balance equation (PBE) model coupled with a mass balance equation. The logarithms of the obtained r values were regressed with a linear model as a function of pH and compared to the model reported earlier [Hänchen, M., Krevor, S., Mazzotti, M., Lackner, K.S., 2007. Validation of a population balance model for olivine dissolution. Chem. Eng. Sci. 62, 6412-6422] for experiments with neither CO2 nor salts. Our results confirm that, at a given temperature, olivine dissolution kinetics depends on pH only, and that fCO2 and the concentrations of NaCl and NaNO3 affect it through their effect on pH. © 2009 Elsevier Ltd. All rights reserved
Il fondo Giuseppe Mazzotti
No full textThe author illustrates and describes the Giuseppe Mazzotti’s fund that includes the library, the archive and the photographic archive of the literary man of Treviso dead in 1981. Through the report of the work of reorganization and inventory emerge with evidence not only the multiform study interests of Mazzotti but also his working method based on the close relationship among documents, images and publications. A conclusion of a work lasted several years in 2008 the Foundation, set at the donation of the fund by daughter, has established a documentation centre open to the public
Influenza di ambienti aggressivi sull’aderenza FRP-calcestruzzo
No full textBonding is a very important issue when Fiber Reinforced Composites (FRP) are used to strengthen reinforced concrete beams. Bonding depends on the mechanical and physical properties of concrete, composite and adhesive. This type of failure can be influenced by the exposition to deicing salts, polluted air, freeze-thaw cycles and other aggressive environmental conditions.
Nevertheless, only few studies can be found on the effect of these degrading actions. Due to the lack of information, design rules against the effect of the aggressive environment are currently very conservative, even in recent recommendations.
The present experimental study is a preliminary investigation aimed at the definition of basic correlations between degradation phenomena and changes in the mechanical parameters of the
FRP-concrete bonding. A number of specimens have been preconditioned by thermal cycles and/or immersion in salt-spray fog environment.
Then, pull-pull delamination tests have been performed under standard conditions. Obtained interface laws and force-plate elongation curves have been finally compared with those obtained from unconditioned FRP-concrete systems
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