Defining a Non-Destructive In Situ Approach for the Determination of Historical Mortar Strength Using the Equotip Hardness Tester
Abstract
:1. Introduction
2. The Historical Masonry Mortars of Camerino Town
3. Materials and Methods
3.1. Data Collection Strategy Using the Equotip Hardness Tester
3.2. The Uniaxial Compressive Tests
4. Results and Discussion
4.1. Uniaxial Compressive Strength of Mortar
4.2. Results of the In Situ and Laboratory Tests
5. Conclusions
- the Equotip device, due to its low impact energy, is able to evaluate the mechanical properties of ancient mortars, characterized by low strength. In particular, the low dimension of the impact tip of the Equotip device investigates the mechanical properties of the first millimeters of the mortars;
- the data collected by using both the ‘single impact test’ and ‘repeated impact test’ methods; results indicate that the first one is strongly affected by the device settling, underestimating the real mechanical properties of the mortar differently;
- the “repeated impact test” method used in this paper allows monitoring of material behavior following repeated impacts and thus discarding initial values affected by settling and final values affected by artificial micro-fracturing of the material because of the impacts. For this reason, the collecting methodology is fundamental to obtain reliable results;
- the comparison between EQ results and UCS laboratory test allowed the calibration of a relationship between the two parameters;
- the investigated mortars are characterized by low values of UCS, ranging from 0.17 MPa to 1.49 MPa, values largely lower than the strength currently required for new structural mortar; they were classified into three groups based on the UCS values and their different stress-strain response to the compression test; in particular, a brittle behavior has been observed for mortars with a higher UCS whereas a ductile behavior was noticed for mortars with lower UCS values; an evidently different mechanical behavior has also been observed between the mortar samples coming from the core of the masonry and the ones coming from the face. In particular, the mortar in the core of walls is generally weaker than the one coming from the wall face. The reasons for the lower strength of the masonry core can be related to a number of aspects such as the different ages of the mortars, their mineralogical composition, the manufacturing, and application method. Such aspects, not so documented in the literature, are of relevant importance in quantifying more realistically the structural behavior of historical masonry structures;
- the EQ data collected in situ always have a lower mean value comparing to the ones measured on the specimens in the laboratory. This is an important observation to consider in order to give a correct estimation of the real UCS. This aspect has been previously evidenced by [15], pointing out that the NDT may allow a superficial evaluation of the mortar properties and, more so of other materials [21,22,23]. In fact, natural environmental processes, with time, cause decay mostly at the most superficial portion of the mortar, in this study evidenced by the reduction in strength derived from the δ parameter.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Building | Sampling Location | Site ID |
---|---|---|
Palazzo Ducale Palace | masonry core | 3000 |
Battibocca Palace | masonry core | 3004 |
San Domenico Monastery | masonry core | 3008 |
San Domenico Monastery | masonry core | 3009 |
Palazzo Ducale Palace | masonry face | 3011 |
Palazzo Ducale Palace | masonry core | 3002 |
San Domenico Monastery | masonry face | 3006 |
San Domenico Monastery | masonry core | 3009 |
San Domenico Monastery | masonry face | 3010 |
San Domenico Monastery | masonry face | 3011 |
Site | Sample | h | lmax | lmin | h/d |
---|---|---|---|---|---|
ID | Name | [cm] | [cm] | [cm] | [-] |
3000 | 3000 | 5.83 | 4.65 | 4 | 1.2 |
3004 | 3004 | 6.9 | 6 | 4.9 | 1.13 |
3008 | 3008 | 4.8 | 3.6 | 3.4 | 1.22 |
3011 | 3011 | 4.7 | 4.5 | 2.6 | 1.22 |
3002 | 3002-C | 4.2 | 3.05 | 2.88 | 1.26 |
3006 | 3006-2 | 4.4 | 2.55 | 2.2 | 1.65 |
3006-3 | 4.55 | 2.25 | 2.2 | 1.81 | |
3009 | 3009 3009-2 | 4.86 3.6 | 2.85 4.2 | 3.35 2.7 | 1.07 0.95 |
3009-3 | 3.3 | 3.5 | 3.4 | 0.85 | |
3009-4 | 4.3 | 3.1 | 2.3 | 1.43 | |
3009-5 | 2.8 | 2.4 | 2.2 | 1.08 | |
3010 | 3010-A | 4.6 | 2.47 | 2.4 | 1.67 |
3010-B | 4.75 | 2.6 | 2.48 | 1.66 |
Sample Name | Sampling Location | UCS [MPa] |
---|---|---|
3008 | masonry core | 0.17 |
3004 | masonry core | 0.19 |
3000 | masonry core | 0.33 |
3009-4 | masonry core | 0.4 |
3009 | masonry core | 0.41 |
3009-2 | masonry core | 0.44 |
3009-3 | masonry core | 0.47 |
3002-C | masonry core | 0.49 |
3006-3 | masonry face | 0.65 |
3006-2 | masonry face | 0.68 |
3009-5 | masonry core | 0.84 |
3010-B | masonry face | 1.25 |
3011 | masonry face | 1.29 |
3010-A | masonry face | 1.49 |
Sampling Location | Site ID | Number of Specimens (pcs.) | Lmeansitu | Lmeanlab * | δ | UCS * [MPa] | ||
---|---|---|---|---|---|---|---|---|
mean | std | mean | std | |||||
masonry core | 3000 | 1 | 160 | 15 | 221 | 42.1 | 0.72 | 0.33 |
masonry core | 3002 | 1 | 263.5 | 91.2 | 349.5 | 30.9 | 0.75 | 0.3 |
masonry core | 3004 | 1 | 143 | 23.5 | 230.6 | 20.5 | 0.62 | 0.19 |
masonry face | 3006 | 2 | 290 | 54.9 | 372.7 * | 34.5 | 0.78 | 0.67 * |
masonry core | 3008 | 1 | 143 | 71.3 | 225.3 | 63.3 | 0.63 | 0.17 |
masonry core | 3009 | 5 | 143.2 | 74.2 | 250.0 * | 107.1 | 0.57 | 0.51 * |
masonry face | 3010 | 1 | 369.6 | 46.5 | 491.4 * | 55 | 0.75 | 1.37 * |
masonry face | 3011 | 1 | 375.6 | 37.9 | 523 | 43.8 | 0.72 | 1.29 |
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Mammoliti, E.; Ferretti, A.; Malavolta, M.; Teloni, R.; Ruggeri, P.; Roselli, G. Defining a Non-Destructive In Situ Approach for the Determination of Historical Mortar Strength Using the Equotip Hardness Tester. Appl. Sci. 2021, 11, 4788. https://doi.org/10.3390/app11114788
Mammoliti E, Ferretti A, Malavolta M, Teloni R, Ruggeri P, Roselli G. Defining a Non-Destructive In Situ Approach for the Determination of Historical Mortar Strength Using the Equotip Hardness Tester. Applied Sciences. 2021; 11(11):4788. https://doi.org/10.3390/app11114788
Chicago/Turabian StyleMammoliti, Elisa, Antonio Ferretti, Michele Malavolta, Riccardo Teloni, Paolo Ruggeri, and Graziella Roselli. 2021. "Defining a Non-Destructive In Situ Approach for the Determination of Historical Mortar Strength Using the Equotip Hardness Tester" Applied Sciences 11, no. 11: 4788. https://doi.org/10.3390/app11114788