Crushed Brick / Lime Mortars of Justinians's Hagia Sophia
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307 Mat. Res. Soc. Symp. Proc. Vol. 462 ©1997 Materials Research Society
SAMPLING The primary structure supporting the main dome of the Hagia Sophia and its orientation are illustrated in a cutaway view in fig 1. The main piers are comprised of stone masonry of almost rigid blocks and relatively compliant mortar, while the main arches, dome, and portions of the main piers and buttresses above it are comprised of brick masonry with characteristic thick mortar joints. The samples examined were obtained by Van Nice (1949, Dumbarton Oaks, Washington, D.C.) and by the authors (Table 1). MATERIAL PROPERTIES - EXPERIMENTAL PROCEDURE Various tests were performed to determine the elastic moduli and mechanical properties of the mortar. A typical mortar-brick sandwich sample (fig 2) was submitted to standard adhesion test at Princeton University and tensile strengths of 0.4 - 0.5 MPa were estimated 9. Another sample was tested at the National Technical University of Athens '0 using the scratch width method with a range of tensile strength estimated to be 0.5-1.2 MPa. Two split cylinder tests on specimens approximately 40 mm long and 35 mm diameter have been taken from the SE buttress stairwell yielded tensile strength are 0.7 and 1-2 MPa". Elastic moduli have been estimated using in-situ, ultrasonic tests at various brick and mortar locations in Hagia Sophia including a main dome rib, the west arch, and the north arch. The estimated dynamic elastic 2 moduli are' : Brick: Eb = 3-10 GPa; Mortar: Em = 0.66 GPa; Composite: Eb = 1.83 GPa. Mineralogical and Physicochemical Properties were studied by Fiber Optics Microscopy (Keyence VH5901), X-Ray Diffraction Analysis (XRD) (Siemens D-500 X-Ray Diffractometer), Optical Microscopy (polarizing Zeiss microscope), Transmission Electron Microscopy (TEM) (Philips M20 / ST of Princeton Materials Institute) (the measurements were performed by Mr C.Chun of Princeton University) accompanied by EDXS, (EDAX PV9900, with 50nm spot size), Scanning Electron Microscopy (SEM) (Philips 515 unit) / Energy Dispersive analysis (EDX) (Super Quantitative EDAX software), Porosimetry (Carlo Erba Porosimeter 4000), the physical separation by means of Granulometric Analysis and Thermo Gravimetric Analyses (TG / DTG) (Mettler TG 50, thermo balance) / Differential Thermal Analyses (DTA) (Perkin Elmer Thermo analyser TG S-2 and DTA 1700). RESULTS AND DISCUSSIONS Macroscopically, the mortar samples la, 2, 2.1, 3.1 (6th century) and 1.1 (10th century) appear to be intact, integral and durable presenting a granoblastic character, while Ib, Ic (6th century) and the 5a, 5b (10th century, from the West arch) are in small pieces and very friable. An almost equal participation of sand-pebbles and crushed brick in the mortar mixture is observed by modal analysis. Fiber optics microscopy (fig 3a, b) identifies a compact microcrystalline matrix containing brick fragments of several dimensions down to nodules and even powder, and several aggregates as well. Strong adhesion bonds are indicated by the reaction rims at the i
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