P.J Garcı́a Casado

Methodology and validation of a hot hydrochloric acid attack for the characterization of ancient mortars

A method for the analysis of the chemical composition of ancient mortars is proposed. The use of the hot hydrochloric acid attack to carry out a separation of the binder and the aggregate is discussed. Different types of mortars of Pamplona Cathedral are analyzed. Traditional chemical methods and atomic emission spectroscopy are employed. The mineralogical studies are carried out using X-ray diffraction. Statistical methods are employed in order to establish a comparison between the different attacks.

Thermal, mineralogical and chemical studies of the mortars used in the cathedral of Pamplona (Spain)

Different ancient mortar samples of Pamplona cathedral have been analysed to characterize their binder and aggregate fractions. A complete characterization has been carried out including chemical (complete macrochemical analysis, analysis of the soluble fraction in hot HCl (1:5) and of the insoluble residue, trace elements and soluble salts, using traditional chemical procedures, ion chromatography and spectrophotometry techniques), mineralogical (structural characterization, granulometric studies and X-ray diffraction) and thermal studies (simultaneous DTA and TG analysis). A lime binder with a silica aggregate has been established. The approximate original compositions of the classes of mortars have been determined using the TG results. A good agreement with the other characterization techniques has been showed by the thermoanalytical techniques. An incomplete carbonation in a sample has been discovered by the thermal analysis.

The series of spinels Co3−sAlsO4 (0 < s < 2): Study of Co2AlO4

Abstract Co(III) of Co 3 O 4 can be gradually replaced by Al to produce the series of spinels Co 3− s Al s O 4 (0 s Fd 3 m (No. 227), Z = 8. For Co 2 AlO 4 ( s = 1), a = 8.086(1)A, U = 528.7(2)A 3 , D x = 5.25 Mgm −3 , u = 0.264, and 27% of Al in 8( a ) positions, R = 0.031. The frequencies of the observed ir absorption bands of Co 2 AlO 4 are also presented.

A study of the ancient mortars in the north tower of Pamplona's San Cernin church

Abstract Different ancient mortar samples of Pamplonas San Cernin church have been analyzed to characterize their binder and aggregate fractions. A complete characterization has been carried out including chemical (rapid approximate analysis, soluble salts and trace elements, using traditional chemical procedures, ionic chromatography and spectrophotometry techniques), mineralogical–petrographic, (structural characterization and X-ray diffraction) and thermal studies (simultaneous differential thermal and thermogravimetric analysis). These studies have established that a type of lime mortar with silica aggregate was employed in the building of the tower. Three different classes of this type of mortar and their approximate original composition have been determined. Recommendations about the employment of new materials in a possible restoration are given.

The new pyrochlores Pb2(M0 · 5Sb1 · 5)O6 · 5 (M = Al, Sc, Cr, Fe, Ga, Rh)

From mixtures of PbO, M2O3 (M = Al, Sc, Cr, Fe, Ga, Rh), and Sb2O3, the new oxides Pb2(M0 · 5Sb1 · 5)O6 · 5 have been obtained as coloured powders giving X-ray diffraction patterns typical of cubic pyrochlores, S.G. Fd3m (No. 227), and aA values from 10.3964(1) (M = Al) to 10.5558(1) (M = Sc). The best R factors were obtained for Pb in 16(c) positions, M and Sb (1:3) randomly distributed in 16(d), oxygen in 48(f) and one half of the 8(a) sites, and x values for the oxygen positional parameter (origin at center, 3m) from 0.430 (M = Sc) to 0.436 (M = Al). Apparent interatomic distances compare with those calculated. The angles of the coordination polyhedra around the metals are reported for the compounds of Al and Sc. Seven-coordination of Pb(II) is accounted for by the non-bonded electron pair effect.

Preparation and crystal data of the spinel series Co1+2sCr2−3sSbsO4 (O ⩽ s ⩽ 23)

Abstract Eight polycrystalline materials of the new spinel series Co1+2sCr2−3sSbsO4(s = 0, 0.10…0.60 or 0.67) have been prepared and studied by X-ray powder diffraction. The series goes from CoCr2O4 (s = 0) to Co 7 3 Sb 2 3 O4 (s = 2 3 ), with a gradually increasing from 8,3346(3) (s = 0) to 8.5330(6) A (s = 2 3 ), and u slightly decreasing from 0.261 (s = 0) to 0.258 (s = 2 3 ). Interatomic distances are given. The series may be thought as the result of progressive substitution of Cr3+ by 2 3 Co2+ + 1 3 Sb5+ in the normal spinel CoCr2O4. This substitution can be total, so that CoCr2O4 becomes Co 7 3 Sb 2 3 O4.

Preparation and crystallographic data of the pyrochlores Gd2MSbO7 (M = Cr,Mn, Fe, In)

Abstract Polycrystalline Gd2MSbO7 (M =Cr,Mn,Fe,In) have been prepared from M2O3 (M = Cr, Fe, In), Mn metal and Sb2O3 at different temperatures above 1470 K. Gd2MSbO7 (M = Cr, Mn,Fe,In) are cubic, pyrochlore-type compounds, space group Fd3m (No. 227), Z = 8, a values varying from 10.266 (1) (M = Cr) to 10.486 (1) A (M = In). For Gd in 16(c), M and Sb at random in 16(d) sites, oxygen atoms in 8(a) and 48(ƒ) positions and x, oxygen positional parameter, equal to 0.412 (M = In) up to 0.425 (M = Mn), origin at center (3m), R values from 0.032 (M = In) to 0.041 (M = Mn) are obtained. X-ray powder diffraction data and interatomic distances are given.

Preparation and crystallographic investigation of the spinel series: Mn1 + 2sCr2 − 3sSbsO4 (0.05 ⩽ , s ⩽ 0.30)

Mn1 + 2sCr2 − 3sSbsO4, a new series of spinels, have been prepared and studied using X-ray powder data. For s going from 0.05 to 0.30, a gradually increases from 8.441(1) to 8.472(1) A, and u slightly decreases, from 0.262 to 0.258. Interatomic distances are given. The Mn1 + 2sCr2 − 3sSbsO4 (0.05 < s < 0.30) series may be conceived as the result of partial substitution of Cr3 + by 2/3Mn2 + + 1/3Sb5 + in the normal spinel, MnCr2O 4.

Simulated Standards for the Characterization of Dolomitic Mortars

In order to clarify the structure underlying the appearance of several compounds in dolomitic mortars (specifically hydromagnesite, Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O), as well as the suitability of the X-ray diffraction (XRD) and thermogravimetric and thermodifferential simultaneous analysis (TGA-DTA) in their determination, different patterns from phases that could be present in mortars of these characteristics have been prepared and studied by these techniques. The standards were prepared from: hydromagnesite (HY) with calcite in weight/weight proportions 1:1 to 1:5; HY with calcite and quartz in proportions 1:1:1 and 1:6:12; HY with quartz, 1:1 and 1:2; HY with portlandite (calcium hydroxide), 1:1 and 1:2; HY with portlandite and quartz, in 1:6:12, and HY with magnesium oxide in 1:1, 1:2 and 2:1. The XRD results have shown that it is possible to detect HY and the other compounds (dolomite, calcite, magnesite, quartz, …), but when the HY is mixed, the intensity of its diffraction peaks is very weak, even not detectable in some cases. The poor crystallinity of the HY could be the reason of this drop in intensity. Therefore thermal studies were necessary to find HY phases in low weight percentages. TGA-DTA led us to establish the experimental conditions most suitable for thermal studies. A high CO2 pressure around the sample was required for the occurrence of an exothermic peak at 500°C. This high pressure was guaranteed in the present work as follows: static air atmosphere, packed sample, high heating rate (20°C.min-1), and alumina crucibles with holed lids in order to establish a selfgenerated atmosphere. The thermal behavior of hydromagnesite phases has been clearly established in contradiction to some references of the literature; specifically, the exothermic peak at 500°C has been observed repeatedly. This result invalidates reports of the crystallization of magnesium carbonate from the amorphous phase.

Characterization of Ancient Dolomitic Binding Materials from Zamarce, in Navarre (Spain)

Ten ancient mortars of dolomitic origin, used in the construction of the church of Santa Maria de Zamarce in Navarre, Spain, have been studied in order to define their composition and to characterize the type of binder employed. A complete characterization has been carried out including: morphological examination (visually and using optical microscopy); mineralogical studies (X-ray diffraction, XRD); chemical analysis (main components and soluble salts); grain size distribution and thermal studies (thermogravimetric and thermodifferential simultaneous analysis, TGA-DTA). Dolomite and calcite, as binders, and quartz, as aggregate, have been found as the main phases. The important variability of the studied samples has confirmed that the choice of the raw materials and their preparation were not taken carefully. Thermal behavior of the samples has shown the endothermic peaks related to calcite and dolomite decarbonations. No hydromagnesite phases have been detected. Finally, the approximate indications of the original composition of the raw materials mixtures are presented.