Jan Elsen

Nineteenth century hydraulic restoration mortars in the Saint Michael's Church (Leuven, Belgium) natural hydraulic lime or cement?

Abstract This research focuses on the characterization of nineteenth century hydraulic restoration mortars used in the Saint Michaels Church in Leuven (Belgium). The mortars were used as restoration mortars for weathered mortar joints. A historical study of old work descriptions and mineralogical, petrographical and chemical analyses have been used to characterize these hydraulic mortars. The different hydraulic phases are identified using petrographical analysis, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDX) and chemical analyses. Based on the presence of gehlenite (C2AS), the dominance of C2S, the large amounts of portlandite, the chemical analyses and on the historical sources, these hydraulic mortars are characterized as natural hydraulic lime mortars.

Study of ancient mortars from Sagalassos (Turkey) in view of their conservation

Abstract Since 1990, regular archeological excavations are done in the Roman city of Sagalassos (southwestern Turkey) by the Catholic University of Leuven (Belgium). The mineralogy and petrography of the lime mortars at Sagalassos have been studied in detail as part of an investigation of the provenance of mineral raw materials present in the territory of Sagalassos. The samples were analysed with optical microscopy on thin sections followed by XRD analyses to design a suitable repair mortar. The lime used as binder was burnt from local Triassic limestones and prepared by dry slaking. Three main types of aggregates have been identified: limestone from local Mesozoic limestones, crushed ceramics from locally produced coarse wares and volcanic tuff from a nearby volcanic region. To preserve the excavated remains in very harsh climatic winter conditions, experimental mixtures of restoration mortar have been tested for strength and frost resistance using similar raw materials as in ancient times. The proposed mortar for further on-site conservation and restoration consists of a mix of lime with crushed volcanic rock from the region of Isparta. This composition is very similar to the original Roman material and shows a high frost resistance in freeze–thaw testing.

Continuous elimination of Pb2+, Cu2+, Zn2+, H+ and NH4+ from acidic waters by ionic exchange on natural zeolites

A study of breakthrough curves for cations usually found in acid mine drainage (Pb(2+), Cu(2+), Zn(2+) and H(+)) and municipal wastewater (NH(4)(+)) have been conducted on some natural zeolitic tuffs. The zeolitic tuffs used in this study are: three zeolitic tuffs from Cayo Formation, Guayaquil (Ecuador), characterized by X-ray diffraction as clinoptilolite (sample CLI-1) and heulandite (samples HEU-1 and HEU-2)-rich tuffs, and two zeolitic tuffs from Parnaiba Basin, Belem do Pará (Brazil), characterized as stilbite-rich tuffs (samples STI-1 and STI-2). The clinoptilolite sample CLI-1 shows an exceedingly good exchange capacities for Pb(2+) and NH(4)(+) as received, and also a very high exchange capacity for Cu(2+) and Zn(2+) when conditioned with 2M sodium chloride, with much higher values than those reported in the literature for other clinioptilolite ores. A general order of effective cation exchange capacity could be inferred from breakthrough curves on these zeolitic tuffs: CLI-1 > HEU-2 > HEU-1 > STI-2. Since it is true for most of the cations studied.

Hydraulicity in Historic Lime Mortars: A Review

Natural hydraulic limes were used in ancient times and are still produced today. A comparison of the chemistry and mineralogy of currently available NHL2 and NHL5 limes indicate that there are no clear differences except for the amount of ‘undefined material’, mainly comprising an amorphous phase. The chemical composition of these different limes is nearly identical. However, the classification of ancient hydraulic limes is mainly based on their chemistry, obtained from the analysis of ancient mortar binders. Moreover, it is shown that the phase composition of these limes evolves with time, making their classification uncertain and difficult.

Susceptibility of mineral phases of steel slags towards carbonation: mineralogical, morphological and chemical assessment

Process limitations have thus far prevented mineral carbonation of alkaline wastes from been widely applied. These barriers are caused by inefficient processing, but also by mineralogical aspects inherent to the materials. Better understanding and predictability of the effects of mineral carbonation on alkaline materials could be obtained by studying the carbonation susceptibility of constituent minerals separately, allowing for detailed and accurate analysis of their reaction kinetics and maximal conversions and of the carbonate products formed. For this purpose, this paper presents the synthesis and carbonation of the seven most abundant alkaline minerals found in AOD, CC and BOF slags, namely: akermanite (Ca 2 MgSi 2 O 7 ), bredigite (Ca 7 Mg(SiO 4 ) 4 ), cuspidine (Ca 4 Si 2 O 7 F 2 ), β– and γ–C 2 S (Ca 2 SiO 4 ), merwinite (Ca 3 Mg(SiO 4 ) 2 ), and srebrodolskite (Ca 2 Fe 2 O 5 ). Two experimental approaches to mineral carbonation of increasing levels of process severity are utilized: (mild) incubator carbonation, and (accelerated) pressurized slurry carbonation. In addition, the slags and two free oxides (CaO and MgO) are equally carbonated and evaluated. Data regarding CO 2 uptake, mineral conversion and formed carbonate and non-carbonate products in the samples were obtained through TGA, QXRD (Rietveld refinement) and SEM techniques. Reduction in material basicity and evolution of particle morphology were also assessed. The synthesized mineral purities (>70 wt% target mineral phase) were found sufficient for more accurate assessment of carbonation behaviour of the individual minerals. Bredigite was found to be the most reactive mineral under all processing conditions; C 2 S and wollastonite were more reactive under slurry carbonation, while srebrodolskite and calcium monoferrite were found to be more reactive under moist carbonation. Merwinite and diopside had the slowest carbonation conversions. Calcite and aragonite were the dominant carbonate products formed, whereby aragonite formation was promoted in Mg-containing materials. The morphology of aragonite crystals and the packing density of its product layer were found to vary depending on the parent mineral. Characteristic slag carbonation products, not observed as extensively from synthetic mineral samples, were magnesian calcite from slurry carbonation, and monohydrocalcite and vaterite from moist carbonation. Wollastonite was the main crystalline non-carbonate product, occurring predominantly from slag carbonation, while silica-rich amorphous matter formed in all samples proportionally to CO 2 uptake. Free lime, when present, controlled material basicity above pH 12, while silicates were found to typically possess pH in the range of 11.3–11.9, and Ca-carbonates eventually controlled the pH of well carbonated samples to values under 10.

Automated air void analysis on hardened concrete: results of a European intercomparison testing program

Abstract This paper presents the results of a European round robin test on air void analysis on hardened concrete (SMT-EC-research project — Contract No. SMT4-CT95-2006). Thirteen laboratories in Europe from seven countries participated in the intercomparison test of which seven used a manual method and six an automated measurement system. The results indicate that the results obtained with measuring methods using image analysis (IA) techniques all statistically lie in the group of all measurement results. The automated methods can be problematic when a high amount of porous sand grains is present in the concrete. A second disadvantage of these automated methods is that it is not possible with the current methods being used to measure the paste content of the sample.

Rilem TC 203-RHM: repair mortars for historic masonry. Performance requirements for renders and plasters

This article gives a summary of functional and performance requirements for renders and plasters for historic masonry (design, execution and maintenance). Specific attention has been paid to degradation effects, such as caused by salt crystallization and freeze–thaw cycling. Traditional as well as designed prefab mortars are considered for repair intervention.

Rilem TC 203-RHM: Repair mortars for historic masonry. Repair mortars for historic masonry: From problem to intervention: a decision

This article focuses on repair or replacement mortars for historical buildings. Both the decision process and questions arising are dealt with, in order to better define and illustrate technical requirements for mortars to be used for the repair or restoration of monuments and historic buildings (masonry mortars, plasters, renders…). The article summarizes a longer document, meant to help professionals in their decisions on the interventions, taking into account aspects, which are ranging from the ethics of restoration to the technical requirements.

Raw materials used in ancient mortars from the Cathedral of Notre-Dame in Tournai (Belgium)

Abstract: Mortar samples from the Notre-Dame Cathedral at Tournai in Belgium have been investigated as part of a broader studyconsidering the transition of ancient cities and their rural territories from Roman to late Roman society and the transformation to theearly Middle Ages. Masonry mortars and mortars used for flooring have been studied from the Imperial Roman period, theCarolingian style period and the Romanesque style period (4th–11th century AD).A selected set of samples has been characterised using a combination of mineralogical, chemical and microscopical techniques.This characterisation enabled us to refine our knowledge of the mortar composition, of the original materials and of their provenance.It appears that both chalk and ‘‘hard’’ Tournaisian limestone were used to produce the lime. Both locally available materials can yieldeither hydraulic or non-hydraulic lime. The aggregates have a local origin. Additionally, several microscopical techniques wereapplied to identify the nature of the overburnt particles. The low abundance of this type of Binder Related Particles in the Gallo-Roman and Palaeo-Christian mortars suggests that technological knowledge, be it empirical or theoretical, was available.Key-words: ancient mortars, raw materials, provenance, lime binder, lime burning, hydraulicity, archaeometry.

Hydration and strength evolution of air-cured zeolite-rich tuffs and siltstone blended cement pastes at low water-to-binder ratio

Abstract This contribution is the second part of an in-depth study on the hydration and strength evolution of blended cement pastes at a water to binder (W/B) ratio of 0.3, cured by two different methods. The blended cement pastes showed significant hydration up to 7 days, when almost all of the hydration products had already formed; thereafter, carbonation played an important role up to, and possibly beyond, 91 days. Likewise, the hydration of alite (tricalcium silicate, Ca3SiO5, C3S) proceeded up to 14 days and then started to slow down. However, the hydration of belite (dicalcium silicate, Ca2SiO4, C2S) was affected most strongly, as it nearly ceased, under the air-curing conditions. During hydration, some of the blended cement pastes had a larger calcium hydroxide (CH) content than the unblended (plain) ones. The accelerating effects of the addition of supplementary cementitious materials (SCMs), the air-curing conditions and the low W/B ratio may explain these unusual results. Under these experimental conditions, the water incorporated into hydrates was about 50% of the total amount of water used during full hydration of the cement pastes. The pozzolanic reaction predominated during the early ages, but disappeared as time passed. In contrast, the carbonation reaction increased by consuming ~45% of the total amount of CH produced after aging for 91 days. Only one blended cement paste reached the compressive strength of the plain cements. The blended cement pastes containing 5% of the zeolitic tuffs, Zeo1 or Zeo2, or 10% of the calcareous siltstone, Limo, developed the greatest compressive strength under the experimental conditions used in this study.