Building pathology and environment: Weathering and decay of stone construction materials subjected to a Csa mediterranean climate laboratory simulation

Building stone materials have to satisfy long-term durability requirements in different environments in terms of mechanical strength and resistance to aggressive conditions. Several studies and field observations show that weathering on geo-materials is related to average annual precipitation and temperature. The decay also depends on salts air/soil concentrations and biological agents, but the more harmful impact is given by greenhouse gas (e.g. CO2, SOX, NOX, O3). These last induce the acidification of the rain and runoff waters. Nowadays, decay prediction is required in order to estimate the behaviour of stone materials over time. This research represents a second part of a previous work where the response to weathering of some construction materials used in ancient and contemporary architecture and cultural heritage has been evaluated by a labo- ratory simulation of hot-summer Csa Mediterranean climate. Simulation consists of accelerate ageing test on climate chamber by reproducing macro (e.g. daily and seasonal cycles of temperature, relative humidity, CO2 air concentration) and micro (e.g. rain, soil capillary rising) environments. Some non-destructive testing were executed to evaluate some physical–mechanical “decay markers” before and after the ageing. Test caused both decreasing and increasing of Leeb D hardness, decreases of permeability and a general decrease of ultrasonic speed, mainly due to the formations of patinas, crusts and efflorescences on the surfaces

Micro Destructive Analysis for the Characterization of Ancient Mortars: A Case Study from the Little Roman Bath of Nora (Sardinia, Italy)

In this work, a protocol of a partially invasive sampling for the archaeometric characteri- zation of ancient mortars from the little Roman Bath of Nora (Sardinia, Italy) is presented. Optical microscopy and different analytical techniques such as X-ray diffraction, X-ray fluorescence, thermo- gravimetric analysis, and physical/mechanical tests have been carried out on the mortars. These analyses were performed to investigate the chemical composition, alteration products, and binder pozzolanic activity. An innovative method of image analysis has been tested to obtain information about the size and shape of both the mortar aggregates and the binder/aggregate ratio. This new particle-size analysis has two different advantages: (i) it saves a huge volume of material compared to a classic granulometric classification through its use of a sieve and (ii) is eco-friendly in respect to the environment by saving a large volume of liquid waste derived from the acid attack for the separation of the insoluble aggregate from the soluble binder, as would be done for a common sieving. Results show a local provenance of the aggregates. The use of two different limestones for the mortars’ binder production was detected and probably this raw material belongs to the nearby Roman town of Karales (current day Cagliari)

Accelerate ageing on building stone materials by simulating daily, seasonal thermo-hygrometric conditions and solar radiation of Csa Mediterranean climate

The maintenance plan of ancient and contemporary buildings today takes on strategic importance and should include the identification of climatic environment where the structures are located. Researcher are trying to evaluate the response to weathering of the building materials by accelerated ageing tests. This technique often consists of the ‘‘aggravations practice”, by subjecting materials to extreme climate parameters not representative of the real environment conditions. For this reason, this type of ageing pre- sents a lot of criticisms. This research addresses the lacking of literature about the realistic simulation of a determinate environment/climate on building stone materials. The aim of this research is to understand if it is possible to recreate in laboratory the pathologies observed on building stones of ancient monuments from Sardinia (Italy) by simulating the climatic context of location. To do so, samples were undergone to accelerated cycles of thermo-hygrometric conditions and solar radiation for simulating realistic param- eters of Csa Mediterranean climate. Monitoring of some physical/mechanical properties before and after ageing indicates an overall decohesion of samples, the appearance of decay patinas and a slight worsen- ing of mechanical resistances. A mathematical equation relates the ageing test duration (6 months) with the hypothetical outdoor exposure quantifiable in %18 years for samples evolved to temperature and humidity cycles while %3.7 years for the samples subjected to only solar radiation. However, the test should to be reproduced in the natural outdoor environment to correlate and verify the reliability of the obtained data (test the test)

Comparative pottery technology between the Middle Ages and Modern times (Santarém, Portugal)

Combining historical, archaeological and experimental data, traditional and archaeological ceramics, from the Santarém district, with different chronology and functions have been studied. Our aim is to understand ancient pottery technology and to evaluate whether ceramic production followed similar principles in the Middle Ages (from the Islamic to the Christian domination) and Modern times. Moreover, traditional ceramics, knowing the productive process, have been used as a tool to interpret ancient pottery technology. We considered different utilitarian ceramic groups, namely fire, table and food-liquid container wares. Through the combination of optical microscopy (OM), X-ray powder diffraction (XRPD), X-ray fluorescence spectroscopy (XRF) with physical and mechanical tests, it has been possible to collect valuable information regarding pottery manufacturing, considering the age and the object function. Moreover, it is also considered the effect of raw materials mixing and ceramic paste preparation on ceramics final characteristics. Our results indicate that both during the Middle Ages and in Modern times, technical expertise played, and still play, a fundamental role in the creation of a specific object. In this specific case, behavioural and socio-cultural factor drove ceramists’ decision when selecting between different technological solutions, and every decision or technical choice is/was taken depending on the functional and performance characteristics desired for a specific artefact. This happened during the Middle Ages, and is still happening nowadays for the production of traditional ceramics in the district of Santarém, Portugal

Microscopia e Microanálise no Estudo de Pedras Ornamentais Carbonatadas

A crescente competitividade de economias emergentes tem criado dificuldades aos países Europeus produtores e exportadores de Pedra Ornamental. Para acrescentar valor, estes países terão que adicionar tecnologia aos seus produtos. São apresentados três casos de como as técnicas de microscopia e microanálise permitem antecipar e compreender o comportamento das rochas, em diversas condições climatéricas. Estas metodologias podem ser usadas em rocha de obra nova, eventualmente seguindo as normas vigentes ou em objetos património

Chemical-physical agents and biodeteriogens in the alteration of limestones used in coastal historical fortifications

The alteration of rocks is usually due to the chemical-physical processes that are initially established on the outer surface of the stone and gradually proceed towards the inner matrix. The chemical alteration generated by the interaction with atmospheric agents (weathering) involves the transformation of the mineral phases constituting the rock that are less stable in the current climatic conditions. That often leads to the formation of new secondary phases more stable with respect to the alteration. However, among these phases are often present some very soluble and hygroscopic phases (i.e., soluble salts, clay minerals) that cause inner degradation of the rock, due to their physical-mechanical actions (inner crystallization pressure, hydration dilation). In the case of carbonate rocks (limestone, sandstone with carbonate cement, etc.), the dissolution is the more frequent process, especially when the monuments were located within the cities, due to the acid meteoric precipitations (with H2CO3, H2SO4) that lead to the sulfation of carbonate matrix with formation of gypsum, very harmful to the stone. When the rock (e.g., clay-arenaceous limestones) naturally contains hygroscopic phases inside the matrix (i.e., marine salts, phyllosilicates) and they are also porous (> 20%), the physical degradation is accelerated, with decohesion of the mineralogical matrix (between the crystalline granules) and consequent disintegration of the stone. In the rock-atmosphere interaction often occurs the presence of biodeteriogens (plants, fungi, lichens, micro- organisms, etc.), which negatively participate and in various ways in the processes of rock alteration. The research aims to define the chemical-physical alteration factors on the limestones exposed to different bioclimatic and biogeographic contexts (Mediterranean and Atlantic), taking two study-case monuments located in the Italian and in the Portuguese coasts. In the study presented in this paper the preliminary results of the case-study of Cagliari fortifications have been discussed. In the study the different vascular plants present on stone surface and crevices and their different role in the degradation of limestone rocks have been also studied