A brief history of the nature, use and technology of binders in ancient constructions and buildings is outlined, including the apparent chronological discontinuities related to technological developments. The skilled and clever use of mineral resources is at the base of the technical achievements related to architectural activities, from simple adobe to high-performance modern concrete. It is argued that among pre-industrial binders the Roman pozzolanic mortars were highly optimized materials, skillfully prepared and very durable. Their innovative use in architecture is one of the keys of the successful expansion of the Roman Empire. The role of mineralogy and mineral reactions is emphasized in terms of: (1) the preparation and manufacturing of the binding materials; (2) the hardening process and the development of the physical properties of the binder; and (3) the archaeometric reconstruction of the ancient materials.

Abstract This study gives an example of the steps that a repair work must include to be successful. It deals with a specific building, repair material (lime mortar) and application (render), but also with the study of the repair mortar in the laboratory and on site. Firstly, the original materials of the wall were characterized to ensure compatibility with the new repair mortars. Secondly, the suitability of different mortar mixes, made with lime and calcareous aggregate, was assessed by characterizing their properties after 15 months. At the same time, the repair mortars were applied in testing panels, and their behaviour under environmental conditions was studied and compared with that of the laboratory mortars. Mortar properties (shrinkage, adhesion, mineralogy, microstructure and texture) developed differently according to the curing conditions. The carbonation degree was higher in mortars cured on site (especially those with higher aggregate content), although in both cases it depended on mortar porosity. Testing the type of application on site was helpful to define the best performance of the designed mixes and to choose the most suitable one among them, which was found to be the 1:6 binder-to-sand ratio mortar applied in both layers of the render.

Abstract This work highlights the importance of applying suitable methods for the design of air-hardening lime mortars with the correct water dosage and binder-to-aggregate ratios. To this end, the recently developed ‘wet packing method’ has been used to assess the optimum water-to-binder ratio at which the packing density is achieved in lime mortars with different binder-to-aggregate proportions. To support the validity of this method, it has been compared with other standardized methods of determining the bulk density of the dry granular components and the consistency of the mortar pastes. The reliability of the wet packing method has then been verified by studying the mineralogical, textural and mechanical properties of mortars after 2 and 6 months of carbonation. Results showed that although the wet packing method seems to be more realistic than the majority of standards used for the determination of the packing density and workability in granular mixtures, it is not totally suitable for the preparation of air-hardening lime mortars with good performances in the fresh and hardened state.

Abstract This research explores preliminary observations regarding the potential effects of local climate conditions on the evolution of binder morphology and the composition or mineralogy of historic lime mortars. Samples were collected from historic buildings, one group dating to c . late nineteenth century and an older group from c . Sixteenth–Seventeenth century, with both groups representing distinct climates. The samples were then prepared and subjected to polarized light microscopy (PLM), point count, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) and backscatter election imaging (BSE) analysis to investigate differences in porosity, environmental contaminants and morphological characteristics of the lime binder. By examining the effects of climate on lime mortars, conservators can improve identification and condition assessment of historic lime mortars, better understand causes of damage and decay attributed to previous mortar repairs, and formulate more appropriate conservation mortars to improve protection and conservation of our architectural heritage.

Abstract Different image analysis (IA) methods have been developed to compute textural parameters of ancient plasters and mortars using standard petrographic thin sections. These IA routines were applied to samples of materials with different technological characteristics from three historical buildings in the city of Pavia (Northern Italy), covering a period from the 12th to the 19th century. The IA techniques tested in this study belong both to classical digital image processing and to neural network modelling. In the first case, analyses were performed by commercial IA software whereas in the second case a Multi-Layer Perceptron neural network (MLP) was tested. Digital image analysis was performed on images taken by means of a petrographic microscope; additionally, analysis of back-scattered electron (BSE) images was performed. Textural data obtained through the IA applied to thin sections were compared with the data from traditional point counting and mechanical sieve analysis of disaggregated samples of the same materials. The results show that the IA of thin sections provides robust results in a fast and easy way. However, the reliability of the analyses can be prejudiced by textural and compositional heterogeneity of the samples.

Abstract The use of gypsum based mortar can be traced back over 4500 years. In Germany, in the vicinity of natural gypsum outcrops, in addition to lime mortars, calcium sulphate based mortars were widely used for joints in exterior walls of sacred buildings. There are several medieval buildings with well-preserved calcium sulphate-based mortars. The high water solubility of gypsum (CaSO 4 •2H 2 O) is a disadvantage that makes it difficult in general to handle calcium sulphate based building materials in areas exposed to weathering. Physico-mechanical as well as mineralogical investigations of historic calcium sulphate based mortars have shown that long-term weathered mortars have a much denser microstructure, larger average grain sizes, and a higher compressive strength than laboratory prepared mortars. Porosity models of these mortars will be presented which are helpful to prepare calcium sulphate based mortars with a higher water resistance for restoration purposes. The reason for the change of crystal size and morphology as well as of porosity and strength can be explained by crystallization and recrystallization processes of these calcium sulphate based mortars, as a consequence of long-term weathering. Since it is obvious that crystal size and its distribution have an enormous effect on the weathering resistance, the development of mortars with comparable structural properties is of present interest. In current use are chemical additives which modify the morphology and size of gypsum crystals of set mortars. Another possibility to influence the weathering resistance is the addition of hydraulic and/or latent hydraulic admixtures.

This chapter, which is concerned with aggregates for mortars, necessarily introduces some degree of overlap with Chapter 8 . However, there are major differences between mortars and concretes, arising mainly from the manner of their use. The term ‘mortar’ is used in the building industry to denote a mixture of natural sand or other fine aggregate and some binding agent, used as a jointing or a surface plastering and rendering material (Fig. 9.1 ). In the United Kingdom the demand for building sand grew steadily up to 1973 to reach a peak of 23.6 Mt, representing some 18% of the total sand and gravel production (HMSO 1989) for the country. Since then it has fluctuated considerably, falling to 15.7Mt in 1981 but rising again to 21.89 Mt in 1988 (Fig. 9.2 ). It should be noted that the output figures for building sands are far in excess of figures for mortar production.Until about 30 years ago the choice of binders in the UK was limited to lime or cement or cement-lime mixes. Mortars made with lime alone as binder are no longer used for building except for some specialist applications in the repair of historic buildings. The choice of cementbinders has been widened to include masonry cementS(specially blended mixtures of Portland cement with finely divided mineral plasticizers and air-entraining agent). Increasingly, air-entrainment in mortars, not only to confer frost resistant properties but also to aid workability, is being used even with cement/lime/ sand mortars. The use FIG. 9.1. Typical brick and mortar construction for joining. FIG. 9.2. Production of building sand for construction purposes (land-use and marine-dredged totals) (BACMI 1991). Until about 30 years ago the choice of binders in the UK was limited to lime or cement or cement-lime mixes. Mortars made with lime alone as binder are no longer used for building except for some specialist applications in the repair of historic buildings. The choice of cement binders has been widened to include masonry cements (specially blended mixtures of Portland cement with finely divided mineral plasticizers and air-entraining agent). Increasingly, air-entrainment in mortars, not only to confer frost resistant properties but also to aid workability, is being used even with cement/lime/sand mortars.