Consolidation and Upgrading of Historic Earth Block Masonry Constructions

Earth structures constitute a great part of European Monumental Heritage and are closely related to the wider historic, socioeconomic and environmental aspects of each region. They have been constructed with various materials and techniques which depict the regional constructional traditions, with respect to economy of resources and energy consumption in building. Many techniques of building with earth have been developed, while in South Eastern Europe the mostly encountered type is buildings with earth-blocks. Nowadays there is no policy for their retrofitting, maintenance and upgrading, since the tradition of manufacturing earth masonry has vanished and there is lack of relevant regulations. As a result, earth-block houses have been abandoned and destroyed due to damages from earthquakes, ageing or unsuitable interventions (use of concrete members, cement based mortars) and many historic centers with earth houses have been marginalized and demolished. In this paper, a methodology is presented regarding the analysis of building materials and techniques of historic earth block houses situated in Northern Greece, as well as the design and testing of compatible repair materials for their rehabilitation. A series of laboratory tests have been performed to the historic materials, in order to define their microstructural characteristics and their physico-mechanical and chemical properties. Results have been evaluated and led to the design of compatible repair materials based on earth. A series of soil based grouts were manufactured and tested, while their properties were enhanced by the use of specific additives and admixtures. Experimental results showed that the development of compatible repair materials for the stabilization and restoration of historic earth-block buildings should be based in scientific criteria. This means that proper mortar and grout compositions based on earth could sufficiently fill joints, cracks and lacunae and could therefore lead to the maintenance and upgrading of historic earth block buildings

Steel Slag Concrete for Pavement Construction

Steel Slags are by-products of Steel Industry using the Electric Arc Furnace method for steelmaking. This methodology is widely used in South Europe where the research on steel slag applications in concrete has been developed. In this paper, the properties in fresh and hardened state of concrete for pavements are described as well as a pilot application of steel slag concrete in road pavement. Based on the results it is obvious that the use of steel slags in pavement application is very advantageous from technical point of view. Basic desirable characteristics are enhanced or significantly increased, such as the compressive strength, ductility and resistance to abrasion. Furthermore, the anti slipping properties of the pavements are considerably enhanced. A comparison of conventional concrete pavement with steel slag concrete is made based on the cost and environmental footprint considerations, taking into account the maintenance cost during the service life of the pavement

DURABILITY OF LIME BASED RENDERS: A REVIEW OF SOME DEGRADATION MECHANISMS AND ASSESSMENT TEST METHODS

Lime based mortars used for the repair and renovation of old lime renders have important functions in historic buildings, such as the protection of the masonry and aesthetics of the surfaces. Hence, they have a significant contribution to the durability of the walls, which often are structural elements. Cracking and loss of adherence are two of the most severe defects for renders, as they drastically affect their functional capacity. Cracking is related to shrinkage, elastic characteristics, and kinetics of the gain of strength as well as to water transport properties of the render. Most of these aspects are governed by the porous structure of the mortar, which is a function of the composition of the mix and application issues. Loss of adherence is related to the compatibility of the render with the substrate, concerning mechanical, thermal and hygric aspects. Loss of cohesion, due to leakage of the binder, freeze-thaw, salts crystallization or other causes, results in significant damage, difficult to repair. The appearance of stains either by pollutants deposition or by biocolonization is also a concern related to durability of renders. In the present paper the degradation mechanisms leading to cracking, loss of adhesion or cohesion and stains formation are analysed based on literature, and a review of assessment test methods are carried out. Finally, the need for test improvement in this area is highlighted.authorsversionpublishe

RILEM TC 277-LHS REPORT: A review on the mechanisms of setting and hardening of lime-based binding systems

The main objective of RILEM TC LHS-277 “Specifications for testing and evaluation of lime-based repair materials for historic Structures” is the revision, adaption and, when necessary proposal, of the test methods to accurately study lime-based binding systems and mixtures, such as mortars and grouts. The empiric use of the lime-based composites and the predominant employ of cement in the field of Civil Engineering have led to the widespread application of test methods developed for cement-based composites to test the former. However, the clear differences in composition and performance between modern cement binders and lime-based materials would advise to explore specific test methods for the latter. To undertake this task the previous knowledge on the mechanisms of setting and hardening of these binders must be revised, arranged and synthesized. Processes such as drying, carbonation, hydration and pozzolanic reaction may occur during the setting and hardening of lime-based mortars and competition between them cannot be underestimated. With the aim of underpinning the revision and proposal of test methods for lime-based systems, this review paper reports a comprehensive study of the mechanisms of setting and hardening of these binders, considering the variability of the composition, which includes pure air lime as well as lime with hydraulic properties, lime-cement and lime-pozzolan systems.authorsversionpublishe

Testing properties governing the durability of lime-based repair mortars

Lime-based mortars (LM(s)) seem to be preferred in repairing historic structures. The long-term performance of repair LM(s) is closely related to durability issues concerning the old structure substrate, the new repair mortars and interface between the two aforementioned materials, which is also much influenced by the technique of mortars application. Durability is a multifunctional property affected by a number of parameters, including local environmental conditions. However, experience showed that some of the characteristics of materials play a dominant role in assessing the durability of repair LM(s) and have a direct impact on longevity of the repaired structure. This paper presents review of research/case studies papers and Master/PhD theses supervised by the members of RILEM TC 277 LHS. Through the review and evaluation of research and common practice concerning durability challenges, we anticipate to find answers to questions arising in assessing durability of repair LM(s), such as: • The most often encountered failures due to mortar durability inadequacy • The mortar properties/characteristics that seem to be influential on durability • The test methods used for testing the durability of LM(s) and comments related to their applicability and performance • The importance of quality control and on site execution practice

Study of materials and technology of ancient floor mosaics' substrate

A floor mosaic's substrate is composed of a variety of preparatory layers of mortar built on natural levelled ground or on top of a previous pavement. Mosaics' substrates differ one from the other in number, thickness and nature of the mortar layers. In this sense, it has been considered relevant to state how these differences are related with historical period, geographical position, function of the pavements within the building, technology of the substrates. A number of floor mosaics' substrates of Hellenistic and Roman period from archaeological sites in Greece and Italy are under study. The stratigraphy of substrates is recorded in situ, and samples from each mortar layer are analysed in the laboratory by means of different techniques. Results obtained so far indicate that characteristics of the Roman substrates mortar layers are clearly dependant on their position in the substrate stratigraphy, whereas in the case of the Hellenistic substrates, characteristics of the mortar layers are less varying with the stratigraphic position. Furthermore results show that floor mosaics' substrates are different according to the function of the pavement in the building

The role of shrinkage reducing admixtures and supplementary cementitious materials in volume stability and strength development

Shrinkage is one of the main reasons for mortar and concrete failures like curling, crack formation and de-bonding. It is a complex phenomenon due to many factors involved, such as the type and amount of cement, water to binder ratio, binder to aggregates ratio and the type and granulometry of the aggregates, relative humidity, air temperature and the temperature of concrete. To reduce this phenomenon, Shrinkage Reducing Admixtures (SRAs) have been studied over the last 30 years. On the other hand, investigation in the field of Supplementary Cementitious Materials (SCMs) has indicated that their use in concrete may improve its volume stability depending on their percentage and the type of the material. In this paper, the addition of a Shrinkage Reducing Admixture and Supplementary Cementitious Materials like ladle furnace slag, calcareous fly ash and limestone filler, were investigated. Their influence, separately and in combination, in volume stability and strength development of cement mortars was identified. Capillary absorption and open porosity were also determined

additives and admixtures for modern lime-based mortars

Publisher Copyright: © 2023, The Author(s). Open access funding provided by HEAL-Link Greece.The scope of this collective paper produced in the frame of RILEM TC 277-LHS is to provide sound knowledge on the use of additives/admixtures in lime-based mortars, based on literature and practice. The most widely known additives/admixtures are systematically presented. Their main effects and testing of their performance have been properly tabulated. It is well known that a plethora of additives/admixtures are produced every year by chemical industries. However, when using them in lime-based mortars, compatibility and durability aspects are of primary importance. The introduction of additives/admixtures in lime mortars was imposed by the need to improve important properties of these composites in the fresh and hardened state, namely, workability, durability, early-age and long-term strength and to reduce defects, such as shrinkage and long setting time. In this review paper, the terminology proposed by EN 16572 is followed, designating additive as a constituent added in small quantity to the binder, and admixture as a substance in quantities at least 1% w/w added to the mix. The additives/admixtures are classified according to their action and their validation with specific testing methodologies highlights the dosage sensitivity and the need to develop further standardization. The combination of different additives proposed in several studies resulted as the most promising strategy to enhance the performance of lime mortars. However, recently developed additives and admixtures need to be further evaluated with reference to their compatibility with other mortar constituents, and their effects on the overall mortar and render durability need to be studied. Finally, adopting similar terminology for additives/admixtures in lime and cement-based mortars will facilitate better comparison and assessment issues.publishersversionpublishe