Air Lime Mortars Research Articles

Can mussel shell waste optimize cement and air lime mortars hygrothermal performance?

Mussel shells used as aggregates for mortars have flaky and irregular particles, which significantly increases the pore volume. This leads to the identification the microstructure of mussel shell mortars as a light and porous composite, which could have good hygrothermal properties. In the present study, the density and thermal properties are assessed on cement and air lime mortars, each with three replacement percentages of replacement of conventional sand by mussel shell sand (25 %, 50 % and 75 %), are evaluated and compared with their respective baselines (0 % replacement). Thermal conductivity measurements are also carried out on different loose fractions of the mussel shell aggregate to understand the behaviour of this material without binder matrix. Finally, adsorption and desorption cycles at 80 % and 50 % relative humidity are carried out on loose aggregate fractions and on the eight mortars. The results are very positive for the mussel shell mortars, as it can be concluded that the use of mussel shell aggregates improves the thermal performance and the potential moisture buffering capacity of both cement and air-lime coating mortars.

Investigation of the Impacts of Nonpolar Amino Acids on Air Lime Mortars

ABSTRACT Natural protein-based additives have been frequently added to lime-based mortars to enhance their properties. However, the possible mechanism underlying this effect is not well understood. All proteins are built up by the basic units of amino acids, which may be viewed as a useful starting point for the research topic. The present study focused on the impacts of nonpolar amino acids on air lime mortars. The results obtained from the present study highlighted that some nonpolar amino acids (represented by glycine, alanine, valine and proline) decrease mortar water retention, decrease consistency, delay and prolong setting, increase compressive strength, and decrease water absorption. However, other nonpolar amino acids (such as leucine, isoleucine, phenylalanine and tryptophan) showed almost opposite results. The addition of all the nonpolar amino acids slowed mortar drying and carbonation, decreased the carbonation degree, inhibited calcite formation, and tended to form metastable calcium carbonate phases, such as vaterite. Studying the effects of single amino acids on lime mortars could contribute to the design of repair mortars with more specific requirements, and the results of the present study could open up a series of future topics to be investigated.

Ceramic-added lime and cement mortars: A review of applications in building products.

Ceramic-added air lime mortars have been used since ancient times owing to the pozzolanic effect provided by crushed ceramic particles that impart hydraulic properties. This work reviews the historical use, composition, reaction mechanisms, characterization techniques, and performance properties of ceramic-added air lime mortars. The fine ceramic powder composed of silica and alumina phases reacts with calcium hydroxide released during lime hydration to form calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH) via pozzolanic reaction. This provides hydraulicity and reduces setting time compared to pure air lime mortars. The coarser ceramic particles also serve as aggregate and refine the microstructure as filler. The reactivity depends on the ceramic composition, amorphous phase content, particle size distribution, and firing temperature. Optimal proportioning of the fine ceramic powder and coarse ceramic aggregate is necessary to achieve desired properties. Ceramic addition enhances the durability of air lime mortars against weathering while maintaining compatibility with lime-based masonry structures. Key novelties of this review include: (i) in-depth analysis of the influence of ceramic characteristics (mineralogy, particle size, pozzolanicity) and processing on reaction kinetics and phase evolution; (ii) systematic assessment of mechanical, physical and durability properties in comparison to conventional air lime mortars and cement-based grouts; (iii) elucidation of microstructural mechanisms governing performance using advanced characterization techniques; (iv) critical appraisal of test methods and standards for evaluation; and (v) rigorous discussion on potential applications in construction, conservation and repair, with case studies.

Numerical study of humidity flux in historical mortars based in air lime mortar: Simulation and a case study

RESUMO A segurança estrutural de edifícios históricos exige uma análise estrutural avançada. A argamassa geralmente apresenta composição e comportamento estrutural complexos. Em diferentes partes do mundo, existe uma quantidade significativa de construções históricas utilizando argamassas de cal aérea. A umidade em estruturas de cal tem uma influência importante no comportamento e desempenho. Resultados experimentais de um programa de monitoramento da argamassa desenvolvido pela equipe envolvida neste trabalho foi usado como referência. Para simular este processo de secagem, é utilizado um software implementado pelo Método das Diferenças Finitas (MDF). O software foi utilizado para identificar os principais parâmetros do material. A estratégia de modelagem (MC 2010) foi primeiramente aplicada aos resultados experimentais de corpos de prova cilíndricos, em sequência, aos resultados experimentais de um molde prismático. O modelo foi capaz de replicar os dados experimentais, de forma satisfatória. Destaca-se a relativa simplicidade da modelagem. Quando comparado com materiais como o concreto, foram encontrados maiores valores para D1 e fboundary. Para os corpos de prova estudados, os resultados experimentais e numéricos indicaram gradiente de umidade reduzido. Esses resultados estão associados à alta porosidade. Em sequência, considerando o par de valores obtidos na simulação numérica, estuda-se uma estrutura simulando uma construção real.

Impact of Physico-Chemical Characteristics on the Mechanical Strength and Pore Structure of Air Lime Mortars with Isparta Tuff and Banahmeta Additives

The physical and chemical interactions between the lime and pozzolans in conservation mortars are fundamental to sustainable building practices. Here, we report experimental investigations on pure air lime mortar, air lime-isparta tuff mortar, and air lime-banahmeta mortar. Isparta Tuff is formed from volcanic rocks found in the Southwest between Isparta and Burdur city centres in Anatolia, belonging to the Gölcük volcanism. The microstructural and physiochemical interactions of these mixed designs were investigated. Importantly, this study quantifies critical performance parameters of air lime mortars incorporating Isparta tuff as a pozzolan. It supports using local and natural volcanic tuffs in developing sustainable mortars for the conservation of historical assets in Turkey.

Mussel shell mortars durability: Study of aggregate replacement limit

The knowledge acquired through previous experimental phases with coating mortars with mussel shell aggregates led to conclude that irregular, flaky and hydrophobic particles of the mussel shell and the organic matter content introduce entrapped air and entrained air in the mixes. This phenomenon causes different and opposite effects on the main properties of mortars, which are in some way positive and negative (for durability), consequently, their durability cannot be easily predicted. The present work pretends to analyse the results of different durability tests, such as water vapour permeability, adhesive strength, and weathering cycles to recommend the maximum percentage of mussel shell sand used in coating mortars that guarantee the required lifespan.After an in-depth literature review, it can be said that it is not easy to predict the durability of mortars using mussel shell aggregates. This question has been hardly analysed in the existing literature and the maximum substitution percentage of conventional aggregate that can be replaced is not clear. This work aims to answer this issue by analysing different properties: water vapour permeability, adhesive strength, and weathering cycles. Mussel shell content improves the water vapour permeability of both air lime and cement mortars but worsens the adhesive strength and weathering cycle behaviour. For most applications, 25 % of mussel shell aggregate can be employed, but for some applications, 50 % or even 75 % of mussel shell aggregate is feasible and will avoid the undesirable landfilling of this waste.

The Influence of Traditional Substrates on the Behaviour of Lime Mortars

ABSTRACTOne of the main functions of mortars is the protection of walls in-service conditions. Mortars, however, are associated with common pathological manifestations, which not only affect substrate strength and other properties, but also the comfort and healthiness of buildings users, being responsible for a significant fraction of rehabilitation expenses. In the last few decades, there has been a growing trend towards the rehabilitation of existing buildings instead of their demolition, not only for economic and urbanistic issues, but also for ecological and sustainability reasons due to the awareness of the limitation of available natural resources. In traditional buildings, lime-based renders (coating mortars) were the most common type of wall coating. Indeed, these renders have properties, such as low mechanical strength and stiffness and high-water vapour permeability, which are compatible with traditional substrates. However, inappropriate coating solutions, such as cement-based mortars, have been used in the rehabilitation of old buildings, leading to the development of anomalies in building walls. Nevertheless, there is an increasing awareness of the need to use coatings that are mechanical-chemical, physical and geometrical compatible with traditional substrates. Mortar characteristics, whether declared by the manufacturer, designer, or established by the user, are currently determined in the laboratory, according to applicable standards. When applied on substrates, mortars have their properties altered due to interaction with them, and various substrates influence differently the same mortar, as showed by extensive work developed in the scope of the IF MORTAR project. Thus, knowledge about in-service behaviour of mortars becomes crucial. The main aim of the research presented in this paper is to assess the behaviour of lime mortars applied on traditional substrates and to discuss how substrate properties affect mortar behaviour. In this way, there is a contribution to improve the understanding required to select materials for interventions in traditional buildings, assuring compatibility between traditional and new elements, with suitable durability. To achieve the above-mentioned aim, hydraulic lime mortars and hydrated air lime mortars, produced with two sands with different particle sizes, were applied on solid ceramic bricks and limestone slabs. These substrates were chosen because they are commonly found in traditional buildings. Physical and mechanical characterisation tests were carried out on the mortars hardened in laboratory moulds and on the mortars hardened on the substrates (after being detached). The substrates used were also characterised, as well as the aggregates and binders. The test results revealed that substrates have an impact on mortars characteristics, and this influence is greater for the more porous supports, and varies depending on the type of binder and aggregate used, being directly related to mortar porosity and pore distribution. For air lime mortars, there was an increase in the range of pores from 0.05 to 10 μm and a decrease for pores above 10 μm. The opposite occurred for hydraulic lime mortars. In addition, for air lime mortars, open porosity and water absorption by capillarity increased, in contrast to what happened to hydraulic lime mortars, the open porosity and water absorption by capillarity decreased, after applied to substrates and when subjected to standard curing. Regarding the type of aggregate, for the same ratio, the use of finer aggregates resulted in more porous mortars.

Karsten tube analysis for joint mortar identification in masonry

The present work examines the Karsten tube penetration test to identify mortar types in existing masonry, for mortars containing air-lime or hydraulic binders. Mortar type identification is e.g. of relevance for the reusability of the fired clay bricks in the masonry, where a hydraulic binder content makes the mortar removal process significantly more difficult. The Karsten tube test makes it possible to make a simple and non-destructive mortar analysis on-site assessing the water absorption of the mortar, via the surface of the mortar joint alone. The present approach considers both the effect of the surrounding bricks and the surface finish of the pointing. Furthermore, the setup masks the brick surface exposed under the Karsten tube to focus the exposure on the mortar. Three different mortar types in existing masonry were tested: air-lime mortar, air-lime/hydraulic lime mortar and air-lime/cement mortar. The results showed linear water absorptions, which were clearly distinguishable for the hydraulic and non-hydraulic binders during the 15-minute tests. The measurement results in the present work document how the Karsten tube penetration test can be used for simple and non-destructive identification of joint mortar types determining whether the masonry was constructed with air-lime mortar or mortar containing hydraulic binders.

‘‘Influence of air entrainers on the properties of hydrated lime mortars’’

Physical, mechanical and carbonation progress properties of air lime mortars, formulated with the addition of air entrainers, were analyzed, aiming to investigate the influence of air entrainers on abovementioned properties of lime-based products. Samples were cured in two curing conditions and their properties were evaluated after 14, 28, 60 and 90 days. The results obtained revealed that the addition of air entrainers influences the change in dynamics between drying and carbonation processes, therefore influencing the rate of carbonation process. This observation was reflected in carbonation progress as well as physical and mechanical properties of the tested samples.

Revamp of masonry structures using bio-additive infused air lime mortar as an applicator

Lime masonry walls have been the initial type of masonry wall construction in the construction era. The minimally processed limestone extracted from the lime quarries gives a lesser carbon footprint than any other present-day construction material, making it superior to other construction materials in the construction industry and is the need of the hour. In this study, naturally fermented Bio-Additives, Jaggery and kadukkai were used to make lime mortar for the masonry prisms and walls, and the strength performance was investigated. The bio-additive and the lime powder combination were studied using a pH meter and pH strips to confirm their acidic/basic nature. The lime mortar was experimented with for its flexural strength using a beam specimen. The masonry prism study was initially made with stacked prisms and wall panels (English bond and Flemish bond) for testing compressive strength. The lime mortar thicknesses were varied into two for all the specimens of 10 mm and 15 mm for both the head and bed joints of the masonry. The experimental analysis revealed that a mortar thickness of 10 mm masonry increased the wall’s strength more than mortar of 15 mm thickness in the masonry, disproving the myth that higher mortar thickness in masonry increases the strength of the masonry. The mineralogical characterization of the mortar was carried out by SEM-EDAX to know the internal composition and morphological reactions, FTIR for the changes in the organic composition, and DSC-TGA to know the thermal properties of the mortar matrix. This study justifies the use of bio-additives-infused lime mortar for contemporary masonry projects.

Carbonation of air lime mortars under natural and accelerated conditions – A systematic review

Lime was a prominent building material in ancient times that was replaced by cement by virtue of its fast application properties. The use of lime as a construction and repair material is gaining significance recently as the conservation of heritage structures has become a concern. Moreover, the CO2 associated with the production of cement is proliferating. The use of cement mortars in repairing heritage structures did not prove to be a good choice as the composition, characteristic properties and strength were very different to that of lime binders and therefore reduced the breathability of the existing structures. Lime mortars generally react with the CO2 present in the atmosphere to gain strength and this property of lime can be employed to use it as a CO2 sink. However, the time associated with the reaction is quite high and the present systematic review focuses on the methods by which the CO2 absorption process can be accelerated. The influence of various organic and inorganic additives in accelerating the reaction in natural and high CO2 environments is critically compared. The influence of carbon curing the lime-based mortars on mechanical and microstructural properties is studied. The current review critically compares the behaviour of lime mortars in the mentioned conditions and gives an insight into the amount of future work to be done to promote lime-based binders commercially.

RILEM TC 277-LHS report: lime-based mortars for restoration–a review on long-term durability aspects and experience from practice

For conservation interventions of historic masonry generally lime-based mortars such as pure air lime mortars, lime-pozzolan mortars, natural hydraulic lime mortars and ternary mortars (lime-pozzolan-cement) are used. The main reason is that their hygric and mechanical (strength and ductility) performance are easy to adapt to most existing historic masonry (compatibility requirements). Although the basic appropriateness of lime-based mortars for restoration is undisputed, there are also some limitations in the application of these mortars. In this report a review is given of the theoretical backgrounds and further of laboratory research developments in the field of lime-based binders and mortars over the past decades. Furthermore, practical experiences in positive and negative sense (damage cases) are elaborated. Drawbacks and points of attention are being dealt with, which are essential for a durable application of lime-based mortars for the conservation of historic masonry. In general, it is concluded that points of attention should be addressed through a thorough evaluation of their potential and through testing of their suitability. For these mortars, even more than for modern cement-based mortars, specifically, environmental exposure conditions and application conditions should be considered.

The use of drilling test to investigate the salt distribution in air lime mortars

• Drilling test (DRMS) to map salt distribution in air lime mortars. • Processing of drilling data to detect salts within air lime mortars. • Diagnostic techniques to evaluate the presence of salts and salt damage in air lime mortars. One of the principal causes of deterioration in historic buildings is the presence of salts. Porous and low-strength materials, such as soft mortars, are particularly susceptible to the deteriorating action of salts. The most severe damage occurs when salts accumulate behind the material surface, causing crumbling, exfoliation, and spalling. For this reason, the use of minimally invasive techniques to locate the presence of salts below the surface can be helpful to make an informed decision on the best practice for conservation strategies. In this work, the effectiveness of the drilling test in investigating the sub-surface distribution of salts in two lime-based mortars was evaluated. The technique proved to be effective as the increase in the recorded drilling forces was well correlated with the salt content measured within the materials. In particular, the drilling test results showed a similar behavior between the two mortar mixes. This finding was confirmed by the ultrasonic pulse velocity tests, visual observations, and weight loss measurements performed after the salt aging test. Another aspect of the work is the contribution to the processing of drilling profiles in salt weathered soft mortars. Indeed, the results of drilling tests in soft mortars are very scattered due to the intrinsic heterogeneity of these materials. Thus, the proposed processing of drilling data was effective in evidencing the effects of salts, by reducing the influence of the chip formation on the drilling profiles.

The effect of alkali activation on the durability, mechanical properties, and characterization of alccofine-modified air lime mortar

The effect of alkali activation on the durability, mechanical properties, and characterization of alccofine-modified air lime mortar

Properties of Air Lime Mortar with Bio-Additives

Lime mortar has been a primary binding material in ancient mortar, and is one of the main reasons behind solid and stable constructions that remain stable even after thousands of years. The benefits of lime are innumerable: it is minimally processed and used with a lesser carbon footprint and embodied energy and, most crucially, it is a carbon absorbent. This research experiments with the strength properties (compression) of lime at 28, 56, and 100 days of air curing. The investigation studies the durability using water absorption, UPV test, and carbonation parameters after 100 days of exposure to air. The tested materials are subjected to SEM analysis to find the morphology of the reaction that takes place and the products that are formed. We also performed a comparative study of two different fermented additives by the duration of fermentation (1 day and 10 days) and two different doses of additives (Jaggery and Kadukkai) with air lime. The bio-additives were experimented with using gas chromatography and mass spectroscopy for the formation of new enriching compounds, which improved the qualities of traditional lime mortar. The formation of fat and protein in the additives was found using IS 7219-1973 (a method for the determination of protein in foods and feeds). Using the AOAC method, the presence of fat confirms the improvement in strength and durability properties. The phytochemical analysis details the alkaloids, terpenoids, steroids, phenols, flavonoids, tannins, glycosides, and saponins. Quantification of phenols and flavonoids adds to the beneficial aspects of the fermented additives. The experimental results indicate that using naturally fermented organic materials in the lime has made the structures stronger with the stable build of calcite and vaterite components. The self-healing capacity of lime mortar makes it time resistant.

Influence of curing conditions on the mechanical and hydric performance of air-lime mortars with nano-Ca(OH)2 and nano-SiO2 additions

In search of compatible materials to speed up the strength and carbonation in lime mortars, nanoparticles show significant potential. This research explores the mechanical and physical characteristics of air lime mortars with silica sand and two types of dispersions based on nanoportlandite (nP) and nanosilica (nS) used as additions according to different curing conditions. Thus, samples kept under laboratory conditions (23 °C, 40% RH and 700 ppm CO2) and in a climatic chamber (20 °C, 75% RH and 1600 ppm CO2) were tested to understand the influence of environmental conditions in these types of systems. ResultsNanoparticle dispersions have a notable effect on the mechanical and hydric performance of lime mortars as a function not only of the components but also of the curing conditions. Solvents modified the water/binder ratio with an increase of microporosity and pore volume, which negatively affected mechanical and hydric properties. However, microporosity is reduced with nanoparticles which favours the deformation capacity of the mortars. Moreover, some interesting findings arise regarding the effect of solvent and the morpho-structural properties of calcium silicate hydrate (C–S–H). Differences in terms of morphology, fibre size, flexibility or content stand out, attending to the type of nanoparticles and the curing conditions. Air lime mortar with one part of nanoportlandite and 2 of nanosilica achieved the highest rates of carbonation and hydration products under chamber conditions compared to those located in laboratory conditions.

Characterisation of the progression of salts in walls of earthen architecture heritage

AbstractTwo hundred years (1750–1950) of earthen architecture represents an important period of construction in the central region of Portugal. Earthen architecture is usually built close to the coast or to rivers and placed in sandy ground. The impact of rising damp is a general problem and efflorescences are a common cause of damage decay. This problem was studied in a building with two types of earthen construction, adobe masonry walls and formed masonry walls. The aim of this research was to characterise the conditions for the appearance and phase transitions of thénardite and mirabilite, and determine how to prevent progression of salt effects in the two types of wall to support future conservation measures. Laboratory capillarity and porosimetry tests with dolomitic air lime mortar and hygrothermal monitoring were pursued along with in situ tests. Visual assessment showed that the progression of salts depends on the composition of the earthen materials. To understand these differences, all crystalline solid phases were analysed by powder X-ray diffraction, and building interior hygrothermal conditions were monitored. An investigation into the influence of surface lime water painting and sacrificial mortar application on the crystallisation of sodium sulfates concluded that these also depend on the wall's composition. Data allowed us to conclude that inside the building the temperature and humidity [relative humidity (RH = 100 pw/p°w > 70)] conditions led to the adobe breakdown by the fast conversion from thénardite to mirabilite. Therefore, contact with wet atmospheres should be avoided and interior hygrothermal conditions should be controlled. Laboratory and in situ tests showed that the environmental conditions of the spaces had effects on the results. The results contribute to understanding of the salt progression and pattern of decay, as well as supporting future recommendations for building conservation, based on the identification of environmental conditions proper to their occurrence.

Lime Based Construction Materials as a Carbon Sink

Lime is used in a variety of industrial sectors (e.g. construction materials, iron and steel industry, flue gas cleaning, etc.) By the thermal decomposition of limestone (CaCO3), known as calcination, two products are obtained: CO2 and quicklime, i.e. calcium oxide (CaO). There is a growing interest in quantifying and improving the potential of CO2 absorption of lime containing products during their operational life. The carbonation occurs during the lifetime of the lime application and it consists in the absorption of atmospheric CO2 that closes the loop by forming calcium carbonate back. Thus, a portion of the CO2 emitted during calcination is reabsorbed and stored in a permanent stable form. A literature review was carried out on the Carbonation Rate (CR) of lime used in three different construction materials: air-lime mortars, mixed air-lime mortars and hemplime. Out of 205 scientific publications reviewed, only 57 provide information about CR, specifically 21 for air-lime mortars, 27 for mixed air-lime mortars and 9 for hemplime. CR is 80-92% for pure air-lime mortars, 20-23% for mixed ones and 55% for hemplime. For all the materials, the CR trend over time was also assessed, according to the Fick’s law.

Experimental and Numerical Mechanical Characterization of Unreinforced and Reinforced Masonry Elements with Weak Air Lime Mortar Joints

This paper deals with the results of an experimental and numerical campaign aimed at characterizing the mechanical response of masonry components and panels made of limestone units kept together by weak air lime mortar joints. The selected air lime mortar, typical of ancient masonry buildings but difficult to be built-up artificially, was specifically prepared for the experimental analyses, with the aim of obtaining a laboratory compression strength of 0.25–0.50 MPa. In the first part of the paper, the performed tests concerning the strength of the units (mean compression strength of 80 MPa) and of the mortar (mean compression strength after 28 days of 0.30 MPa), are described for different curing periods. Moreover, tests of masonry triplets in shear (shear strength of 0.11 MPa for null axial forces) are shown and used in order to establish the main parameters of the Mohr–Coulomb failure criterium. Then, the calibration of a continuous numerical micro-model implemented in Kratos Multiphysics is presented. The model is used for reproducing the behavior of an unreinforced panel in shear made of the studied masonry and to appraise the effectiveness of a FRCM- (Fiber Reinforced Cementitious Matrix) based reinforcement intervention applied. The obtained results proved that FRCM allows to increase the strength of the considered masonry type by about eight times and the ductility by about thirteen times.

Effect of Type of Curing and Metakaolin Replacement on Air Lime Mortars for the Durability of Masonries

The interest in restoration and maintenance of old masonries towards their durability is nowadays combined with the concept of sustainability and the need to implement more suitable materials for building heritage interventions. This has led to the importance of having a better knowledge of air lime mortars, namely on the effect of pozzolanic additions, curing conditions and evolution at early stages. This study consisted in the characterization of mortars based on hydrated air lime and sand, with 1:2 (lime:sand) volumetric composition, with different weight percentages of substitution of lime by metakaolin (Mk): 0%, 10% and 20%. Mortar prisms were analyzed in three different curing environments: maritime (by the Atlantic Ocean), in laboratory humidity (95 ± 5% relative humidity, RH) and standard (65 ± 5% RH) conditioning. Tests were conducted to evaluate fresh and hardened properties of mortars, considering physical, chemical and mechanical performance at 28, 90 and 180 days. Results showed the viability of applying air lime-Mk mortars with curing conditions similar to the tested ones. In the standard curing, the mortar with 20% Mk revealed advantages in mechanical parameters. Concerning the behaviour towards water, improvements were shown at an early stage with the humid curing, while maritime curing benefited its behaviour for at least up to 6 months.