Aerial Lime Mortars Research Articles

Impact of in-situ CO2 injection on natural and accelerated carbonation performance of aerial lime mortar

Aerial lime is a well-known carbonatable binder. To address some limitations of slow carbonation speed and low initial strength, this study proposes an internal carbonation technique for field-casting aerial lime mortar using in-situ CO2 injection. The technique was found to be significantly effective in accelerating the carbonation and strength development of the mortar. For the first 28 days, the mortars mixed with CO2 injection showed 1.25–1.68 times faster carbonation and 1.5–2.3 times higher compressive strength than the mortar mixed without CO2 injection. This improvement can be explained by the internal carbonation effect, which effectively refines the pore structure while providing a nucleation site for subsequent carbonation. The early refinement of the pore structure also increased later carbonation performance under both natural and accelerated conditions.

Effect of curing conditions and formulation on the adhesive strength of stone-siporex mortar composite

Background: Adhesive strength is one of the most important properties of the hardened mortar, and influenced by mortar workability (i.e. mortar water content), and substrate roughness surface degree. Objective: This study aims to measure the adhesion strength between three different hydrated aerial lime mortars, and the two most common building units in old and modern building in Loire valley in France: Tuffeau and Siporex, under different relative humidity (12,66,98%) and curing periods (7,28,90 days). Materials and Methods: These mortars include: B/F (1:5.6: Moisture=46 %, aggregate stone powder pass sieve NO.2mm), B/W (1:5.6: Moisture=44 %, aggregate stone powder pass sieveNO.2mm and retained on sieve NO. 0.16mm), and B/F/M (1:5.6: Moisture=35%: superplasticizer water reducer Melment F10 (2.5% of lime amount), aggregate stone powder pass sieve NO.2mm). Numerous complementary techniques have been used to achieve this study, such as: x-ray diffraction, coupled plasma optical emission spectrometry, mercury intrusion porosimetry, mortars axial expansion by consolidation apparatus, and Proceq-DY-215 apparatus for adhesive strength measurement. Results: The results showed that expansion of B/F, B/W, and B/F/M has little effect on their adhesion strength with Tuffeau /Siporex substrates. Also, the adopted relative humidity variations had a limited effect on the adhesion strength of B/W along the curing periods (7, 28, and 90 days), with noticeable effect for the other mortars. Conclusions: The conclusions referred to the important impact of the degree of substrate surface roughness on the adhesive strength of all used mortars, where the use of Siporex as substrate recorded a clear advantage compared to Tuffeau under all used relative humidity and curing periods.

Characterization of archaeological lime mortars in a Ming dynasty tomb: A multi‐analytical approach

AbstractLime mortars have played an important role in constructing ancient Chinese masonry structures, including city walls, buildings, and tombs. A tomb built with lime mortars and stones belonging a Ming high‐ranking official, Xu Jie, was discovered in Huzhou City of China. Eight different samples from Xu Jie’s tomb, representing four types of lime‐mortar‐based materials: joint mortar between stone bricks, bedding mortar, grouting mortar, and plaster mortars were collected for analysis and comparison. The characterization of the construction materials has therefore become of primary importance. The function of each mortar was reported and studies into the micro‐textural features and mineralogical compositions of those mortars were performed via a multi‐analytical approach. The joint mortars were all found to be aerial lime mortars with predominately lime. The bedding mortar was found to consist of lime, soil and sand, typical of a tabia mortar. The grouting mortar was found to consist of lime and ground contact metamorphosed limestone. Analysis of plaster sample taken from the roof of the main tomb identified the presence of calcium stearate/palmitate, indicating the usage of plant‐based tung oil as an additive. The analytical results will promote our understanding of Ming architectural technology and craftsmanship, and provide critical information for the conservation of Xu Jie’s tomb.

Chitosan as a carbonation catalyst in lime mortars

The investigation evaluates the influence of unmodified chitosan on the carbonation behavior of aerial lime mortars, determining the main properties in hardened state. The work was developed experimentally, starting from lime pastes elaborated according to European Standards. Initially, different contents of chitosan were dissolved in the mixing water, keeping constant the quantity of aerial lime and water, according to the consistency standardized by the type of lime. The samples cured for 4 days in an oven at 30 °C, were subjected to a carbonation process. The carbonation conditions established for the lime samples, with and without chitosan, were in all cases the same. It was observed that the chitosan content positively influences the kinetic reactions of lime with CO2, modifying its mineralogical, macro and microstructural properties and improving its mechanical behavior.

Aerial Lime mortars: An introduction and a brief discussion / Argamassas aéreas de cal: Uma introdução e uma breve discussão

In the history, different mortars compositions have been used during the ages in masonry structures. Lime was frequently adopted in the past. In summary, there are two main types of lime: hydraulic and non-hydraulic (aerial). The present review deals with the second type. Herein, the studied lime is specially obtained from the thermal decomposition, called calcination, of limestone (calcium carbonate (CaCO3). Aerial lime mortars have a complex structural behavior. Several aspects influence the material performance. It should be highlighted the carbonation process; it modifies the material properties in time.Historic buildings are subjected to longer exposures, with changing and often unknown environmental conditions, affecting the structural behavior. In the present work a literature review about the use and application of aerial lime mortar as binder in historical mortars is discussed. There are relatively few studies about aerial lime mortar in literature, in this sense the work aims to contribute to the theme. The present text is partially based on the PhD thesis of the first author.

Simulation of humidity fields in aerial lime mortar

• Pioneering simulation of humidity diffusion in aerial lime mortars. • Modeling the humidity diffusion in aerial lime mortar using a model proposed to concrete. • Modeling strategy able to appropriate simulate the experimental results. • Best pair of D 1 and f boundary presenting values higher than in concrete. The structural safety of historic buildings frequently demands an advanced structural analysis. These constructions often have cultural and architectonic values and were constructed with porous materials bond with mortar. Mortar usually presents a complex composition and structural behavior. This fact supports the requirement for a meticulous analysis of the role of mortar within the scope of the structural behavior of historic masonry construction. In different parts of the world, there is a significant quantity of historic constructions comprehending binders based on aerial lime mortars. Aerial lime is one of the oldest binders discovered and used. Moisture content in aerial lime structures has an important influence on their behavior and performance. An experimental program was developed to study the humidity flux in aerial lime mortar including the self-desiccation phenomenon. In order to simulate this drying process, a software based on a Finite Difference Method Algorithm (1D and axisymmetric cases) is used. The pioneer software used to identify the main material parameters that better fit the experimental data, considering the approach presented by Model Code 2010. The modeling strategy was firstly applied to experimental results of cylinders specimens and in sequence to experimental results of a prismatic mold. In general, the model was able to satisfactory fit the experimental results. When compared to concrete material, higher values for diffusivity and for boundary coefficient were found. For the studied specimens, the experimental and numerical results indicated reduced humidity gradient. These results are probably associated with the high porosity of the mortar.

New insights into the use of drilling test for the characterization of soft lime mortars

In this paper, the results of drilling tests performed on different formulations of aerial lime mortars are presented. A new methodology of analyzing results is proposed to overcome the well-known difficulties in the back-analysis of soft mortar drilling profiles, due to their scattering. A new parameter (AN) is introduced, which showed a good correlation with porosity, ultrasonic pulse velocity, and uniaxial compressive strength of the mortars. AN, used together with the other drilling parameters in bilinear models, improved their correlations with the compressive strength. The influence of the drilling setting conditions on the frequency distribution of the drilling forces is also investigated. It was found that the ratio between the penetration rate and rotational speed strongly affected the shape of the distributions.

Characterization of Fresh and Durability Properties of Different Lime Mortars for Being Used as Masonry Coatings in the Restoration of Ancient Constructions

Coatings and plasters are an integral part of masonry cladding, having a fundamental protective and aesthetic function. They are exposed to numerous aggressive actions, which produce their degradation over time. The utilization of lime, as a binder in masonry lining mortars, plays an important role in their durability and conservation. The objective of this work is to analyze the fresh and durability properties of lime-based mortars for their application in the restoration of old buildings. Four different kinds of mortars were studied with similar workability, using as binders lime putty, aerial lime, and hydraulic lime. The aggregates used consisted of sand and crushed rock powder. As fresh properties, the consistency (by using the flow table) and water retentivity were determined. With respect to durability-related properties, water absorption by capillarity and by immersion, drying kinetics, and carbonation depth were studied. Bulk density and porosity of the mortars were also obtained. Mortars with lime putty showed higher global porosity and water absorption by immersion, while aerial lime mortars presented lower porosity and higher water absorption by capillarity. Finally, the durability performance of all the studied lime mortars was overall adequate for being applied as masonry coatings in the restoration of old buildings.

Erosion of aerial lime and sticky rice mortars by cyclic wetting–drying and dilute sulfate acid actions

Lime mortar with organic additives is one of the most widely used building materials in ancient China and continues to play an important role in historic structure restoration. This study investigated the erosion of ordinary aerial lime and sticky-rice mortars under the cyclic actions of wetting–drying (WD) and dilute sulfate acid (DSA). Comprehensive experimental tests were conducted to study the mechanical properties, quality, microstructure and pore structure of the mortars according to cyclic WD and DSA actions. Results showed that both the WD and DSA actions can significantly degrade the compressive and shear strengths of the mortars. The DSA softens the mortar matrices more severely than the WD by a leaching mechanism. Apparently, sticky rice does not change the micro morphology, pore structure and packing pattern of the mortar matrices, but it inhibits the carbonation of the lime. Both the WD and DSA actions can erode the ordinary aerial lime and sticky-rice mortars, causing more porous matrices and coarser particles. The results of this study make it possible to clarify how the WD and DSA actions affect the durability of partially matured aerial lime mortars with or without sticky rice, with potential uses in the restoration of ancient buildings.

Loading-Rate Effect on the Fracture Response of Natural Hydraulic and Aerial-Lime Mortars

This paper presents the influence of the loading velocity on the fracture response of mortars with both natural hydraulic and aerial limes under three different rates (loading-point displacement rates, 5.0×10−4, 5.0×10−1, and 1.6×101 mm/s). According to the results, the fracture energy and the peak load are sensitive to the loading rate. The maximum dynamic increase factors (DIF), of the peak load are 1.4 and 1.6 for the natural hydraulic and aerial lime mortars, respectively, while it is 1.9 for the fracture energy for both mortars. Moreover, the increase in the peak load and fracture energy of the natural hydraulic lime mortar is basically the result of the viscous effect of free water in the mortar. However, for the aerial lime mortar, the rate effect is chiefly related to the crack path and propagation velocity.

Characterization of ancient building lime mortars of Anhui province, China: A multi‐analytical approach

The characterization of lime mortars has become of primary importance in order to obtain information about the raw ingredients and building technology of ancient masonry structures. Five different samples from Anhui province, China, representing two types of lime mortar‐based materials: joint mortars between the bricks of the city wall and lime mortar sealing a tomb coffin, were collected for analysis. Archaeological information about the samples was reported and studies into the microtextural features and mineralogical compositions of those mortars were performed via a multi‐analytical approach. The joint lime mortars between the bricks of city walls, including Mingzhongdu city wall, Mingzhongdu Xihua gate foundation, Zhengyangguan city wall and She county city wall, were found to be aerial lime mortars. The lime mortar from Nanling Tieguai Song dynasty tomb was analysed and found to be a pozzolanic mortar consisting of lime, clay, sand and cocciopesto‐like materials. The analytical results serve as a critical reference for the maintenance and restoration of ancient city walls in Anhui province, and as a starting point for searching for ancient Chinese pozzolanic mortars and technology for making those mortars.

Controlling the hydration and carbonation in lime-based materials: Advantage of slow carbonation in CO2 curable construction materials

In this study, the role of natural additives (sodium chloride or sugar) in aerial lime mortar was elucidated. It was found that both the hydration and carbonation were accelerated by sodium chloride but retarded by sugar. Especially, sugar prevented the rapid clogging of pores around the mortar surface, which caused the even formation of calcium carbonate crystals throughout the volume of mortar. Therefore, the strength development was significantly accelerated. The slow carbonation and resulting rapid strength development can be practically implementable since it does not rely on long term atmospheric carbonation or use of high concentration of CO2 gas.

Impact of a viscosity-modifying admixture on the properties of lime mortars

Viscosity-modifying admixtures are frequently used in mortars to improve their fresh state properties, especially in pre-mixed products, with consequences for their hardened properties. However, the knowledge on the influence of these admixtures on lime-based materials is still incipient. In this context, this paper intends to analyse the impact of a viscosity-modifying admixture (VMA) in the fresh and hardened state properties of aerial lime mortars. In the fresh state, the VMA led to a thickening of the lime suspension, which translated into a progressive increase in torque, plastic viscosity and yield stress (after an initial decrease) with increasing dosage. At the same time, it increased air content, which made the mortars easier to handle, and increased the bleeding rate, but the amount of bleed water was lower. In the hardened state, the VMA did not improve mechanical strength owing to a porosity increase (based on a rise in large pores).

Age effect on the mechanical properties of natural hydraulic and aerial lime mortars

This paper focuses on the advanced mechanical characterization of natural hydraulic and aerial lime mortars presenting a lime/aggregate ratio of 1:3 and a water/lime ratio of 0.9. Seven properties, such as density, flexural, compressive and splitting tensile strengths, fracture energy, elastic modulus from prisms and carbonation depth by means of the phenolphthalein method, were measured at different moments. The results show that the greatest increase in the mechanical properties of both mortars occurs up to the first 56 days. This increase ranges between 60% and 90% of their corresponding value at an age of 448 days depending on the mechanical property and type of mortar. Between day 56 and day 224, there is a more moderate, but progressive evolution. However, after day 224, the evolution of the mechanical properties in light of their mean value, is very slow for the aerial lime mortar and shows a slight increase for the natural hydraulic mortar. Furthermore, various empirical equations of such behavior over time are proposed for both mortars.

Sustainable polymer-based Phase Change Materials for energy efficiency in buildings and their application in aerial lime mortars

An experimental study aimed at investigating the possibility to produce a Phase Change Material (PCM) for mortars by incorporating through the “form-stable method” a thermoplastic low-melting polymer (PEG 1000) into a porous inert substrate (i.e., Lecce Stone), obtained as residue from processing stone, is reported. The viscosity of pure PEG at different temperatures was first assessed to identify an appropriate processing temperature to introduce fluid PEG into the pores of the stone. A complete (chemical, thermal and morphological) characterization was performed on the developed PCM composites, varying the impregnation times. Aerial lime-based mortars were produced with the addition of the selected experimental PCM composite, taking as comparison the mortar containing only the stone as inert aggregate. On the different mortars, mechanical tests were performed in both compression and bending mode and the thermal conductivity was measured.

Cylindrical samples of brick masonry with aerial lime mortar under compression: Experimental and numerical study

This research presents an experimental and numerical study focusing on the compression test of cylindrical samples core drilled from existing masonry walls. This method is suitable for the minor destructive assessment of the mechanical properties of historical masonry, like that composed of aerial lime mortar joints and solid clay bricks. This particular material combination, frequently found in the vast majority of the built cultural heritage, was utilized to build representative specimens that were stored in the laboratory for one year until their testing. Cylindrical samples of 150 mm diameter were extracted from the masonry walls by using a dry core-drilling procedure, and then regularized to be tested under compression in the laboratory. A comparison is presented between the experimental results on cylindrical samples and those obtained from standard compression tests on prismatic samples consisting in stack bond prisms. Numerical simulations by finite element micro-modelling of the compression tests on the core samples were carried out to investigate the experimental behaviour of the specimens and evaluate the compressive strength of the material from this nonstandard technique. The combined experimental and numerical study allows the assessment of important mechanical parameters for the compressive characterisation of masonry composed of aerial lime mortar joints and solid clay bricks.

Fresh and hardened state behaviour of aerial lime mortars with superplasticizer

Water-reducing admixtures have the potential to minimize the disadvantages that typically discourage the use of lime in restoration works. However, the knowledge on the effect of these admixtures on the properties of lime mortars is not as consolidated as it is for cement-based materials. Therefore, this paper aims at studying the influence of two types of superplasticizer, one based on polycarboxylate ether (PCE) and the other on polynaphthalene sulfonate (PNS), on the fresh and hardened state properties of lime mortars. PCE was found to be more effective (higher dispersing ability) and efficient (less quantity needed) than PNS, leading to a lower fluidity loss over time, but to a higher tendency towards bleeding. Both admixtures led to a substantial mechanical strength increase, even at early ages, and just to small changes in the porous structure of the mortars, which suggests that lime mortars with superplasticizer have potential to be used in restoration.

Assessment of historic brickwork under compression and comparison with available equations

Abstract There is a lack of knowledge related to laboratory results on historic brick masonry made from lime mortars, given the time necessary to assure the mortar carbonation. Thus, this study contributes to the mechanic characterization, after 730 days of curing, of brickwork made from old solid clay bricks, acquired from building demolition, and two types of low-strength aerial lime mortars. Besides, the physical-mechanical characteristics of materials (bricks and mortars) were analysed over time. The experimental values were compared with analytical ones obtained using the main recommendations, research works, standards and the empirical equation obtained in this study. The most adequate analytical formulations are identified.

Evolution of mechanical properties in aerial lime mortars of traditional manufacturing, the relationship between putty and powder lime

In recent years, numerous studies have been published on the technology of industrial aerial lime mortars. These papers refer to the incidence of carbonation process and mechanical behavior in its properties as construction material, of interest for its application in Cultural Heritage conservation. Among other issues, the importance of the type of aggregate (composition and granulometry) and relation binder/water (B/W) in its properties are highlighted. There are fewer papers in which the type of lime is about, especially on the basis of its manufacturing process (traditional or industrial), on the presentation of the product (powder or putty), or referred to the different types of mortars (prepared in situ or pre-dosed). In this paper, the behavior of aerial lime mortars elaborated with traditional lime has been determined and a comparative study has been carried out with pre-dosed mortars of powder (mCL) and in putty (mSPL) lime for its application in render mortar (B) and plaster mortar (F). The control parameters have been mechanical resistances-elasticity, ultrasound velocity, carbonation process and distribution pore size and surface area by mercury porosimetry. It is concluded that the behavior of traditional lime mortars, both in putty and powder, depends on the B/W ratio, the type of aggregates and the lime content. The importance of the application of the product in the building as the behavior of the mortar is very sensitive to kneading water content it shows; aspects that define the plasticity of the mortar. It is also concluded that the carbonation of traditional lime mortars is not slow and that, under optimal dosages conditions, can be finished before 90 days. It is also verified that a higher carbonation rate does not imply better properties of the mortar in its long-term construction. The utility of ultrasound velocity test as a non-destructive test and easy to apply on building for the quality control of traditional lime mortars and its consistence values it highlights, as is a macroscopic property of easy control during the elaboration of the product.

Comparing the pozzolanic activity of aerial lime mortars made with metakaolin and fluid catalytic cracking catalyst residue: A petrographic and physical-mechanical study

We investigated the viability of a fluid catalytic cracking catalyst residue (FC3R) as an alternative sustainable pozzolanic additive in aerial lime mortars. The pozzolanic activity of FC3R was compared to that of metakaolin (MK) by chemical-mineralogical, petrographic and physical investigations. The FC3R showed lower pozzolanic activity than MK when added to aerial lime mortars, owed to the size of FC3R particles that generate less hydrated phases and give place to lower mechanical resistances in mortars. We also demonstrated that FC3R is not a compatible material for use in repair mortars, due to the formation of the harmful soluble salt ettringite.