Natural Hydraulic Limes Research Articles

The manufacture of natural hydraulic limes: Influence of raw materials' composition, calcination and slaking in the crystal-chemical properties of binders

This study aims to achieve an in-depth understanding of the manufacturing process of natural hydraulic lime (NHL) by assessing the influence of raw materials' chemical- mineralogical composition and the effect of the slaking process. NHLs with variable hydraulicity were manufactured using 56 raw materials from carbonate outcrops in Andalusia (Spain). This study shows that siliceous limestones with microcrystalline quartz generate hydraulic phases after calcination. However, when the amount of this reactive silica exceeds 18% by weight, CaO is not formed, and only calcium silicates appear. It was also found that slaking of NHL leads to partial hydration of the most reactive calcium silicates, reducing the expected reactivity of the lime. Instead, exposure of NHL quicklimes to environmental relative humidity promotes the formation of disordered portlandite and reduces the partial hydration of hydraulic phases. Our findings demonstrate that standard slaking can be replaced by alternative methods for the studied binders.

Piezoresistive Properties of Natural Hydraulic Lime Binary Pastes with Incorporated Carbon-Based Nanomaterials under Cyclic Compressive Loadings.

Natural Hydraulic Limes (NHL) are extensively used for the restoration of Monuments of Cultural Heritage, often combined with pozzolanic materials, such as natural pozzolans and metakaolin etc. In the present study, five (5) different cases of binary lime-based pastes composed of a specific type of NHL (NHL5) and metakaolin as pozzolanic addition were examined, that were reinforced with carbon nanostructures, namely graphene and carbon nanotubes. For the first time in restoration mortars, the incorporation of carbon nanostructures was investigated, aiming to produce materials with adequate piezoresistive response, so that they have the potential to be exploited for in situ structural health monitoring. The compressive strength, flexural strength, electrical resistance and piezoresistive response of the composite pastes was examined. The results showed that all modified carbon nanostructures lead to a significant reduction in electrical resistance. The pastes reinforced with 2D nanostructures (graphene family) displayed up to 30% increase in compressive strength and the pastes reinforced with 1D nanostructures (carbon nanotubes) displayed enhanced flexural strength (up to 100% increase). Piezoresistivity was attained for almost all investigated pastes, nevertheless the graphene oxide (GO) was considered as optimal reinforcement as the sensing ability of such pastes was found to be almost proportional to the applied compressive load level.

The micro-structural character of limestone and its influence on the formation of phases in calcined products: natural hydraulic limes and cements

The micro-structural character of limestone and its influence on the formation of phases in calcined products: natural hydraulic limes and cements

LIKE-FOR-LIKE AND COMPATIBLE MORTARS FOR THE REPAIR OF TRADITIONAL BUILDINGS

Abstract. The subject of this paper is traditional mortar preparation and materials, particularly earth-lime and air or feebly hydraulic hot mixed lime mortars with particular emphasis upon British practice and experience, whilst stressing their international ubiquity historically. It will demonstrate their appropriate functional performance and attest to the need to use similar mortars, similarly composed and prepared, in the repair and conservation of traditionally constructed buildings. It will question how commonly modern Natural Hydraulic Limes may be considered to be like-for-like or of compatible strength and functional performance. The paper will draw upon extensive research into historic texts, as well as primary archive research into historic building accounts and the latest research into the properties of lime rich air lime mortars and NHL mortars.

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.

Assessment of the effect of natural hydraulic lime on the stabilisation of compressed earth blocks

Earthen construction is an alternative construction method that allows for the reduction of the embodied energy of building materials and the promotion of sustainability in the construction sector. Among the different earthen building techniques available, compressed earth blocks offer a remarkable potential for industrialisation. Due to the drawbacks associated with the use of non-stabilised blocks, such as the impact of weathering, previous researches had addressed the development of compatible stabilisers for performance improvement. Lime is a traditional binder whose properties are compatible with earth, especially when fine particles are present. Yet, there is limited research on the use of natural hydraulic lime, as most previous studies have focused on the use of hydrated lime, which requires an extended curing time.In the present study, two types of natural hydraulic limes (NHL2 and NHL3.5), in ratios ranging from 3% to 12%, were investigated for the stabilisation of compressed earth blocks. The results revealed that the replacement of soil with lime led to a reduction of the bulk density of the samples of up to 12.8% while increasing their mechanical strength by 48–56% and 12–35% in NHL2 and NHL3.5 respectively. Furthermore, the type of lime has a clear influence on the pore size and volume, and consequently, on both the capillary absorption and the absorption under atmospheric pressure. The results suggested that the addition of NHL2 induced an increase in pore size and volume, in line with the behaviour exhibited by hydrated lime, while the opposite took place when NHL3.5 was used.

Traditional hot mixed lime mortars for conservation and repair

Earth-lime and hot mixed lime mortars were the almost ubiquitous materials of traditional construction over many thousands of years but have been sorely neglected, if not ignored, by a building conservation community philosophically wedded to the principle of like-for-like and compatible repair in favour of materials with minimal historic precedent for the purposes to which they have been put. This situation has begun to change over recent years based upon growing craft experience using these mortars once more, as well as mounting evidence of the damaging potential of modern natural hydraulic limes (NHL). Historic England, Historic Scotland and CADW are reiterating the demand for like-for-like repair of historic fabric and, in most cases, this will indicate the use of hot mixed air lime or feebly hydraulic hot mixes.

Rheology of lime pastes with biopolymer-based additives

The use of industrial limes implies obtaining mortar pastes with worse plasticity and workability compared to lime putties. To overcome this inconvenience, a great number of additives can be used, the majority of them being plasticisers and water-retaining agents. In this work three natural polysaccharides with hydrogel properties (agar–agar, alginate and hyaluronate derivatives) were added to dry-hydrated and natural hydraulic limes to investigate their influence on the rheology of the lime suspensions, as a function of the mixing and dissolving procedures, the additive type and concentration, and the type of lime. Rheological measurements have shown that the yield stress and viscosity of the lime pastes are increased if the additives are pre-mixed with water before adding the lime powder. All additives significantly increase the rheological parameters of the natural hydraulic lime pastes (with a maximum additive concentration of 0.2 g in 1 L of water) but only sodium hyaluronate is effective when mixed with dry hydrated lime. Notwithstanding this, sodium hyaluronate-lime pastes have shown a time-dependent behaviour that must be taken into account during mortar formulation and use. This study lays the foundations for the development of new sustainable lime mortars made with additives derived from natural sources.

Experimental Study and Modeling of Rheological and Mechanical Properties of NHL Grouts

AbstractThis paper aims to model the effect of grout composition on properties of two natural hydraulic lime (NHL) grouts based on the correlation between grout rheometer results and simple flow tests. First, the effects of water:binder ratio and superplasticizer dosage on its rheological properties and flowability were analyzed. Dosage of superplasticizer and water:binder ratio were varied from 0.6 to 1.2% (by mass of binder) and 0.45–0.55, respectively. A good correlation between classical flow tests and the rheological properties was obtained. Then, statistical models were formulated in order to estimating the grout parameters, such as plastic viscosity and yield stress just by performing simple flow tests. The models coefficients were calculated using multiple regression analysis. The statistical modeling results indicated that the properties of the grouts studied are linearly related to water:binder ratio, superplasticizer dosage, and specific surface area of natural hydraulic limes. Finally, the acc...

Determination of optimal burning temperature ranges for production of natural hydraulic limes

There has been an increasing interest in the reproduction of natural hydraulic limes, as they are considered an appropriate material for conservation and restoration of historic buildings. This study assessed the influence of different calcination temperatures (850–1200°C) on the mineralogical composition and the reactivity of quicklime, as well as the setting time and the mechanical performance of mortar specimens. The limestone was acquired from a single quarry and contained 8.7% SiO2, 45% CaO. The results of XRPD and slaking reactivity of the produced quicklime confirmed a clear dependency on the calcination temperature. The performance properties of mortars made with the produced lime did not demonstrate a clear relation to the calcination temperature. The experiment confirmed that calcination temperatures from 850 to 1200°C can be used to produce natural hydraulic lime from the selected limestone. The optimal calcination temperature range from 1000 to 1100°C is recommended.

The effect of aggregate size and type of binder on microstructure and mechanical properties of NHL mortars

Natural hydraulic limes are used as an alternative to cement-based binders in mortars and renders for the repair and maintenance of historic structures as well as in new building. This paper discusses the role of the binder type, the grain size and the packing density of aggregates on the physico-chemical and mechanical characteristics of hydraulic lime mortars. Empirical formulae connecting the compressive strength with: (a) dynamic modulus of elasticity and (b) mean pore radius, have been extracted and discussed. Overall, the results have indicated that the microstructure of the binder and the packing density aggregates are the parameters that dominate the performance of the hydraulic mortars and therefore should be seriously considered during field applications.

Building limes for cultural heritage conservation in China

Lime has been used as a building and decoration material for thousands of years in China. Recent research has focused on developing new air lime with higher bonding strength, grouts and restoration mortars etc. based on natural hydraulic lime, which is both chemically and mechanically more compatible with historic substances. The most applied lime in China was, and is still air lime, and the traditional slaking and preparation technique has been passed over to the modern generation for most restoration projects. Optimum dosage of Tungoil to lime-earth as damp proofing barrier lies at app. 5 wt%. A kind of patented dispersed air lime modified with additives has been developed, which can be applied as a binder for restoration of traditional lime ornaments or lime paints. Natural hydraulic lime has been introduced into China from 2008 Recently, adhesives and grouting slurries based on natural hydraulic lime have been developed and applied for refitting and cavity filling of delaminated cultural surfaces with proven satisfaction. The preliminary research works show, both air lime and natural hydraulic limes through modification of latest construction chemistry achievements can meet most of restoration requirements.

Application of 1H NMR to hydration and porosity studies of lime–pozzolan mixtures

1H nuclear magnetic resonance (NMR) relaxation is applied to lime–pozzolan mixtures to monitor in real-time the hydration and porosity evolution during setting. The hydrated products formed during the setting of these mixtures are similar to those formed in hydraulic binders (e.g. cement and natural hydraulic limes). In this work, we demonstrate that by using a portable, low field (0.29 T) Halbach magnet it is possible to study in detail, the evolution of the pore structure, modified through the formation of C–S–H and C–A–H, by means of the 1H NMR technique. Contrary to the standard porosimetry methods, which require drying procedures before analysis, NMR is a non-invasive straightforward technique, allowing the study of the hydration kinetics in real-time, during the setting and hardening of the lime–pozzolan binding system. Thus, by measuring the 1H NMR spin–lattice relaxation T 1 of two lime–pozzolan mixtures, it was possible to distinguish between different pore populations within the system (at different setting periods), and to study the growth of the hydrated phases. The interpretation of the results proved that, similarly to mercury intrusion porosimetry (MIP) and nitrogen adsorption, 1H NMR probes the development of the pore structure within the lime–pozzolanmortar matrix, indicating key changes of pore size populations.

Effect of Dewatering on the Strength of Lime and Cement Mortars

This paper investigates the effects of dewatering on the strength and microstructure of mortars manufactured from Portland cement, hydrated calcium lime (CL90), and natural hydraulic limes of classification 2, 3.5, and 5 with binder/aggregate/water ratios of 1:2:0.78. Dewatering was achieved by placing the mortars on a high porosity brick. Dewatered and nondewatered specimens were exposed to an atmosphere containing 400 ppm carbon dioxide with a relative humidity of 65%, at 20°C for periods of 14, 28, and 56 days. Following hardening for these periods, compressive strengths were compared with evaluate the mechanical performance. The structural morphology of the samples was determined using scanning electron microscopy and chemical composition by Raman spectroscopy. Results showed CL90 mortars are unaffected by dewatering. However, dewatering resulted in an increase in the compressive strength for the hydraulic limes and cement mortars tested.

Quantitative phase analysis of hydraulic limes using the Rietveld method

Quantitative phase analyses of three commercial samples of hydraulic limes have been performed using the Rietveld method. Although the Rietveld method has been already applied to cement analysis, we report here the first application to different classes of hydraulic binders, such as hydraulic limes (HL) and natural hydraulic limes (NHL). Unlike HL, that are simple diluted cement, NHL are specific product of great interest for its application in building restoration and conservation. Samples were also characterized by laser granulometry and chemical analysis. Thermogravimetric analysis/Differential Scanning Calorimetry (TG/DSC) and calcimetric analyses were conducted to compare the results of such well-established techniques with those obtained with the Rietveld method. Taking advantage of the Rietveld method with the addition of an internal standard, the phase fraction of all the crystalline phases as well as the amorphous component, have been accurately determined. This technique offers a valid support for the characterization of hydraulic limes in the light of the EN classification of such industrial products.

Succeeding with Hydraulic Lime Mortars

The paper describes what natural hydraulic limes are, how they relate to hydrated lime or Portland cement, and the role of pozzolanic materials when used in conjunction with them. The applications for natural hydraulic limes, including their benefits in terms of flexibility and permeability and their limitations in terms of speed of strength development and necessary curing precautions, are explained. The paper sets out some of the common misconceptions in understanding the basic materials and common mistakes encountered on apparently well-controlled sites, and outlines the provisions to be included in the code of best practice being developed as part of a the Foresight lime project.

5544760 Flotation of lead sulfides using rapeseed oil : Benn Freddy; Dattilo Mario; Cornell William L Rolla, MO, United States

There has been an increasing interest in the reproduction of natural hydraulic limes, as they are considered an appropriate material for conservation and restoration of historic buildings. This study assessed the influence of different calcination temperatures (850–1200 °C) on the mineralogical composition and the reactivity of quicklime, as well as the setting time and the mechanical performance of mortar specimens. The limestone was acquired from a single quarry and contained 8.7% SiO2, 45% CaO. The results of XRPD and slaking reactivity of the produced quicklime confirmed a clear dependency on the calcination temperature. The performance properties of mortars made with the produced lime did not demonstrate a clear relation to the calcination temperature. The experiment confirmed that calcination temperatures from 850 to 1200 °C can be used to produce natural hydraulic lime from the selected limestone. The optimal calcination temperature range from 1000 to 1100 °C is recommended.