Building hydraulic lime

Over the centuries, other pozzolanic substances were blended with slaked lime to produce what are now called synthetic (or artificial) hydraulic limes. Both naturally occurring pozzolans (such as trass, found in Germany), and synthetic pozzolans (such as ground blast furnace slag) have been, and still are used. It was also found that some impure limestones, containing silica and alumina, produced slaked limes with a range of hydraulic properties. Such natural hydraulic limes were widely used in construction and building for mortar and concrete. 

A wide variety of lime products have been used in lime treatment. In general, however, calcium limes are recommended [26.4, 26.5], which meet the requirements for building lime [26.18]. Dolomitic and hydraulic lime products are less suitable, as indicated below. 

Limes for building purposes are specified in CEN Standard EN 459 [26.18]. They are divided into the 8 groups listed in Table 26.7. Calcium limes (CL, which may be in the form of quicklime, powdered hydrated lime, or putty) are sub-divided into three - CL 90, CL 80 and CL 70 — on the basis of their chemical analysis. Dolomitic limes (DL) are sub-divided into DL 85 and DL 80, also on the basis of their chemical analysis. Hydraulic limes (HL) are described in section 26.9. 

Building limes are limes used in building and construction, the main constituents of which, on chemical analysis, are the oxides and hydroxides of calcium, with lesser amounts of magnesium (MgO, Mg(OH)2), silicon (Si02), aluminium (AI2O3) and iron (Fc203). They include calcium limes, dolomitic limes and hydraulic limes (see EN 459). 

There ate proofs that already in buildings in Create the cmshed ceramic potsherds (minoyen culture) were added to lime to give it the hydrauhc properties [1]. On this basis the assumption was developed that Romans used firstiy artificial pozzolanic materials, before they check the natural pozzolanas. Jaworski stats that in twelveth century before Christ Phoenician used hydraulic lime to mortar building the temple in Cypms [2]. Already about tenth century before Christ they used the bricks flour as the admixture giving to hme mortar hydraulic properties [2]. 

The design of adhesive mortars was based on binders of either hydrate lime-metakaolin or natural hydraulie lime, with the aim of formulating a complex system characterized by the highest compatibility. Nowadays, both hydrate lime-metakaolin and natural hydraulic lime mortars are widely used in the field of restoration and conservation of architectural monuments, due to their capability to enhance the chemical, physical, structural and mechanical compatibility with historical building materials (stones, bricks and mortars) (Rosario 2009). This compatibility is a very critical prerequisite for the optimum performance of conservation mortars, considering the damage caused to historic monuments dming the past decades, due to the extensive use of cement-based composites. 

In the hiatus between 1970 and 2004, during which commercial sources of natural cement were absent, the importance of its technical and historical role was temporarily obscured. The use of Ume and hydraulic lime-based materials enjoyed a revival, but they do not accurately represent the major portion of mainstream, large-scale, 19" century building practices in the United States. Indeed, many of the advances achieved during that period were only made possible by the replacement of Mme-based technology with natural cement. 

A variety of materials, ranging from mineral binders to polymers, can be used as binder. However, materials based on polymers, such as epoxy or polyester resins, which are often used for concrete structures, should undergo careful assessment before use in historical masonry, due to possible issues regarding the mechanical and physical compatibility. Much more common for the repair of historical buildings are mineral binder systems based on cement or hydraulic lime with the addition of admixtures and fillers or aggregate. To inject bore holes, usually pure water/binder systems are used with typical w/b values of 0.8-1.0. However, the w/b ratio has to be adjusted according to the volume to be injected and to the moisture content of the substrate. 

Category 1 building lime — hydrated 2 building lime — putty 3 hydraulic building lime 4 high calcium quicklime — hydrated lime 5 high calcium quicklime — milk of lime 6 hydrated lime... 

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