Early mortars were produced by calcining limestone in a kiln and slaking it for long periods of time in water creating lime putty. This was necessary to enhance the workability and the soundness of the mortar. Locally available sand was added to the slaked lime putty to create lime mortar. These mortars were used to construct masonry walls containing brick, block or stone. The lime in these mortars absorbed carbon dioxide from the air to convert it back to its original chemical form (limestone). This process was slow and further inhibited in underwater applications.
To increase the speed of construction, pozzollans such as brick dust and volcanic ash were added to lime. Natural cements and hydraulic lime products were produced by calcining limestone high in silica content or with clay. These products would develop strength without the addition of pozzollans and would set under water.
In the early 1870s portland cement was introduced in the United States. Portland cement provided a more uniform alternative to pozzollans, natural cement and hydraulic lime and became widely used. Combinations of lime and cement were developed using alternate letters of the phrase MASON WORKS. Type M mortar is the strongest mortar with the least lime and Type K is the weakest mortar with the most lime. In these formulations, lime enhances workability, water retention and bond strength. The carbonation of lime also enhances long term strength development.
There are several types of hydrated lime products defined for masonry applications in the ASTM standard C207 (Standard Specification for Hydrated Lime for Masonry Purposes).
Type N, or Normal hydrated lime, products are only partially hydrated and/or have poor workability. Additional additives and/or long soak periods are required for these products to perform effectively in masonry applications. ASTM C270 (Mortar for Unit Masonry) specification states that if a portland cement-lime blend contains Type N hydrate, the blender must show through performance testing that the Type N product is not detrimental to the soundness of the mortar.
Type S, or Special hydrated lime products are a combination of calcium and magnesium hydroxides. In building applications, Type S dolomitic hydrated lime products have high hydration levels and controlled plasticity (water retention). This allows for minimal soak periods prior to application.
Both Type N and Type S hydrated lime products can contain air entrainment additives. Air-entrained lime products must have a minimum air entrainment level of 7% and a maximum air level of 14%.
Modern cement-lime mortars can be specified by the properties (air content, compressive strength and water retention) of the mortar or by volume proportions of cement, lime and sand according to ASTM C270 (Standard Specification for Unit Masonry) requirements.
Graymont's building lime product manufacturing plants are located in Genoa, OH and Eden, WI. Graymont masonry products offer exceptional plasticity for increased water retention and workability in mortar applications.
Super Limoid® Type S, Miracle® Type S and Mortaseal® Mason's Lime are fine-grind, white, high-purity dolomitic limes, fully hydrated for immediate use. These products both comply with ASTM C207 standards for a Type S hydrated lime. When properly combined with portland cement, they create a lime mortar having excellent bond strength, water retentivity and weather resistance at an economical cost. These products are available in 50 lb. bags or bulk.
Super Limoid® Type SA and Bondcrete® Stucco Lime are air-entraining hydrated lime products which are pressure-hydrated for immediate use in stucco applications. These products meet the requirements of ASTM C207 for a Type SA hydrated lime. When properly combined with portland cement and sand, it creates a stucco having superior performance, economical results and ageless durability. Type SA hydrated lime should not be used in smooth coat plaster applications. These products are available in 50 lb. bags or bulk.
Niagara® Mature Lime Putty is a high-purity dolomitic lime putty fully slaked and screened for immediate use. Niagara Lime Putty is slaked for a minimum of 2 months and complies with ASTM C1489. This product is available in 45 gallon drums or 3 gallon pails.
Graymont distributes two blended hydraulic lime products, BL150 (Building Lime 150) and BL200 (Building Lime 200), for Virginia Lime Works. These products have been designed for use in restoration applications. They can be used in repointing, plastering, and grouting applications on historic or contemporary projects. These products are perfect for restoration applications where ordinary Portland cements or masonry cements are not compatible with the existing masonry system. BL150 and BL200 are available in 50 lb. bags. Please consult the catalogue for more specialized products available directly from Virginia Lime Works.