ROSENDALE NATURAL CEMENT CHEMISTRY:
HOW IS IT DIFFERENT FROM OTHER CEMENTS AND BINDERS?

What is Natural Cement?
Natural cement is hydraulic cement made from limestone that has a high clay content (argillaceous limestone). It is different from building lime, which is made from limestone with a lower clay content, in that lime is not hydraulic (does not set under water).

Lime and Natural Cement are both produced by heating limestone to approximately 900 to 1100⁰C, at which point carbon dioxide bound within the stone is released. In the production of lime, the burnt material is quicklime, which is then mixed with water to make building lime, also referred to as hydrated lime, or as lime putty if excess water is used. The process of hydrating quicklime is slaking, and when quicklime is slaked, it crumbles to a fine particle size. The burnt natural cement rock does not slake when mixed with water, however. Instead, it must be crushed into a powder before use. The resulting powder is natural cement, which will set when mixed with water, and hardens through a process of cement hydration.

When lime is used in masonry mortar and renders, it does not set due to being mixed with water, but rather, must react with carbon dioxide in the air in order to cure and harden. This is a slow process, often requiring weeks or months to build significant initial strength.

Portland cement is made from artificial mixtures of limestone, shale, gypsum and other additives. The mixture is heated to approximately 1400⁰C, at which point components fuse to form a clinker. The clinker is then ground to a fine powder that sets when mixed with water.

Hydraulic lime may be made either from blends of lime and pozzolans (such as slag, trass, clay, natural cement, portland cement or ash) or by burning of limestone with naturally occurring silica and/or alumina impurities. It is related to natural cement, but contains excess free lime, allowing the material to be slaked to a fine powder after burning. This excess of lime may reduce durability, lengthen set time and diminish initial resistance to weather, however, particularly in severe exposures such as coastal and cold weather environments.

Natural cement is simply the product of burning and grinding natural cement rock. American natural cement was never a mixture of ingredients such as clay or other pozzolans and lime or hydraulic lime. The use of such artificial mixtures is historically incorrect, therefore, and it is not “replacement-in-kind”. Only authentic Rosendale Natural Cement from Edison Coatings, Inc. is an historically accurate replacement in kind for the restoration of natural cement buildings, structures and monuments.

ROSENDALE NATURAL CEMENT vs. OTHER BINDERS

BINDER	COMPOSITION	REACTIONS	CHARACTERISTICS	STANDARDS
NATURAL CEMENT	Dicalcic Silicate (Belite); Produced from argillaceous limestone	Hydration, Crystallization Upon Water Contact	Fast Initial Set, followed by slow, gradual rise to final strength. Lower strength than Portland cement, similar strength to fully-cured lime, lime putty, hydraulic lime.	ASTM C10
HYDRATED LIME & LIME PUTTY	Calcium and Magnesium Hydroxide; Produced from limestone.	Forms Calcite and Magnesium Carbonate w/Prolonged Carbon Dioxide Exposure	Slow set and cure, tends to react incompletely below surface.	ASTM C207 (Hydrated Lime) ASTM C1489 (Lime Putty)
PORTLAND CEMENT	Dicalcic and Tricalcic Silicate, Tricalcium Aluminate; Produced from mixtures of limestone, shale, gypsum, other additives	Hydration, Crystallization upon Water Contact	Controlled Set Times, Rapid Strength Gain	ASTM C150 (Portland Cement) ASTM C91 (Masonry Cement)
HYDRAULIC LIME	Calcium Hydroxide, Dicalcic Silicate and/or Aluminate. Produced from limestone with silica or alumina impurities, or from blends of lime and pozzolans.	Forms Calcite w/Prolonged Carbon Dioxide Exposure; Hydration, Crystallization upon Water Contact	Slower set than natural and Portland cements, faster than lime/lime putty, slow rise to moderate/low strength	ASTM C1489

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Rosendale Natural Cement Products are manufactured in
the United States of America
from 100% American Natural Cement conforming to the requirements of
ASTM C 10.
This is the authentic historic material originally used in construction of thousands of American and Canadian buildings and structures in the 19th and 20th Centuries.
Accept No Substitutes!