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Kicking the Cement Habit:
The Return of Lime Mortars
While portland cement has been the dominant building material for the past hundred years, traditional lime mortars are often the best choice for historic buildings. Lime mortar is also appearing in “green” building projects, which focus on sustainable materials and energy efficiency. by Elisabeth Logman
"The present age may well be classified in history as the 'Concrete Age.'" So wrote one H.F. Porter in 1909, noting that portland cement "…is indeed a product of evolution, and because of quality and economy, is rapidly displacing all other cementitious materials. More than that, it is creating entirely new, ever-widening fields of usefulness, and is exerting a revolutionary effect on modern industry and progress."
For the most part, Porter's words have held true for nearly a hundred years. Portland cement has inarguably been the dominant building material of the twentieth century, and it has indeed evolved — modern cements are achieving impressive compressive strengths, and decades of research have created a consistent, fast-setting product. Just about every mason now works in portland cement-based mortars — specifically, types M, S, and N.
What Porter probably couldn't have imagined, however, was that traditional lime mortars would ever re-emerge — he had rejected lime mortars, noting that the use of lime "today is confined to the less progressive people and sections and to the poorest grades of brick and masonry…." He would have undoubtedly been surprised to see lime mortars in twenty-first specifications and on today's jobsites, but these historic formulations are indeed back — which is good news for our historic masonry buildings.
