An introduction to lime - The Hempcrete Topic: Designing and Building with Hemp-lime - page 62

Cement causes damage to natural materials because it is not breathable enough. Here, bricks ori-
ginally laid in lime mortar have been repointed in Portland cement, which is harder than the brick.
Any water that penetrates into the face of the brick, instead of wicking away into the softer mortar,
now stays there - and when it freezes it expands, blowing the face of the brick.
Since the 1980s there has been a growing understanding of the damage done to traditional
and historic buildings through the use of cement and, as we saw in the last chapter, there
has been a huge resurgence in the use of lime mortars and renders in older buildings, es-
pecially in historically significant buildings, where the importance of lime in preserving
these structures in good repair is now widely recognized.
From the point of view of those interested in sustainable building, limes are also preferable
to cement for a number of other reasons:
The burning temperatures needed for the production of limes are lower than for cement
(approximately 900 ℃ compared with around 1,400 ℃ ), so their embodied energy is
lower in that respect.
Those limes that set by carbonation reabsorb carbon dioxide during the setting process,
thus taking out of the atmosphere at least some of the CO 2 that was given off during the
manufacturing process.