Sulfate-Resistance of Lime-Pozzolan-Cement Grouts


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Title: Sulfate-Resistance of Lime-Pozzolan-Cement Grouts

Author(s): E.-E. Toumbakari and D. A. Van Gement

Publication: Special Publication

Volume: 212


Appears on pages(s): 771-788

Keywords: cement; durability; lime; pozzolan; silica fume; sulfate

Date: 6/1/2003

One of the major concerns during application of cementitious grouts inside his- toric masonry is the possible presence of gypsum, which may lead to the creation of ettringite and the subsequent damage of the masonry. The design conccpt ofthe presented hydraulic grouts is based on the reduction ofthe portland cement content to the 30%-wt of the total hinder mass, in favour of appropriately proportioned mixtures of hydrated lime and natural and artificial (silica fume) pozzolans. The behaviour of the system lime-pozzolan-ponland cement in the presence of gypsum is investigated. A series of mortar specimens are made, in which a part of the sand is replaced by gypsum. The various grouts are used as hinders. The evolution of the length change and the modulus of elasticity are followed for 730 days. A very big expansion is recorded in the Iime-natural pozzolan-portland cement mortars, which may be considered as non-sulfate resistant. On the contrary, the substitution of a part of the natural pozzolan (10%-wt of the pozzolan) by an equal in weight amount of silica fume leads to a drastic reduction of the recorded expansions.