Limestone-filled, hydraulic-lime mortars for historic and traditional fabrics

Author(s): Marwa Aly, Sara Pavía
Paper category: Proceedings
Book title: Proceedings of the 5th Historic Mortars Conference
Editor(s):José Ignacio Álvarez, José María Fernández,Íñigo Navarro, Adrián Durán, Rafael Sirera
e-ISBN: 978-2-35158-222-0
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 1251-1266
Total Pages: 16
Language : English

Abstract: Hydraulic lime (HL) mortars are considered compatible with historic fabrics and used in
repairs. They consist of lime and clinkers (mainly belite). As belite hydrates slowly, some HLs
develop strength for up to a year. This has raised concerns with conservationists. This paper
partially replaces natural HL (NHL5) with limestone to lower ultimate strengths that can
damage for some fabrics. It investigates the hydration of NHL5 in the presence of limestone
and the impact on mortar properties.
Despite the NHL’s low aluminate content, limestone reaction is evident. Limestone-triggered
hydrates appear in the matrix and at interfaces, likely strengthening the transition zone. The
limestone fineness and permeability, and the significant specific surface area of its
microcrystalline carbonate may have enhanced reactivity.
The 10-20% limestone replacements increased the 28-day strength. However, they lowered
the NHL5 strength after 90 days (flexural) and 180 days (compressive). In contrast, the NHL5
mortar keeps developing compressive strength, increasing by c.14 between 90 and 180 days
and c. 10% between 180 days and 1 year. The strength raise did not significantly affect the
hygric properties. When NHL5 is replaced with 10-30% limestone, the finest mortar pores
are preserved (water vapour permeability varies insignificantly). Contrary to Portland
cement (PC), the limestone lowers the water demand of the NHL5 mortars. To achieve a
proper workability using less water has benefits relevant for those involved in mortar design.

Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00

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