Journal Published Online: 06 June 2019
Volume 8, Issue 3

Sustainable, Hydraulic-Lime-Limestone Binders for Construction

CODEN: ACEMF9

Abstract

This work intends to reduce the carbon footprint and increase the sustainability of hydraulic lime (HL) mortars and concretes, a growing market in both new building and refurbishment, by partially replacing HL with limestone. Limestone cements are widely used in the world. Portland cement (PC) is partially replaced with limestone to reduce the large carbon print of cement and improve sustainability. The effect of limestone in PC has been widely investigated; however, the effect of limestone in HL has not yet been investigated. HLs contain clinkers identical to those in PC; therefore, this article first reviews the effect of limestone in PC and then experimentally investigates its impact in HL. The results showed that limestone is active in HL. The limestone changed the microstructure of the HL paste and the nature of the phases formed upon hydration, with calcium carbosilicate hydrates (resulting from dicalcium silicate and calcium carbonate [C2S-CaCO3] reaction) and carboaluminate hydrates (resulting from tricalcium aluminate and calcium carbonate [C3A-CaCO3] reaction) growing on interfaces and in the matrix. Limestone replacement enhanced the performance of the HL by improving strength: a 10 % replacement increased HL strength (compressive by 36 % and flexural by 56 %). A 20 % replacement enhanced strength up to 125 and 40 days (compressive and flexural, respectively); therefore, the limestone replacement threshold is higher in HL than in PC. The rise in strength does not affect moisture and vapor permeability, and the composites remain ‘breathable.’ Contrary to PC, limestone reduces the water demand of HL mortars. The superior strength of the limestone-filled HL mortars is attributed to their lower water demand, an increase of early hydrates, and their placement—strengthening transition zones and interparticle links.

Author Information

Pavía, S.
Department of Civil Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
Aly, M.
Department of Civil Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
Pages: 20
Price: $25.00
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Stock #: ACEM20180124
ISSN: 2379-1357
DOI: 10.1520/ACEM20180124