The influence of metakaolin on the properties of natural hydraulic lime-based grouts for historic masonry repair. (30th May 2018)

• Record Type: Journal Article
• Authors: Vavričuk, Anja; Bokan-Bosiljkov, Violeta; Kramar, Sabina
• Is Part Of: Construction & building materials. Volume 172(2018)
• Page Start: 706
• Page End: 716
• Publication Date: 2018-05-30
• Subjects: Natural hydraulic lime -- Metakaolin -- Injection grouts -- Hydration products -- Cultural heritage; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2018.04.007
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: The influence of MK1 and MK2 on the properties of NHL-based grouts was studied. For target fluidity MK increases w/b and water retention of fresh grout. MK contributes to early age and long-term increase of grout's compressive strength. MK1 is more efficient due to higher reactivity and different evolution of phases. MK1 highly improves bond strength of the NHL-based grout. Abstract: This paper investigates the properties of injection grouts with different amounts of natural hydraulic lime (NHL) replacement by metakaolin MK1 or MK2. The focus is dedicated to the fresh properties of the NHL-based grouts, as well as to a parallel study of the evolution of compressive strength and phase composition of hardened grouts, through tests at 28, 56, 90 and 900 days. Additionally, at 90 days, the influence of the MK1 and MK2 incorporation on the porosity characteristics of hardened grouts was determined. Tensile bond strength, being one of the key hardened properties of the injection grouts, was for the time being determined only at an early age of 28 days. The results showed that by adding metakaolin at constant fluidity, the water demand of the fresh mixture increases with the increase of the metakaolin content. At the same time the water retention capacity of the grout is enhanced. In a hardened state the addition of metakaolin increases early age and long term compressive strength of the grout. Also, its bond strength can be considerably increased, by applying MK1. Mixtures with metakaolin resulted in the formation of hydration products such as ettringite, hemicarboaluminate and monocarboaluminate, whereas stellerite was present only in the case of higher proportions of metakaolin with a higher BET surface area and Al2 O3 content.