Impact of natural pozzolan addition on rheological properties of air lime-based injection grouts

abstrakt

angličtina

Grout injection is one of the techniques used in the repair works on the masonry and plasterwork of heritage structures. As grouting is an irreversible technique, the compatibility of grout with the surrounding materials has to be emphasized during the design period [1]. For this reason, the cement-based materials are usually found unsuitable for their high elastic modulus, strength, and risks of efflorescence; therefore in the built heritage practice the grouts with other binders, mainly natural hydraulic lime (NHL), are used [1–3]. Their design is rather empirical with several recent studies on the rheology of NHL-based grouts following the approach established for more broadly studied cementitious materials [3, 4]. Air lime – pozzolan systems are another viable option for more compatible slightly hydraulic grout systems. The presented study examines the influence of natural pozzolanic additives on the rheological characteristics of air lime-based grouts prepared with the same flow value, usual in the practice. The flow properties and amplitude sweep test were used to study the behavior of pastes prepared by replacing part of lime by one of the natural pozzolanic additives (chalcedony, pumice, zeolite, and trass). Expectedly, the grouts with natural pozzolana replacement required lower water/solid ratio to achieve the same flow value as control grout as the specific surface area of the pozzolans is smaller than that of aerial lime. To determine the yield stress and the plastic viscosity, the Bingham model was used.. Incorporation of any pozzolan into the mixture resulted in an increase in the yield stress value, which then decreased with growing pozzolan content, down to the values similar to the control grout. Contrary, the plastic viscosity grew further with increasing pozzolan content. Amplitude sweep test showed the gel-like behavior of all the grouts with pozzolan addition slightly shortening the linear viscoelastic region (LVR) and increasing the storage modulus. The further development of air lime-pozzolan grouts is discussed with emphasis on modification of rheological parameters.

ŽIŽLAVSKÝ, T.; VYŠVAŘIL, M.

11. 6. 2025

University of Aegean

Řecko

81

81

1

https://mathweb.aegean.gr/hsr2025/HSR_2025_Book_of_Abstracts_FFF.pdf