Combination of Polymeric Superplasticizers, Water Repellents and Pozzolanic Agents to Improve Air Lime-Based Grouts for Historic Masonry Repair

Abstract

This paper presents the experimental procedure to develop air lime-based injection grouts, including polymeric superplasticizers, a water repellent agent and pozzolanic agents as additives. Our research focuses on the development of grouts to improve various characteristics simultaneously by combining different additions and admixtures. Aiming to improve the injectability of the grouts, in this study, different polymeric superplasticizers were added, namely polycarboxylated-ether derivative (PCE), polynaphthalene sulfonate (PNS) and condensate of melamine-formaldehyde sulfonate (SMFC). As a water-repellent agent, sodium oleate was used to reduce the water absorption. The enhancement of the strength and setting time was intended by using microsilica and metakaolin as pozzolanic mineral additions. Compatibility between the different admixtures and action mechanism of the different polymers were studied by means of zeta potential and adsorption isotherms measurements. Diverse grout mixtures were produced and investigated by assessing their injectability, fluidity, stability, compressive strength, hydrophobicity and durability. This research led to several suitable mixtures produced by using more than one component, to enhance efficiency and to provide better performance of grouts. According to the results, the grout composed of air lime, metakaolin, sodium oleate and PCE was found to be the most effective composition, improving the mechanical strength, injectability and hydrophobicity.

RILEM TC 277-LHS report: a review on the mechanisms of setting and hardening of lime-based binding systems

“…Lime-based binding materials can be used in a wide variety of mixtures depending on their function [12], such as masonry bedding mortars [2,13], renders and plasters [14][15][16], repointing materials as grouts [17][18][19][20][21], whitewash [22,23], ornamental pieces [24], wall painting support [25,26], finishing mortars [27], surface repair [28] or flooring mortars [29,30]. All these materials can be produced from diverse raw materials, obtaining both air lime (calcitic [31,32] and/or dolomitic [33][34][35][36]) or limes with hydraulic properties [37][38][39], all classified by EN 459-1 (2015) [40].…”

Improving lime-based rendering mortars with admixtures

“…• Water-repellent agent (0.5% bwol): Sodium oleate (O), provided by HISA A 2388 N from ADI-Center-S.L.U. The well-known structure of the oleate, with its long nonpolar hydrocarbon chain and its polar carboxylate group at one end, has been also reported elsewhere [10,24]. • Rheology modifier (0.5% bwol): a potato starch derivative Casaplast KO09 (S).…”

“…Literature has shown the positive effect of waterproofing agents for lime-based mortars [10,24]. Sodium oleate and other anionic surfactants are the most commonly used admixtures.…”

The Influence of Dry Hydrated Limes on the Fresh and Hardened Properties of Architectural Injection Grout

“…The reproducibility of the injection grouts’ properties is better when dry hydrated lime is applied as the binder. Moreover, the dry hydrate enables an easy application of different chemical admixtures in the grout mixtures—such as superplasticisers that reduce the water content of the grout considerably and thus increase its mechanical properties [ 3 , 4 ]. Additionally, a range of the lime-based grouts’ proportions are easily prescribed [ 5 ].…”