Assessment of Laboratory and Field Testing Methods in Lime-based Grouts for the Consolidation of Architectural Surfaces

Abstract

ABSTRACT Lime-based grouts are usually applied for the consolidation and strengthening of historic structures. In the case of architectural surfaces (renders, plasters, murals, wall mosaics), the testing procedure of grouts may concern laboratory (according to relevant standards) and field test methods (simple tests without specialized instrumentation that can be easily applied on-site). In the present study, three often used compositions of lime-based grouts were manufactured and tested, regarding lime-pozzolan (L:P – 1:1 by mass), lime-pozzolan-white cement (L:P:C – 1:0.8:0.2 by mass) and natural hydraulic lime (NHL 3.5). The methodology applied concerned the assessment of laboratory and field test methods as defined by literature and relevant standards. At fresh state, the properties measured were fluidity, penetrability and volume stability, recorded both with the laboratory and field testing tools. At hardened state, shrinkage tendency was determined, as well as the mechanical characteristics of the specimens at the age of 28, 90 and 180 days (Dynamic Modulus of Elasticity, Flexural, Compressive strength). From the evaluation of the results, it was concluded that the laboratory and field test values were in agreement, providing valuable information for the grouts’ performance. All compositions presented acceptable results, while their mechanical characteristics were significantly enhanced up to the age of 180 days. The early strength development (28d) of the mixtures seemed to be favoured by the addition of 10% w/w of white cement in the lime:pozzolan matrix.