Abstract
The present work aims to define the mechanical behavior of a new composite material for the preservation and enhancement of the vast historical and architectural heritage particularly vulnerable to environmental and seismic actions. The new composite represents a novelty in the landscape of the fibrous mortars and consists of natural hydraulic lime (NHL)-based mortar, strengthened by Sisal short fibers randomly oriented in the mortar matrix. The developed mortar ensures the chemical-physical compatibility with the original features of the historical masonry structures (especially in stone and clay) aiming to pursue the effectiveness and durability of the intervention. The use of vegetal fibers (i.e., the Sisal one) is an exciting challenge for the construction industry considering that they require a lower level of industrialization for their processing, and therefore, their costs are considerably lower, as compared to the most common synthetic/metal fibers. Samples of Sisal-composite are tested in three-point bending, aiming to estimate both their bending stress and fracture energy. Tensile and compressive tests were also performed on the composite samples, while water retention and slump test were performed on the fresh mix. At last, the tensile tests on the Sisal strand were performed to evaluate the tensile stress of both strand and wire. An original mechanical interpretation is proposed to explain two interesting phenomena that arose from the analysis of experimental data. The comparison among the performances of unreinforced and reinforced mortar suggests that the use of short fibers is recommendable as coating in the retrofitting interventions alternatively to the long uni or bi-directional fiber strands adopted in the classic fibrous reinforcement (i.e., FRCM). The proposed composite also ensures mix-independent great workability, excellent ductility, and strength, and it can be considered a promising alternative to the classic fiber-reinforcing systems. As final remarks, the use of fiber F1 (length of 24 mm) with respect to fiber F2 (length of 13 mm) is more recommendable in the retrofitting interventions of historical buildings, ensuring higher strength and/or ductility for the composite.
Highlights
This work presents a study on the use of the Sisal natural fibers, extracted from Aloe plants, in the strengthening of stone and brick-masonry structures, especially when the intervention regards architectural heritage
A total of 53 specimens have been tested at the Laboratorio Prove Materiali e Strutture (LPMS) of L’Aquila with the Zwick Roell machine; specimens were tested under displacement control and subjected to 3PBTs, Brazilian tests (BT), Compression Tests (CT)
Two Sisal strands were pulled with the same machine under displacement control, with the aim to compare the experimental ultimate tensile strength of strand and yarn with both literature and technical data provided by manufacturer
Summary
Masonry structures constitute a significant part of the most important existing historical and artistic property heritage around the world. These structures are vulnerable to environmental and seismic actions, as highlighted during recent calamities (e.g., Kashmir 2005, L’Aquila 2009, Christchurch 2011, Emilia 2012, Amatrice 2016). Masonry structures are subjected to multi-directional ground motions, which causes in-plane and out-of-plane loads and eventually provokes their collapse [1,2,3,4,5,6,7,8]. There has been a growing demand in protecting masonry heritages because of decades of studies and investments in this field as well as the necessity to maintain and to pass them on to future generations
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