Rui André Martins Silva

Conservation and New Construction Solutions in Rammed Earth

The conservation and rehabilitation of several sites of cultural heritage and of the large housing stock built from rammed earth requires adopting intervention techniques that aim at their repair or strengthening. The present work discusses the main causes of the decay of rammed earth constructions. The intervention techniques used to repair cracks and lost volumes of material are also discussed. Regarding the strengthening of rammed earth walls, the discussion is focused on the techniques that improve the out-of-plane behaviour. Special attention is given to the injection of mud grouts for crack repair in rammed earth walls, including the presentation of the most recent developments on the topic, namely regarding their fresh-state rheology, hardened-state strength and adhesion. Finally, the use of the rammed earth is discussed as a modern building solution. In addition, several typical techniques for improving rammed earth constructions are discussed, aiming at adequate those to modern demands. In addition, the alkaline activation of fly ash is presented and discussed as a novel improvement technique.

A TRM-Based Compatible Strengthening Solution for Rammed Earth Heritage: Investigation of the Bond Behavior

Raw earth is among the most ancient building materials and the related building techniques are found widespread around the world. Currently, it is estimated that about 25% of the global population lives in earthen buildings and about 10% of the UNESCO World Heritage is built with earth. Nevertheless, an important overlap can be observed when the geographical distribution of raw earth constructions is compared with that of the seismic hazard. This circumstance, combined with the seismic vulnerability of earthen buildings, results in a high seismic risk, as demonstrated by recent moderate earthquakes. Despite the current awareness for this problem, little has been done so far to develop proper strengthening solutions for the rammed earth heritage. Based on the effectiveness of externally bonded fibers for masonry buildings, the strengthening of rammed earth walls with an earth mortar coating reinforced with a geomesh is here adopted as a compatible solution. The objective of this work is to investigate and characterize the bond behavior of the above mentioned strengthening solution to further describe the response of the interaction mortar-mesh. To this purpose, an experimental program was undertaken based on a series of pull-out tests. Specimens were prepared using earth mortar, two different types of meshes (glass fiber and nylon) and considering different bonded lengths. The results highlighted distinct bond behaviors. In the case of the glass fiber mesh, the bond was granted by friction and mechanical interlocking, while the mechanical anchorage promoted by the transversal yarns granted the bond of the nylon mesh.

Experimental Investigation of the Structural Response of Adobe Buildings to Lateral Loading Before and After the Implementation of Compatible Grout Repairs

In the framework of this study, a 1:2 scaled replica of a traditional single-storey adobe building was constructed and tested at the laboratories of the University of Cyprus. The main objectives of the experimental program were to evaluate the structural performance of adobe buildings under horizontal loads (simulating seismic action) and to investigate the effectiveness of cracking repair by means of injection with a compatible grout. The model was initially subjected to a series of monotonic static lateral loading cycles that led to the development of extensive cracking damage and to significant reduction of the load-bearing capacity and overall stiffness. A compatible clay-based grout was then developed using the same soil as the one composing the model’s adobes. This material was injected into the cracked sections of the masonry and the repaired model was re-tested. The clay-based grout successfully restored structural continuity, precluding the re-opening of injected cracks during subsequent loading cycles. The recorded load-deformation response revealed that the grout repair reinstated the original stiffness of the structure and recovered more than 90% of the initial lateral strength. The results indicate that clay-based grouts can be used for re-establishing the stability of adobe constructions under static loads.

Characterization of a Compatible Low Cost Strengthening Solution Based on the TRM Technique for Rammed Earth

Rammed earth constructions are widely found worldwide, but they are endangered by their recognised high seismic vulnerability. As compatible and affordable reinforcement approaches are important requirements for these constructions, a strengthening solution based on low cost textile reinforced mortars (LC-TRM) is proposed here, within the framework of a large research project. This paper presents the results of an experimental program aimed at characterising low cost meshes available in the market (glass fibre, plastic, metallic and nylon) and at assessing possible mortars (unstabilised earth, stabilised earth, commercial earth and cement-based) capable of integrating the LC-TRM strengthening system. In general, the results obtained seem to indicate that the glass fibre meshes and the earth mortar are good options.

In-plane behaviour of earthen materials: a numerical comparison between adobe masonry, rammed earth and cob

The paper presents a comparison between different numerical modelling ap-proaches aiming to simulate the in-plain behaviour of three types of earthen materials, name-ly adobe masonry, rammed earth and cob. For this purpose, uniaxial and diagonal compression tests were carried out, which allowed determining important mechanical param-eters, such as compressive strength, Young’s modulus, Poisson’s ratio, shear strength and shear modulus. Furthermore, the tests allowed assessing the level of non-linear behaviour of the respective stress–strain relationships as well as the failure modes. The experimental results were then used for the calibration of numerical models (based on the finite element method) for simulating the non-linear behaviour of the earth materials under in-plane shear loading. Both macro- and micro-modelling approaches were considered for this purpose. The procedures adopted for model calibration established the reliability of various modelling strategies for the different loading conditions. The simplified approach based on macro-modelling shows a satisfactory accuracy and low computational costs. The results reproduc-ing the uniaxial compression are in good correspondence with the post-elastic behaviour ob-served in the experimental campaign. The micro-modelling approach adopted to reproduce the shear behaviour, even with higher computational cost, represents a suitable tool to pre-dict the adobe masonry and rammed earth collapse mechanisms