Academic literature on the topic 'Reinforced Rammed Earth'

This study analyses the durability of rammed-earth wall construction techniques. The analysis focuses on three medieval masonry types from the Castle of Villavieja (Castellón, Spain) using two variations of lime-reinforced rammed earth in its walls: lime-crusted rammed earth and brick-reinforced rammed earth. Materials analysis reveals the good properties of the materials used in the outer wall facing despite its age. It also clearly shows how deterioration depends more on the construction technique (construction of the wall with a base, cornice, facings, core; on-site installation, bonds, etc.) than on the material itself. These two types of lime-reinforced rammed earth (lime-crusted rammed earth and brick-reinforced rammed earth) are the most common kinds of fortified architecture in the Iberian Peninsula as well as in northern Africa and the Middle East. The case presented herein is therefore highly relevant as it advances our knowledge of the behaviour of the materials comprising these walls and lays the foundations for suitable future conservation works of a vast array of architectural heritage.

Purpose This study aims to investigate the optimum proportion of coconut fibre and cement suitable for rammed earth wall construction. Coconut fibres and cement can be easily incorporated into the soil mixture which adds strength and durability to the wall. This paper highlights the salient observations from a systematic investigation on the effect of coconut fibre on the performance of stabilized rammed earth blocks. Design/methodology/approach Stabilization of soil was done by adding Ordinary Portland Cement (2.5, 5.0, 7.5 and 10.0 per cent by weight of soil), whereas coconut fibre in length about 15 mm was added (0.2, 0.4, 0.6, 0.8 and 1.0 per cent by weight of soil) as reinforcement. Thirty types of mixes were created by adding different proportions of cement and fibre to locally available soil and compacting the mix at constant compaction energy in three layers with Proctor rammer. Findings Samples were tested for compressive strength and tensile strength, and failure patterns were analysed. The use of cement and fibre increases ultimate strengths significantly up to an optimum limit of 0.8 per cent fibre content, provides a secondary benefit of keeping material bound together after failure and increases residual strength. Benefits of fibre reinforcement includes both improved ductility in comparison with raw blocks and inhibition of crack propagation after its initial formation. Originality/value After analysing the results, it is recommended to use 0.8 per cent fibre and 5-10 per cent cement by weight of soil to achieve considerable strength. This research may add a value in the areas of green and sustainable housing, waste utilization, etc.

With the introduction of the modern rammed earth technique, a large number of modern rammed earth buildings were constructed in China Mainland. China has a vast territory, which faces the Circum-Pacific seismic belt on the east and the Eurasian seismic belt on the south; earthquake has constantly threatened the safety of people’s lives and property. Consequently, it is necessary to probe in the seismic performance of rammed earth buildings. Two un-stabilized rammed earth specimens, one un-stabilized rammed earth reinforced with geogrid sheets’ specimens, and four stabilized rammed earth specimens were built for obtaining a better insight on the behavior of un-stabilized rammed earth/stabilized rammed earth walls under cyclic in-plane loads. Testing results are discussed in terms of failure mode, shear capacity, hysteretic curve, stiffness degradation, and total energy dissipation to provide comparisons of the seismic performance between un-stabilized rammed earth and stabilized rammed earth specimens. Different failure modes indicated that the cohesion between particles and the bond strength between layers are the two key parameters for the shear capacity of rammed earth buildings. It is also demonstrated that stabilized rammed earth specimens have higher shear and energy dissipation capacity but weaker deformation capacity than un-stabilized rammed earth.

This paper presents an experimental study on the behavior of cement stabilized rammed earth (CSRE) column reinforced with steel under axial loading and its comparison with unreinforced and bamboo reinforced columns. Effects of structural parameters such as tie / stirrup spacing on the failure pattern, lateral and axial deformation of columns are studied. Test results show that the load-capacity of columns increases with increase in lateral / tie reinforcement ratio. Maximum axial and lateral deformations occur in columns with least tie spacing. Behavior of CSRE columns reinforced with close tie spacing is characterized by gradual spalling of cover at the failure zone. Steel reinforced columns perform better than other column types in terms of load-capacity; hence it may be used as structural member adjacent to walls for low-rise rammed earth houses. Proposed reinforcement technique can be adopted in the field for enhancement of greater strength and performance of columns.

Buildings of the future are called to meet increasingly high-performance requirements and to ensure adequate environmental sustainability of the production and construction chain. This issue has stimulated a keen interest in the use of natural materials in construction. Among these, raw earth has proved to be particularly interesting for its intrinsic availability, sustainability, and recyclability. In Europe, the spread of raw earth building technologies has often been hindered by the lack of specific legislation regulating its use for load-bearing structures, even if in many countries, it can be noticed a widespread and well-established constructive tradition. Some transoceanic research experiences attest that unfired earth can be used, together with different types of reinforcements, to create seismic-resistant buildings. After presenting a review of the main raw earth reinforced technologies, the present study focuses on a novel reinforced and modular rammed earth construction made with natural or recycled materials, developing a technology with low energy consumption and low environmental impact, specifically designed for areas with high seismic risk. In particular, the work presents the results of a prototyping procedure aiming at developing a new seismic-resistant construction system that combines rammed earth with timber reinforcement elements and nylon/polyester ropes. These elements have a dual function: (1) they are fundamental components of the construction process (as they integrate the formwork system), and (2) they act as seismic-resistant devices once the structure is completed. In line with the performance-based approach required by the construction sector, the study aims at defining a controlled and standardised supply chain for rammed earth construction.

Abstract. During the Nasrid Kingdom of Granada, the alcazaba of Oria (Old citadel) was considered one of the most outstanding medieval defensive ensembles in the province of Almeria. This defensive complex, located in the Almanzora Valley at an altitude of over a thousand metres, was built around the 12th-14th centuries and has been registered as an Asset of Cultural Interest since 1985. Nevertheless, unfortunate decisions to intervene in the monument and lack of maintenance facilitated the loss of most of its wall, which had been preserved until the twentieth century. Despite the critical situation of the complex, two sections of the rammed-earth wall are currently identified as standing. This study represents an opportunity to broaden the knowledge of this relevant wall structure and the characterisation of the rammed-earth reinforced wall with lime mortar layers. As a preliminary step towards the rammed-earth walls analysis, the graphic representation of wall elevations by photogrammetry tools is proposed. This technique allows to graphically define the morphology of the rammed-earth wall, to perform its typological analysis and constructive characterisation; and furthermore, to evaluate the state of constructive elements conservation by means of the identification of its damages. The information and results obtained will allow to establish the appropriate laboratory tests for the rammed-earth materials characterisation and to define a report that justifies the inexcusable need to consolidate and preserve them.

The paper presents experimental and numerical works to assess the in-plane shear characteristics of rammed earth (RE) structures in Bhutan. The material characterization works involve compressive and tensile splitting strength tests on extracted cylindrical core samples. The effects of the RE layer thickness and drying period in the strength characteristics of the rammed earth is presented. The main experimental part reports in-plane shear tests on 3 test specimens, 1200 mm long, 1200 mm high, and 600 mm wide. The test matrix has unreinforced and reinforced specimens with variable RE layer thicknesses. For the reinforced RE specimen, the effectiveness of a simple intervention with insertion of reinforced concrete dowel at the RE block interface as a strengthening measure is discussed. Furthermore, corresponding finite element models were developed to verify the test observations. Both the experimental observations and numerical computations showed the effectiveness of proposed intervention technique in enhancing the shear strength and delaying the slip along the RE joint interface. The results showed that the shear strength of the reinforced specimen increased by 12.3% over the benchmark specimen.

The renewed attention paid to raw earth construction in recent decades is linked to its undoubted sustainability, cost-effectiveness, and low embodied energy. In Italy, the use of raw earth as a construction material is limited by the lack of a technical reference standard and is penalised by the current energy legislation for its massive behaviour. Research experiences, especially transoceanic, on highly performative contemporary buildings made with natural materials show that raw earth can be used, together with different types of reinforcements, to create safe, earthquake-resistant, and thermally efficient buildings. On the basis of experimental data of an innovative fibre-reinforced rammed earth material, energy analyses are developed on a rammed earth building designed for a Mediterranean climate. The paper focuses on the influences that different design solutions, inspired by traditional bioclimatic strategies, and various optimised wall constructions have in the improvement of the energy performance of the abovementioned building. These considerations are furthermore compared with different design criteria aiming at minimising embodied carbon in base material choice, costs, and discomfort hours. Results have shown the effectiveness of using the combination of massive rammed earth walls, night cross ventilation, and overhangs for the reduction of energy demand for space cooling and the improvement of wellbeing. Finally, the parametric analysis of thermal insulation has highlighted the economic, environmental, and thermophysical optimal solutions for the rammed earth envelope.

The renewed attention paid to raw earth construction in recent decades is linked to its undoubted sustainability, cost-effectiveness, and low embodied energy. In Italy, the use of raw earth as a construction material is limited by the lack of a technical reference standard and is penalised by the current energy legislation for its massive behaviour. Research experiences, especially transoceanic, on highly performative contemporary buildings made with natural materials show that raw earth can be used, together with different types of reinforcements, to create safe, earthquake-resistant, and thermally efficient buildings. On the basis of experimental data of an innovative fibre-reinforced rammed earth material, energy analyses are developed on a rammed earth building designed for a Mediterranean climate. The paper focuses on the influences that different design solutions, inspired by traditional bioclimatic strategies, and various optimised wall constructions have in the improvement of the energy performance of the abovementioned building. These considerations are furthermore compared with different design criteria aiming at minimising embodied carbon in base material choice, costs, and discomfort hours. Results have shown the effectiveness of using the combination of massive rammed earth walls, night cross ventilation, and overhangs for the reduction of energy demand for space cooling and the improvement of wellbeing. Finally, the parametric analysis of thermal insulation has highlighted the economic, environmental, and thermophysical optimal solutions for the rammed earth envelope.

The rammed earth technique has been explored in the past, for the construction of load bearing walls in the buildings. Rammed earth construction involves compaction of partially saturated loose soil-sand mix in a rigid formwork. The thesis presents results of investigations on cement stabilised rammed earth (CSRE). A brief summary on the origin and development of rammed earth has been summarised in the first chapter. The literature review highlights the gaps in the current knowledge on CSRE and the need for such studies. Initial part of the investigations examines the optimum compacted layer thickness needed for CSRE resulting in maximum compressive strength for the CSRE. Also, the influence of super-plasticiser additives in reducing the compaction energy in CSRE and the effects on mechanical characteristics of CSRE has been dealt in detail. The results show that the optimum compacted layer thickness for CSRE is in a narrow of range of 90 – 100 mm and small dosages of superplasticiser reduce the compaction energy of CSRE drastically. The stress-strain characteristics of CSRE have been examined in greater detail. The influence of dry density, soil composition, cement content and moisture content on the compressive strength and stress-strain characteristics of CSRE are presented. An analytical model to predict the stress-strain response of CSRE was developed and validated. Establishing the shear strength parameters and developing Mohr-Coulomb failure envelopes for CSRE in dry and wet conditions formed the next part of the investigations. The influence of cement content and moisture content on the shear strength parameters of CSRE was investigated in greater detail. The thesis delves on reinforced CSRE mainly to improve the flexure strength due to out of plane bending. The bond strength between rebars and CSRE matrix was assessed through standard pullout tests and the results presented. With this background, the study focuses into the flexural behaviour of plain and steel reinforced CSRE beams. Development of the stress block and stress block parameters, and thereby arriving at the design calculations for reinforced CSRE were the main contribution of the study. The thesis concludes by providing a summary of all the investigations carried out. The immediate usefulness of the results of the thesis to the construction industry has been highlighted.

Dissertação de mestrado em Structural Analysis of Monuments and Historical Constructions
Earth constructions cover 30% of the total built heritage in the world, some of which are Unesco World Heritage listed. Building in rammed earth consists in compacting layers of moist earth within a formwork to erect walls. Rammed earth constructions are known for presenting high seismic vulnerability, due to their high dead-weight, low mechanical properties (especially very low tensile strength) and poor connections between structural elements. During a seismic event of moderate intensity, the walls tend to fail in their plane and in out-of-plane mechanisms. In South Portugal, the regions of Alentejo and Algarve are seismically active and a significant part of the built heritage is made of rammed earth. The structural vulnerability of rammed earth buildings puts the heritage and the life of their inhabitants at risk. Hence, the mitigation of the aforementioned risks demands the development of adequate interventions for the seismic strengthening of rammed earth constructions. In Peru, coatings reinforced with geomesh have been used for the strengthening of adobe constructions, where this solution has been shown to be highly effective in increasing their bearing capacity and energy dissipation capacity under seismic loading. This type of solution can also be applied to rammed earth with the same purpose, nevertheless little investigation has been carried out on its development and validation. Little literature available for conservation principles and structural retrofitting makes it even more challenging. The development of this solution, in this case, needs the investigation of compatible materials and of the characterization of its mechanical behaviour. Proceeding in this way will make possible to create bases for proper design, namely with respect to the development of numerical tools. In this context, the main objective of this dissertation is to contribute for the development of the knowledge on the strengthening of rammed earth walls by means of reinforced coatings. The proposed objective integrates the following methodology: a) literature review on rammed earth construction, namely focused on their seismic behaviour and intervention approaches, and on the strengthening of masonry with reinforced coatings; b) proposal of an approach for strengthening rammed earth constructions with reinforced coatings within the international principles and guidelines for heritage conservation; c) execution of an experimental program dedicated to the characterization of the behaviour of the solution (individual materials and interaction). The experiments were carried out in the structural laboratory of University of Minho, followed by evaluating the results and discussing the findings.
A construção em terra cobre 30% de todo o património construído no Mundo, onde se inclui alguns sítios listados como património Mundial pela Unesco. Construir em taipa consiste em compactar camadas de terra húmida no interior de um molde para erguer paredes. As construções em taipa são conhecidas por apresentarem elevada vulnerabilidade sísmica, devido ao seu elevado peso próprio, propriedades mecânicas baixas (especialmente uma resistência à tração muito baixa) e fracas ligações entre elementos estruturais. Durante um evento sísmico de intensidade moderada, as paredes de tendem a romper no seu plano e através de mecanismos de rotura para fora do plano. No Sul de Portugal, o Alentejo e o Algarve são regiões sismicamente ativas, onde uma parte importante do património construído é de taipa. A vulnerabilidade sísmica das construções em taipa põe em risco a sua preservação e a vida dos seus moradores. Assim, a mitigação destes riscos exige o desenvolvimento soluções de reforço sísmico adequadas para construções de taipa. No Perú, têm sido utilizados rebocos armados com geomalhas no reforço de construções de adobe, onde esta solução tem demonstrado enorme eficiência no melhoramento da capacidade resistente e da capacidade de dissipar energia da ação sísmica. Este tipo de solução pode ser aplicado com o mesmo objetivo, porém tem sido desenvolvida pouca investigação sobre o desenvolvimento e validação da técnica. A pouca bibliografia existente sobre princípios de conservação e reforço estrutural, tornam esta tarefa ainda mais difícil. Neste caso, o desenvolvimento desta solução requer a investigação de materiais compatíveis e da caracterização do comportamento mecânico. Através desta abordagem, tornar-se-á possível criar bases para dimensionamento, nomeadamente no que diz respeito ao desenvolvimento de ferramentas numéricas. Neste contexto, o principal objetivo desta dissertação é contribuir para o desenvolvimento do conhecimento sobre o reforço de paredes de taipa com rebocos armados. O objetivo proposto será conseguido seguindo a metodologia seguinte: a) revisão bibliográfica sobre construções em taipa, nomeadamente focada no seu comportamento sísmico e abordagens de intervenção, bem como no reforço de alvenaria com rebocos armados; b) proposta de uma abordagem o reforço sísmico de construções de taipa com rebocos armados, seguindo princípios e recomendações internacionais para a conservação do património; c) execução de um programa experimental dedicado à caracterização do comportamento da solução (dos materiais individuais e da sua interação). T Os ensaios foram realizados no laboratório de estruturas da Universidade do Minho, seguindo-se a análise e discussão dos resultados.

Cement stabilised rammed earth (CSRE) is a monolithic construction used for the loadbearing walls in the buildings and other structures. The soil, fine aggregates and cement form the basic materials for the CSRE construction. The partially saturated processed materials are compacted in layers in a rigid formwork, to construct the CSRE structural elements such as walls. The CSRE walls in a building can experience compression, tension, and shear. The literature review on the mechanical behaviour of the CSRE walls reveals that the CSRE wall elements undergo sudden catastrophic shear failures under compression, and shear loading, and under out of plane bending exhibit brittle flexure failures. Generally, the brittle and catastrophic failures are avoided in the structural elements. The short randomly oriented fibres in the brittle matrices can help promoting ductile failures by bridging the cracks and inhibiting the crack propagation. The limited R&D on the fibre reinforced CSRE reveal that the fibre inclusion can enhance the tensile strength, energy absorption capacity and the post peak response of the CSRE. However, the behaviour of the fibre reinforced CSRE is a scantily explored area. The present thesis is focused on investigating the mechanical behaviour of the coir fibre reinforced CSRE. The investigations were focused on (a) characterising the physical, chemical and mechanical properties of coir fibre and assessing the fibre durability, (b) examining the bond strength of coir fibres in the CSRE matrix and assessing the influence of fibre embedment length, matrix’s dry density, cement percentage and moisture at test, (c) determining the influence of fibre volume fraction (VF) on the compressive strength and stress-strain characteristics of coir fibre reinforced CSRE composite and finding the optimum fibre volume fraction, (d) establishing the shear strength and shear stress-shear strain relationships and understanding the flexure strength and flexure behaviour of the composite, (e) assessing the durability characteristics of the coir fibre reinforced CSRE when exposed to cyclic wet and dry cycles, and (f) exploring the novel concept of the shear studs across the rammed earth layers on the flexure, shear and compression. The major conclusions of investigations are (a) coir fibres show high tensile strength (~100 MPa) and large failure strain (23%), (b) the critical fibre embedment length yielding maximum pull-out resistance was 25 mm, (c) coir fibre addition eliminated the sudden shear failures in the CSRE under compression and improved the energy absorption capacity and post peak response, (d) the optimum fibre volume fraction yielding the maximum compressive strength was 1%, (e) the coir fibre inclusion significantly improved (30 – 40%) the split tensile strength of the CSRE and there was marginal improvement in the shear strength but significant enhancement in the post peak response, (f) improved the straining capacity of CSRE in the direction when flexure tension is parallel to the compacted layers and (g) the coir fibre reinforced CSRE is durable when exposed to cyclic wet and dry cycles. The last part of the thesis work was devoted to developing a novel concept of using shear studs across the compacted layers of the CSRE for the first time. The steel studs embedded CSRE specimens were tested under compression, diagonal tension (shear) and four-point bending. The introduction of steel studs across the compacted layers enhanced the shear strength of CSRE by 50%. The steel studs embedded CSRE showed extremely ductile failures under flexure. The thesis ends with highlighting major scientific contributions to the domain knowledge and scope for future work.

Dissertação de mestrado integrado em Engenharia Civil
Estima-se que cerca de 25% do património construído tenha a terra crua como material de construção principal, de onde se destacam várias construções listadas com Património Mundial pela UNESCO. Este tipo de construções é conhecido pela sua elevada vulnerabilidade sísmica, devido ao seu elevado peso próprio, baixas propriedades mecânicas (resistência à tração muito baixa) e fracas ligações entre elementos estruturais. De facto, este tipo de construções encontrase também edificado sobre zonas de perigosidade sísmica não negligenciável, pondo em risco a vida dos seus moradores e a preservação das mesmas. Este é o caso concreto de várias construções de taipa edificadas no Sul de Portugal. Existe a necessidade de se desenvolverem técnicas de reforço de forma a minimizar-se a vulnerabilidade sísmica das construções de taipa. Nos últimos anos, tem sido desenvolvida alguma investigação sobre a aplicação da técnica TRM (Textile Reinforced Mortar) na construção em adobe. Os resultados obtidos demonstraram um aumento do desempenho estrutural, através de uma maior capacidade resistente e de dissipação de energia. Pensa-se que esta técnica possa ser aplicada também em construções de taipa, no entanto, devido à pouca investigação existente sobre os princípios de conservação e reforço estrutural, esta tarefa tornase mais difícil. Assim sendo, o desenvolvimento desta solução requer a investigação de materiais de baixo custo e compatíveis com este tipo de construções, bem como da caracterização do seu comportamento mecânico. Com esta dissertação pretende-se contribuir para o desenvolvimento do conhecimento sobre o reforço de paredes de taipa com LC-TRM (Low Cost Textile Reinforced Mortar), através da execução de um programa experimental. Os resultados obtidos permitiram caracterizar o comportamento mecânico isolado de potenciais componentes da solução, bem como da sua interação.
The percentage of the built heritage using raw earth as main building material is estimated to be of about 25%, from where are highlighted several constructions listed as World Heritage by UNESCO. The high seismic vulnerability of this type of construction is acknowledged by their high dead-weight, low mechanical properties (very low tensile strength) and poor connections between structural elements. In fact, many of these construction are built on region with nonnegligible seismic hazard, putting in risk the life of their inhabitants and of their preservation. Several rammed earth constructions built in Southern Portugal are identified within this situation. The development of strengthening techniques is required to mitigate seismic vulnerability of rammed earth constructions. In the last years, some research has been carried out regarding the application of the TRM (Textile Reinforced Mortar) technique to adobe construction. The results obtained showed an improvement of the structural performance, by means of improved load capacity and energy dissipation. The application of this technique is expected to provide a similar effect on rammed earth constructions, but the little investigation on conservation principles and structural strengthening difficult its implementation. Thus, the development of this strengthening solution requires researching for compatible materials with low cost, as well as for the characterisation of their mechanical behaviour. This dissertation intends to contribute for the development of the knowledge on the strengthening of rammed earth walls with LC-TRM (Low Cost Textile Reinforced Mortar), by means of the execution of an experimental program. The results obtained allowed characterising the individual mechanical behaviour of potential components of the solution, as well as of their interaction.
O presente trabalho foi executado no âmbito do projeto SafEarth - Proteção sísmica do património construído em terra POCI-01-0145-FEDER-016737 (PTDC/ECMEST/2777/2014);
Financiado por fundos do FEDER através do Programa Operacional Fatores de Competitividade (COMPETE) e por fundos nacionais através da Fundação para a Ciência e a Tecnologia (FCT).

<p>Raw earth is one of the most widely used building materials and is employed in different techniques, among which adobe and rammed earth are the most common. The respective structural systems, like in masonry buildings, acceptably withstand against gravity loads, though they are significantly vulnerable to earthquakes. Moreover, a great percentage of the World’s population is still inhabited in such environments, which are endangered by future earthquakes. The current article investigates the seismic in-plane performance of an I-shaped rammed earth component by means of advanced nonlinear finite element modelling. In this regard, conventional pushover analyses were conducted to evaluate load/displacement capacities and to assess probable failure modes. It was observed that the component fails mainly due to detachment of the wing walls from the web wall and due to occurrence of diagonal shear cracks at the web. Subsequently, the application of Textile Reinforced Mortar (TRM) strengthening solution to the component was studied and shown to be able to maintain the integrity of the component for larger lateral load levels. Finally, the reliability of the pushover analyses to predict the seismic response was evaluated by comparison with outcomes from incremental nonlinear dynamic analysis.</p>