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STRUCTURAL BEHAVIOUR OF PLASTERED STRAW BALE ASSEMBLIES UNDER CONCENTRIC AND ECCENTRIC LOADING
... In terms of published data, Ashour et al. (2010) examined the compressive strength of plasters typically used for straw bale construction. Vardy and MacDougall (2007) and Vardy (2009) developed and validated models for predicting the compressive strength of straw-bale assemblies when subjected to concentric and eccentric in-plane loading. Gross et al. (2009) performed racking tests of plastered straw bale walls. ...
... Note that the compressive strength in Equation 5 is for cylinder strength tests, while cube compression tests are typically used for plasters. Cube compression strength values are known to be on average about 20% higher than cylinder strength values (Vardy 2009). The applicability of Equation 5 to the low strength plasters used in straw-bale construction was investigated by comparing the cube compression strength to the tensile strength obtained from split cylinder tests for the plaster used for the tests carried out in this paper. ...
... The modular ratios required values of the elastic modulus for each material. For the plaster, this can be determined using f c ′ (Vardy 2009): ...
The search for more sustainable construction methods has renewed interest in straw-bale construction. Rectangular straw bales stacked in a running bond and plastered on the interior and exterior faces have been shown to have adequate strength to resist typical loads found in one- and two-storey structures. The straw bales provide excellent insulation, while possessing low embodied energy compared to conventional insulation materials. The structural behaviour of a load-bearing plastered straw-bale wall subject to uniform compressive loading has been the focus of a number of studies reported in the literature. However, in a typical building wall, there will be numerous locations (such as around window and door openings) where the load paths produce areas of concentrated stress. The behaviour in these regions cannot necessarily be predicted using tests from uniformly loaded wall assemblies. This paper describes experiments on plastered single bale assemblies subjected to three-point bending. These assemblies develop shear and flexural stresses, and so simulate the stresses that exist around door and window openings in a wall. The specimens were rendered with lime-cement plaster, and were either unreinforced, or contained steel "diamond lath" mesh embedded within the plaster. The specimens were pin-supported at various centre-to-centre distances (L) ranging from 200 mm to 500 mm. The height (H) of all specimens was constant at 330 mm. This gave a range of H/L values of 0.66 to 1.65. Two distinct types of failure were observed. For tests with H/L < 1, failure was due to flexural tension cracks in the plaster which propagated through the depth of the plaster skin. For tests with H/L > 1, failure was due to crushing of the plaster in compression under one of the loading points. It was shown that models based on simple mechanics were able to adequately predict the assembly strength. In particular, analysing the assemblies with H/L < 1 as simple beams, and using the transformed section concept to deal with the straw and steel mesh, was adequate for predicting their strength. The results suggest that current practice for straw bale construction is generally appropriate. To avoid tensile cracking of plaster due to flexure, regions around doors, windows, and other openings should be designed such that H/L > 1. In regions where H/L < 1, the use of steel reinforcing mesh can increase the plastered bale strength by 30% on average.
... Portland cement sets by reaction with water in the mix while hydrated lime must expel excess water before it can set by reaction with atmospheric carbon dioxide (Thomson, 2005). The setting process of hydrated lime is much slower than cement; therefore the cement-lime plaster is kept in moist curing conditions for the first few days to initiate the cement"s curing process, at which point, the specimen is moved to a more arid environment (Vardy, 2009). ...
... found that each of the bales plastered flat had satisfied the limits. In fact, Vardy (2009) demonstrated that most concentric compression testing results satisfy the limits outlined by Riley and Palleroni (2001). ...
... Grandsaert (1999), Arkin and Donahue (2001), and Vardy (2009) conducted experiments on eccentrically loaded walls. "In this situation, the straw will act to tie the two plaster skins together, allowing them to work as a stressed skin panel to resist" the applied bending moment within the wall (Vardy, 2009). Donahue observed that the wall "panel behaved as a true sandwich panel with fully composite action" between the plaster and the straw and that "virtually all deflection [was] due to shear deformation of the straw bale". ...
... His results showed that tensile strength was in the range of 21.2 to 31.2 MPa, and the shear strength was in the range of 4.91 to 7.26 MPa. e strength of straw bale or straw bale walls is very different from that of the straw stem, because there exist too many void spaces in large volumes. Vardy's PhD thesis [10] presented new models for predicting the compressive strength of plastered straw bale assemblies that are subjected to concentric and eccentric loading [11]. A constitutive model for lime-cement plaster was adapted from a stressstrain model for concrete available in the literature. ...
... erefore, the bearing capacity of straw bales could be insufficient, if and when the plaster is compressed to failure. According to literature [10], the maximum strain in plaster at failure is in the order of 0.00253. If uniform deformation of plastered straw bale is achieved, the strain in the straw (ε 0 ) will also be approximately 0.00253 at failure. ...
Investigations were carried out to study the mechanical performance under uniaxial load of unplastered and plastered straw bales. Results from tests on 30 rice straw bales indicated nonlinear load-bearing properties with large deformations and anisotropy. Since the deformations observed did not conform to the current building code requirements, the evaluation of ultimate bearing capacity through the maximum axial vertical load was not possible. To obtain the design strength of rice straw bales in composite walls, further 21 specimens of plastered straw bales were also tested in compression. The permissible deformation of the straw bales was evaluated. It is noteworthy that the large deformability of straw bales can reduce the damage to structures after an earthquake. Consequently, the straw bale use can widely enhance the seismic performance of low-rise buildings.
... Using Lecompte and Duigou [49] as reference, the Young's modulus values between 100 and 200 kPa were observed from wheat straw bale samples with density of 80 to 100 kg•m À3 . Vardy [53] reported modulus values are ranging from 150 to 430 kPa for flat bale, and 210 kPa for on-edge bale at density 85 kg•m À3 . A non-linear rheological model of straw bales behavior under compressive loads has also been proposed by Molari et al. [54], with the geometry and density aspects of a straw bale taken into account in their model. ...
... Using Maraldi et al. [51] as reference, Poisson's ratio of 0.2 to 0.5 with mean value of 0.4 were observed Traditionally, straw bales used in building construction are applied with plasters/stucco such as lime, clay or cement, and the plaster will act as weather resistance barrier and provide additional reinforcement. The strength of the plastered straw bale mainly depends on the compressive resistance and thickness of the plaster, and the structure failures could be caused by either buckling or crushing of the plaster [53,55,56]. A refined compressive field theory for plastered straw bale walls had been investigated Palermo et al. [57] to predict the stress-strain response to in place shear and axial loads. ...
Straw bale constructions are considered as a promising solution towards the goal of decarbonisation of building sector. In particular, its use as an alternative thermal insulation and load-bearing material has been promoted. This study provide a thorough review of material properties of straw bale including mechanical, thermophysical and hygric. Furthermore, mechanical, hygrothermal, energy and acoustical performance as well as life cycle assessment of straw bale constructions are reviewed and discussed. The critical evaluation of the recent research confirms that straw bales can provide satisfactory results as thermal insulation material compared to conventional materials, while in parallel reflects a high potential for constructions with low embodied emissions. The potential of straw bale is tackled by the lack of consistent representation of material properties, which is controversial to the significant amount of the relevant scientific results that have been reported during the last years. This review provides a systematic framework that can function as basis for future research on straw bales as building material.
... Based on the experimental results augmented by experimental tests performed on similar plastered straw bale walls [23], the following constitutive equations are used: ...
... and f 0 c is the concrete compression strength. Eq. (4) was obtained by adapting the concrete stress-strain relation proposed by Collins and Mitchell [24] to experimental results obtained testing cement-lime plaster [23]. This equation was calibrated assuming the modulus of elasticity of the cement-lime plaster is given by Ec = 818f c2,max and the strain at peak stress is 0.00253, resulting in the proposed stress-strain relationship for cement plaster in compression shown in Fig. 12a. ...
Results of tests of plastered straw bale wall assemblies under in-plane shear and axial load are used together with proposed refinements to compression field theories for reinforced concrete members to predict ultimate shear strengths of plastered straw bale walls. Two parameters of the so-called “refined compression-field theory” are calibrated for use with straw bale walls. Experimental results are compared to theoretical expectations determined according to existing compression field theories and the calibrated, refined compression-field theory. Shear strengths are estimated for a variety of plastered straw bale wall configurations that have been recommended for inclusion in building codes, based on the calibrated refined compression-field theory.
... The compressive resistance of straw is around 0.017 N/mm 2 , around 2000-5000 times lower than for normal concrete. 20 C wheat straw (Lawrence et al., 2009) 21 C Thatcher Wheat (Hedlin, 1967) 21 C Cypress Wheat (Hedlin, 1967) Isotherm model (Lawrence et al., 2009) 23 C wheat straw (Carfrae, 2011) Therefore, rendered straw-bale construction derives its load resistance primarily from the relative strength and stiffness of the render coats, usually lime, cement-lime-based, rather than the much weaker straw (King, 1996;Vardy, 2009). However, in this composite behaviour, the straw bonded to the render provides important lateral restraint to the slender load-bearing coats. ...
Whilst the majority of bio-based building focuses on wood, the use of nonwood materials
in the built environment is an area of growing importance.
This chapter focus on the background and importance of nonwood bio-based
building materials in the construction market and will review the properties, present
and historic use, and the state-of-the-art research of the most relevant or innovative
raw materials, in particular, flax, hemp, straw, bamboo and rattan, reed, wool, peat,
grass and several pith plants.
... Tests were performed using custom-designed devices for the creep and relaxation tests and a properly modified ultimate testing machine for the other tests. Vardy (2009) presented the results of compression tests conducted on two wheat bales, one laid flat and one laid onedge. Load was applied at a constant rate using a ultimate testing machine which had plywood load plates combined with steel beams and wood braces to ensure even load distribution and vertical displacement was recorded using four linear potentiometers. ...
The use of straw bale construction is strongly on the rise. Despite the need for a deep understanding of the mechanical behaviour of straw bales, there is little research on the testing of single unplastered straw bales and a standard test method does not exist. In this paper, a method able to evaluate the mechanical behaviour of single straw bales is proposed. Force and displacement of the bale in all the three directions was measured in real time without stopping the test; this allowed to best deal with the time-dependent nature of the mechanical behaviour of the bales to be. The test apparatus included a hydraulic press for loading plus digital cameras and a 3D laser scanner for measuring the lateral displacement of the bale. The method was validated by testing six rice bales (three bales laid flat and three on-edge). Results showed that there is no significant difference in the elastic modulus between flat and on-edge orientations. For on-edge bales, string burst was observed, whereas for flat bales no string failure occurred. By using digital image correlation it was observed that straw bales exhibit a typical deformation pattern which is due to the baling process. Measurements also showed that the Poisson's ratio does not remain constant along the longitudinal direction during loading and it is null along the transverse direction. The proposed method can be implemented to evaluate the influence of a variety of parameters and loading conditions on straw bales mechanical response.
... Analyses for Wall E were made using a modulus of elasticity of plaster, E p , taken as 818 f 0 p , where f 0 p is the cube compressive strength of the plaster, and the strain at ultimate strength was taken as 0.0025, based on results presented by Vardy (2009). Parker et al. (2006 reports the mean strength of the mesh wire to be 384.2 ...
Although straw-bale construction originated in the midwestern United States in the late 1800s, the engineering of plastered straw-bale walls to resist in-plane lateral loads is a modern development. Relevant experimental studies are reviewed and allowable shears are developed for use in design for wind and seismic loading. Clay, soil-cement, lime, lime-cement, and cement plasters having various thicknesses and reinforced with welded steel wire mesh, woven steel wire mesh, or polypropylene mesh are considered. Experimental values are adjusted on the basis of moment-curvature analysis results to account for lower-bound model code material strengths, plaster thicknesses, and mesh reinforcement. A conventional model for shear strength is used to provide a preliminary assessment of true shear strength. The resulting design values and associated detailing requirements are summarized in a format suitable for implementation in model code provisions for straw-bale construction. (C) 2014 American Society of Civil Engineers.
... They were loaded with a concentric vertical compressive load. Vardy (2009) found that the model over predicted the strength of the 0.99m high walls by an average of 14% and under predicted the strength of the 2.31m high walls by an average of 10%. However, overall it was found that the model was 99% ...
Growing awareness of the impacts of anthropogenic climate change is driving the demand for sustainable alternatives to conventional building materials. Alongside modern high-performance materials, construction methods utilising traditional renewable raw materials and techniques are garnering increasing attention within society. Square straw bales can offer environmentally friendlier building solutions due to their excellent thermal properties and their ability to withstand mechanical loads when sufficiently compacted. This article focuses on experimental investigations into the biaxial load-bearing behaviour of vertically loaded wheat straw big bales intended for use in load transfer within buildings. The primary emphasis lies on analysing the short-term load-bearing behaviour under cyclic loads and the short-term creep behaviour under permanent loads. Utilising electromechanical and optical metrology, both vertical and horizontal deformation states are determined, forming the basis for establishing biaxial stress-strain relationships. It can be demonstrated that big bales display a notably stiffer behaviour in contrast to the small bales which have predominated scientific studies thus far. The stiffness characteristics are heavily influenced by bale density and the inhibition of pronounced lateral expansion behaviour. However, the creep behaviour is positively impacted by bale compaction due to mechanical preloading. Furthermore, the article aims to comprehensively document all pertinent specimen properties (such as appearance and straw structure), growth, manufacturing, and storage conditions (including environmental factors and pressing technology), as well as experimental parameters (such as test setup and metrology), test procedures (including load regimes and visual observations), and evaluations (such as stress-strain relationships and creep curves). This documentation aims to ensure traceability and reproducibility, facilitating comparisons with future test series and contributing to the development of standardised test methods for load-bearing straw bales.
Growing awareness of the impacts of anthropogenic climate change is driving the demand for sustainable alternatives to traditional building materials. Alongside modern high-performance materials, construction methods utilising traditional renewable raw materials and techniques are garnering increasing attention within society. Square straw bales can offer environmentally friendlier building solutions due to their excellent thermal properties and their ability to withstand mechanical loads when sufficiently compacted. This article focuses on experimental investigations into the biaxial load-bearing behaviour of vertically loaded wheat straw big bales intended for use in load transfer within buildings. The primary emphasis lies on analysing the short-term load-bearing behaviour under cyclic loads and the short-term creep behaviour under permanent loads. Utilising electro-mechanical and optical metrology, both vertical and horizontal deformation states are determined, forming the basis for establishing biaxial stress-strain relationships. Alongside exploring fundamental aspects of the non-linear load-bearing behaviour, the influence of bale bulk density and horizontal deformation constraints is examined. Furthermore, the article aims to comprehensively document all pertinent specimen properties (such as appearance and straw structure), growth, manufacturing, and storage conditions (including environmental factors and pressing technology), as well as experimental parameters (such as test setup and metrology), test procedures (including load regimes and visual observations), and evaluations (such as stress-strain relationships and creep curves). This documentation aims to ensure traceability and reproducibility, facilitating comparisons with future test series and contributing to the development of standardised test methods for load-bearing straw bales.
Background
The negative impacts of the construction industry are compelling arguments for embracing technology that contributes to carbon footprint reduction and resources conservation. Toward the achievement of objective 9 of the Sustainable Development Goals, the development of new building’s materials like straw bale has advanced in the construction industry. As demonstrated in the literature, straw bale is an eco-friendly material that presents many advantages, like its contribution towards a circular economy. However, it has low compressive strength and displays high displacement under compression load. So far, no attempt has been made in order to enhance the strength of straw bales.
Objective
This study aimed to develop alternative material to straw bale using chopped straw stems mixed with a binder (gum Arabic) and determine its stress-strain characteristic.
Methods
The manufacturing process of the new material involved the use of chopped straw and gum Arabic to form straw blocks.
Results
Results obtained show that the compressive strength of straw block (1.25MPa) is greater than the strength of straw bale (0.02MPa). Also, the average displacement recorded during compression load on straw blocks (29mm) was 2.8 times smaller than the displacement in straw bale (80mm). In terms of shape and size, straw blocks match with conventional materials like cement or compressed block. This will facilitate their use in construction compared to straw bales that require skilled laborers for pre-compression and plastering.
Conclusion
The use of gum arabic helps in holding straw stems together and forms a compact material with improved strength compared to straw bale. Performance improvement of the characteristics of load-bearing straw bale walls can be addressed by using straw blocks.
Strohballen als landwirtschaftliches Nebenprodukt bestehen aus nachwachsenden Rohstoffen, sind regional verfügbar, besitzen ausgezeichnete Dämmeigenschaften und können in hochverdichteter Form großen Beanspruchungen standhalten. Als lasttragende Elemente in Gebäuden des Wohn‐ und Gesellschaftsbaus sowie in landwirtschaftlichen Nutzbauten können sie zu einer Antwort auf die gestiegene Nachfrage nach ökologisch nachhaltigen Lösungen im Bauwesen beitragen. Während der vertikale Lastabtrag bereits Gegenstand mehrerer Forschungsarbeiten war, sind viele Fragen zur aussteifenden Wirkung von Strohwänden gegenüber Horizontallasten noch nicht geklärt. Als Grundlage für die Erarbeitung von Berechnungsmodellen zur realitätsnahen Abbildung des Last‐Verformungsverhaltens sowie zur Definition von Versagenszuständen und Grenzwiderständen ist eine solide experimentelle Datenbasis unerlässlich. In diesem Aufsatz werden Planung, Durchführung und Auswertung experimenteller Versuche zum horizontalen Lastabtrag in Wänden aus hochverdichteten Strohballen vorgestellt. Ziel der Untersuchungen ist ein besseres Verständnis des Last‐Verformungsverhaltens von in der Ebene belasteten Strohwänden. Die Auswertung basiert dabei auf dem Einsatz klassischer mechanischer sowie moderner optischer Messmethoden. Da die Untersuchung des Reibungsverbunds und des Einflusses von Auflasten im Mittelpunkt des Interesses steht, wird dabei bewusst auf den Einsatz mechanischer Verbundmittel verzichtet.
In this article, the planning, execution, and evaluation of experimental tests on horizontal load transfer in walls made of highly compacted straw bales are presented. The investigations aim to better understand the load-deformation behaviour of straw walls loaded in their plane. The assessment of the results is done by using classical mechanical and modern optical measurement methods. To study the frictional bond between the straw bale layers and the influence of vertical loads, the use of mechanical shear connectors is deliber-ately avoided.
Interest of using straw bale as construction material has increased worldwide. This result from the need of developing building envelopes which are climate responsive and can significantly reduce building’s energy consumption. Research on straw bale has shown that straw bale has good thermal conductivity while plastered straw bale assemblies has good mechanical properties. Up to date, straw bale construction consists of stacking straw bale in a running bond and use different techniques to push down straw bale wall before plastering them. No clue has been given if this method is structurally beneficial than to stabilized single straw bale before assembling them into a structural panel. This paper presents a method of construction that consist of manufacturing straw blocks before using them in masonry. Blocks of dimension 29 × 14 × 14 mm were manufactured using chopped straw with a natural binder. The average compressive strength and density of blocks are respectively 1.25 MPa and 522 kg/m³; which are respectively 73 and 5 times greater than that of straw bale. Also the average thermal conductivity of straw block and straw are similar (0.06 W/mK). Thus the use of straw blocks will improve the structural performance of straw houses.
Background
In recent decades, the enduring interest and continued development of straw bale as a walling material are based on its beneficial properties. Straw bale is a biomaterial that contributes greatly to carbon footprint reduction and offers excellent thermal insulation. It is proved that plastered straw bale assemblies have good mechanical properties and can be used for the construction of a single storey building. It is known that straw bale presents high displacement in the assemblies; thus, pre-compression is a major step that helps to push down straw bale so as to avoid future structural failure in the wall. There is no clue yet if this method is structurally beneficial than to stabilized single straw bales before assembling them into a structural panel.
Objective
This paper presents the structural performance of straw block assemblies under compression loads.
Method
Straw blocks and mortar were used to construct plastered and un-plastered wall panels, which were tested under uniformly distributed compression load till failure.
Results
The results obtained show that plastered straw block assemblies can support at least 286 KN/m ² , which is higher than the minimum slab load 18.25KN/m ² , including imposed load for a residential house. In addition, the strength of plastered straw block assemblies plastered with cement-gum mortar, 0.3 N/ mm ² is greater than the strength of a single storey building (0.19N/mm ² ). Furthermore, results indicate that un-plastered and plastered straw block assemblies perform better than un-plastered and plastered straw bale assemblies. Plastered straw block assemblies support up to 52KN while plastered straw bale assemblies support only 41.1KN.
Conclusion
Under compression load, straw block assemblies have a load carrying capacity greater than the minimum slab load. Therefore, Straw block can be used for the construction of a single storey building.
Experimental data describing the mechanical performance of Portland cement-hydrated lime mortars used for straw bale construction is presented. Straw bale construction uses stacked straw bales plastered on each side to form load-bearing elements. Mortars used have slumps of approximately 50 mm, compared to slumps up to 279 mm for conventional masonry mortars. Cylinder and cube tests of a range of typical straw bale mortar mixes were carried out. The mortars had compressive strengths ranging between 0.3 MPa and 13 MPa. Empirical equations describing the relationships between compressive strength and curing time, w/cm ratio, proportions of lime, cement and sand, and modulus of elasticity are presented. The data show that cement-lime mortars for straw bale construction will have a higher modulus of elasticity and lower failure strain than a conventional mortar of equivalent compressive strength. The Modulus of Elasticity is on average 818 times the compressive strength of a straw bale mortar, compared to 100 to 200 times as reported in the literature for conventional mortar. The average failure strain for straw bale mortar is 0.00253 compared to 0.0087 to 0.0270 reported in the literature for conventional mortar.
Straw bale construction is a nonconventional technique that involves stacking common straw bales and then applying layers of plaster to form load-bearing walls. The straw bales provide insulation, whereas the plaster protects the bales from moisture and provides strength and stiffness for the wall. This technique has experienced a revival because of its environmental benefits. Because there are few codes and standards for this construction technique, engineers are often required to check and approve designs using straw bale construction before building permits will be issued. An understanding of the behavior of straw bale construction is needed for engineers to approach this system with confidence. A model for predicting the response of plastered straw bale walls subjected to concentric and eccentric compressive loading was proposed in this paper. The model was verified using experimental tests of wall panels loaded until failure. The eccentrically loaded specimens were found to have load-deflection behavior (lateral and vertical) that could be predicted by theoretical models based on the stress-strain behavior of the lime-cement plaster. Failure of the specimens was observed to occur as a result of compressive failure of the plaster and was predicted based on the theoretical models.
Although rice straw and other grains have been used in building since pre-history, in the past two decades, there has been a move to utilize this rapidly renewable, locally available, agricultural byproduct as part of the sustainable construction movement. Up to this point, this has been done by simply stacking up the full straw bales. Stak Block, invented by Oryzatech, Inc., is a modular, interlocking block made of a composite of rice straw and binding agent that serves as an evolution in straw construction. This study investigates the feasibility of using these Stak Blocks as a structural system. The report was divided into four main parts: material testing, development of effective construction detailing, full-scale physical shear wall testing, and a comparison with wood framed shear walls.
The first section investigated the feasibility of using the Stak Blocks in a load-bearing wall application. Constitutive properties of the composite straw material such as yield strength and elastic stiffness were determined and then compared to conventional straw bale. Next, the decision was made to prestress the walls to create a more effective structural system. Various construction detailing iterations were evaluated upon the full-scale shear wall testing using a pseudo-static cyclic loading protocol. Finally, the available ductility of the prestressed Stak Block walls in a lateral force resisting application is quantified along with an approximation of potential design shear forces.
It was determined that the Stak Block material performed satisfactorily in gravity and lateral force resisting applications, in some respects better than conventional wood-framed construction, and has great potential as a seismically-resistant building material.
This 358 page book presents the properties of concrete as needed in concrete construction, including strength and durability. All concrete ingredients (cementing materials, water, aggregates, admixtures, and fibers) are reviewed for their optimal use in designing and proportioning concrete mixtures. Applicable ASTM, AASHTO, and ACI standards are referred to extensively. The use of concrete from design to batching, mixing, transporting, placing, consolidating, finishing, and curing is addressed. Special concretes, including high-performance concretes, are also reviewed. Available at http://www.cement.org/pdf_files/EB001.14.pdf.
The basic unit for straw bale constructions is the straw bale, so bales preparation in the field is very important for this purpose. Therefore, it must be produced with a good properties and tested for building purposes. Straw bale buildings are capable of successfully surviving humid climates, but less is known about the interaction of humid air and bales than probably any other aspect of bale building. Hopefully future research will help provide greater clarity in understanding how humidity affects bales in different climates and conditions (Steen et al., 1994). Agricultural waste utilization depends on the presence of information about the physical, mechanical and thermal properties of these materials. This knowledge helps the designer
and decision makers to asses the best ways to get benefits from those wastes also to avoid the hazards resulting from burning it or leaving it to deteriorate in the field.
In the last few years, Egypt has had a difficult problem with air pollution because most of the farmers burn rice straw illegally after harvesting. This, is because of the huge production of this straw (about 3 million tons / year) which is considered a big problem for the farmer when he stores it near to his house or in his field. The straw is a suitable medium for the growth of insects and pests. Moreover, during the summer this straw could
burn by itself. Each ton of rice straw produces 56 kg CO when burned (Steen et al., 1994). The farmers need to get rid of it and consequently, they start to burn it, causing also the black cloud and severe pollution in the atmosphere, especially in delta regions. Health problems are caused by the smoke. As a partial contribution to solve all of these problems, this study aimed to investigate the role of using straw bales in building construction in Egypt to insure comfort, safety, low costs and low energy consumption and more important to reduce air pollution. Due to the lack of information about the straw bale properties (physical, mechanical and thermal), it was necessary to study these properties and the thermal behavior of such buildings.
Objectives
The specific objectives of this work are as follows:-
(1) Studying physical properties of the straw and bales, which include, bale dimensions, density, straw particles lengths, moisture content and equilibrium moisture content.
(2) Studying the mechanical properties of straw bales that include stress, vertical strain, horizontal strain, stress-strain relation, modulus of elasticity and Poisson’s ratio.
(3) Studying the thermal properties of straw bales, which include thermal conductivity, thermal capacity, thermal effusivity, thermal diffusivity and time lag.
(4) Studying the thermal performance and stability of using straw bales as building’s walls.
The construction and testing of six full-scale plastered straw bale wall assemblies is described in this report. The specimens consisted of three cement stucco skinned walls and three earth plaster skinned walls representing varying levels of reinforcement detailing. All walls were tested in-plane under either cyclic or monotonic lateral loadings. Measured behavior is presented in this report, along with recommendations for future work.
A deformation measurement system based on particle image velocimetry (PIV) and close-range photogrammetry has been developed for use in geotechnical testing. In this paper, the theory underlying this system is described, and the performance is validated. Digital photography is used to capture images of planar soil deformation. Using PIV, the movement of a fine mesh of soil patches is measured to a high precision. Since PIV operates on the image texture, intrusive target markers need not be installed in the observed soil. The resulting displacement vectors are converted from image space to object space using a photogrammetric transformation. A series of validation experiments are reported. These demonstrate that the precision, accuracy and resolution of the system are an order of magnitude higher than previous image-based deformation methods, and are comparable to local instrumentation used in element testing. This performance is achieved concurrent with an order of magnitude increase in the number of measurement points that can be fitted in an image. The performance of the system is illustrated with two example applications.
The structural performance of plastered straw bales under compressive loading is extremely important when considering the suitability of plastered straw bales as a construction material. Most currently available results do not investigate how different construction methods and practices can affect the strength of a plastered bale. The experiments discussed in this paper illustrate how the strength of the plaster, the thickness of the plaster and the orientation of the bale itself can affect the strength of the plastered bale. It was found that the bales plastered flat were 36% stronger than those plastered on edge. In addition it was found that although the plaster strength does affect the strength of the plastered bale, it does not have as significant an impact as the plaster thickness. It was also found that nearly all plastered bales tested had higher strengths than would be required in typical residential construction. The strengths were found to be in the same range as the values reported in the existing literature. The plastered bale modulus was found to be highly variable and un-predictable.
The use of lime in the construction of modern buildings is presented. Buildings constructed with lime mortars can be altered easily. More energy is required to produce a tonne of cement than a tonne of hydraulic line, thereby increasing CO2 emissions. The bulk density of lime is half that of cement, leading to energy savings when using lime of approximately 30-50%.
Compares the compressive strengths of 127 pairs of 6 × 12 in. (152 × 304 mm) concrete cylinders capped with neoprene pads restrained by aluminum caps to compressive strengths of cylinders capped with a traditional sulfur mortar compound. Twelve testing variables were examined to determine whether the two capping methods would give similar results under different testing conditions. Although neoprene caps gave significantly different results from the sulfur caps for several testing variables, the results were not significantly different from the mean of the sulfur-capped specimens when proper ASTM procedures were followed for molding and testing cylindrical specimens.
Over the past hundred years, plastered straw bale construction has shown itself to be strong and durable in both load-bearing and post-and-beam structures. In load-bearing straw bale systems, the relatively strong, stiff plaster plays a significant role as it works together with the ductile straw bale core to function as a stress skin panel, resisting compressive, in-plane and out-of-plane loading. In post-and-beam straw bale systems with properly detailed connections, the plaster can act as a shear wall, resisting in-plane lateral loads. The final strength of these wall systems depends both on plasters and straw bales. The following tests begin to show the basic structural capacity of a variety of plasters.
This research investigated the influence of different capping materials on the compressive strength of controlled low-strength material (CLSM). These capping materials included a sulfur compound, gypsum capping compound, and neoprene pads with different durometer hardness values. Neoprene pads with Shore A durometer hardness values of 20, 40, 50, 60, and 70 were incorporated into the test program. A total of eight CLSM mixtures that covered a wide range of mixture compositions was included in this study. Sulfur capping compound was found to generate the most consistent compressive strength values and was thus used as a control in qualifying other capping materials. With a slightly modified ASTM C 1231 procedure, neoprene pads with a Shore A durometer value equal to or less than 50 were qualified to yield compressive strength values not less than 80% of the corresponding value from the sulfur mortar capping compound results at a significance level of 5%, as required in ASTM D 4832. At this same level of significance, the compressive values from CLSM cylinders capped with gypsum capping compound were found to be more than 92% of the control values from the sulfur mortar capped cylinder results. But, this capping procedure was found to be more time consuming than the neoprene pad testing. As such, sulfur capping compound and neoprene pads with a Shore A durometer value of not more than 50 are recommended to evaluate the compressive strength of CLSM cylinders.
Straw bale structures are cost efficient as well as environmentally friendly. These types of buildings make use of straw, a by product of nature, and use volunteers as a labor force. This research is a part of an ongoing plastered straw bale wall project. Recent research has shown that moderate as well as complete confinement of plastered skins have been used on the straw bale wall assemblies. This project will continue this investigation and will include the results of compressive tests of confined straw bale specimens. It will also include an evaluation of construction details for confining skins, and how further research can clarify which techniques are most beneficial when building straw bale structures.
The use of plastered straw bale walls for residential construction has found increasing popularity in Canada and the United States in recent years. Straw bales provide excellent insulation and a sustainable building material, while the plaster skins carry the majority of the loading on the wall. Therefore, it is essential to have an understanding of the structural properties of plaster. This paper presents the results of cube compression tests conducted on a lime-cement plaster typically used in straw bale wall construction. It was found that similar to concrete, the compressive strength of plaster increases with an increase in curing time and a decrease in water-cementitious materials ratio. It was also determined that a relationship exist between slump and strength for plasters and that slump tests can be used as plaster strength quality control on construction sites.
The uniaxial monotonic compressive stress-strain behavior and other characteristics of unreinforced masonry and its constitu-ents, i.e., solid clay bricks and mortar, have been studied by several laboratory tests. Based on the results and observations of the comprehensive experimental study, nonlinear stress-strain curves have been obtained for bricks, mortar, and masonry and six "control points" have been identified on the stress-strain curves of masonry, which can also be used to define the performance limit states of the masonry material or member. Using linear regression analysis, a simple analytical model has been proposed for obtaining the stress-strain curves for masonry that can be used in the analysis and design procedures. The model requires only the compressive strengths of bricks and mortar as input data, which can be easily obtained experimentally and also are generally available in codes. Simple relationships have been identified for obtaining the modulus of elasticity of bricks, mortar, and masonry from their corresponding compressive strengths. It was observed that for the strong and stiff bricks and mortar of lesser but comparable strength and stiffness, the stress-strain curves of masonry do not necessarily fall in between those of bricks and mortar.
Straw-bale construction is an emerging building method and many builders choose to plaster the straw bales with earthen plaster
to reduce the embodied energy of the structure. A better understanding of the parameters affecting earthen plaster strength
is essential for safe and effective use of this building technique. This study investigated the importance of initial plaster
moisture content, drying time, clay content and, moisture content at the time of testing. Clayey silt soil, bagged ball clay
and lime-cement are compared as plaster binders for straw-bale applications. Compressive testing was conducted on 50-mm plaster
cubes and 100-mm by 200-mm plaster cylinders. It was found that as initial moisture content increased, strength and modulus
of elasticity was unaffected for the earthen plaster. As the drying time increased between 10 days and 18 days, strength was
unaffected but modulus of elasticity increased proportionally. As clay content increased, strength increased proportionally
and stiffness was unaffected. As moisture content at the time of testing increased, both the strength and the stiffness decreased
proportionally. Plaster made with soil was found to have greater strength than the plaster made with bagged clay or lime-cement
plaster.
Design Dead Load of a Straw Bale Wall
- E Arbour
Arbour, E. (2000). "Design Dead Load of a Straw Bale Wall," Thesis Project,
Department of Civil Engineering, University of Manitoba, Winnipeg, Manitoba.
Preliminary Report on the Out-of-Plane Testing of an 8 foot by 8 foot Straw Bale/PISE Wall Panel
- D Arkin
- K Donahue
Arkin, D., and Donahue, K. (2001). "Preliminary Report on the Out-of-Plane Testing
of an 8 foot by 8 foot Straw Bale/PISE Wall Panel," in First International Conference
on Ecological Building Structure, San Rafael, California. 5 pp. Retrieved January 9,
2009 from http://www.cc-w.co.uk/Documents/DonahueArkin.pdf
Missile Perforation Threshold Speeds for Straw Bale Wall Construction with a Stucco Finish
- J Bilello
- R Carter
Bilello, J., Carter, R., (1999). "Missile Perforation Threshold Speeds for Straw Bale
Wall Construction with a Stucco Finish," Project Report, The Wind Engineering
Research Centre, Texas Tech University. 9 pp. Retrieved May 23, 2009 from
http://www.osbbc.ca/wordpress/wpcontent/uploads/2009/02/missile_perforation_threshold_speeds.pdf
Load Carrying Behavior of On Edge Straw Bale Walls
- B Blum
Blum, B. (2002). "Load Carrying Behavior of On Edge Straw Bale Walls," University
of Manitoba, Winnipeg, Manitoba.
Straw Bale Exterior Pinning Report
- R Bolles
Bolles, R. (1998). "Straw Bale Exterior Pinning Report", Research Report,
Sustainability International, Poway, California.
Straw Bales and Straw Bale Wall Systems
- G Bou-Ali
Bou-Ali, G. (1993). "Straw Bales and Straw Bale Wall Systems," M.Sc. Thesis,
Department of Civil Engineering and Engineering Mechanics, University of Arizona,
Tucson, Arizona.
Undergraduate Research Project, Architectural Engineering Department
- J Boynton
Boynton, J. (1999). "Straw-Bale Bending and Cement Plaster/Straw Bale Bond
Testing," Undergraduate Research Project, Architectural Engineering Department,
California Polytechnic State University, San Luis Obispo, California.
Strength Considerations in Mortar and Masonry
- R S Boynton
- K A Gutschick
Boynton, R.S. and Gutschick, K.A. (1964). "Strength Considerations in Mortar and
Masonry." Technical Note, National Lime Association, Arlington, Virginia, 10 pp.
Retrieved January 10, 2009 from
http://www.nationallimeassociation.org/PublicationArchives/StrengthConsiderationM
ortarMasonry1989.pdf
Design of Concrete Structures
Canadian Standards Association (CSA) (2004) "Design of Concrete Structures,"
CSA Standard A23.3-04, Toronto, Ontario
Compressive, Transverse and Racking Tests of Load-Bearing Walls
- J Carrick
- J Glassford
Carrick, J., and Glassford, J. (1998). "Compressive, Transverse and Racking Tests
of Load-Bearing Walls," Research Report, Building Research Centre, University of
New South Wales, Australia.
Design Approach for Load-Bearing Strawbale Walls
- K J Dick
- M G Britton
Dick, K.J., and Britton, M.G. (2002). "Design Approach for Load-Bearing Strawbale
Walls," CSAE Annual Conference, Saskatoon, Saskatchewan, July 2002.
Testing of Straw Bale Walls with Out of Plane Loads
- K Donahue
Donahue, K. (2003). "Testing of Straw Bale Walls with Out of Plane Loads"
Research Report, Ecological Building Network, Sausalito, California. 11 pp.
Retrieved January 10, 2009 from http://www.ecobuildnetwork.org/pdfs/Out-of-plane_wall_tests.pdf
Compression Resistance of a Stuccoed Straw Bale Wall
- D Dreger
Dreger, D. (2002). "Compression Resistance of a Stuccoed Straw Bale Wall,"
Undergraduate Thesis, University of Manitoba, Winnipeg, Manitoba.
A Pilot Study Examining and Comparing the Load Bearing Capacity and Behaviour of an Earth Rendered Straw Bale Wall to Cement Rendered Straw Bale Wall
- M Faine
- J Q Zhang
Faine, M., and Zhang, J.Q. (2002). "A Pilot Study Examining and Comparing the
Load Bearing Capacity and Behaviour of an Earth Rendered Straw Bale Wall to
Cement Rendered Straw Bale Wall," International Straw Bale Building Conference,
Wagga Wagga, Australia, 19 pp. Retrieved January 10, 2009 from
http://www.strawbalebuilding.ca/pdf/Mike%20Faine%20and%20Dr%20John%20Zha
ng's%20Earthen%20Render%20Tests.pdf
A Pilot Study Examining the Strength, Compressibility, and Serviceability of Rendered Straw Bale Walls for Two Storey Load Bearing Construction
- M Faine
- J Zhang
Faine, M., and Zhang, J. (2000). "A Pilot Study Examining the Strength,
Compressibility, and Serviceability of Rendered Straw Bale Walls for Two Storey
Load Bearing Construction," First International Conference on Ecological Building
Structure, San Rafael, California, 14 p. Retrieved January 10, 2009 from
http://www.strawbalebuilding.ca/pdf/Two-Storey%20LB.pdf
Developing and Proof-Testing the 'Prestressed Nebraska' Method for Improved Production of Baled Fibre Housing
- Fibrehouse Ltd
- Scanada Consultants
- Ltd
Fibrehouse Ltd and Scanada Consultants Ltd. (1996). "Developing and Proof-Testing the 'Prestressed Nebraska' Method for Improved Production of Baled Fibre
Housing," Research Report, Canada Mortgage and Housing Corporation (CMHC),
Ottawa, Ontario.
Structural Testing of Straw Bales in Axial Compression
- K Field
- J Woods
- C Fedrigo
Field, K., Woods, J., Fedrigo, C. (2005). "Structural Testing of Straw Bales in Axial
Compression," Undergraduate Presentation, University of Colorado at Boulder,
Colorado.
A Compression Test of Plastered Straw-Bale Walls
- M Grandsaert
Grandsaert, M. (1999). "A Compression Test of Plastered Straw-Bale Walls," M.Sc.
Thesis, University of Colorado at Boulder, Boulder, Colorado.
2-Hr Fire Resistance Test of a Non-Loadbearing Wheat Straw Bale Wall
- Intertek
Intertek (2007b) "2-Hr Fire Resistance Test of a Non-Loadbearing Wheat Straw Bale
Wall," Project No. 3098054A, Intertek Testing Services, Elmendorf, Texas, Research
Report, Prepared for the Ecological Building Network, Sausalito, California.
Retrieved January 9, 2009 from
http://www.ecobuildnetwork.org/pdfs/Cement_Stucco_Wall.pdf
Design of Straw Bale Buildings
- B King
King, B. (2006). Design of Straw Bale Buildings, Green Building Press, San Rafael,
California. 260 pp.
Buildings of Earth and Straw
- B King
King, B. (1996). Buildings of Earth and Straw. Green Building Press, San Rafael,
California. 169 pp.
Effect of Mesh and Bale Orientation on the Strength of Straw Bale Walls
- C Macdougall
- S Vardy
- C Magwood
MacDougall, C., Vardy, S., Magwood, C. (2008). Effect of Mesh and Bale Orientation
on the Strength of Straw Bale Walls. Research Report, External Research Program,
Canada Housing and Mortgage Corporation, 60 pp.
More Straw Bale Building: How to Plan, Design and Build with Straw
- C Magwood
- P Mack
- T Therrien
Magwood, C., Mack, P., Therrien, T. (2005). More Straw Bale Building: How to Plan,
Design and Build with Straw. New Society Publishers, Gabriola Island, B.C., 288 pp.
Straw Bale Building: How to Plan, Design and Build with Straw
- C Magwood
Magwood, C., and Mack, P. (2000). Straw Bale Building: How to Plan, Design and
Build with Straw, New Society Publishers, Gabriola Island, B.C., 256 pp.
Bearing Test of Plastered Straw Bales
- D Mar
Mar, D. (2003). "Bearing Test of Plastered Straw Bales." Research Report,
Ecological Building Network, Sausalito, California.
Fact Sheet: Hydrated Lime for Masonry Purposes
- D Mar
Mar, D. (1998). "Full Scale Straw Bale Vault Test," Research Report, Skillful Means
Architecture and Construction, Berkeley, California.
National Lime Association (NLA) (2002). "Fact Sheet: Hydrated Lime for Masonry
Purposes." National Lime Association, Arlington, Virginia, 7 pp. Retrieved January
10, 2009 from http://www.lime.org/Masonry.pdf
Straw Bale Shear Wall Lateral Load Test
- J Nichols
- S Raap
Nichols, J., Raap, S. (2000). "Straw Bale Shear Wall Lateral Load Test," First
International Conference on Ecological Building Structure. San Rafael, California, 24
pp. Retrieved January 9, 2009 from http://www.cc-w.co.uk/Documents/nichols.pdf
Community-Built Housing Solution: A Model Strawbale Home Design
- D Riley
- S Palleroni
Riley, D., and Palleroni, S. (2001). "Community-Built Housing Solution: A Model
Strawbale Home Design." Proceedings of Sustainable Buildings III, Fall BETEC
Symposium, Santa Fe, New Mexico, CD-ROM.