A micromechanical model for linear homogenization of brick masonry

A micromechanical model, originally developed for long-fiber composites, is applied to determination of the overall linear-elastic mechanical properties of simple-texture brick masonry. The model relies upon exact solution after Eshelby and describes brickwork as a mortar matrix with insertions of elliptic cylinder-shaped bricks. The macroscopic elastic constants are derived from the mechanical properties of the constituent materials and the phase volume ratios. The ability of the suggested model to predict the behavior of real brickwork has been checked by performing uniaxial compression tests on brick masonry panels of two types, with cement mortar and lime mortar. The results obtained through the proposed model fit experimental data more closely than other models selected from the literature for the sake of comparison.     

Equilibrium moisture content of earth bricks biocomposites stabilized with cement and gypsum

In recent years, energy efficient and ecologically friendly buildings have been important in the housing and construction sector. One of the major barriers to producing good and useful products is the lack of detailed information about natural materials, in particular their moisture related properties, as these materials are hygroscopic and sensitive to moisture. This research aimed to determine the equilibrium moisture content of earth block materials, as an extremely important characteristic variable for all physical simulations. Earth bricks with different compositions were fabricated from cohesive soil, cement, and gypsum combined with two kinds of natural fibers. Wheat and barley straw were used as reinforcing fibers and materials were treated at various temperatures (10–40 °C) and relative humidity (33–95%). The moisture content was considered in dynamic equilibrium with the environmental conditions and the effects of relative humidity and temperature were investigated. The effect of relative humidity was observed more pronounced than that of temperature. The test results are discussed with reference to the relevance of the earth bricks as an ecologically friendly building material that is directly associated with the moisture related properties of buildings. The results also showed significant improvement in the durability.     

Strength and elasticity of brick masonry prisms and wallettes under compression

The characteristics of brick masonry are influenced by the properties of bricks and mortar. This paper attempts at studying the properties of brick masonry using table moulded bricks and wire-cut bricks of India with various types of mortars. The strength and elastic modulus of brick masonry under compression have been evaluated for strong-brick soft-mortar and soft-brick strong-mortar combinations. Various sizes of prisms and wallettes have been tested during these experiments to study the size effect and different bonding arrangements. The failure mechanisms of such specimens have been studied. Attempts are also made to derive empirical relationships for masonry strength as a function of brick and mortar strength in the Indian context.     

Cement stabilised rammed earth. Part B: compressive strength and stress–strain characteristics

Strength and behaviour of cement stabilised rammed earth (CSRE) is a scantily explored area. The present study is focused on the strength and elastic properties of CSRE. Characteristics of CSRE are influenced by soil composition, density of rammed earth, cement and moisture content. The study is focused on examining (a) role of clay content of the soil on strength of CSRE and arriving at optimum clay fraction of the soil mix, (b) influence of moisture content, cement content and density on strength and (c) stress–strain relationships and elastic properties for CSRE. Major conclusions are (a) there is considerable difference between dry and wet compressive strength of CSRE and the wet to dry strength ratio depends upon the clay fraction of soil mix and cement content, (b) optimum clay fraction yielding maximum compressive strength for CSRE is about 16%, (c) strength of CSRE is highly sensitive to density and for a 20% increase in density the strength increases by 300–500% and (d) in dry state the ultimate strain at failure for CSRE is as high as 1.5%, which is unusual for brittle materials.     

Laboratory scale testing of extruded earth masonry units

There has been a resurgence in use of earth as a construction material largely driven by environmental concerns. Extruded earth masonry is a method of earth brick production that utilises existing fired brick manufacturing techniques. Extruded earth has distinct physical characteristics compared to other earthen building techniques. As industrial scale extrusion trials require large volumes of material, laboratory scale material development relies on samples prepared using alternative forming methods, such as moulding and compaction, which do not reliably reproduce the full-scale manufacturing process. The paper presents a representative method of manufacturing small scale extruded earth bricks. A suitable testing methodology is proposed, with varying curing conditions investigated. The small scale bricks are compared against equivalent large scale unfired earth bricks. The small scale bricks achieved a compressive strength of 3.39 MPa and with a corrected difference compared to the full scale bricks of 0.07 MPa; were found to be a reliable basis for laboratory scale investigation of material performance. The relationship that describes the effect of moisture content on strength exists for both small and large scale bricks.     

Cement stabilised rammed earth. Part A: compaction characteristics and physical properties of compacted cement stabilised soils

Strength and behaviour of cement stabilised rammed earth (CSRE) is a scantily explored area. The present study is focused on the strength and elastic properties of CSRE. Characteristics of CSRE are influenced by soil composition, density of rammed earth, cement and moisture content. The study is focused on examining (a) role of clay content of the soil on strength of CSRE and arriving at optimum clay fraction of the soil mix, (b) influence of moisture content, cement content and density on strength and (c) stress–strain relationships and elastic properties for CSRE. Major conclusions are (a) there is considerable difference between dry and wet compressive strength of CSRE and the wet to dry strength ratio depends upon the clay fraction of soil mix and cement content, (b) optimum clay fraction yielding maximum compressive strength for CSRE is about 16%, (c) strength of CSRE is highly sensitive to density and for a 20% increase in density the strength increases by 300–500% and (d) in dry state the ultimate strain at failure for CSRE is as high as 1.5%, which is unusual for brittle materials.     

Limestone dust and glass powder wastes as new brick material

Large amounts of glass and limestone wastes are accumulating all over the world. Disposal of Limestone Powder Waste (LPW) and Waste Glass Powder (WGP) is a rapidly growing problem for some municipalities, so research for alternative utilization of these disposals is needed. In this respect, the objectives of this study are to investigate both physical and mechanical properties of samples containing LPW–WGP combinations for producing as new building brick material. An experimental approach to develop a new brick material including mainly LPW, a small quantity of Portland cement and WGP is presented. The LPW, WGP and cement are mixed, humidified and compacted under high pressure in the moulds. The values of compressive strength, flexural strength, unit weight, water absorption, abrasion resistance, freezing–thawing (F-T) resistance and thermal conductivity satisfy the relevant international standards and introduces smoother surface compared to the current concrete bricks in the market. The process undertaken can easily be applied within the current brick plants. The WGP used in LPW remarkably improves the compressive strength, flexural strength, modulus of elasticity, abrasion resistance, F-T resistance, and thermal conductivity of LPW brick samples produced in this study. The test results indicate that the samples containing LPW–WGP combinations provide better results for a potential of producing economical new brick materials.     

Numerical derivation of homogenized dynamic masonry material properties with strain rate effects

Masonry is a composite material composed of bricks and mortar disposed in a regular arrangement. It is commonly used as load bearing or partition walls in building structures. Owing to limitations of computer power, detailed distinctive modelling of brick and mortar of a realistic masonry structure or a structure with masonry infilled walls is usually not possible. Moreover, no dynamic masonry material model can be found in the open literature. Dynamic masonry material properties are important for an accurate prediction of masonry failure and fragmentation under dynamic loads. In this paper, a continuum damage model with strain rate effect is developed for masonry materials based on the homogenization method. The equivalent elastic properties, strength envelope and dynamic increase factors (DIFs) of strength and moduli for the homogenized masonry material are numerically derived from the simulated responses of a representative volume element (RVE). A numerical model of an RVE is analyzed with detailed distinctive modelling of brick and mortar with their respective dynamic material properties obtained from laboratory tests. The homogenized material model can be used to analyse large-scale masonry structures subjected to dynamic loading.     

Masonry infilled reinforced concrete frames under horizontal loading / Stahlbetonrahmen mit Ausfachungen aus Mauerwerk unter horizontalen Belastungen

The behaviour of infilled reinforced concrete frames under horizontal load has been widely investigated, both experimentally and numerically. Since experimental tests represent large investments, numerical simulations offer an efficient approach for a more comprehensive analysis. When RC frames with masonry infill walls are subjected to horizontal loading, their behaviour is highly non‐linear after a certain limit, which makes their analysis quite difficult. The non‐linear behaviour results from the complex inelastic material properties of the concrete, infill wall and conditions at the wall‐frame interface. In order to investigate this non‐linear behaviour in detail, a finite element model using a micro modelling approach is developed, which is able to predict the complex non‐linear behaviour resulting from the different materials and their interaction. Concrete and bricks are represented by a non‐linear material model, while each reinforcement bar is represented as an individual part installed in the concrete part and behaving elasto‐plastically. Each brick is modelled individually and connected taking into account the non‐linearity of a brick mortar interface. The same approach is followed using two finite element software packages and the results are compared with the experimental results. The numerical models show a good agreement with the experiments in predicting the overall behaviour, but also very good matching for strength capacity and drift. The results emphasize the quality and the valuable contribution of the numerical models for use in parametric studies, which are needed for the derivation of design recommendations for infilled frame structures.     

中国传统建筑营造技术中的砖瓦设计研究

以传统建筑材料的砖瓦为研究对象，基于设计学视野，运用纵向考证与横向比较的研究方法，系统梳理了古代砖瓦的发展脉络及其应用场景。通过对条砖的尺寸进行数据量化分析，明晰了条砖尺度自汉代以降日趋变小并趋于固定，且更具有适人的特征，并逐渐替代大型空心砖成为主流。随着楔形砖与曲尺形砖的创制及大半圆瓦当的普及，至宋代砖瓦制作朝向规范化路径发展。以此探明古代烧造技术与建筑材料发展的相互关系。     

Development of bio-cemented constructional materials through microbial induced calcite precipitation

Microbial induced calcite precipitation (MICP) is an environmentally friendly technology to bond sand particle together to form sandstone like materials. In this paper, MICP-treated bio-specimen was developed through MICP. The property of bio-specimen was compared with beams or bricks made through lime modification and cement modification. Ottawa sand was used in MICP-treated bio-specimen preparation. The proportion of lime or cement was in the range of 10–40% by weight of dry sand. The four-point bending tests, brick compression tests and unconfined compression tests were conducted. The test results indicated that flexure strength of MICP-treated bio-specimen was 950 kPa which was similar to flexure strength of 20–25% cement-treated sand beams, but was much higher than flexure strength of 30% lime-treated sand beams. The brick compression strength of MICP-treated bio-specimen achieved 500 kPa, which was similar to brick compression strength of 30% lime-treated sand bricks. The unconfined compression test results showed that the unconfined compression strength (UCS) of MICP-treated bio-specimen (1300 kPa) was higher than UCS of 10% cement-treated specimen (900 kPa), and much higher than UCS of lime-treated sample (around 140 kPa). The relative uniformity of precipitated CaCO₃ distribution was achieved through the sample immersing preparation method. SEM images showed that failure pattern of MICP-treated, cement-treated and lime-treated specimens were bond-particle failure.     

Optically stimulated luminescence in retrospective dosimetry

Since the beginning of the 1990s the exploration of optically stimulated luminescence (OSL) in retrospective accident dosimetry has driven an intensive investigation and development programme at Ris? into measurement facilities and techniques. This paper reviews some of the outcomes of this programme, including the evaluation of the single-aliquot regenerative-dose (SAR) measurement protocol with brick quartz and the determination of dose-depth profiles in building materials as a guide to determining the mean energy of the incident radiation. Investigations into heated materials are most advanced, and a lower detection limit for quartz extracted from Chernobyl bricks was determined to be <10 mGy. The first results from the measurement of doses in unheated building materials such as mortar and concrete are also discussed. Both small-aliquot and single-grain techniques have been used to assess accident doses in these cement based building materials more commonly found in workplaces. Finally some results of a preliminary investigation of the OSL properties of household chemicals are discussed with reference to their potential as accident dosemeters.     

Measurement of natural radioactivity in sand samples collected along the bank of rivers Indus and Kabul in northern Pakistan

Radioactivity is a part of the natural environment. The presence of natural radioactivity in sand and other building materials results in internal and external exposure to the general public. Therefore, it is desirable to determine the concentration of naturally occurring radionuclides, namely (232)Th, (226)Ra and (40)K in sand, bricks and cement which are commonly used as building materials in Pakistan. In this context, sand samples were collected from 18 different locations covering an area of ～1000 km(2) along the banks of river Indus (Ghazi to Jabba) and river Kabul (Nowshera to Kund) in the northern part of Pakistan, whereas bricks and cement samples were collected from local suppliers of the studied area. In order to measure the specific activities in these samples, a P-type coaxial high-purity germanium-based gamma-ray spectrometer was used. In sand samples, the average specific activities of (226)Ra, (232)Th, and (40)K were found to be 30.5±11.4, 53.2±19.5 and 531±49 Bq kg(-1), whereas in brick samples, specific activities of 30±14, 41±21 and 525±183 Bq kg(-1) were observed, respectively. In cement samples, measured specific activity values were 21±5, 14±3 and 231±30 Bq kg(-1), respectively. Radium equivalent activities were calculated and found to be 143.8±38.6, 124±49.8 and 56.69±7 Bq kg(-1) for sand, brick and cement samples, respectively. The annual mean effective dose for the studied sand samples was found to be 0.40 mSv. External and internal hazard indices were less than unity for all the studied samples. The present results have been compared with those reported in the literature.     

Influence of the design materials on the mechanical and physical properties of repair mortars of historic buildings

Historic buildings are subjected to deterioration by natural weathering or by corrosion due to polluted atmosphere and the materials more susceptible are the mortars used. This study examines the influence of the type and quantity of design materials on compressive strength, creep, water absorption and length change of repair mortars produced. The design materials used were lime, natural pozzolan, sand and brick fragments in order to obtain the compatibility required between historic and repair mortars; different quantities of Portland cement were also used in order to quantify his influence. Nine mixtures were then designed and produced considering as parameters two binder: aggregates ratios, three pozzolan: cement ratios and three sand: brick fragments ratios. The experimental measurements continued until the age of 3 years or the stabilization of the test values. The results indicate that compressive strength is strongly affected by cement content and aggregates dosage and type. It appears that the increase of cement as well as brick fragments leads to confinement of creep deformation, while the mixtures with high pozzolan and sand content experience considerably high creep values. Water absorption reaches higher values when pozzolan or aggregate dosage arises and brick is in excess. Shrinkage increases when binder or brick quantity arise and is considerably influenced by cement content.     

A numerical insight into the response of masonry reinforced by FRP strips. The case of perfect adhesion

In this study a heterogeneous model at the meso-scale is presented, suitable to interpret delamination phenomena of FRP strips glued to masonry. Both mortar and bricks are modeled independently in tension and compression, through different isotropic damage variables and activation criteria. Reference is made to a masonry pillar, constituted by three Italian standard bricks interspersed by two mortar joints, reinforced by a perfectly-adherent FRP external sheet. The overall response and the collapse mechanism are investigated, induced by different boundary conditions and mechanical properties of constituent materials. Numerical predictions are compared to those provided by the Italian design code, with the aim of assessing pros and cons of simplified formulae. As a valid alternative for practitioners, the recourse to a numerical database is proposed, generated by combining FE predictions and best fitting, suitable to specify closed-form interface laws with brick and mortar compressive strengths as entries.     

Derivation of 3D masonry properties using numerical homogenization technique

Lots of research work has been conducted on homogenization technique, which derives global homogenized properties of masonry from the behaviour of the constitutive materials (brick and mortar). Such a technique mainly focused on two‐dimensional media in the previous studies with the out‐of‐plane properties of masonry material neglected. In this paper, homogenization technique and damage mechanics theory are used to model a three‐dimensional masonry basic cell to numerically derive the equivalent elastic properties, strength envelope, and failure characteristics of masonry material. The basic cell is modelled with distinctive consideration of non‐linear material properties of mortar and brick. Various displacement boundaries are applied on the basic cell surfaces in the numerical simulation. The detailed material properties of mortar and brick are modelled in a finite element program in the numerical analysis. The stress–strain relations of masonry material under various conditions are obtained from the simulation. The homogenized elastic properties and failure characteristics of masonry material are derived from the simulation results. The homogenized 3D model is then utilized to analyse the response of a masonry panel to airblast loads. The same panel is also analysed with distinctive material modelling. The efficiency and accuracy of the homogenized model are demonstrated. The homogenized material properties and failure model can be used to model large‐scale masonry structure response. Copyright © 2006 John Wiley & Sons, Ltd.     

Compressive strength and elasticity of pure lime mortar masonry

The procedure and findings of an experimental campaign for the mechanical characterization of brick masonry with lime mortar joints are presented. The campaign includes the determination of the properties of the constituent materials and of the resulting masonry composite. The masonry consisted of masonry stack bond prisms made of solid clay bricks and two types of pure lime/sand mortars, material combinations which correspond to the vast majority of historical and existing masonry structures. The paper includes a discussion on the ratio between the elastic modulus and the compressive strength of the masonry constituents and the comparison of these ratios with the ones suggested in design codes. The implications of this comparison are discussed in the context of interventions on historical masonry structures using modern and traditional materials.     

An anisotropic linear elastic boundary element formulation for masonry wall analysis

This work presents an application of a Boundary Element Method (BEM) formulation for anisotropic body analysis using isotropic fundamental solution. The anisotropy is considered by expressing a residual elastic tensor as the difference of the anisotropic and isotropic elastic tensors. Internal variables and cell discretization of the domain are considered. Masonry is a composite material consisting of bricks (masonry units), mortar and the bond between them and it is necessary to take account of anisotropy in this type of structure. The paper presents the formulation, the elastic tensor of the anisotropic medium properties and the algebraic procedure. Two examples are shown to validate the formulation and good agreement was obtained when comparing analytical and numerical results. Two further examples in which masonry walls were simulated, are used to demonstrate that the presented formulation shows close agreement between BE numerical results and different Finite Element (FE) models.     

Heat and Moisture Transport and Storage Parameters of Bricks Affected by the Environment

The effect of external environment on heat and moisture transport and storage properties of the traditional fired clay brick, sand–lime brick and highly perforated ceramic block commonly used in the Czech Republic and on their hygrothermal performance in building envelopes is analyzed by a combination of experimental and computational techniques. The experimental measurements of thermal, hygric and basic physical parameters are carried out in the reference state and after a 3-year exposure of the bricks to real climatic conditions of the city of Prague. The obtained results showed that after 3 years of weathering the porosity of the analyzed bricks increased up to five percentage points which led to an increase in liquid and gaseous moisture transport parameters and a decrease in thermal conductivity. Computational modeling of hygrothermal performance of building envelopes made of the studied bricks was done using both reference and weather-affected data. The simulated results indicated an improvement in the annual energy balances and a decrease in the time-of-wetness functions as a result of the use of data obtained after the 3-year exposure to the environment. The effects of weathering on both heat and moisture transport and storage parameters of the analyzed bricks and on their hygrothermal performance were found significant despite the occurrence of warm winters in the time period of 2012–2015 when the brick specimens were exposed to the environment.     

Valorization of stabilized river sediments in fired clay bricks: factory scale experiment

The objective of this study is to demonstrate the practical use of polluted river sediments after treatment into brick production. Consequently, a full-scale industrial experiment was conducted at a brick factory in the north of France. Polluted sediment was stabilized by the Novosol process and then was introduced in the mix-design with a substitution ratio of 15% as a partial replacement of quartz sand. Approximately 15,000 perforated sediment-amended bricks were produced. The produced bricks were then subjected to several qualification tests (compressive strength, freeze and thaw resistance, water absorption). The results obtained showed that the substitution of quartz sand by treated sediment resulted in a significant increase in brick compressive strength and firing shrinkage, and in a decrease in porosity and water absorption. Moreover, leaching tests performed according to different standards on substituted brick samples showed that the quantities of heavy metals leached from crushed bricks were within the regulatory limits. Thus substituted bricks can be regarded as non-hazardous material.