Solid Clay Bricks Research Articles

Research on 3D Model Calculation of Green and low-carbon New Buildings

Due to the widespread use of solid clay bricks in building houses in China, the annual destruction of farmland by burning bricks amounts to about 100000 acres. Faced with these problems, China has an extremely urgent demand for green and low-carbon buildings. Therefore, this article conducts computational research on the 3D model of a new type of green and low-carbon building. Due to the significant differences in the geometric form and texture representation of a large number of green and low-carbonl new buildings, it is difficult to uniformly quantify their level of detail. This article considers the usefulness and accessibility of 3D model calculation data separately. The shadow length is generally the distance from the selected building's facade roof to the end of the shadow, which can avoid the influence of building shape on its length. The determination of these two points and the calculation of the distance between them will directly affect the accuracy of shadow length calculation. Therefore, when users need to add an application subsystem to the system, they must add information such as the input and output data structures of the subsystem to the module. The height information calculation method uses the building and shadow imaging geometric modeling to calculate the building height by establishing the relationship between the shadow length and the corresponding building height.

Preliminary evaluation of predictions from compressive strength models for masonry

Compressive strength is the most essential design parameter of load-bearing masonry structures. The performance of masonry under compression depends on numerous parameters and is linked to the properties of its component materials, which enclose high variability, and to its geometrical characteristics and interlocking arrangement. Available predictive models are usually based only on few variables and therefore their estimates are liable to uncertainties. In this paper, the performance of four existing models for the estimation of the compressive strength of masonry made of solid units, is evaluated. To this end, experimental data from tests on single-layered specimens made of solid clay bricks, and subjected to monotonic compression, were collected from the literature. The predictions of the four models are compared to the experimental strength of the masonry specimens. The performance of each model is assessed through statistical analysis indices. From the analysis, it is concluded that the examined predictive models overestimate the masonry specimens with experimental strength less than 5 MPa.

Diagonal Compression Tests on Unfired and Fired Masonry Wallettes Retrofitted with Textile-Reinforced Alkali-Activated Mortar

This paper discusses the integration of an alkali-activated mortar (AAM), based on industrial waste, into a novel composite material fit for structural upgrading purposes and rendered with high temperature endurance and a low CO2 footprint. The AAM combined with carbon fiber textiles form a new generation of sustainable inorganic matrix composites—that of textile-reinforced alkali-activated mortars (TRAAM). A test program was designed to assess the effectiveness of carbon TRAAM overlays in increasing the shear capacity of masonry wall specimens comprising solid clay bricks bonded with lime-based mortar and furnished with TRAAM jackets on both sides. The initial and the residual capacity of the reinforced walls were evaluated, the latter by performing diagonal compression tests after exposure to 300 °C and 550 °C. It was shown that TRAAM jacketing can increase the shear capacity of unfired masonry walls by 260% and 335% when a single or a double layer of textile is used, respectively. Rapid heating to temperatures up to 550 °C, one-hour-long steady-state heating, and natural cooling bore no visible thermal cracks on the specimens and had little effect on their residual capacity. Based on these results, the prospect of using TRAAM for retrofitting applications for fire-resilient structures seems very auspicious.

Anchors to Solid Clay Brick Masonry in Tension: Behavior under Monotonic and Repeated Loading for Constant Embedment Depth

This paper presents a part of an extensive experimental campaign performed at the National Technical University of Athens (NTUA) with the purpose of investigating the behavior of chemical anchors embedded in solid brick masonry. Anchors are tested in tension under monotonic or repeated loading. All tests are performed under displacement-controlled conditions. The experimental setup and the instrumentation are presented, along with the investigated parameters and the rationale for the selection of the values of those parameters. In this part of the experimental work, comprising fifty-six (56) tests, the examined parameters are the anchor locations (in mortar joints and in the center of bricks), the state of the substrate (cracked or uncracked), the width of the crack crossing the anchor or at its vicinity (up to 1.20 mm), as well as the loading history (monotonic or repeated). In the tests presented herein, the embedment length of the anchors is equal to 100 mm. The anchors are embedded in solid brick masonry wallettes, and subjected to a normal compressive stress equal to 0.20 MPa. The observed failure modes are explained, and the overall behavior of anchors subjected to tension is presented and commented upon, along with the effect of the investigated parameters on the measured tension resistance, and on the corresponding displacement.

Shear performance of brick masonry walls reinforced with twisted steel bars

The present paper presents a study on the in-plane shear performance of solid clay brick masonry walls reinforced with near-surface mounted twisted steel bars. Masonry assemblages were fabricated representing those used in masonry-concrete buildings such as those found in Lisbon, built during the decades of 1930–1950. Solid clay bricks laid in Flemish bond using cement-lime blended mortar were used in the construction of fifteen wallette specimens. Three reinforcement layouts were applied on both faces of the wallettes, namely: grid (vertical + horizontal bars), vertical-only, and horizontal-only. Three unreinforced and nine reinforced specimens were subjected to diagonal compression tests. Three other unreinforced specimens were subjected to axial compression tests. The effectiveness of the proposed strengthening solution was discussed. The findings indicate that the proposed strengthening solution substantially increased the shear strength and greatly improved the ductility of the masonry wallette assemblages, pointing to its interest in practice. Although the number of tests performed is significant (considering its complexity), it should be noted that the representativeness of the results could be improved by performing more tests. The incorporation of results from other studies (in progress within the RESIST2020 research project), namely, regarding the walls out-of-plane behavior, will allow for a more complete characterization of the benefits of the reinforcement solution.

Cyclic behavior of masonry walls retrofitted with post-installed twisted bars or bonded rebars

The damage observed after the recent earthquakes showed that the most common failures for masonry buildings involve out-of-plane mechanisms associated to the ineffective connection between walls. For this reason, retrofitting techniques aiming to achieve a box-like behavior are of great interest. This paper presents the results of an experimental study conducted to investigate two different retrofitting solutions used to improve the structural connection between orthogonal walls: a mechanical connection by means of twisted bars and a fastening solution with rebars and injection mortar. Two full-scale T-shaped masonry specimens were realized in solid clay brick, with a “weak” connection between the front and the back wall. The specimens were tested in unreinforced and strengthened configurations, considering different retrofitting layouts. An out-of-plane load was applied on the front wall, together with a vertical prestress to simulate the gravity load coming from the floors and walls above. Each specimen was tested in three consecutive runs: a monotonic one on the unreinforced masonry, a first cyclic run with the wall intersection reinforced with twisted bars, and a second cyclic run on the wall retrofitted with rebars and injection mortar, after the removal of the twisted bars. The twisted bar solution resulted in a significant increase of the dissipative capacity of the wall despite the number of adopted bars, while, in the case of rebars and adhesive, a higher resistance was achieved together with a perfect box-like behavior.

Geometric characterization of solid ceramic bricks for construction in Ecuador

In Ecuador, about 95.9% of dwellings are built with masonry, however the local production of bricks does not meet technical standards and there is no scientific research on its geometric characterization and the technical state of their production. The geometric characterization of bricks is essential for the standardization of materials and constructions and allows the design of structures with a higher degree of accuracy. This research, conducted in 12 provinces of the 3 continental regions of the country, where 79% of the buildings are concentrated, studies for the first time the geometric characteristics of solid clay bricks in Ecuador. The results show that 67% of the brick production in Ecuador is artisanal and 98% of the factories do not comply with the technical standards for brick production. The authors present the characteristic dimensions of solid bricks produced in different regions of Ecuador. The results show a high variation in brick dimensions depending on the region, and even in a same province the dimensions depend on the factory, since its production does not comply with any standard. Ecuadorian standards regulating brick geometry need to be updated taking into account the real characteristics of the national brick production.

Early age strength of ambient-cured geopolymer mortars from waste concrete and bricks with different alkaline activators.

Background: The dataset in this work emanates from preliminary studies comparing early-age compressive strengths of geopolymer mortars produced from construction and demolition wastes (CDW) commonly found in Qatar using different alkaline activators. Methods: Waste concrete, waste bricks and steel slag - an industrial waste produced in large quantities in the country - were used as aluminosilicate sources. Waste concrete was used as fine aggregate (75 μm to 4 mm), while solid or hollow red clay bricks were used together with steel slag as aluminosilicate powders. Solid red clay brick (75 μm to 1.4 mm) was also used as fine aggregate in some mixes. Different alkaline activators including solid powder or ground pellet forms of Ca(OH)2, CaO, and Ca(OH)2-NaOH, NaOH-CaCO3 and Na2SiO3-Na2CO3-Ca(OH)2 mixtures were employed by just adding water. A few mixes included both solid powder Ca(OH)2 and viscous solutions of NaOH and NaOH-Na2SiO3 as alkaline activators. The geopolymer mortars also included small amounts of some other additives such as gypsum, microsilica and aluminium sulfate to enhance the geopolymerization and hydration process. Random proportions of the materials were considered in the range-finding experiments, and the mortars produced were tested for compressive strength. Results: The data show the 7-day compressive strengths and densities of the 40 mixtures considered with mostly ambient temperature (20°C) curing. It also shows such data for mixtures in which variables such as curing at 40°C, mixing with hot water at 50 - 60°C temperature, grading of waste concrete aggregates, and collective grinding of the powdered materials were considered. Conclusions: The dataset shows possible early-age compressive strengths of different geopolymer mortar mixture designs and the materials and mixture design methods that can be used to achieve desired early-age strengths from waste concrete and bricks.

Distinct element modeling of the in‐plane response of a steel‐framed retrofit solution for URM structures

AbstractThis paper presents the results of a numerical study aimed at assessing the effectiveness of an innovative steel modular retrofit system on improving the in‐plane lateral capacity of unreinforced masonry (URM) load‐bearing structures. The investigated retrofit solution consists of modular steel frames fastened to the external surface of masonry piers through chemical anchors. Distinct element models are built and calibrated against experimental data coming from a series of in‐plane quasi‐static tests performed on piers in both bare and retrofitted conditions. Two different masonry typologies are considered herein: one made up with solid clay bricks and lime mortar, assembled in a header bond pattern, and the other with typical Italian hollow clay units and cement‐lime mortar, arranged in a Flemish bond pattern. A simplified microscale approach, combined with a mesh‐refinement strategy, is adopted to decrease computational demand without losing numerical accuracy. All in‐plane failure mechanisms, such as mortar and unit tensile failures, as well as masonry crushing for high compressive stresses, are included in the developed numerical models. Moreover, a methodology to explicitly account for the contribution of the investigated retrofit in the distinct element method (DEM) framework is presented and discussed. The proposed modeling strategy yielded a good prediction in terms of lateral stiffness, lateral strength, hysteretic response, and crack pattern for unreinforced and strengthened specimens. A novel set of metrics is proposed to quantitatively assess the retrofit performance benefits.

Laboratory-testing and industrial scale performance of different clays from eastern Morocco for brick manufacturing

This study aims to the valorization of soil materials (unfired and fired) for sustainable buildings in eastern Morocco. To make this study more representative, four clay soils from different areas were considered in this investigation (i.e., Zaio, Oujda, Lota, and Midar). Geotechnical tests revealed that all samples exhibit a high clay content and medium plasticity. X-ray diffraction, thermal gravimetric analysis and energy dispersive X-ray spectroscopy of the soils showed the presence of quartz, calcite and several clay minerals. The significant clay content and the high density of the bricks (1589–1713 kg.m−3) have an effect on the properties of the unfired solid clay brick. Experimental results have shown that the thermal conductivity and compressive strength of the unfired solid clay brick vary between (0.77–1.07 W.m−1K−1) and (1.7–2.4 MPa) respectively. The cavities and firing process for fired hollow clay bricks contributed to the increase in thermal and mechanical resistance of the bricks by (0.19–0.4 W.m−1K−1) and (2.9–5 MPa) respectively. After identification of all the samples, the authors' justified choice was to use the soil collected from the Lota site for the ANSYS-Fluent hybrid wall case studies. In comparison to the other cases, the configuration (Mortar/Fired hollow clay brick and unfired solid clay brick/Mortar) demonstrated a 2 h improvement in time lag and a considerable decrease in the amplitude of the temperature fluctuation. Therefore, unfired solid clay bricks and fired hollow clay bricks may be used in combination to provide thermal comfort for a sustainable building.

The Influence of the Rebound Hammer Test Location on the Estimation of Compressive Strength of a Historical Solid Clay Brick

This paper presents the study of a two-hundred-year-old, demolded solid clay brick using the rebound hammer test for the estimation of the compressive strength. During the test, the location and face type influence on the rebound values are monitored and recorded. In addition, the calculation of the average rebound value has been modified to encounter the influence of location and face types. Furthermore, the estimated compressive strength is compared with the normalized mean compressive strength to check the accuracy of the rebound hammer test if it is within the confidential limit of ±25%. The result shows that the location and surface types have influence on the rebound value, which in turn affected the compressive strength.

In-plane seismic performance of an innovative steel modular reinforcement system for URM walls

An experimental and numerical research, aimed at evaluating the in-plane seismic performance of an innovative steel modular system for the reinforcement of load-bearing masonry walls (named "Resisto 5.9", designed by Progetto Sisma s.r.l.), is currently underway at the EUCENTRE Foundation in Pavia. Two different masonry typologies, representing common solutions in Italian existing buildings, were considered in this campaign: one made up with solid clay bricks and lime mortar, with "header bond" pattern, and the other with a typical Italian hollow clay "doppio UNI" unit and cement-lime mortar, assembled in a "Flemish bond" pattern. The experimental tests included first the complete mechanical characterization of units, mortars, masonry typologies and of the strengthening system components (i.e. steel elements and anchors). In-plane quasi-static tests were performed on different batches of full--scale specimens to investigate the influence of the proposed reinforcement system on the lateral in-plane response of the walls, compared to their unreinforced conditions. The cyclic behaviour of the masonry piers was analysed in terms of elastic stiffness, lateral strength, displacement capacity and energy dissipation, depending on the achieved damage mechanism. The numerical study of the ongoing campaign consisted of a series of parametric analyses on advanced discontinuous models based on the Distinct Element Method (DEM), considering different wall dimensions, vertical load levels and boundary conditions, in addition to those tested experimentally. Moreover, the numerical campaign was extended also to other possible masonry typologies, varying the bond pattern and the mechanical properties with respect to the experimentally tested solutions. In this paper, the results of the experimental tests on solid brick masonry together with a preliminary overview of the findings of the numerical study, still ongoing, were reported.

Anisotropy and compressive strength evaluation of solid fired clay bricks by testing small specimens

A study is presented on the use of a non-standard 40 × 40 × 40 mm3 specimen for the experimental measurement of the compressive strength of solid fired clay bricks extracted from existing masonry buildings. The viability of such specimen has been assessed by comparison with experimental results obtained with the standard 100 × 100 × 40 mm3 specimen. The use of the non-standard 40 × 40 × 40 mm3 has two main advantages. First, it significantly reduces the volume of sampled material, which can be severely restrained in architectural heritage buildings. Second, it allows carrying out tests in the three brick dimensions (length, width and thickness), and therefore investigating the anisotropy that clay bricks can exhibit depending of their manufacturing process. The experimental campaign has focused on three different types of solid fired clay bricks, namely mechanically extruded, hydraulic press moulded, and handmade units, with a total amount of 461 specimens. Using the mentioned small cubic specimen, a detailed research on the compressive strength and the anisotropy of different solid clay brick types has been carried out by applying a statistical approach. The experimental results and the statistical processing have shown that the proposed specimen can be utilized for a reliable estimation of the compressive strengths along the three main directions of solid fired clay bricks.

FAST-NEPAL: Regionally Calibrated Spectral Method for Reinforced Concrete With Masonry Infills

Reinforced concrete (RC) with masonry infill is one of the most common structural typologies in Nepal, especially in the Kathmandu Valley. Masonry infills are typically made of solid clay bricks produced locally in Nepal. This study aims to calibrate the spectral-based analytical method, namely, FAST, for Nepalese RC-infilled buildings. The FAST method has been initially conceived for Southern European RC buildings with hollow clay brick infills. The calibration is achieved by reviewing code prescriptions and construction practices for RC masonry infills in Nepal and updating the FAST method. The variables of FAST method are calibrated using different information sources and a Bayesian updating procedure to consider the global and local material properties for solid clay bricks. The FAST-NEPAL method obtained is then verified, considering a single school design, for which a detailed state-of-the-art vulnerability assessment is available. Being particularly suitable for large-scale assessment, the method is further validated using data from Ward-35 of Kathmandu Metropolitan City (in the vicinity of Tribhuvan International Airport) obtained from photographic documentation included in a geo-referenced database of buildings collected after the 2015 Nepal earthquake and prepared for census purposes. The comparisons show that the FAST-NEPAL method can be conservative relative to the other data sources for vulnerability and is more accurate at capturing low-level damage. This makes the approach suitable for large-scale preliminary assessment of vulnerability for prioritisation purposes.

Experimental cyclic behaviour of shear masonry walls reinforced with single and double layered Steel Reinforced Grout

Recent research on the mechanical characterisation of Steel Reinforced Grout (SRG) has highlighted its excellent performance as strengthening solutions for masonry structures. Using SRG with limited fabric density ensures a good textile-matrix interlocking, preventing at the same time the failure due to slippage or debonding from the substrate. This paper presents an experimental investigation on the use of SRG as in-plane strengthening solution for shear masonry walls composed of handmade solid clay brick and hydraulic lime mortar. Cyclic shear compression tests were carried out on walls strengthened with SRG comprising low density steel sheets (LDS). The SRG was applied on both faces of the walls with a strip configuration, using one and two layers of LDS. The experimental programme aimed to study the influence of the number of textile layers on the in-plane response of strengthened masonry walls in terms of failure mechanism, load-bearing capacity, energy dissipation, and ductility.

Cyclic shear-compression testing of brick masonry walls repaired and retrofitted with basalt textile reinforced mortar

This paper reports an experimental programme on masonry walls composed of handmade solid clay brick and hydraulic lime mortar. Reversed cyclic shear compression tests were carried out on the walls in three different configurations: unreinforced, repaired and retrofitted, and just retrofitted. Damaged walls were repaired and retrofitted with Basalt Textile Reinforced Mortar (B-TRM) and tested again to investigate the recovery of strength, stiffness and the improvement in drift capacity. The repair consisted in filling the open cracks and replacing the damaged bricks by following the so-called “scuci-cuci” technique. The just retrofitted configuration consisted of externally bonded B-TRM on undamaged walls. The B-TRM system comprised continuous bidirectional grids of basalt fibre embedded in hydraulic lime mortar on both surfaces of the walls. The experimental results showed the suitability of the proposed solutions for seismic retrofit and post-earthquake repair of existing masonry buildings. The research results highlighted the capacity of the proposed repair technique to reinforce damaged walls and the effectiveness of the investigated B-TRM system in increasing the resistance, the ductility, and the energy dissipation of unreinforced clay brick masonry. In addition, the results allowed a better understanding of the behaviour of masonry walls subjected to cyclic horizontal displacement in terms of failure mechanism and displacement capacities.

Development and Validation of a Modified Equivalent Strut Model of Lightweight Masonry Block Infill Walls for Quasi-static In-plane Cyclic Analysis

ABSTRACT Lightweight masonry blocks (LMBs) are more environmentally favorable than solid clay bricks, and have gradually become the main material for the infill walls of modern buildings. It is of great importance for proposing a suitable hysterical model of LMBs infill walls to accurately predict the seismic responses of modern buildings. However, cyclic loading tests of LMB infill walls demonstrate that the existing formulas of equivalent strut models significantly overestimate the stiffness and underestimate the peak strength. To this end, the force-displacement curves of 24 cyclic loading tests of LMB infill walls sourced from existing literature are statistically analyzed. The modification coefficients of stiffness and peak strength are put forward, and other parameter values such as yield strength coefficient, unloading stiffness coefficient and pinching effect coefficient are also recommended. Then a full-scale cyclic loading test of an LMB infill wall is designed and conducted to verify the accuracy of the modified model. In addition, the applicability of the modified model is also verified by two infill wall tests from existing literature. The results indicate the modified model can accurately simulate the global hysteretic response of LMB infill walls, and the simulation accuracy of the peak strength is increased to more than 90%. This model provides a useful tool for the accurate evaluation of the seismic performance of modern buildings infilled with LMBs.

Mechanical modelling of the axial behaviour of traditional masonry wall metal tie connections in cavity walls

The seismic assessment of unreinforced masonry (URM) buildings with cavity walls is a relevant issue in many countries, such as in Central and Northern Europe, Australia, New Zealand, China and several other countries. A cavity wall consists of two separate parallel masonry walls (called leaves) connected by metal ties: an inner loadbearing wall and an outer veneer having mostly aesthetic and insulating functions. Cavity walls are particularly vulnerable structural elements. If the two leaves of the cavity wall are not properly connected, their out-of-plane strength may be significantly smaller than that of an equivalent solid wall with the same thickness.The research presented in this paper focuses on a mechanical model developed to predict the failure mode and the strength capacity of metal tie connections in masonry cavity walls. The model considers six possible failures, namely tie failure, cone break-out failure, pull-out failure, buckling failure, piercing failure and punching failure. Tie failure is a predictable quantity when the possible failure modes can be captured. The mechanical model for the ties has been validated against the outcomes of an experimental campaign conducted earlier by the authors. The mechanical model is able to capture the mean peak force and the failure mode obtained from the tests. The mechanical model can be easily adopted by practising engineers who aim to model the wall ties accurately in order to assess the strength and behaviour of the structures against earthquakes. Furthermore, the proposed mechanical model is used to extrapolate the experimental results to untested configurations, by performing parametric analyses on key parameters including a higher strength mortar of the calcium silicate brick masonry, a different cavity depth, a different tie embedment depth, and solid versus perforated clay bricks.

In-Plane Seismic Response of Unreinforced and Jacketed Masonry Walls

Low-rise residential and public masonry structures constitute a large portion of the building patrimony, yet they were erected during the massive reconstruction of Southeast Europe after World War II before any design rules existed in the engineering praxis. Unreinforced unconfined masonry buildings (URM) were proven rather vulnerable during stronger earthquake motions in the recent past. To determine lateral strength, stiffness, and capacity of energy dissipation of the URM walls, in-plane tests were performed at the University of Sarajevo. Two full-scale plain walls (233 × 241 × 25 cm) built with solid clay brick and lime-cement mortar and two walls strengthened with RC jacketing on both sides were subjected to cyclic lateral loading under constant vertical precompression. Plain walls failed in shear with a typical cross-diagonal crack pattern. Jacketed walls exhibited rocking with characteristic S-shaped hysteretic curves and significantly larger ductility compared with plain walls. Wallets were tested for modulus of elasticity and compressive strength of masonry and the results showed considerable variations.

Performance of solid masonry columns after strengthening

Brick masonry is one of the widely used materials for the construction of walls and columns in buildings. In many cases, the built walls and columns fail due to excess lateral loads, environmental degradation, and increased loading requirments due to changes in occupancy. In this paper, an experimental was conducted to understand the performance of building columns made of solid clay bricks strengthening with fiberglass and ferrocement techniques materials. In total, six columns were constructed, two columns were control columns (unconfined), two columns were strengthened and confined with fiberglass mesh and plaster, and the other two columns were strengthened and confined with ferrocement. The experimental results showed that the maximum axial load of unconfined specimens can be increased if they are confined by fiberglass or ferrocement systems. Both systems can be used to repair uncollapsed columns which have been loaded close to failure or exposed to strength deterioration.