Clay Masonry Research Articles

Incorporation of spent bleaching earth and glass sediment as an alternative raw material for the manufacture of eco-products based on fired clay

This study explores the use of two industrial residues: spent bleaching earth (SBE) and glass sediment (GS), as alternative raw materials in the production of ceramic materials from fired clay. The mixtures incorporating 0%, 10%, 30%, and 50% by weight of these residues, were examined. The impact of quantity and type of waste on product properties (density, water absorption, compressive strength, and thermal conductivity) was assessed against NTC 4205 standards. Incorporating 50% SBE reduced thermal conductivity by 35%, but increased porosity affected compressive strength. Glass sediment incorporation increased thermal conductivity but surpassed pure clay in mechanical behavior. The triphasic mix (20% GS, 10% SBE with lime) demonstrated optimal mechanical performance, meeting fired clay masonry unit standards. An eco-product prototype based on this mix was successfully manufactured, affirming that industrial waste is a viable alternative raw material, yielding ceramic materials with properties meeting or surpassing Colombian construction industry standards.

Recovery of mining and agri-food wastes in fired materials: a case study of the Moroccan industry.

The linear economy follows the "take-make-dispose" model and generates huge amounts of waste without consideration for recycling or reuse. This model which deals with raw materials puts pressure on natural resources and creates a serious environmental impact. In a circular economy, the "reduce-reuse-recycle" model is applied to recycle waste into resources and reduce the impact on the environment and society. This work aims to highlight the significance of implementing a circular economy approach in the construction sector by merging two different production lines, notably mining activity and agri-food industry. The investigation presents sustainable management of coal mine waste (CMW) and olive pomace (OP) in the production of eco-friendly fired materials and introduces an innovative approach for manufacturing lightweight fired bricks. Microstructural, physical, mechanical, and thermal properties were determined to evaluate the technological quality of fired materials at 900°C. As a pore-forming agent, adding 10 wt% OP yielded specimens with a bulk density of 1552kg/m3, water absorption of 19.80%, apparent porosity of 29.61%, loss on ignition of 26.98%, and compressive strength of 7.08MPa, satisfying standards for clay masonry units. Simultaneously, it enhances the thermal insulation by reducing thermal conductivity by 18% compared to the control sample with CMW. In this regard, the transition to a greener construction sector necessitates the immediate implementation of a circular economy approach to developing eco-friendly building materials by recovering large amounts of industrial waste, limiting the overuse of natural resources (e.g., clays), and improving the engineering properties of the final product.

Test of three-storey confined masonry structure built from clay blocks and PU glue

The paper presents an experimental test of a nearly full-scale three-storey model of a confined masonry structure. The walls were constructed using newly developed clay masonry blocks, with large holes filled with thermal insulation and polyurethane glue instead of mortar. In the construction,relatively thick 38 cm walls and large tie-columns with 25 cm × 25 cm plan dimensions. The test model was built as confined masonry according to Eurocode 8. The innovative materials and construction were developed for thermal efficiency and the test was intended to verify the structural response. The model, test setup, and test procedures are described, and the results of the tests are analysed. The building responded primarily in shear, and ultimately failed in the ground floor in a storey mechanism, but there was also substantial damage on the floor above. Due to the non-standard dimensions of the tie-columns and because masonry was thicker than the tie-columns, the in-plane loaded walls developed an interesting response mechanism in which protruding masonry sheared off. Although this did not significantly impact the overall response, it led to the earlier onset of the significant damage limit state of the structure. The model responded well with wide hysteretic loops and distributed damage, which indicated large energy dissipation capacity, and the response envelopes showed gradual strength deterioration after peak load. The response of the model was quantitatively estimated using the N2 method. Calculations showed that the tested model could withstand a design seismic load corresponding to a 0.21 g peak ground acceleration with significant damage and almost 0.52 g before collapsing. The overstrength was estimated at 1.71.

Calibrating failure surfaces for vertically perforated clay block masonry using a validated numerical unit cell model

Finite element software is nowadays an essential part of a structural engineer’s modeling process. The simulations range from trivial linear elastic models to highly non-linear ones, accounting for contact, plasticity, viscoelasticity, or fracture. Though fired clay blocks are an excellent and widely used building material, little effort has been made to extend available failure surfaces for simulating vertically perforated clay block masonry in modern FE Software. Therefore, developing reliable and efficient ways to predict the effective strength of vertically perforated clay block masonry subjected to different loading states is critical. In this study, we aim to qualitatively analyze the failure surface of vertically perforated clay block masonry under in-plane loading, using numerical simulations. Using a previously validated unit cell FE model, we derived the peak stresses from 471 simulations. Subsequently, we compared these results with two failure surfaces from the literature and identified qualitative differences. Taking these differences into account, we propose a concept for numerically calibrating the parameters of the Rankine–Hill failure surface proposed by Lourenço (1997).

Improvement of the thermal performance of hollow clay bricks for structural masonry walls

Although structural masonry walls are widely used in construction, achieving lower U-value is crucial to minimize energy losses and greenhouse gas emissions. The effect on the U-value of hollow clay masonry walls is evaluated by modifying the clay and mortar thermal conductivities, as well as the brick grid and thickness. Heat transfer through bricks and walls was modeled using a 3D-finite element method while model validation was based on experimental tests. Smaller rectangular cavities reduce the U-value to 0.761 W/m2K; increasing the brick thickness reduces the U-value to 0.563 W/m2K. Moreover, reducing the clay thermal conductivity showed negligible reductions in the wall U-value.

Numerical and Experimental Behavior of Two-Story Confined Masonry Structure Subjected to Cyclic Loads

This research presents the numerical and experimental results of lateral cyclic loading applied on a two-story confined masonry structure utilizing local materials and standards. Two half-scale confined masonry structures were constructed using clay masonry units, confining columns, tie beams, and reinforced concrete slabs. The assemblies were tested up to failure using a displacement controlled loading methodology under vertical self-weight and lateral reversed cyclic loading. The walls of the assemblies have varying perforations (solid / windows / doors) to examine the influence of perforation on in-plane and out-of-plane performance. A strengthened assembly with an exterior layer of ferrocement has been used and this suggested upgrading approach enhanced the lateral resistance of the confined assembly by about (61–95%) while improving ductility and total energy absorbed by 27%. The maximum lateral drift at failure have been decreased to (23–31%), however the corresponding load for the first visible fracture have been raised by (150–175%). Furthermore, total failure has been delayed for the strengthened walls (all sides, particularly the perforated sides). Comparing distorted forms, fracture patterns, and capacity curves of finite element models included in this research yielded excellent agreement.

An Automated Classification of Recycled Aggregates for the Evaluation of Product Standard Compliance

Nowadays, recycling of construction and demolition waste (C&DW) is a challenging opportunity for the management of such end-of-life (EOL) materials through alternative methods to environmentally unsustainable methods (i.e., landfilling). In order to make recycling processes more effective, quality control systems are needed. In this work, the possibility of developing a sensor-based procedure to recognize different demolition waste materials from a recycling perspective was explored. An automatic recognition of different predefined constituent classes of recyclables (i.e., concrete, mortar, natural stones, unbound aggregates, clay masonry units, bituminous materials) and contaminants (i.e., glass, metals, wood, cardboard, and gypsum plaster), as established by an European standard, was carried out using hyperspectral imaging (HSI) working in the short-wave infrared (SWIR) range (1000–2500 nm). The implemented classification strategies, starting from the collected hyperspectral images of the analyzed constituents, allowed for the identification of the different material categories. Two main models were built for identifying contaminants in recyclable materials and categorizing material groups based on technical specifications. The results showed accurate category identification with Sensitivity and Specificity values over 0.9 in all models. The possibility of performing a full detection of C&DW recycling products can dramatically contribute to increasing the quality of the final marketable products and their commercial value, at the same time reducing the amount of waste and the consumption of primary raw materials.

Effects of the In-Plane Flexural Behavior Modeling Choices for Hollow Clay Masonry Brickwork with Horizontal Holes

Buildings with load-bearing structures made of hollow clay blocks with horizontal holes and cement-based mortar are quite common in Italy, yet the current design standards do not consider specific modeling issues to be addressed by practicing engineers. In the absence of peculiar specifications, the prescriptions given for ordinary masonry walls are thus commonly adopted. However, experimental tests proved that walls built with hollow brick masonry performed quite differently from ordinary masonry walls. Considering the in-plane flexural behavior under horizontal loads, unlike ordinary masonry walls that exhibit some ductility, this construction typology performs quite poorly, showing very little deformation capacity and ductility. In recent experimental campaigns, a brittle collapse mechanism was observed due to the toe crush, which entailed the inability of the wall to further withstand the vertical loads. In this paper, the effects of incorrect modeling choices on the characterization of the in-plane behavior of this construction typology and the consequences related to overestimating ductility are discussed; the effects of the reduced ductility on the reliability of the assessment of an existing building as well as on the conceptual design of possible structural retrofit measures are investigated. From the critical discussion, the need emerged to accurately model the in-plane flexural behavior and to update the code provisions to explicitly consider masonry walls with hollow clay bricks with horizontal holes.

The impact of thermal insulation on the vulnerability of hollow masonry walls under elevated temperatures

There is little doubt that masonry walls have, throughout the history of mankind, been a critical part of building construction. From this standpoint, the present study aims to unfold the thermal behaviour of masonry walls when subjected to the standard cellulosic curve prescribed in ISO 834. Particular attention has been paid on temperature variations that are intimately connected to insulation fire resistance. The investigation initially focuses on the vulnerability of clay hollow-brick masonry wall arrangements with a varying thickness and position of insulation. These parameters are shown to significantly affect the penetration of heat through walls. In addition, temperature-dependent relationships among thermophysical properties of a combustible and a non-combustible insulation material, are examined. Alongside this, the effect of volumetric mass density on thermal conductivity for two sets of masonry units has been also taken into account. At last, this work is extended to identify the heat storage capacity of masonry walls depending on the construction arrangement of materials which can affect compartment fire dynamics. Within this framework, a numerical technique has been implemented to realise a finite element analysis (FEA) with respect to this transient thermal problem. Computational simulations have been carried out by adopting a well-known FEA modelling program.

Recycling of dolomite powder in clay bricks: Effects on characteristics and gas release

This paper evaluates the influence of dolomite industrial waste (dolomite powder (DP) on the properties, structure and durability of clay bricks. Four clay samples fired at 900 °C and 1000 °C containing 0 wt%, 10 wt%, 20 wt% and 30 wt% DP were prepared and investigated to measure their properties (shrinkage, bulk density, water absorption, thermal conductivity, apparent porosity, compressive strength), structure and durability (compressive strength after freeze thaw). The results showed a decrease in bulk density, compressive strength and an increase in apparent porosity and water absorption of the clay bricks produced by mixing 70–90 wt% clay and 10–30 wt% DP compared to the control bricks. Also, a significant improvement in the thermal conductivity of clay bricks produced by 70 wt% clay and 30 wt% DP (0.407–0.420 W/(m⋅K) compared to the control clay bricks (0.839–0.845 W/(m⋅K). As clay mixtures contain DP (chemical composition: CaO-49.68%, Loi-42.80%), CO2 emissions during the firing process are increased (decarbonation reactions). However, the thermal conductivity of the fired clay bricks is significantly reduced (to 50%). These results showed the potential of DP for the manufacturing of clay masonry units.

Exploitation of rice agriculture wastes in clay masonry units preparation

This paper deals with the exploitation of both rice husk and straw as partial constituents in the fabrication of clay masonry units. This allows for using harmful wastes that were otherwise burnt besides lowering the amount of clay used in brickmaking. Clay was mixed with different percentages of each waste and water was added in a suitable amount to produce mixes that were molded and dried. Drying shrinkage and green compressive strength were determined for these dry samples. The firing of the dried samples was then carried out at temperatures ranging from 700 to 800ºC with a one-hour soaking time. The following properties were investigated as a function of both firing temperature and percent waste added: loss of ignition, firing shrinkage, cold and boiling water absorption, saturation coefficient, apparent porosity, bulk density, and compressive strength. The properties of masonry units produced by firing at 700ºC and containing 3% of either waste were in good agreement with ASTM C 62 specifications for clay made bricks.

In-plane seismic fragility models for clay masonry infills in reinforced concrete frames

This study aims at deriving multi-damage state fragility functions/curves for clay masonry infills in low-to-medium-rise reinforced concrete frames designed according to a performance-based seismic design methodology. Different structural archetypes were identified and modelled numerically by means of distributed plasticity approaches in order to undertake multi-stripe nonlinear dynamic analysis and derive seismic lognormal fragility models through regression analysis. Both infilled and bare frame configurations were simulated and compared together, providing fragility curves corresponding to immediate occupancy, damage prevention, and, ultimately, life safety limit states, all of which can be integrated in general frameworks for seismic risk/loss assessment and management. To this end, fragility models are given in terms of three different intensity measures, namely peak ground acceleration, peak floor acceleration, and peak floor spectral acceleration, considering also two different methods for the calculation of the probability of occurrence/exceedance of a certain damage state, namely building-wise and storey-wise approaches.

A numerical unit cell model for predicting the failure stress state of vertically perforated clay block masonry under arbitrary in-plane loads

As vertically perforated clay block masonry advances into more demanding building categories, knowledge of the effective masonry strength under different loading states becomes crucial. However, experimentally identifying macroscopic failure surfaces for such masonry requires a massive effort. In this study, we propose a FEM-based simulation concept to predict failure stress states of masonry under arbitrary in-plane loading. The proposed concept is validated using seven experiments from the literature. Subsequently, subjecting the validated model to various load cases allows for deriving a failure surface comparable to the Rankine–Hill surface. Thus, by applying the presented concept, we can effectively generate macroscopic failure surfaces for any perforated clay block design.

Out-of-plane flexure of external Thermal-insulation attached to Non-load-bearing masonry walls

The out-of-plane flexure of thermo-insulation attached on the external facades of full-scale clay masonry walls is studied. This is of importance because a considerable number of multistory buildings are in need of thermal insulation considering at the same time the seismic performance of such attachments together with the unreinforced masonry walls. Full-scale clay masonry wall specimens with or without thermal insulation were subjected in the laboratory to out-of-plane flexure. Such thermo-insulating attachments resulted in noticeable increase of the total out-of-plane flexural capacity and deformability when the thermo-insulating panels are subjected to flexural-tension. This increase is quite substantial when these panels are of either expanded polystyrene (EPS) or extruded polystyrene (XPS) and insignificant for mineral wool (MW). The observed response was used to validate a numerical methodology aimed at predicting this out-of-plane flexural performance of masonry walls with thermal insulation attachments. The beneficial effect of the thermo-insulating attachments on the out-of-plane flexural response of masonry facades depends on the adopted construction technique. This is also true for the safe performance of the thermo-insulating attachments themselves after their debonding. Despite that both the masonry facades and their attachments are considered as non-structural elements appropriate construction techniques should safeguard their acceptable out-of-plane performance when subjected to seismic type loads.

Recycling argan nut shell and wheat straw as a porous agent in the production of clay masonry units

The present work aims to study and compare the effect of incorporating argan nut shell (ANS) and wheat straw (WS) into clay mixtures as construction materials additives on physical, mechanical, structural, and thermal properties of fired clay bricks. Five clay mixtures were prepared, including a control sample free of waste, two clay samples containing 5 wt% and 10 w.t% of ANS (ANS5 and ANS10), two others containing 5 wt% and 10 wt% of WS (WS5 and WS10), all specimens were fired at 900 °C, and their technological properties in term of loss on ignition, firing shrinkage, water absorption, apparent porosity, bulk density, flexural strength, compressive strength, and thermal conductivity were evaluated. A reduction in bulk density and thermal conductivity has been observed with the incorporation of ANS and WS, leading to an increment in the apparent porosity and water absorption in their turn, which is typically due to the specimen’s porous structure. The thermal conductivity of clay brick samples containing 5–10 wt% of ANS or WS decreased by 5–17% and 27–46%, respectively. Thus, the thermal insulation property is improved while the mechanical properties (flexural and compressive strength) meet the requirements of the standards for clay masonry units, except for WS5 brick. Test results highlighted the potential of recycling ANS and WS in clay masonry units and thus, the production of lightweight material.

Out-of-Plane behavior of clay brick masonry infills contained within RC frames using 3D-Digital image correlation technique

The present study investigated the out-of-plane (OOP) behavior of traditional solid clay brick masonry-infilled reinforced concrete frames for different slenderness ratios, bonding patterns, and connection details to assess the development of arching mechanism, infill-frame interaction, and failure mechanisms. Full-field strain and crack width analysis, failure progression, and out-of-plane deformation characteristics were evaluated using a non-contact 3D-DIC (digital image correlation) technique. The experimental investigation ascertained that full-brick thick lower slenderness ratio (13.4) specimens observed higher capacity (3.7 times), deformation ability (>1.2 times), and energy dissipation characteristics (>3.5 times) compared to half-brick thick slender (28.8) specimens. The presence of tie bars enhanced the stability of the wall against out-of-plane failure. However, it did not significantly modify the load and deformation behavior in the peak and post-peak stages. The OOP deformation profiles, arching mechanism, and the distributed damage in infill in lower slenderness ratio specimens, which led to higher OOP lateral load resistance, were precisely captured using the 3D-DIC technique. The increase in width of the cracks (1.6–2.9 times) in Flemish bond (lower slenderness ratio) specimens compared to their running bond counterparts was accurately appraised using the DIC. Based on the experimental results, a unified out-of-plane lateral load–deflection idealized model was proposed. The appropriateness of the proposed model was further verified by comparing it with previously developed models and experimental studies. The research study revealed that the out-of-plane lateral load behavior of infilled frames was significantly modified due to strong and stiffer solid clay masonry, considering different structural bonding patterns and slenderness ratios. The 3D-DIC technique was found to be a resourceful tool for comprehending the deformation and damage characteristics of infilled frames, especially under out-of-plane lateral loads.

The performance of vertically perforated clay block masonry in fire tests predicted by a finite-element model including an energy-based criterion to identify spalling

Fire tests on masonry are one of the most expensive experiments in developing new vertically perforated clay block geometries. Numerical simulations might be a reasonable substitute for such experiments, leading to a significant cost reduction in the development phase. However, the prediction of such tests with numerical modeling concepts is challenging due to large temperature and stress gradients, highly non-linear material effects, and the complex geometry of the blocks. Herein, we present a finite-element-based concept, including thermal and mechanical simulations, a unit-cell approach, a smeared damage model, and a novel energy-based spalling criterion to describe the structural and material behavior of a masonry wall in a fire experiment. We could predict the obtained spalling times of longitudinal webs and the total endurance of a masonry wall without any empirical fitting parameters in good agreement with experimental data. These results show that we can use our modeling approach for simulating such fire tests, enabling a much cheaper and more efficient development of block geometries.

In-plane cyclic response of unreinforced masonry walls retrofitted with ferrocement

Unreinforced masonries are weak against seismic loads which necessitates their retrofitting. Ferrocement is widely used as it is cheaper than alternative methods of retrofitting. Some crucial parameters can significantly affect the performance of such retrofitted structures under cyclic loading conditions, such as: aspect ratio, difference of wire mesh arrangements & pattern of retrofitting. To quantify the impact of these parameters, this study has implemented two variations of each parameter. This study conducts experimental investigations of the ferrocement retrofitted unreinforced masonry walls (URM) and evaluation of their properties such as energy dissipation, stiffness degradation, hysteretic damping, ductility, and load deformation responses. Results show notable increase in strength after ferrocement retrofitting of URM walls. Retrofitting of URM walls with inexpensive material such as ferrocement is gaining popularity, our research is guided towards finding the in-plane cyclic load characteristics of such method of retrofitting. Sample walls were prepared in two categories: (1) Long walls (aspect ratio 0.57) and (2) Short walls (aspect ratio 1). A total of ten clay masonry walls (five for each category) were constructed with reinforced concrete base slab. The first variable parameter for the tests was ferrocement coating difference. Some sample walls were retrofitted completely even the base slab & wall panel connection point while on some walls the ferrocement lamination was only applied on the wall panels. Steel wire mesh’s opening size is another crucial variable test parameter. Two different wire mesh opening sizes: (1) 3.2 × 3.6 mm and (2) 8.5 × 8.5 mm were used on the walls. One control specimen with no retrofitting for both short and long walls were prepared for test comparison purpose. Laterally reversed cyclic loads and vertical loads both were applied to the sample walls during tests. Improvements in hysteretic damping, stiffness, energy dissipation and ductility were scrutinized in particular. Finally, a comparison was drawn between the test findings and allowable load provisions prescribed in the Bangladesh National Building Code (BNBC) 1993.

Mould Growth Risks for a Clay Masonry Veneer External Wall System in a Temperate Climate

To reduce greenhouse gas emissions, nations have introduced energy efficiency regulations for new and existing buildings. This has been considered advantageous as more efficient building envelopes would reduce energy consumed to heat and cool home interiors to within accepted thermal comfort bandwidths. However, as these methods have been adopted, many nations have identified an unintended visible presence of surface and interstitial condensation and mould in new code-compliant buildings. In Australia, it has been estimated that up to 50% of Australian houses constructed in the last decade (2006–2016) have a presence of condensation and mould. Australia introduced its first condensation and mould-related building regulations for new homes in 2019. This paper reports on the hygrothermal and mould growth analysis of the most common low-rise residential external wall system, a timber-framed clay masonry veneer wall. A key component of this paper discusses the application of innovative methods in the Australian context. The external wall’s moisture accumulation and mould growth were simulated for a period of ten years using the transient hygrothermal simulation tool, WUFI® Pro, and the mould growth model, WUFI® VTT. This study identified significant risks for this typical external wall system when constructed in a temperate climate.

Fragility curves for light damage of clay masonry walls subjected to seismic vibrations

The probability of light damage to unprepared, unreinforced masonry structures exposed to induced seismicity due to gas extraction in the north of the Netherlands is still under investigation. Repeated light seismic excitations caused by frequent, light and nearby earthquakes have been linked to economical losses and societal unrest in particular, with extensive damage claims. Moreover, the damaging potential of the seismic events has been related to the condition of the structure, especially if damage corresponding to settlement causes is already present. A comprehensive testing campaign oriented towards the initiation and progression of light damage of replicated clay brick masonry has been conducted at Delft University of Technology. Based on these tests, calibrated finite element models have been produced. This article uses the calibrated non-linear time-history models to simulate the effect of earthquake ground motion on a variety of initial conditions, wall geometry, material properties, and number, type and intensity of earthquakes. The results are then used to regress a relationship between damage and these parameters. This is subsequently employed to run a MonteCarlo simulation and produce fragility curves where the probability of exceeding specific damage values for various initial damage levels is presented against the seismic hazard. The vulnerability or fragility curves show that visible damage, with cracks wider than 0.1 mm, appears, with a 10% exceedance probability, at 13 mm/s of peak ground velocity; but, if the masonry had already undergone some light, yet imperceptible damage, a PGV of 6 mm/s was sufficient to aggravate it into visible cracks. To attain a 1% probability of exceeding light damage however, for which the masonry would need more invasive repair, it was observed that PGVs larger than 15 mm/s were required. These fragility curves were finally compared to graphs from other authors and found to capture well the variability in the range assigned to light damage.