Clay Masonry Units Research Articles

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.

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.

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.

Statistical assessment of tensile and shear properties of unreinforced clay brick masonry

This paper presents the results of an extensive set of material characterisation tests performed on unreinforced clay brick masonry. The results of these experiments allow for the estimation of relationships between the measured material parameters. This study considers the relationships of flexural tensile bond strength to direct tensile bond strength, flexural to direct tensile strength of fired clay brick masonry units, and flexural tensile to shear bond strength. A mean ratio of flexural tensile bond strength to direct tensile bond strength of 2.06 and a COV of 31.5% were determined. For the flexural to direct tensile strength of fired clay brick masonry units, a mean ratio of 1.29 with a COV of 14.7% was estimated. Finally, considering the ratio of the shear bond to flexural tensile bond strengths, a mean ratio of 1.34 with a COV of 28.4% was found. In addition to these relationships, suitable probabilistic models were determined to describe the relationship between the flexural and direct tensile bond strengths, and the flexural tensile and shear bond strengths. These results may be used in future studies of URM structures, in particular finite element modelling and stochastic analyses of masonry.

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.

The Influence of External Environmental Conditions on Properties of Ceramic Building Materials with Waste Material Additives.

In this paper, we analyze the state of conservation of ceramic building materials (clay masonry units) containing a large share of waste materials in the form of ash and slag from coal combustion and sawdust from wood processing, operated for several decades in facing walls of religious buildings, in external environment conditions. For the purpose of this analysis, comparative tests were carried out on the samples of ceramic materials cut out from facing walls and samples extracted from the same ceramic materials; they were stored in laboratory conditions for the entire time. The following were investigated: initial water absorption, capillary rise, and porosity structure determined with mercury intrusion porosimetry (MIP). The research has shown, among other things, that the ceramic materials exploited in the external environment are characterized by an almost twofold increase in the initial rate of water absorption and by a different size of dominant pores and a pore size distribution in comparison with ceramic materials stored in laboratory conditions. The results, obtained for ceramic building materials (clay masonry units) containing the above-mentioned waste materials in their composition, constitute a novelty. They fill a gap in the literature by establishing how decades-long operation in natural conditions affected the capillary properties and the porosity structure of the ceramics under investigation. Based on the obtained research results, conclusions of cognitive and practical significance have been formulated that relate to the possibility of the exploitation of facing walls made of investigated ceramic materials.

Alkaline Activation of Basic Oxygen Furnace Slag Modified Gold Mine Tailings for Building Material

The mining industry generates large quantities of waste as tailings. The tailings have an adverse environmental impact. This study explored the utilization and stabilization of Barberton gold mine tailings (GMTs) and basic oxygen furnace slag (BOFS) to synthesize geopolymers for other applications. The geochemical, chemical, and geotechnical properties of GMT, BOFS, GMT geopolymer, and GMT: BOFS geopolymer were also studied. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) were used as alkaline activators. The highest unconfined compressive strength (UCS) recorded for GMT geopolymers cured for 5 days at the elevated temperature of 90°C was 4.31 MPa and 6.59 MPa for NaOH and KOH, respectively. GMT: BOFS geopolymer attained the UCS of 20.0 MPa and 25.7 MPa, with NaOH and KOH, respectively, at the same curing conditions. Characterization of the binders showed that BOFS was a good source of calcium, which had a positive effect on the geopolymer gels by balancing the ionic charges. The developed GMT: BOFS geopolymers satisfied the minimum requirements for nonfacing building masonry as stipulated by the ASTM C34‐17a, ASTM C129‐14c 0076a, and the SANS 227: 2007 for burnt clay masonry units and can be used as a mine backfill paste and for lightweight civil applications. The geopolymers passed the toxicity characteristic leaching procedure (TCLP), and the results yielded low heavy metals concentration, indicating that the geopolymers will not leach to the environment.

Titelbild: Mauerwerk 6/2019

AbstractThe exceptional apartment building project from HPA+ Architektur in Bergisch Gladbach has altogether six varied residential units in a total usable floor area of about 600 m2. Clay masonry units were chosen for the facade material of the three buildings, with detailed planning being necessary to enable the maintenance of all crossing, bed and head joints in all parts of the facade. Other materials in addition to clay masonry are exposed concrete and galvanised steel, which should give the most ”rough“ possible appearance. Another special feature of the project is the projecting gables, which are provided with insulation to the underside, resulting in a continuous external envelope. Further details: www.hpa.de (Photo: Detlef Podehl)

Comparative study of the use of different biomass from olive grove in the manufacture of sustainable ceramic lightweight bricks

In the present study, residue from olive groves has been used for the manufacture of clay ceramic bricks as a new environmentally-friendly solution. For this purpose, waste products of olive cultivation, such as olive prunings, leaves and wood, were ground to obtain a particle size of 0–2 mm; 7.5%, 15% and 25% of olive waste was added to the clay, clay bodies were moulded in pastes with the incorporation of 7.5, 15 and 25% by volume of waste; and finally, the green bodies were fired at 850 °C. The influence of the type and ratio of waste on the physical and mechanical properties of waste clay bricks was studied and compared with clay bricks without waste following standard procedures. Ceramic samples were characterized using a series of technological tests, such as linear shrinkage, bulk density, apparent porosity, water absorption, suction, compressive strength and thermal conductivity. The best results were obtained from the samples containing 7.5% olive waste showing that these organic pore-forming wastes have the potential for producing lighter bricks that could be marketed as low density clay masonry units with adequate mechanical properties and higher thermal insulating capacity.

Assessment and Restoration of an Earthquake-Damaged Historical Masonry Building

This paper presents an assessment of the capacity and enhancement of the seismic performance of a historical masonry structure in Plomari, a town on the south coast of Lesbos island in Greece. Owing to uncertainties regarding the properties of the material and the effectiveness of the members in providing lateral resistance, the study was particularly challenging. In addition, the fact that the structure consisted of a variety of structural element types, e.g., unreinforced masonry from natural stones, timber-framed masonry (with burned clay masonry units) and timber girders, while lacking horizontal diaphragms, introduced complexities to the response of the structure in both directions. In the design of the retrofit, the need to preserve the building’s architectural and historical value by minimizing interventions posed several problems. To solve them, conventional as well as state-of-the-art strengthening methods are proposed. Moreover, the procedures of these methods are in accordance with the Greek seismic design code of 1959 and European standards (Eurocodes) related to earthquake-resistant masonry as well as guidelines for the design of timber and reinforced concrete. Seismic analyses of the structure were carried out with two different methods (statically applied load and time history analysis) for comparison. The results verify the improvement in its behavior in response to earthquakes as a result of the proposed strengthening methods.

Mechanical properties of clay masonry units: Destructive and ultrasonic testing

The compressive and flexural strength of old and new clay bricks are investigated in this paper. Total 52 specimens comprising of old bricks collected from four different building sites in Western Australian and five different types of commonly used new bricks are used in the study. Ultrasonic pulse velocity (UPV) of the bricks were measured along the parallel and normal to the bed joint and parallel to the wall thickness directions. Compressive and flexural strength tests were conducted after the UPV testing. Results showed that the old bricks provided lower compressive strength which was well picked by the UPV readings. The flexural strength of the old bricks was comparatively higher than the new bricks. A common correlation between the compressive and flexural strength of the old and new bricks and the corresponding UPV readings is proposed, which can assist in on-site UPV testing of clay brick masonry buildings.

Schubtragfähigkeit von Ziegelmauerwerk mit teilweise aufliegender Deckenplatte

AbstractIn order to investigate the influence of a partially supported slab on the in‐plane shear resistance of masonry walls, six shear tests on full scale walls were performed at the Chair of Structural Concrete of the University of Kassel in cooperation with ”Arbeitsgemeinschaft Mauerziegel“. The walls were made of large chamber clay masonry units and the depths of the partially supported slabs were different. The large chamber units are typically used for thermally insulated exterior walls, with the slabs only being partially supported. The influence of this constellation is not taken into account in shear capacity assessment according to the current version of Eurocode 6 for Germany. This article describes the test results and provides a comparison with Eurocode 6. In addition, the results of older shear tests on masonry walls made of vertically perforated units with eccentric load application were used.

Application of the Extrapolation standard DIN EN 15080‐12

AbstractFor highly insulated clay masonry units, fire resistance is verified in the course of the approval procedure through fire tests according to harmonised European standards. The fire resistance class in the relevant national technical approval is then based on these tests. Classification according to these testing standards in combination with the extrapolation standard DIN EN 15080‐12 represents a justifiable option for the fire resistance classification of masonry walls according to harmonised European standards.In this paper, the extended scopes of application of the extrapolation standard are presented through the example of tests on precision clay masonry.

Titelbild: Mauerwerk 2/2018

AbstractThe decision to build ones' own house is a decision for life. Ziegel fired clay masonry has been a proven building material for thousands of years, is long‐lived, healthy for living space, maintains value, is low‐maintenance and saves energy. Various architectural styles can be built with modern clay masonry units, such as the Bauhaus style in this example. Photo: Lebensraum Ziegel / Unipor

Development, engineering properties and potential applications of unfired earth bricks reinforced by coal fly ash, lime and wood aggregates

The current study developed and evaluated the engineering properties of improved low-cost UEBs reinforced with various lime (L)-coal fly ash (F)-wood aggregate (W) mix ratios. The objectives were; (1) to determine the effects of lime-coal fly ash-wood aggregate mixtures on mechanical strength and water resistance properties of UEBs; and (2) to determine the comparative cost of the improved UEBs to that of the control (10% cement). Four UEBs with various lime (L)-coal fly ash (F)-wood aggregates (W) mix ratios (L4%-F16%-W1.5%; L4%-F16%-W3%; L8%-F12%-W3%; L10%-F10%-W1.5%) were fabricated and their engineering properties compared to those of unstabilised (negative control) and 10% cement stabilized (positive control) unfired earth bricks. Dry compressive strength (DCS) of UEBs stabilized by L10%-F10%-W1.5% (8.3 MPa) was significantly higher (p < 0.001) than that of 10% cement stabilized unfired bricks (7 MPa). DCS and dry density of the four UEBs conformed to the British Standards for low-density clay masonry units. DCS increased with lime-fly ash ratio according to a power function (y=−5.41x2+11.18x+2.22; r2 =0.95, p = 0.018), attaining a maximum of 8.3 MPa at a ratio of 1: 1. However, UEBs had low wet strength, but incorporation of 4% cement significantly increased (p < 0.001) the wet compressive strength of UEBs to 0.94 MPa. UEBs stabilized by 10% lime, 10% coal ash, 1.5% wood aggregates and 4% cement (L10%-F10%-W1.5%-C4%) had water absorption (15.8%) similar to that of 10% cement stabilized UEBs. Moreover, unfired earth bricks reinforced by L10%-F10%-W1.5%-C4% conformed to British Standards engineering specifications for low-density clay masonry units, while the cost was 50% lower than that of cement stabilized bricks, demonstrating the low-cost of the UEBs. In summary, the results demonstrate that improved low-cost UEBs can be developed by incorporating lime, coal fly ash and wood aggregates, but a little cement (4%) may be required to increase the wet compressive strength. Potential applications of the UEBs include, (1) internal partitioning; (2) construction of low-cost housing for low-income households in developing countries, and (3) the provision of temporary or short-term low-cost shelter for displaced persons in humanitarian emergencies.

Characterization of the clay masonry units and construction technique at the ancient city of Nippur

Abstract This paper describes a programme of experimental measurements performed in support of a parallel programme of field investigations to evaluate the construction methods used at the site of the ancient city of Nippur. The experimental programme investigated both the mechanical properties and durability of the ancient clay masonry units used in the construction of buildings at Nippur including tests for dimensional consistency and flatness, density, compressive strength, initial rate of water absorption and thermal properties. The test results have been compared with those for modern brick units available nowadays in Iraq and with hard natural stone samples. The field investigations showed that the important buildings were constructed using composite walls inclusion firing clay masonry units with two nominal dimensions (30 × 30 × 7) cm and (30 × 15 × 7) cm (l, w and h). The formulation of working design technique was followed to achieve the member stability under applied loads. Layers of bitumen material were used as a binder for both bed and head joints in order to provide the desired strength level for the masonry wall. The experimental results show that the ancient brick units and stone samples exceed the tolerance and range of dimensions limits recommended by current EN Standards. Lower density values were recorded for the ancient brick units compared with that for both modern clay brick and stone specimens and these values showed agreement with the modern classification of high density (HD) units. Approximately similar values of compressive strength were observed for both ancient brick units and natural stone samples reaching about 17 MPa, whilst modern clay brick samples showed lower compressive strength value suitable for application of partition walls. The initial rate of water absorption increases with an increase of the soaking time, but tends to decrease after 90 min for both ancient and modern brick units. Superior performance in terms of thermal conductivity, thermal resistance and durability under fire action were observed for the ancient brick samples compared with modern clay brick and stone samples.

Titelbild: Mauerwerk 3/2017

AbstractTimeless elegance and organic forms – these are the characteristics of a detached house in Medebach. For good reason, the house won first place in the competition ”MASSIVHAUS 2017“. The photo house competition MASSIVHAUS 2017 awards prizes to the most attractive massively built houses in Germany. It looks for examples of innovative and modernistic detached and semi‐detached houses. The only conditions of entry: the house must be built with masonry of calcium silicate, lightweight concrete or aerated concrete blocks or clay masonry units (s. p. 205).(Photo: Massiv mein Haus/Christoph Hesse Architekten)

Analysis of Unreinforced Ceramic Wall Panels in the Mounting State

Properties of building materials used for the construction of surrounding structures significantly contribute to creating a healthy and comfortable microclimate inside the rooms. Ceramics belong among materials which exhibit very suitable properties for the formation of the healthy environment. It is also one of the reasons that the fired clay structures remain popular among builders and that recovery of ceramic prefabrication can be seen in the Czech Republic. The important step towards rediscovering the benefits of the prefabricated ceramic elements is forthcoming production of unreinforced ceramic wall panels made of fired clay masonry units with tongue and groove, connected in the bed joints by two-component adhesives. Conventional analytical model for vertical loads is used in the operating state. However, in the transport and mounting state it is a structure stressed by bending in its own plane. This paper is focused on the issue of load-bearing capacity of structures with masonry units cross-sections that are not filled in head joints and therefore are unable to transfer either tensile or compressive stresses. On the segment of the wall panel is performed numerical model analysis using the finite element method in the computing program ANSYS and comparison of this analysis results with the results of the experimental tests.