Earthen Bricks Research Articles

Optimizing alkali-activated clay with rubber waste for sustainable earthen bricks: A comprehensive study

This study explores the potential of optimizing alkali-activated clay with rubber waste to create sustainable earthen bricks. The research addresses the environmental challenges associated with traditional cement-based construction materials by incorporating locally sourced calcined clay and recycled rubber tire waste. The experimental program involves testing different proportions of sand with calcined clay, varying sodium hydroxide (NaOH) concentrations, and integrating rubber content. The aim is to develop a material that balances environmental sustainability with improved mechanical and durability properties. The mechanical and microstructural properties of the resulting materials were evaluated through compressive and flexural strength tests, wetting and drying cycles, and advanced analysis techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that while the inclusion of rubber enhances certain properties such as reducing the unit weight and Structural Integrity During Wet-Dry Cycles, it adversely affects compressive and flexural strengths. This study highlights the importance of optimizing the balance between durability and mechanical strength to develop effective and sustainable construction materials.

Investigation of the thermomechanical characteristics of compressed earth bricks reinforced with cement and corn straw waste fibers

The earthen construction sector attracts worldwide attention, and earthen bricks are widely used. The construction industry has also progressed in its use of natural green resources such as plant fibers to design building materials that are both economically and ecologically sustainable. However, the valorization of plant waste in construction represents a crucial environmental challenge. The present study focuses on the development and characterization of a new, low-cost earth-based building material stabilized with cement and corn straw fibers in southeastern Morocco. Different earth bricks stabilized with different cement contents and corn straw fibers were developed. The physico-chemical characterization of the soils used in the design of the bricks was carried out, using physico-chemical, mineralogical and geotechnical characterization, including X-ray diffractometer (XRD) analysis, Fourier transform infrared (FTIR) spectra and energy dispersive X-ray (EDX) analysis. The first results reveal that the predominant minerals in oasis soils include ferrous clinochlore, muscovite, calcite and quartz, which are mainly composed of silt and sand. Then, the eligibility of these soils for compressed earth brick (CEB) construction was assessed, adhering to established guidelines for the identification of suitable soil types. In addition, the thermal properties of the bricks were determined, finding that the use of corn straw fibers improves the thermal performance of the bricks, and cement stabilization leads to an improvement in the bricks' mechanical properties.

Study of the effect of adding Portland cement on the thermal insulation of compressed earthen bricks produced from the Daquq area - South of Kirkuk - Northwest of Iraq

Study of the effect of adding Portland cement on the thermal insulation of compressed earthen bricks produced from the Daquq area - South of Kirkuk - Northwest of Iraq

The impact of fibres reinforcement on the thermal characteristics of lime-stabilised compressed earth blocks

In civil engineering, the use of fibers in construction has spread recently, because of their many benefits in terms of increasing the cohesion of buildings and their thermal insulation. In addition to having several good physical and mechanical properties. Thermal insulation has become an important thing in the field of construction. Because it is linked to increasing the lifespan of buildings and predicting their thermal behavior. It includes increasing energy efficiency and reducing its costs. Fibers are used to increase thermal insulation, because it creates voids inside the structures that are within its content, and thus impedes the transfer of heat, regardless of the type of transfer by convection, radiation, or conductivity. This study aims to determine the amount of thermal insulation in compressed earth bricks with dimensions of 20 × 10 × 10 cm3, to which palm fibers and glass are added in different proportions: 0%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5%.In earthen bricks composed of soil, sand and lime. The study includes the physical, mechanical and thermal properties of these bricks. We focus on thermal insulation in the best samples in terms of hardness. Laboratory samples were taken according to standard experiments in university laboratories. Preliminary results showed a decrease in bulk density between 6% and 8.34%, an increase in mechanical stresses between 42.85% and 45.45%, and an increase in thermal insulation between 26% and 29%. These results give us an overview of the impact of using fibers in construction in terms of increasing weight bearing and predicting the amount of thermal insulation.

A Comprehensive Investigation for the Production of Optimized Interlocking Compressed Earthen Bricks with Varying Proportions of Stabilizer, Water, and Fine Aggregate

The global construction industry is shifting toward eco‐friendly building materials to reduce environmental impact while ensuring affordability, energy efficiency, and resource conservation. Interlocking compressed earthen bricks (ICEBs) offer a sustainable alternative to traditional bricks. However, ICEB composition significantly impacts their performance. This study investigates the interplay of stabilizer, water, and fine aggregate content to optimize ICEBs. Soil properties were assessed through particle size gradation analysis, Atterberg limits, and the modified Proctor test. ICEBs were manufactured using cement as a stabilizer, with various combinations of stabilizer proportions, water‐to‐soil ratios, and inclusion of fine aggregates. Compressive strength tests were conducted for each mix. Results showed that increased cement content enhanced ICEB compressive strength by promoting the formation of calcium silicate hydrate gel. Water content increments from 12% to 21% improved strength up to 18% but declined thereafter. Higher sand percentages initially reduced compressive strength but improved it with higher cement proportions. The optimal mix ratio was selected for ICEB production, followed by tests including flexural strength assessment, forensic investigations, curing regimes impact, and comprehensive durability and structural performance evaluation. Findings highlight ICEBs’ potential as a sustainable alternative to conventional brick masonry.

Influence of sawdust and soil type on the high temperature behavior of raw earth bricks

The current study looks into the high temperature behavior raw earth bricks made with varying amounts of sawdust additives. In addition to the various sawdust amounts, two different soil types were used: “Limon des Plateaux” soil from Beauvais city and clay from Barremian. Before being tested at high temperatures, those bricks were referred to an initial characterization to assess their physical and mechanical properties. At room temperature, the compressive strength decreased with increasing the sawdust mass fraction. The “Limon des Plateaux” soil presented a better resistance than the Barremian clay. After that, the blocks were exposed to high temperatures at a slow heating rate of 1 °C/min inside a furnace programmed to attain target temperatures of 150 °C, 300 °C, 450 °C and 600 °C. The residual physical and mechanical properties of the specimens were then determined. High temperature measurements were also assessed during the heating inside the samples by means of thermocouples that were embedded in their center. The obtained results showed that the compressive strength of the earthen bricks without sawdust increased as the temperature was raised. However, the compressive strength of the bricks with sawdust decreased between 150 °C and 300 °C due to the pyrolysis of the sawdust and then increased again between 300 °C and 450 °C as a result of clay dehydroxylation. The “Limon des Plateaux” soil and Barremian clay with sawdust demonstrated a similar evolution with respect to temperature. The temperature measurements in the center of the samples revealed the influence of the sawdust additives on the temperature distribution inside the sample. The amount of sawdust has an influence on the evolution of the residual properties with temperature. The higher the volume fraction of sawdust, the lower the compressive strength increased with temperature between 20 and 600 °C.

Conservation of Earthen Bricks in Architecture: An Experimental Campaign to Test Different Treatments on Vernacular Built Heritage

Earthen architecture, by its nature, is a fragile because it has a poor resistance toward the action of weathering, which has also increased in recent years through the effects of climate change. The presence of interesting examples of earthen brick buildings, for example, in the Piedmont Region of Italy, is characterised by the absence of rendering, which reveals the need to test treatments for the protection and/or strengthening of the walls of these buildings. This action is of fundamental importance to improve its resistance to the aggressive action of atmospheric agents and avoid their disappearance. A testing campaign adopting protective products with sustainability characteristics and low environmental impact was carried out on earthen brick walls. Different products belonging to various categories (synthetic polymers, natural resins, nano-structured materials) and selected based on previous experiments or tested for the first time on earthen surfaces were selected. The performance assessment of the products was carried out by taking into account the standardised procedures in the field of cultural heritage conservation through the following tests: water absorption, water vapour permeability, drilling resistance, water erosion tests (Geelong and spray), contact angle measurements, colorimetric measurements, and ageing tests. Although the choice of the optimal protective product should be made on a case-by-case basis, where it is not sustainable to proceed in this way, the results of this experimental campaign—in the presence of materials and weathering conditions similar to those of the case study analysed—will provide indications in identifying of the most appropriate product.

Assessment of optimal specimen to measure the compressive strength of earthen-based masonry

The compressive strength of masonry is regarded as an essential primary mechanical parameter of this kind of structure. However, standard specimens used to test compressive strength of earthen-based masonry vary considerably in issued codes, which hinders the intercomparison of experimental results. In this study, two kinds of adobe and two kinds of new earthen bricks were selected for preparing masonry specimens. A series of uniaxial compression tests were performed to reveal the compression behaviors of several types of earthen-based masonry, while considering the influence of the specimen bonding arrangement and h/t ratio. Analytic hierarchical processes were used to evaluate the bonding arrangement and h/t ratio of earthen-based masonry specimens from operability, reproducibility, instrument, and equipment requirements for determining an optimal specimen with excellent comprehensive performance. The results showed that optimal specimens for compressive strength tests of different earthen-based masonry can use the same bonding arrangement and h/t ratio. The stretcher bonded specimen with a h/t ratio of 3/1–4/1 should be used as the optimal specimen for compressive strength testing of earthen-based masonry. The results can be used as a reference for establishing a simple and general compressive test method for earthen-based masonry.

Mechanical, thermal and durability investigation of compressed earth bricks stabilized with wood biomass ash

There is a growing interest in raw earth as an eco-material of building for its local character and the low energy consumption that characterizes its overall life cycle. This work evaluates the effect of the recovery of two biomass ashes (WBAa, WBAb), resulting from domestic wood heating on the mechanical, thermal and durability properties of compressed earth bricks (BWBAa, BWBAb). These specimens were obtained in a partial substitution of a silty-clay soil by WBA, in various proportions (0, 5, 10, 15 and 20 wt%). The specimens manufactured were compacted with a compaction stress of 10 MPa, exposed to the open air and kept in the laboratory at a 20 ± 2 °C temperature, then allowed to harden for 7 and 28 days. The mechanical level strength increases with wood ash content and with curing time. BWBAb has the best flexural and compressive levels strength caused by formation of compounds with binding properties, but BWBAa shows good thermal insulation. Capillary water absorption test was performed to prevent the durability of the elaborated specimens under water action. These bricks showed different behaviors in contact with water based on the different microstructure present in the two ashes. The experimental study conducted highlighted the benefits of the high periclase (MgO) content on the mechanical properties and durability of compressed earthen bricks.

Freezing–thawing curves of earthen bricks with dielectric measurement: Insight into the influence of pore structure and initial moisture content

Under cold climate, poral water of building materials can be exposed to freezing–thawing (F–T) cycles that induce severe frost damage and jeopardize their durability. The F–T curve (variation in ice or unfrozen liquid content with negative temperatures) is a key property to examine and predict the behavior of porous materials under freezing temperatures. However, there is a lack of adapted procedures to evaluate the F–T curves of unsaturated earthen bricks. To fill this gap, this study proposes an experimental protocol, based on time domain reflectometry (TDR), to quantify the remaining liquid water in unsaturated earthen building materials at different temperatures from ＋10 °C to −20 °C. The validity of the device developed to determine F–T curves was verified with low temperature calorimetry (LTC). The dielectric measurement with TDR provides consistent quantification of remaining liquid water content with freezing temperatures. In this study, the influence of initial moisture conditions was investigated through both normal and pathological humid situations of earthen buildings. The normal service situation in winter season was studied with samples conditioned at relative humidity (RH) of RH75% and RH95% which lead to initial liquid saturation SL0 lower than 35% in the tested materials. The moisture pathological case was investigated with initial liquid saturation degrees of 75%, 85% and 95%. The necessary condition of water freezing in earthen materials, in function of their initial saturation ratio or conditioning relative humidity, was examined through a microstructural analysis. This approach also brought understanding about the dependency of the remaining unfrozen water with the freezing temperature.

CRITICAL REVIEW ON THE MATERIAL CHARACTERIZATION OF ADOBE ELEMENTS

ABSTRACT Adobe is a traditional masonry made of sundried earthen bricks and mud mortar. Despite a millennial history of buildings of architectural value, adobe still connotes a so called ‘not engineered’ construction type. Namely, the material and structural properties of adobe are still not entirely addressed, resulting in an equally uncertain normative framework for adobe buildings design. However, over the last ten years, a large research program has been conducted in the Netherlands to qualify the material and structural properties of this sustainable building technology. In this paper, a critical analysis of the current normative body for the material characterization of adobe is addressed. Guidelines, prescriptions and requirements related to test methods, materials selection and properties contained in the available building codes for adobe around the world are assessed. A critical normative review is performed using the most recent literature produced on adobe, with particular regards to the results of experimental tests and numerical simulations performed by the authors. On the basis of these findings, some issues have been identified in relation to the knowledge currently condensed in the norms for adobe. A series of programmatic guidelines is aimed at orienting future research on adobe as well as fostering the process of updating its current normative body.

Physico-chemical, mineralogical, and technological characterization of stabilized clay bricks for restoration of Kasbah Ait Benhadou- Ouarzazate (south-east of Morocco)

Due to ageing, the unfired brick masonry may detach and fall off, or deteriorate to such an extent that it becomes necessary to restore them. Such is the case, for instance, of the Ksar of Ait Benhadou in Ouarzazate, Morocco. Our study aims to provide compatible and sustainable earthen bricks to restore this monument. Samples were collected from facades that were under conservation/restoration at the time when sampling was performed.Clayey soil samples were collected vicinity to the Ksar and analyzed by X-ray diffraction and X-ray fluorescence. A representative sample was stabilized with three aggregates (lime, cement and straw). The effect of ageing of the stabilized briquettes on shrinkage, water absorption, mechanical and thermal properties, compressive strength and thermal conductivity was studied on stabilized specimens. The samples consist mainly of clay minerals, calcite and quartz. They are rich in iron, aluminium and potassium. These samples are sandy with low plasticity (PI = 7%), which is slightly lower than the plasticity value required by the Moroccan standard for earth constructions. The results showed that the stabilized clayey soils have suitable properties such as density, porosity, water absorption and high thermal insulation. The best compressive strength performance is obtained for clay-stabilized samples with a high sand fraction. The thermal conductivity of clay-stabilized specimens increases as the specimens become denser and more compact, lime and straw have the opposite effect.

Physico-mechanical Characterization of Composite Bricks from Laterite, Typha and/or Rice Hull

This study is part of the valuation of local materials in order to build economic, sustainable and resilient housing. The objective is to characterize composite bricks made from a mixture of laterite and straw (rice hull and typha) with proportions between 3 to 6%. These mixtures are stabilized with 1% cement and with proportions of 48.5 and 50% sand. The physical and mechanical characteristics were obtained from water immersion absorption and compression tests, respectively. The results show that the high immersion water absorption and porosity of these composite bricks is due to the low density of typha and rice hull and therefore the durability of these bricks is low. To overcome this problem, the use of plaster is recommended. On the other hand, the compressive strength of all the bricks varies between 2.09 to 3.64 MPa. This resistance falls within the range of admissible values for earthen bricks. These resistances are sufficient to build a two-story house [3,8,10].

Assessment of local earthen bricks in perspective of physical and mechanical properties using Geographical Information System in Peshawar, Pakistan

Due to good quality of soil in the Peshawar region (North-West of Pakistan) and the expertise of the local labors in brick’s production, bricks of this region is more popular in the country and exported to different provinces of the country as well as to Afghanistan. There are approximately 450 brick kilns in Peshawar and their production per day/brick-kiln is around 75,000 bricks; hence the daily production is about 3.4 Million. This study examines the physical and mechanical properties of local earthen clay bricks and their production in Peshawar city. There is a lack of relevant data about the excellence of locally made bricks and the selection of proper bricks kiln for any intended use of suitable bricks. Initially, out of 450 brick kilns, the location of 254 were noted through the Global Positioning System (GPS) to represent their location on google map using their coordinates. However, the whole area was distributed in four zones from which 50 brick kilns were selected from all zones. The analysis shows that bricks from all the selected kilns have acceptable engineering properties fulfilling American Society for Testing and Material (ASTM C67) guidelines. The mechanical properties of 1st class bricks have large variability, showing less porosity (19%), high compressive strength (CS) up to 24.27 MPa, and low water absorption (WA) rate of 11.9%. The CS of 1st class bricks was 56.73% greater than the standard CS whereas, it was 46.2% and 38.88% greater in case of 2nd and 3rd class bricks, respectively. A strong correlation was found in CS and WA, which was 76.83% in 1st class bricks and 77.44% and 85.29% in the 2nd and 3rd class bricks. Using Quantum Geographical Information System (QGIS), the results obtained along with kiln coordinates and other required parameters have been presented graphically. Inventory of the brick kilns for the selected zones has been developed using QGIS, which can be used by various relevant departments, contractors, and environmental protection agencies.

Susceptibility of earth-based construction materials to fungal proliferation: laboratory and in situ assessment

The impact of building materials on the environment and the health of occupants is nowadays a priority issue. Ecological construction materials such as earthen materials are currently experiencing a regain of interest due to both ecological and economic factors. The microbial proliferation on indoor materials can induce a deterioration of the building air quality and lead to an increase of health risks for the occupants. The issue of indoor air quality raises questions about the use of earthen building materials and their possible susceptibility to fungal development. The microflora of earthen materials and their ability to grow on such support are indeed poorly studied. This study focused on the quantification of both bacterial and fungal microflora along the manufacturing process. The impact of extreme humidity, simulating a hydric accident, on microflora development was analyzed on the surface and inside earthen bricks. The initial microflora of these materials was dramatically reduced during the manufacturing process, especially after heat treatment for drying. Proliferation of remaining microorganisms was only observed under high humidity condition, in particular for earthen materials with vegetal aggregates. Moreover, in situ samplings were performed on naturally dried earthen materials used in buildings. The characterization of the microbial density revealed a higher microbial density than on manufactured specimens, while microbial concentration and detected taxa seemed mainly related to the room use and building history. These results provide a better understanding of microbial proliferation on these materials.

NaOH Activation of Raw Soils: Effect of NaOH Content on the Drying Kinetic and Its Modelling

NaOH activation of soils is an affordable and promising way to improve mechanical properties of earthen bricks. If for well-activated geopolymers, the hard polymeric network limits the influence of water on mechanical properties, for the weakly activated one, as non-calcined raw clayey soils, the influence of water on these properties would be more critical. This work aims to determine the effect of sodium hydroxide concentration on the drying kinetics of bricks made with raw clayey soils, and to model this kinetics. The results show that the drying kinetics is governed by the diffusion of water due to the absence of free water. The drying duration increases linearly with the increasing of NaOH content, while the volumetric shrinkage decreases, probably thanks to the reduction of the material porosity during the formation of the zeolitic structures. Besides, the drying duration is strongly and negatively correlated with the initial drying rate (−0.97) and bricks did not show visible cracks. Among the five parametric models tested, the Khazaei’s model is the best in terms of all statistical criteria considered. For all models used, the coefficient of determination is ranged from 0.993 to 0.999, and the evolution of the models’ parameters is in accordance with that of the drying kinetics observed.

Hygrothermal properties of compressed earthen bricks

The present study investigates the relationship between bulk density and hygrothermal behaviour of compressed earthen bricks. The experimental results show that the thermal conductivity linearly increases from 0.5228 W/(m K) to 0.9308 W/(m K) as the bulk density increases, and that the equilibrium moisture content increases with increasing relative humidity. Hysteresis effects are observed. When relative humidity changes, compressed earthen bricks usually reach an equilibrium in four days and it means compressed earthen bricks can be used to regulate indoor relative humidity. The hysteresis values of compressed earthen bricks with different bulk densities are close to each other, especially low relative humidity, as the results of Brunauer-Emmett-Teller (BET) show that samples with different bulk densities have similar porous structure including specific surface area (15.5008–16.2091 m2/g), micropore volume (0.000867–0.001221 cm3/g) and mesopore volume (0.030785–0.032239 cm3/g). Moreover, the hysteresis loops in this study belong to the type H3 hysteresis loops which indicate that there are some slitlike pores inside the matrix.

Geopolymer Stabilisation of Unfired Earth Masonry Units

Contemporary domestic structures typically use masonry units that are approximately 100mm thick. There is interest in using commercial methods of manufacture to produce earthen bricks that have a similar form factor to conventional masonry The large scale adoption of thin walled unfired earth masonry is dependent on its suitability for use in a load bearing application. High moisture content leading to full saturation, for example as a result of flooding, is a concern for unstablised earth construction, especially as wall thickness reduces. The greatest barrier for earth masonry adoption is the durability of the material when affected by high moisture content. Accidental and intentional wetting of a 100mm thick load bearing unfired earth wall could lead to disproportionate collapse. The paper presents initial findings from an investigation into the use of geopolymer mechanism as a method of stabilisation. The use of geopolymer mechanism was chosen as a possible method of improving the water resilience. Soil that is used for commercial extruded fired brick production was chosen. The soil was selected as the precursor (source of the required silica and alumina) and this was mixed with various sodium hydroxide and sodium silicate activators. Specimens were tested both in their dry sate as well as following 24 hours of submersion in water. Compressive strength of cylinders after saturation, was used as an indicator of effective stabilisation. The maximum dry compressive strength achieved was 10.4N/mm2with the addition of 5% sodium hydroxide and 20% sodium silicate after curing at 105°C. The most significant contributor to the strength gain was the addition of sodium silicate. Although some of the cylinders were able to be tested under fully saturated conditions the strengths achieved were negligible and insufficient for structural application. The potential for geopolymers as a method of stabilising unfired earth bricks is discussed with respect to the compressive strengths achieved.

Wind Load Test of Earthbag Wall

Earthbag construction is a sustainable, low-cost, housing option for developing countries. Earthbag structures are built of individual soil-filled fabric bags (i.e., sand bags) stacked in a running bond pattern. Once stacked, earthbags are compacted and the soil inside the bags is dried in-place to form earthen bricks. Barbed wires are placed between each course to affect shear transfer within the wall. Results of an out-of-plane load test on a full-scale earthbag wall are presented in this paper. The wall was subjected to out-of-plane pressure up to 3.16 kPa, which resulted in plastic deformations up to 50 mm. The wall did not collapse during loading. Wall behavior and force transfer mechanisms are discussed.

Developing enhanced, lignocellulosic fibre reinforcement for low-cost, cementitious, construction materials

The research reported in this article is based on an NSF (National Science Foundation) project aimed at advancing the structural use of earth-based technologies through addressing durability concerns within the hot and humid context. This article focuses on one aspect of the research directed at developing an enhanced, lignocellulosic fibre-reinforced, cementitious composite. In this research, soil–cement masonry is the cementitious matrix and coconut fibre (coir) the natural fibre. In the case study context, this cementitious composite is highly susceptible to physical damage due to intense rainfall and chemical deterioration that can be linked to the hydration of cement. The use of natural fibres, such as coir, compounds this problem. For the research to adequately address durability concern problems, accurate empirical data quantifying the damage to the natural fibre-reinforced cementitious composite are required. The discussion identifies the key knowledge gaps. It also describes the methodology adopted to produce and test the cementitious bricks investigated in the research. In addition to summarizing the main physical and mechanical properties, the findings presented in this article also (i) establish the bricks' resistance to wind-driven rain erosion and (ii) characterize the performance of the units on the basis of hydration-triggered chemical deterioration that can be expected in cement-stabilized earthen bricks. The article ends with a discussion of the key findings and a description of further research activities.