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Article

The Contribution of Earth Bricks Reinforced with the Aqueous Maceration of Néré Pods (Parkia biglobosa) to Sustainable Construction in Togo: Characterization, Formulation, Mechanical Performance, and Recommendations

by
Magnouréwa Josiane Tossim
1,*,
Cyprien Coffi Aholou
1 and
Yawovi Mawuénya Xolali Dany Ayité
2
1
Regional Center of Excellence for Sustainable Cities in Africa (Cervida-Dounedon), University of Lomé, Lomé 01BP1515, Togo
2
Department of Civil Engineering, École Polytechnique de Lomé (EPL/UL), University of Lomé, Lomé 01BP1515, Togo
*
Author to whom correspondence should be addressed.
Constr. Mater. 2025, 5(2), 19; https://doi.org/10.3390/constrmater5020019
Submission received: 23 January 2025 / Revised: 11 March 2025 / Accepted: 12 March 2025 / Published: 1 April 2025
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Abstract

:
Faced with environmental challenges posed by traditional building materials and the management of agricultural waste, this study uses dwarf hulls, an abundant waste product in West Africa, as a natural stabilizer for earth bricks. Three mixtures were studied: soil + water (reference), soil + néré husk decoction, and soil + decoction with weekly sprinkling. The results show a significant improvement in compressive strength with the decoction. At 28 days, it increases from 0.967 MPa (reference) to 1.251 MPa with decoction and 1.360 MPa with sprinkling. At 90 days, these values reach 1.060 MPa, 1.39 MPa, and 1.502 MPa, respectively, confirming the beneficial effect of tannins and humidification. On the other hand, the tensile strength decreased from 0.10 MPa for the reference mixture to 0.08 MPa and 0.08 MPa with decoction and sprinkling. This study highlights the potential of using néré husk as a durable stabilizer. However, further research is needed, particularly on the addition of plant fibers, to improve tensile strength.

1. Introduction

Human activities generate a considerable amount of waste from agriculture, industry, and households. The transition to a circular economy requires a radical rethink of the waste streams generated by human activities. Among these residues, agricultural waste, by-products of crop processing, livestock farming, and forestry [1], represents a critical source, with global production estimated at 998 million tonnes per year [2,3]. In developing countries, where agriculture contributes more than 25% of GDP, these biomasses are often perceived as an environmental burden. Treating this waste is a major challenge. Their inadequate management, open burning, uncontrolled burial or abandonment in landfills [4,5], exacerbates soil degradation, air pollution, and the loss of biodiversity [6,7]. This situation, exacerbated by climate change, highlights the need to find sustainable solutions to recover this waste, which is hard gold instead of ordinary waste. This is because these lignocellulosic residues contain organo-mineral compounds (cellulose, lignin, tannins, and silica) that could transform them into strategic resources for sectors such as bioenergy, the food industry, and construction.
In this context, concrete is a ubiquitous material in the construction sector, used in large quantities every year [8,9,10]. Its global production has almost quadrupled since 1990 [11] and is expected to increase by 12–23% worldwide by 2050 [12]. However, concrete is at a critical crossroads. Concrete has a high environmental impact because of the high consumption of energy and greenhouse gases associated with its manufacture and use [13,14,15]. For every tonne of cement produced, 0.9 tonnes of CO2 are released into the atmosphere [16]. In addition to the pollution linked to the production of this material, its use, particularly in hot climates, also generates significant greenhouse gases, which contribute to the destructuring of the environment [9], thus threatening the climate objectives of the Paris Agreement. Yet only 30% of the world’s population still lives in earthen buildings [17], a figure that is declining due to negative perceptions of its limited durability and vulnerability to the elements [18]. Faced with this urgent need, the scientific community and practitioners are revisiting ancestral materials such as raw earth, whose hygrothermal advantages (natural regulation of humidity and temperature) and low embodied energy [19,20,21] make it a credible alternative to conventional materials.
There is therefore an opportunity to combine these two major challenges, namely the sustainable management of agricultural waste and the promotion of environmentally friendly building materials. It is for this reason that the development of new stabilizers for buildings with earth materials that have a lower environmental impact seems to be attracting a great deal of interest among researchers. The stabilization of earth matrices is therefore emerging as a key area of research. Conventional methods (adding cement, lime, or bitumen) improve mechanical properties but offset the initial ecological advantage. Hence, the growing interest in biostabilisers derived from agricultural waste: sisal fibers, rice ash, or tannin extracts, which act as natural binders while making the most of local resources [22].
Among these biomaterials, néré pods (Parkia biglobosa), abundant residues in West Africa, present a singular profile. The pods of this tree, grown mainly for its protein-rich seeds and medicinal uses (treatment of malaria and antifungal properties), contain up to 18% condensed tannins [23,24,25,26]. These polyphenols, known for their adhesive and hydrophobic properties, are exploited empirically in vernacular practices, such as in West Africa, where the decoction of néré pods is traditionally used as a coating for walls or as a natural binder to improve the durability of earthen constructions [27,28].
In the northern regions of Togo, there is an ancestral practice of using a decoction of néré pods as a plaster for walls and as a soil improver. Soaking the pod in water for a few days produces a liquid rich in tannins and other organic compounds with remarkable binding and waterproofing properties [29]. Applied to walls, these natural coatings offer effective protection against water and the elements, while making buildings more durable.
However, this traditional knowledge has yet to be rigorously translated into scientific terms. While recent studies have shown that adding Parkia tannins to lightweight concrete can reduce cement content by 25% without affecting compressive strength [27], the mechanisms of interaction with earth matrices remain poorly understood. As a result, there is a lack of awareness of the potential of aqueous extracts, even though they are compatible with low-tech techniques in rural areas. In addition, critical parameters such as optimal maceration time, tannin concentration, impact on microstructure, etc., have not been systematically explored, leaving a gap between empirical practice and academic validation.
This study is positioned at this intersection between endogenous knowledge and scientific innovation, by investigating the impact of maceration of cowpea hulls on the mechanical properties of mud bricks. The main objective is therefore to assess the mechanical properties of earth bricks reinforced by maceration of cowpea hulls. More specifically, the aim is to: (i) Develop different earth brick formulations incorporating or not incorporating the decoction of cowpea hulls; (ii) Assess the mechanical performance of the formulated bricks using compression and tensile tests.
This study is part of a global initiative to promote the use of local and sustainable building materials while contributing to the recycling of agricultural waste. The results obtained will provide a better understanding of the interaction mechanisms between soil and cowpeas and the potential of this new formulation for the construction of energy-efficient and environmentally friendly buildings.

2. Materials and Methods

2.1. Materials Used and Properties

The materials used in this study are essentially clay and néré husk in the form of aqueous maceration.
The clay soil used for the tests was sampled at coordinates 6°25′13.9″ N and 1°13′20.3″ E, in Tsévié, a town located in the maritime region of Togo. The pedological profile shows that it has a blackish vegetation layer about 25 cm thick on the surface. Beyond this depth is a reddish layer. The soil sampled is therefore more than 60 cm deep. The soil used in this work has already been characterized and tested with a reinforcement of cowpea pod powder [30]. In the following, this soil will be referred to as Tse-1 and its main properties are listed in Table 1.
In addition to the previous tests, further analyses were carried out on the Tse-1 soil. These were as follows:
-
Chemical analysis using XRF spectrometry, a technique that is suitable for various types of samples and can identify and quantify the chemical elements present, with a sensitivity ranging from 100% to a few ppm. The analysis was carried out using the SMART—QUANT WDISMART Oxides application, combining calcination and molten bead analysis. The results are shown in Table 2.
-
Mineralogical analysis, carried out by X-ray diffraction (XRD) on samples previously reduced to powder. A Bruker D8 Advance diffractometer, equipped with a monochromator and a rotating sample holder, was used. The detector measured the intensity of the reflected X-rays, enabling the minerals present to be identified. The results are shown in Table 3.
The néré pod was obtained from néré fruits harvested in the Kara region, more precisely at Soumdina, in a field located at coordinates 9°38′07.6″ N and 1°16′00.6″ E. Table 4 and Table 5 show the main chemical and physical properties of the néré pod.
The water used to prepare the maceration was drinking water supplied by Togolaise Des Eaux (TDE). Figure 1 shows the materials used.

2.2. Equipment

The equipment used included sieves from the AFNOR series for granulometric analysis, a Casagrande cup for consistency testing, an oven and a dryer for drying the samples, and a smooth marble slab for preparatory work. An electronic balance was used for precise weighing, along with containers, graduated test tubes, spatulas, wooden rulers, and trowels for various manipulations. The Proctor tests required specific molds and a modified Proctor tamper. Cylindrical molds measuring 10 cm in diameter and height were used to mold the samples, with a metal plate for leveling and de-molding oil to facilitate extraction.
The analyses were carried out in different laboratories: The identification, classification, and formulation tests were carried out by the Soil Mechanics Laboratory of the Training Center for Road Maintenance (CERFER). Meanwhile, the National Laboratory of Building and Public Works (LNBTP) carried out compression and tensile tests.

2.3. Experimental Procedure

2.3.1. Preparation of the Solution by Maceration

Preparation of the solution begins with drying of the Parkia biglobosa pods, followed by grinding using a RETSCH-type knife mill fitted with a 2.5 mm screen, made in Ghana, Accra. Once reduced to powder, the material is subjected to a process to extract the tannic compounds. To do this, 1000 g of powder is immersed in a container containing 5 L of tap water. The mixture is carefully stirred for 5 min to ensure even dispersion of the particles, before being left to stand at room temperature for 48 h to allow optimal maceration. The resulting solution is then filtered through a 0.08 mm sieve, and the filtrate collected is used to formulate the brick samples for testing. The mill is shown in Figure 2.

2.3.2. Mixture Compositions

This study distinguishes three types of mixture: one composed of soil and water (M1), the second of soil and filtrate obtained by macerating the néré pod powder (M2), and the third of soil and filtrate, plus weekly watering by spraying the maceration solution for 21 days. Manual mixing was carried out by mixing practice, as indicated by [36]. The compositions of the mixture are presented in Table 6. The water content of the aqueous maceration is 92%.

2.3.3. Production of Test Specimens

The test specimens used in this study are cylindrical, with an identical height and diameter, each measuring 10 cm. The procedure is the same for the two mixes M1 and M2. It is the materials used in the mix that differ. To do this, begin by weighing the required mass of soil in a container, making sure that the soil has been dried in an oven at 105 °C until its mass has stabilized. Then, add the percentage of filtrate obtained after maceration of the pods for mixture M2, or the quantity of water required for mixture M1, as appropriate. Mix by hand until a homogeneous paste is obtained. Prepare the molds by coating them with a thin layer of oil to make them easier to remove from the mold. Place the mold on a work surface, filling it gradually with a spatula while compacting the material with a force of 10 kN. Finally, carefully remove the specimens from the mold to preserve their integrity. Figure 3 shows the appearance of the samples.

2.3.4. Storage and Curing of Test Specimens

After demolding, the test specimens will be stored for 28 days in an enclosure at room temperature, with a temperature range of between 20 °C and 25 °C and relative humidity maintained between 45% and 55%. Drying is considered complete when the variation in weight of the sample is less than 1% over 24 h.

2.4. Mechanical Resistance Tests

Two types of tests were carried out on the dried samples: uniaxial compression strength tests, by standard NF EN 13286-41 [37], and splitting tensile strength tests, by standard NF EN 13286-42 [38]. These tests were carried out using a CONTROLS electronic universal press, imported from France and capable of applying loads at a rate of 0.2 kN/s and equipped with sensors for accurately measuring loads and displacements.
For the compression tests (Figure 4), the specimens were subjected to increasing loads until failure, with the maximum force applied before cracks appeared recorded. Tensile splitting tests involved applying a linear and diametrical load along the length of the specimens, which were positioned between two flat loading plates, as shown in Figure 5.
For each type of test and each mixture, three samples were tested. The loading speed was kept constant at 2 mm/min. A computer connected to the press automatically recorded the key parameters, including specimen dimensions, maximum load supported, and strengths obtained.

2.5. Statistical Analysis

The statistical analysis was carried out using R 4.4.1 software. The tests were as follows:
-
Normality (Shapiro–Wilk): For each mixture, a p-value is calculated. If it is greater than 0.05, the data follow a normal distribution.
-
Homogeneity of variances (Levene): This test checks whether the variances of the groups are homogeneous. A p-value greater than 0.05 indicates that the variances are homogeneous.
-
ANOVA: This is a two-factor analysis of variance (two-factor ANOVA) where factor A is the type of mix (M1, M2, M3) and factor B is the time (28 days, 90 days) for the compression tests. For the tensile tests, a one-factor ANOVA analysis was performed with the type of mix as the quantitative variable and tensile strength as the qualitative variable. If the p-value is less than 0.05, then there is a significant difference.

3. Results

3.1. Formulation Results

The various mixtures and experimental tests carried out were used to identify a reference mixture as shown in Table 7.

3.2. Results of Uniaxial Compression Tests

The results of the compression tests carried out on the specimens are shown in Table 8.
The results of the compression tests show a significant improvement in the average compressive strength of bricks reinforced with cowpea husk decoction, compared with reference bricks made of earth and water alone (M1).
Indeed, at 28 days, the performance of the different mixes shows significant variations depending on the formulations. The base mix (M1: Earth + Water) shows an average strength of 0.97 MPa, the lowest among the samples tested. In contrast, the M2 mix (Soil + Maceration) had an average strength of 1.25 MPa, a 29% improvement on M1. Finally, the M3 mix (soil + maceration + weekly sprinkling) performed best, with an average strength of 1.36 MPa, representing a 41% increase on the base mix
At 90 days, average strengths increase for all mixes, reflecting a gradual improvement in mechanical properties over time. Mix M1 (Soil + Water) reaches an average strength of 1.06 MPa, an increase of 9.6% compared to 28 days. Mix M2 (Soil + Maceration) recorded a strength of 1.39 MPa, representing an improvement of 11.1%. Finally, mix M3 (Soil + maceration weekly sprinkling) performed best, with an average strength of 1.50 MPa, representing a 10.4% increase on day 28 and a 42% overall improvement on the base mix (M1).
Levene’s test gives p = 0.241 and p = 0.346 on days 28th and 90th, respectively, so we conclude that the variances are homogeneous. As for the ANOVA test, we have the following:
-
Day 28: F = 13.979 and p = 0.0055.
-
Day 90: F = 20.908 and p = 0.0020.
There is a significant difference between the mixes in terms of compressive strength on the 28th and 90th days.

3.3. Tensile Test Results

Table 9 shows the results of the tensile tests on the specimens, which are the averages of the strengths of the three samples tested.
The results of the split tensile tests show that the strengths of the M2 (Soil + Maceration) and M3 (Soil + Maceration + Weekly Spray) mixes are lower than those of the M1 (Soil + Water) mix. Specifically, M1 has an average tensile strength of 0.10 MPa, the highest of the mixes tested. M2, and M3 on the other hand, recorded a strength of 0.08 MPa, corresponding to a reduction of around 19% compared with M1.
Levene’s test revealed the homogeneity of the groups’ variances with p = 0.452.

4. Discussion

4.1. Compression Tests

Compression tests show that the strength of the mixes increases with the addition of néré husk maceration (M2 and M3) compared with the base mix (M1). At 28 days, M1 has a strength of 0.967 MPa, M2 reaches 1.251 MPa (+29%) and M3 reaches 1.360 MPa (+41%). At 90 days, the strength continues to increase for all mixes: M1 rises to 1.060 MPa (+9.6%), M2 to 1.39 MPa (+11.1%), and M3 to 1.502 MPa (+10.4%). The effect of weekly wetting (M3) remains dominant, with a 42% improvement on M1.
Firstly, adding néré pod maceration clearly improved the strength of the bricks, demonstrating the positive role of the tannin compounds present. These compounds act as binders, promoting cohesion between the earth particles. This result is confirmed by the work of Labintan et al. [39] on improving the properties of banco by the addition of néré infusion. Similarly, previous research carried out by [35,40,41] maintains that thanks to the compounds contained in the néré pod, the compressive strengths of the samples tested are significantly improved. According to [28,32,42], tannins act as a binder in the soil, increasing cohesion between soil elements and therefore mechanical strength.
Secondly, the increase in compressive strength of bricks containing néré pod maceration (M2 and M3) can be explained by the chemical and mineralogical composition of the materials used. The high silica content (SiO2—74.824%) in chemical composition and 74.685% in the form of quartz—is a key factor in mechanical strength. Quartz is known for its hardness and stability [43], which improves the rigidity of the brick matrix. The presence of alumina (Al2O3—12.3%) and kaolinite—11.7% promotes cohesion and grain structuring within the brick, contributing to improved strength [44,45]. The positive effect of néré husk maceration could be attributed to the interaction between tannins and clay elements such as kaolinite and minerals from the illite–smectite group (2.211%). These swelling minerals have the ability to absorb water and modify the plasticity of the mixture. Maceration acts as an additional organic binder, limiting the effect of shrinkage and improving the cohesion of the material.
In addition, the results also show a continuous improvement in resistance over time. This evolution suggests that setting and hardening reactions, influenced by interactions between the soil and the tannic compounds in the decoction, continue to develop. The curing process of the bricks appears to intensify between 28 and 90 days, progressively strengthening the bonds in the matrix and thus increasing their performance. Banakinao [35] and Keita et al. [40] have obtained similar results in their studies, which show an increase in compressive strength as the brick cures. The work of Banakinao et al. [46] reveals that when the bricks are wet, the compressive strength is much lower, regardless of the type of soil and the age of the bricks. However, if the bricks are dried, they become very strong and can reach a maximum value after 90 days. His results also show us that the type of soil is very decisive in improving mechanical strength since some soils (clayey sands with plastic matrices) show no improvement whatever the age of the brick.
Weekly wetting showed an additional positive impact. This process favors the penetration of the maceration solution into the soil matrix, thus increasing the contact surface between the soil particles and the organic binder. This phenomenon optimizes the action of the tannins, which explains the better resistance observed for M3 on day 28, with an increase of 41% compared to M1. The effect of wetting therefore appears to be a key factor in improving long-term mechanical properties. On the one hand, the work of Aguwa and Okafor [47], reveals that the higher the concentration of carob extract, the greater the compressive strength. The weekly wetting experiment in the present study can be assimilated to an increase in the concentration of the solution of néré maceration, which is why a significant increase in compressive strength was observed. However, the results of this study also conclude that compressive strength increases with age, contrary to the conclusions of [47], for which the samples do not need additional time beyond seven days to reach full maturity.
The loss on ignition of 6.83% also indicates the presence of organic matter and carbonates, which can affect the setting and hardening of bricks. However, the low lime (CaO—0.3%) and magnesite (MgO—0.422%) content suggests limited reactivity to carbonation and chemical hardening phenomena typical of clay-rich soil [48].
Previous research is not limited solely to the contribution of the husk element to cowpeas. Some focus on other elements of cowpea and other techniques of use, revealing important information that will continue to improve the properties of construction elements. For example, Tamou [49], whose work focused on the influence of cowpea infusion on the mechanical performance of banco composites, concluded that the decoction of cowpea increased the strength of banco. Similarly, the work of Flora et al. [50] on the influence of the decoction of néré seeds on the mechanical properties of earth materials revealed that this decoction improves the wear resistance of bricks by improving their physical appearance and reducing their crumbling. Néré husk has also played an important role in reducing the quantity of cement used to make sand concrete.

4.2. Tensile Tests

Tensile tests showed that the strength of the M2 (Soil + Maceration) and M3 (Soil + Maceration + Weekly Spray) mixes was lower than that of the reference M1 (Soil + Water) mix. This means that the addition of the solution from the maceration of the cowpea pod had no positive effect on tensile strength. This suggests that specific mechanisms, linked to the chemical, physical, and mineralogical composition of the mixture, could be responsible for this reduction in performance. One possible explanation is unfavorable interaction between the substances in the solution and the soil particles.
Firstly, the dominant presence of quartz (74.685%) gives the material a relatively rigid granular structure [43], which limits the brick’s ability to absorb tensile deformation. Secondly, the low percentage of illite and smectite (2.211%) reduces the plasticity of the material [51], making it more brittle in tension. In addition, the potash (K2O—1.12%) and soda (Na2O—1.035%) content can influence the reactivity and structuring of the clays, thus modifying the mechanical properties of the material [52].
Furthermore, the interaction between the organic compounds in cowpea pod maceration and the clay minerals appears to disrupt the material’s microstructure by creating additional pores or reducing intergranular adhesion. This increase in porosity compromises the homogeneous distribution of loads, which can lead to premature failure under the effect of tensile forces. In addition, the presence of traces of haematite and goethite (up to 3%) could also play a role, as these iron oxides influence cohesion and stress distribution in the matrix [53].
In comparison, unlike plant fibers that reinforce the tensile strength of earth bricks (maize stalks, straw bales, rice), as demonstrated in studies by [18,54,55,56,57], maceration of cowpea hulls does not appear to provide any additional mechanical reinforcement. These fibers act as bridges between the particles, improving internal cohesion and overall mechanical performance.
These observations highlight not only the importance of the choice of materials but also the need to adopt a more systematic approach to the formulation of mixtures. By exploring the chemical and physical interactions between components, it would be possible to optimize formulations. It is therefore essential to continue research to identify more effective combinations. For example, combining fibers from cowpea pods with the maceration liquid could be an interesting solution. This approach would make it possible to take advantage of the mechanical properties of the fibers while reducing any negative effects of the solution on the cohesion of the soil particles. Such studies would help to design more robust construction materials adapted to local contexts.

5. Conclusions

This study demonstrated that cowpea husk maceration can serve as a natural stabilizer for compressed earth bricks, offering a sustainable alternative to conventional building materials. The results showed that the compressive strength of the bricks improved significantly due to the presence of tannins, which enhance soil particle cohesion. However, a slight reduction in tensile strength was observed, likely due to structural changes within the material. These findings highlight the potential of agricultural by-products in construction, reducing reliance on industrial stabilizers like cement while promoting waste valorization.
To optimize the performance of these bricks, further research is needed to refine the formulation of the maceration solution and explore the addition of plant fibers to counteract the decrease in tensile strength. Additionally, long-term durability studies should be conducted to assess their resistance under real-world conditions. This study paves the way for the development of low-carbon, locally sourced building materials, emphasizing the importance of a multidisciplinary approach that integrates material science, sustainability, and traditional construction techniques to address both environmental and housing challenges.

Author Contributions

Conceptualization, M.J.T. and C.C.A.; methodology, M.J.T. and Y.M.X.D.A.; software, M.J.T.; validation, M.J.T., C.C.A. and Y.M.X.D.A.; formal analysis, C.C.A. and Y.M.X.D.A.; investigation, M.J.T.; resources, M.J.T.; data curation, M.J.T.; writing—original draft preparation, M.J.T.; writing—review and editing, C.C.A. and Y.M.X.D.A.; visualization, Y.M.X.D.A.; supervision C.C.A. and Y.M.X.D.A.; funding acquisition, M.J.T. and C.C.A. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the World Bank through the Regional Center of Excellence on Sustainable Cities in Africa (CERViDA-DOUNEDON), funding number IDA 5360 TG.

Data Availability Statement

Informed consent was obtained from all subjects.

Acknowledgments

The authors would like to thank the World Bank and the University of Lomé (UL) via the Regional Center of Excellence for Sustainable Cities in Africa (CERViDA-DOUNEDON) for their financial contributions and scientific supervision.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
kNkilo Newton
MPaMegapascal
mmMillimeter

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Constrmater 05 00019 g001
Figure 1. Materials used: (a) soil used, (b) dwarf hull, (c) hull powder ready to be soaked, (d) appearance of aqueous maceration of dwarf hull powder, and (e) filtrate obtained after sieving.
Figure 1. Materials used: (a) soil used, (b) dwarf hull, (c) hull powder ready to be soaked, (d) appearance of aqueous maceration of dwarf hull powder, and (e) filtrate obtained after sieving.
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Figure 2. RETSCH type knife mill.
Figure 2. RETSCH type knife mill.
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Figure 3. Specimen appearance.
Figure 3. Specimen appearance.
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Figure 4. Uniaxial compression test.
Figure 4. Uniaxial compression test.
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Figure 5. Split tensile test.
Figure 5. Split tensile test.
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Table 1. Soil properties and classification by the authors of [30].
Table 1. Soil properties and classification by the authors of [30].
SoilOptimum Water ContentOptimum Density% 0.075 mm PassPlasticity Index (PI)Liquidity Limit (Wl)LCPC ClassificationAASHTO ClassificationType
Tse-18.27%2.19 g/cm331.15 < 3514.13 > 1132.5 < 40B4A2-6Clayey sands with little plasticity
Table 2. Chemical composition of the earth Tse-1.
Table 2. Chemical composition of the earth Tse-1.
LOI (%)Na2O (%)MgO (%)Al2O3 (%)SiO2 (%)Fe2O3 (%)CaO (%)K2O (%)
6.91.0.412.374.83.40.31.1
Table 3. Mineralogical composition of the earth Tse-1.
Table 3. Mineralogical composition of the earth Tse-1.
Quartz (%)Albite (%)Kaolinite (%)Illite and Smectite (%)Hématite and Goethite (%)
74.78.411.72.23
Table 4. Summary of the constituents and characteristics of pod tannins [31,32,33,34].
Table 4. Summary of the constituents and characteristics of pod tannins [31,32,33,34].
Constituents AnalyzedContent (%) per 100 g of Selected Dry MatterAssociated Features or Elements
Dry matter content91.68Indicates the percentage of dry matter in the sample
Mineral matter2.9Inorganic compounds (mineral salts, etc.)
Lipids0.9Fats and oils
Crude protein4.69Proteins, amino acids
Cellulose49.76Main component of holocelluloses
Hemicelluloses22.52Associated with the long chains to which flavonoids are potentially linked
Lignin32.95Portion of non-extractable polyphenols in the form of tannins
Total polyphenols33Around these polyphenols are extractable tannins.
Tannic condensatesNot specifiedOligomers linked to flavonoids, often without carbohydrate chains after industrial extraction.
Hydrolysable tanninsLow proportionTraces identified: trimer (569 Da), pentamer (835 Da), and pentagalloyl glucose (960 Da).
Sugar solubles (glucose, lactose, etc.)Low proportionResidues associated with holocellulose chains or fragments attached to flavonoids.
Flavonoid linkage structuresNot specifiedGlycosides (3-O, 7-O) or ethers are associated with carbohydrates and holocelluloses.
Table 5. Physical characteristics of néré pod [35].
Table 5. Physical characteristics of néré pod [35].
ParametersValues
Grain diameter (mm)Lower limit
0.0839%
0.190%
0.12595%
0.299%
0.4100%
0.5100%
1.00100%
bulk density0.69 g/cm3
Absorption rate0.44 mL/g
Table 6. Proportion of different components used to formulate test specimens.
Table 6. Proportion of different components used to formulate test specimens.
Mixed IDSoil (Tse-1)Water (W)Cosse de Néré (MCne) Maceration % (%)Weekly Watering (AMCne)
M11001100
M21000210
M31000211
Table 7. Composition of blends.
Table 7. Composition of blends.
Mixed IDSoil (Tse-1) gWater (W) gMaceration of Cosse de Néré (MCne) gWeekly Watering (AMCne) g
M1190020900
M219000 g3940
M31900039420
Table 8. Compression test results.
Table 8. Compression test results.
MixesAverage Compressive Strength σc (MPa): 28 DayStandard DeviationCoefficient of Variationp-ValueAverage Compressive Strength σc (MPa): 90 DayStandard DeviationCoefficient of Variationp-Value
M10.97 0.12512.90.6371.060.098.480.92
M21.250.0453.620.9901.390.0161.140.95
M31.360.0090.670.7021.500.0825.490.82
Table 9. Results of tensile tests.
Table 9. Results of tensile tests.
MixesTensile Strength in MPaStandard DeviationCoefficient of Variationp-Value
M10.100.000.48-
M20.080.0055.2300.157
M30.080.0069.440.688
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Tossim, M.J.; Aholou, C.C.; Ayité, Y.M.X.D. The Contribution of Earth Bricks Reinforced with the Aqueous Maceration of Néré Pods (Parkia biglobosa) to Sustainable Construction in Togo: Characterization, Formulation, Mechanical Performance, and Recommendations. Constr. Mater. 2025, 5, 19. https://doi.org/10.3390/constrmater5020019

AMA Style

Tossim MJ, Aholou CC, Ayité YMXD. The Contribution of Earth Bricks Reinforced with the Aqueous Maceration of Néré Pods (Parkia biglobosa) to Sustainable Construction in Togo: Characterization, Formulation, Mechanical Performance, and Recommendations. Construction Materials. 2025; 5(2):19. https://doi.org/10.3390/constrmater5020019

Chicago/Turabian Style

Tossim, Magnouréwa Josiane, Cyprien Coffi Aholou, and Yawovi Mawuénya Xolali Dany Ayité. 2025. "The Contribution of Earth Bricks Reinforced with the Aqueous Maceration of Néré Pods (Parkia biglobosa) to Sustainable Construction in Togo: Characterization, Formulation, Mechanical Performance, and Recommendations" Construction Materials 5, no. 2: 19. https://doi.org/10.3390/constrmater5020019

APA Style

Tossim, M. J., Aholou, C. C., & Ayité, Y. M. X. D. (2025). The Contribution of Earth Bricks Reinforced with the Aqueous Maceration of Néré Pods (Parkia biglobosa) to Sustainable Construction in Togo: Characterization, Formulation, Mechanical Performance, and Recommendations. Construction Materials, 5(2), 19. https://doi.org/10.3390/constrmater5020019

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