This study assessed the potential of pulverised rabbit droppings as a stabiliser in compressed earth blocks (CEBs) to minimise the adverse impact of these droppings on the environment and also advance the discourse on sustainable building construction materials. Fresh rabbit droppings were collected, sun-dried, crushed, and sieved with a 2 mm mesh; 0%, 2.5%, 5%, 7.5%, 10% and 15% of the pulverised droppings were mixed with dried laterite soil to produce the CEBs. Split tensile strength, compressive strength, dry density, water absorption, and erosion tests were conducted on the CEBs. The 5% inclusion of rabbit droppings resulted in an optimum split tensile strength of 0.215 N/mm2 and compressive strength of 1.368 N/mm2, representing 17.5% and 8.1% increases, respectively, over the control. The erosion resistance of the blocks improved with the pulverised rabbit droppings from 5% and above. The water absorption reduced to 2.70% for 5% rabbit droppings inclusion from the control of 5.01%, representing a 46.1% reduction. The study concludes that the pulverised rabbit dropping inclusions in CEBs positively improved the properties of CEBs and, therefore, have great potential for use as a soil stabiliser in CEBs. It is recommended that 5% pulverised rabbit droppings should be used by CEB manufacturers to improve the properties of the blocks. Further studies should investigate the thermal, fire-resistance, chemical composition, and long-term durability properties of CEBs stabilised with pulverised rabbit droppings.
compressed earth blockscompressive strengtherosion resistancelateritepulverised rabbit droppingssplit tensile strengthsustainable building construction materialswater absorptionThe author(s) declared that financial support was not received for this work and/or its publication.section-at-acceptanceConstruction MaterialsIntroduction
Shelter is classified as a basic necessity of life, offering both humans and animals some degree of benefit, such as comfort and security against adverse weather (Conzatti et al., 2022). According to Abraham Maslow’s Hierarchy of Needs, shelter comes only after the need for food, air, and water (McLeod, 2007). The delivery of decent housing is acknowledged as imperative for the wellbeing of people in any country. For this reason, building construction materials prepared from natural resources are often classified as sustainable materials. Examples are the use of laterite soil for manufacturing bricks and pit sand for manufacturing sandcrate blocks (Korankye and Danso, 2024). While very important in life, shelter is quite expensive to acquire, especially in developing countries (Klaassen et al., 2022). Despite all the investment and effort being made in this sector, the demand for housing units outstrips supply in most developing countries and has created a huge gap between the housing units needed and those available—a situation commonly known as the “housing deficit” (Ansah and Danso, 2025; Afrane et al., 2016). One of the major causes of the huge housing deficit in developing countries is the increased cost of building construction materials. Danso and Obeng-Ahenkora (2018) and Danso (2018) identified the high prices of raw materials and the cost of transportation as major causes of increased prices of building construction materials in developing countries.
The contemporary building construction material that is most used as a binder in most building construction materials is Portland cement. Unfortunately, some of the raw materials that are used in the manufacture of cement in developing countries are imported at a higher cost (Bediako et al., 2016). This increases the price of cement and makes the cost of building houses very high. The manufacture of Portland cement also contributes to carbon dioxide (CO2) emissions in the atmosphere, resulting in global warming (Naapuo and Danso, 2025). There is therefore a need to conduct research on the potential of locally available binding agents which would be low-cost and also have minimal adverse effects on the environment.
Earth is one of the oldest known building materials, available locally in almost every community (Ahmad et al., 2010). Despite its advantages of having relatively low embodied energy (Jayasinghe et al., 2016), economic and environmental benefits (Danso, 2017a), a low level of waste generation, and its high ability to be recycled (Villamizar et al., 2012), earth has the weakness of being easily eroded by water (Carriço et al., 2018; Elahi et al., 2021; Danso, 2013), making its use in wet environments problematic. Research has focused on ways of stabilising or reinforcing earth to improve its water-resistant properties for construction applications (Elahi et al., 2020; Adiama et al., 2024; Danso, 2017).
Recent studies on earth-based construction materials have considered the use of different stabilisers for improving the engineering properties of materials for construction applications. Affan et al. (2025) determined the thermal and mechanical properties of clay-based masonry walls through a comprehensive experimental program on earthen mortars, bricks, and their interfaces, considering both cement-stabilised and non-stabilised formulations. The study found that well-optimised clay-based mortars can satisfy the structural and thermal requirements of non-load-bearing applications, offering a practical and sustainable alternative to conventional construction materials. Arairo et al. (2023) investigated the use of alternatives to cement for the stabilisation of earth blocks, finding that the incorporation of an alkali activator and metakaolin improved the mechanical and durability properties of earth blocks.
Studies have shown that the use of animal faeces can improve the properties of earth-based material for construction applications. Naapuo and Danso (2025) used cow dung for stabilising earth mortar and concluded that the properties of earth mortar are significantly enhanced by its inclusion. Millogo et al. (2016) used cow dung for stabilising adobe blocks and found that its addition to adobe improve the water resistance of the blocks, making them suitable as building materials in wet climates. Similarly, Uche (2007) used donkey dung to stabilise laterite soil and reported that lateritic soil blocks stabilised with donkey dung have better compressive strength and durability properties than unstabilised blocks. As far as the research is concerned, not all animal faeces have been used as stabilisers in compressed earth blocks (CEBs), creating a gap in literature. One such faeces that has the potential for use as a stabiliser in CEBs is rabbit droppings. Research is, therefore, needed on the use of rabbit droppings as a stabiliser in CEBs to increase their properties. This extends prior research on animal-waste-based stabilisers such as cow dung and donkey dung and represents a novel contribution to earth-based construction materials and supports circular economy principles in construction.
Rabbits (Oryctolagus cuniculus) are prolifically breeding domesticated animals with very nutritious meat which require minimal resources for their upkeep (Krupová et al., 2020; Siddiqui et al., 2024). Their production on a commercial scale is gaining popularity in developing countries (Wongnaa et al., 2023; Mensah et al., 2014). The rabbit, though small in size, eats and produces lots of droppings (faeces) which, if not properly managed, could pose challenges to the health and safety of the environment (Mailafia et al., 2010). Rabbit droppings are pelleted in nature, have strong particle bonding, and take a very long time to break down (Gonzalez-Redondo, 2009; Varga, 2013). It is not certain whether the particle-cohesive nature of rabbit pellets could improve the binding and water resistance characteristics of compressed earth blocks.
Few studies have been conducted on the use of rabbit droppings for stabilising soil. Ogbonna et al. (2024) compared the sustainable quality and efficacy of rabbit droppings and fowl droppings for the bioremediation of crude-oil-impacted soil and found that such soil treated with droppings and fowl droppings was effectively restored to its natural state compared to untreated soil. Awopegba et al. (2025) investigated the comparative effects of rabbit droppings and NPK (15-15-15) fertiliser on the soil properties and performance of Amaranthus cruentus L. under rainfed conditions in Ekiti State Polytechnic, Isan-Ekiti, Nigeria; they found an improvement in the properties of the soil. Opara et al. (2007) examined the effects of different applications of rabbit waste on the water stability of natural aggregates collected from Nsukka, Adani, and Ihiagwa (Owerri) in Southeastern Nigeria and found an improvement in aggregate stability. No study has been conducted on rabbit droppings as a stabiliser in CEBs. This study, therefore, aimed to assess the potential of pulverised rabbit droppings as a stabiliser in CEBs.
The use of pulverised rabbit droppings as a stabiliser in CEBs has the potential of reducing the environmental impact of conventional building construction material production and can also contribute to the manufacture of sustainable building construction materials. The findings of this study have the potential to develop eco-friendly and affordable housing solutions for low-income communities by assessing the potential of using pulverised rabbit droppings as a stabiliser in CEBs. Split tensile strength, compressive strength, water absorption, and erosion tests were used to determine the properties of CEBs stabilised with pulverised rabbit droppings. The microstructural properties of the CEBs stabilised with pulverised rabbit droppings were also determined. The results provide important implications for sustainable construction materials and the performance of stabilised CEBs for sustainable construction applications.
Materials and methodsMaterials
The principal materials used for this experimental study were rabbit droppings, laterite soil, and water. Fresh rabbit droppings (Figure 1a) were obtained from commercial rabbit farms within Odumase-Krobo in the Eastern Region of Ghana for use in this study. The droppings were spread on polythene sheets and sun-dried at an average temperature of 29 °C for 2 weeks. They were bagged and transported to the laboratory for further processing and analysis. The dried droppings were crushed into powdered form and manually sieved using a 2 mm standard sieve. A sieve analysis test was conducted on the pulverised rabbit droppings (Figure 1b) to determine the particle size distribution according to British Standard (BS 1377:2, 1990). Scanning electron microscopy (SEM) analysis was performed on a sample of the rabbit droppings—the microstructural image captured is shown in Figure 1c. The image shows elongated, fibrous, and layered fragments, which is an indicative of partially digested plant material. This microstructural feature of the rabbit droppings is a hallmark of herbivore faeces, suggesting cellulose-rich residues, possibly from grasses or hay in the rabbit’s diet which are not fully broken down in the digestive system. Reddish-brown laterite soil (Figure 1d) was obtained from a burrow pit approximately 1.5 m deep.
Materials for experiment: (a) rabbit droppings, (b) pulverised rabbit droppings, (c) SEM image of a sample of pulverised rabbit droppings, and (d) laterite soil.
Panel a shows clusters of small, round, blue-gray and brown granules. Panel b features a mound of fine, light brown granular powder. Panel c presents a grayscale microscopic image of irregular, layered fragments at one hundred times magnification. Panel d displays a pile of reddish-brown fine powder.
The soil was spread on a metal tray and sun-dried at an average temperature of 29 °C for 2 weeks. In the course of drying, lumps were crushed with a wooden club to ensure uniform drying and mixing of the various particles. A compaction test, following ASTM D698-12 (2021), was performed to assess the maximum dry density (MDD) and optimum moisture content (OMC) of the pulverised rabbit droppings (Figure 2a) and the laterite soil (Figure 2b). It was observed that the pulverised rabbit droppings recorded an OMC of 95% and an MDD of 695 kg/m3, while the laterite soil recorded an OMC of 13% and an MDD of 1944 kg/m3. The respective particle sizes of the pulverised rabbit droppings and laterite soil are shown in the particle size distribution curve in Figure 3. It can be observed that approximately 60% of the laterite soil passed through a 5 mm sieve, while approximately 92% of the pulverised rabbit droppings passed through a 2 mm sieve, indicating that the particles of the pulverised rabbit droppings were smaller than the laterite soil. Tap water was used in the experiment.
Maximum dry density and optimum moisture content: (a) pulverised rabbit droppings and (b) laterite soil.
Panel a shows a line graph with a blue curve depicting maximum dry density versus optimum moisture content, summarizing OMC as ninety-five percent and MDD as six hundred seventy-five kilograms per cubic meter. Panel b presents a similar graph with a red curve, summarizing a compaction test with maximum dry density of one thousand nine hundred forty-four point ninety-nine kilograms per cubic meter and optimum moisture content of thirteen point zero nine percent.
Particle size distribution of the laterite and pulverised rabbit droppings.
Grain size distribution graph comparing laterite soil and rabbit dropping, showing percentage passing against sieve size in millimeters. Laterite soil contains sixty point eight three percent gravel, thirty nine point zero four percent sand, and zero point one three percent pan. Rabbit dropping contains two point one percent gravel, ninety two point nine percent sand, and five percent pan. Red line represents laterite soil and blue line represents rabbit dropping.Preparation of earth blocks
Earth blocks were made using the dried laterite soil and pulverised rabbit droppings according to the methods described by Danso (2017) and Uche (2007). CEBs (140 × 100 × 100 mm) were made with laterite soil and varying percentages of the pulverised rabbit droppings (i.e., 0%, 2.5%, 5%, 7.5%, 10%, and 15%) by weight of the laterite soil. The laterite soil was measured by weight and was spread on a platform without pulverised rabbit droppings (0%) as control. The other treatments contained laterite soil and 2.5%, 5%, 7.5%, 10%, and 15% of pulverised rabbit droppings, respectively. The OMC of the soil used as the water content was sprinkled on the laterite soil/laterite soil-pulverised rabbit droppings mixture and mixed until uniform consistencies were obtained. The mixture was used to mould the blocks with a hydraulic block-making machine with a constant pressure of 130 bar. Approximately 30 blocks were moulded for each mix, making a total of 180 block specimens. The block specimens produced were arranged in the sample room for drying (Figure 4) at an average room temperature of 26 °C and relative humidity of 72%. The blocks were covered with polyethylene sheeting to gradually dry and were tested at 14, 21, 28, and 56 days. After drying, the block specimens were tested to assess compressive strength, split tensile strength, density, water absorption, and erosion properties.
Drying of laterite-soil-pulverised rabbit droppings blocks.
Multiple rows of small, square clay bricks are arranged closely together on a rough surface, with several bricks topped by small pieces of white paper or foil and unknown materials.Testing of blocksCompressive strength test
An ELE International brand compression machine, product number 1706D0001, was used. The test was performed to assess the strength of the block specimens and their ability to resist vertically applied loads. This test was performed following British Standard test (BS EN772-1, 2011). The block specimens were tested after 14, 21, 28, and 56 days of curing. Five block specimens from each test category were selected for the test. Individual units were capped and tested directly between plates (the stable bottom plate and the upper plate, which is lowered gently onto the top surface of the sample before load was applied to it) (Figure 5a). The load was applied gradually at a rate of 0.5 MPa/s until the block specimen failed. The maximum failure load was recorded, and the compressive strength was determined using the following equation:fc=FA,where fc represents the compressive strength in N/mm2, F represents the maximum load at which the block specimens failed in N, and A represents the area of the block specimens where the force was applied in mm2.
Experimental test setup: (a) compressive strength, (b) tensile strength, and (c) water absorption.
Panel a shows a single rectangular clay brick under a compression testing machine before failure. Panel b displays the same brick fractured under compression, with visible cracks and debris. Panel c presents a top-down view of multiple hand-labeled clay bricks arranged in a blue metal tray.Split tensile strength test
The split tensile strength test was performed on the block specimens to determine their tensile strength and the maximum load that they could carry before cracking/breaking. The same ELE split tensile testing machine was used for the test (Figure 5b). British Standard test (BS EN772-1) was followed for conducting the split tensile strength test. The block specimens were tested after 14, 21, 28, and 56 days of curing. Five block specimens from each test category were selected for the test. The weights of the specimens were then recorded after being labelled. After this, a metal jig was placed on the lower plate, the block specimens were placed on it, and then another metal jig was placed on the specimen. The upper plate of the machine was lowered so that it just touched the metal jig. The load was then applied continuously without shock within the range of approximately 0.05 MPa/s. Finally, the maximum breaking load was then recorded, and the tensile strength was determined using the following equation:ft=2PлLd,where ft represents the split tensile strength in N/mm2, P represents the maximum load where the block specimens split in N, L represents the length of the block specimens in mm, and d represents the width of the block specimens in mm.
Water absorption test
A water absorption test was conducted on the block specimens to measure the rate at which each absorbs water. The test was performed in line with British Standard test (BS EN 771-1, 2003). The specimens were dried overnight in an ELE International oven, Model number SDO/225/TDIG, at an average temperature of 105 °C. The block specimens were then removed from the oven and allowed to cool down, after which each was weighed to obtain the oven dry weight (w1). After these weights were obtained, the samples were carefully arranged on wooden strips in a sample tray, and water was poured into the tray up to 10 mm depth of the block specimens (Figure 5c). The block specimens were then left partially immersed for 20 min, after which they were weighed to obtain the saturated surface dry weight (w2). The water absorption capacity was then calculated using the following equation:WA=M2−M1M1×100,where WA represents the water absorption in %, M1 represents the mass of the block specimens after oven-drying in kg, and M2 represents the mass of partially absorbed block specimens in kg.
Density test
The dry density of the block specimens was evaluated following the procedure in BS EN 771-1 (2003). Five block specimens from each test category were selected to evaluate density. The specimens were oven-dried at a 105 °C for 4 h, after which they were allowed to cool, their mass values recorded using an electronic weighing balance, and their volumes calculated. The dry density of the block specimens was then calculated using the following equation:ρ=MV,where ρ represents the density in kg/m3, M1 represents the mass of the oven-dried block specimen in kg, and V represents the volume of the dried block specimen in m3.
Erosion test
An erosion test was carried out following New Zealand Standards NZS 4298 (1998) to determine the level of resistance of the block specimens to erosion by water. The test was conducted on the block specimens after 56 days of drying. Apparatus for the erosion test include a 500 mL beaker, a wick approximately 16 mm wide, clean water, a laboratory table, steel stands adjusted to 400 mm height to support the beakers containing the water, and 45-degree wooden angle blocks. The setup was arranged with the block specimens placed on wooden blocks at 45 degrees to the horizontal and at a vertical distance of 400 mm from the beakers containing water and wick. Water was then allowed to drip from the wick onto the sloped surface of the test blocks for approximately 45 min, after which the depth of erosion/pit depth was measured and recorded for analysis. The setup of the erosion test is shown in Figure 6a and the block specimen after the test is shown in Figure 6b.
Erosion test: (a) test setup, and (b) block specimen after erosion test.
Panel a shows three adobe blocks set under drip setups on wooden bases with dark plastic sheeting in the background, demonstrating a water erosion test. Panel b provides a close-up view of a single adobe block with visible surface erosion and wet patches, indicating water absorption and degradation.Scanning electron microscope test
SEM analysis was conducted on both the rabbit droppings and the block specimen made with laterite soil and pulverised rabbit droppings. An SEM model number ZEISS EVO MA 15 was used for the tests. The test produced images to show the microstructural properties of the materials in the rabbit droppings and the block specimen.
Data analysis
The data obtained from the studies were organised and analysed using one-way analysis of variance (ANOVA) with GenSTAT Statistical Software (15th Edition). Where significant differences were observed, these were separated using the Tukey pairwise comparison at 5% level of significance. The results obtained were presented in tables and graphs, with error bars showing standard errors. The results obtained from the SEM analysis tests were presented in images.
Results and discussionMechanical properties
The mechanical properties of the block specimens were assessed with the results of their compressive and tensile strengths. The results of the compressive strength of the block specimens are illustrated in Figure 7. It can be observed that the compressive strength of the block specimens with pulverised rabbit droppings increased with increasing inclusion rates up to 5%, beyond which the compressive strength started to decline. For example, the compressive strength test results after 56 days of drying were 1.265 N/mm2, 1.319 N/mm2, 1.369 N/mm2, 0.882 N/mm2, 0.869 N/mm2, and 0.729 N/mm2 at 0%, 2.5%, 5%, 7.5%, 10%, and 15% pulverised rabbit droppings inclusion, respectively. It was further observed that the strength increased as the days of drying increased; thus, at 5% inclusion of pulverised rabbit droppings the results were 0.829 N/mm2, 1.13 N/mm2, 1.194 N/mm2, and 1.368 N/mm2 at days 14, 21, 28, and 56 of drying, respectively.
Average compressive strength of block specimens.
Bar chart comparing compressive strength in Newtons per square millimeter for different percentages of an additive (zero percent, two point five percent, five percent, seven point five percent, ten percent, fifteen percent) across four drying periods: fourteen, twenty-one, twenty-eight, and fifty-six days. Compressive strength increases with higher percentages and longer drying times, peaking at fifteen percent and fifty-six days.
The current findings are similar to those of Uche (2007), who recorded a maximum compressive strength of 1.52 N/mm2 for CEBs stabilised with donkey dung at 15% inclusion. Naapuo and Danso (2025), using cow dung in earth mortar, also recorded a maximum compressive strength of 1.8 N/mm2 at 7.5 cow dung inclusion in earth mortar. Turkson et al. (2024) stabilised CEBs with eggshell and recorded a maximum compressive strength of 1.331 N/mm2 for blocks with 1% inclusion eggshell. Manu et al. (2025) studied the use of goat hair fibre in earth blocks and recorded a maximum strength of 12% strength enhancement over the control. The improved compressive strength of the block specimens over control can be attributed to the fibrous fragments of layers of the pulverised rabbit droppings, as in the SEM image in Figure 1c. Danso et al. (2015) established that the improved strength is due to increased friction between the fibres and the soil matrix and the prevention of the spread of cracks in the blocks, as fibres form bridges across cracks and therefore contribute to improved strength. Furthermore, the particle sizes of the pulverised rabbit droppings were smaller than the laterite soil (Figure 3) and therefore acted as filler in the soil matrix.
The results also indicate that pulverised rabbit dropping inclusions above 5% reduced the compressive strength of the block specimens to even less than the control block specimens. The reduction in strength can be a result of the high level of fibrous substances in the rabbit droppings introduced in the block specimens, which weakens the blocks due to reduced soil bonding in the blocks and the overlapping of the fibres (Danso et al., 2015). Naapuo and Danso (2025) indicated that higher percentages of animal faeces may result in declining returns or deterioration causing extensive mechanical damage to the specimens. The maximum compressive strength (1.369 N/mm2) of the block specimens with 5% pulverised rabbit droppings recorded 8.1% strength increase over the control compressive strength of 1.265 N/mm2. The optimum compressive strength of block specimens of 1.369 N/mm2 obtained from this study was above the recommended 1 N/mm2 value for use in building applications according to TS 704 (1985). However, the strength value is slightly less than the 1.4 N/mm2 requirement specified by the Ghana Building Code (GhBC GS1207, 2018) for building and construction. To determine whether the differences in compressive strength of the block specimens were significant, a one-way ANOVA test was performed, with the result (Table 1) suggesting a statistically significant difference among the treatment values with a p-value <0.001. A Tukey pairwise comparison at 5% level of significance was performed to identify the pairs of the treatment where the significant difference existed. The results showed a significant difference among the pairs, except for 2.5% vs. 0%, 5% vs. 2.5%, and 7.5% vs. 10%.
One-way ANOVA of the compressive strength test.
Treatment
N
Source of variation
DF
SS
MS
F
p
0%
5
Between subjects
4
0.002
0.001
2.5%
5
Between treatments
5
1.144
0.229
112.188
<0.001
5%
5
Residual
10
0.021
0.002
7.5%
5
Total
17
1.166
0.069
10%
5
15%
5
N (number of specimens); DF (degrees of freedom); SS (sum of squares); MS (mean square); F (F ratio); p (significant level at 0.05).
The tensile strength results of the block specimens are illustrated in Figure 8; it can be observed that the tensile strength of the block specimens with pulverised rabbit droppings increased with increasing inclusion rates up to 5%, beyond which the tensile strength started to decline, as was also observed in the compressive strength. For example, the tensile strength test results after 56 days of drying are 0.183 N/mm2, 0.210 N/mm2, 0.215 N/mm2, 0.175 N/mm2, 0.166 N/mm2, and 0.157 N/mm2 at 0%, 2.5%, 5%, 7.5%, 10%, and 15% pulverised rabbit droppings inclusion, respectively.
Average tensile strength of block specimens.
Bar graph comparing split tensile strength in newtons per square millimeter for different percentages of an additive (ranging from zero percent to fifteen percent) across four drying durations: fourteen, twenty-one, twenty-eight, and fifty-six days. Split tensile strength increases with drying time for all percentages, and the maximum strength at fifty-six days is observed at five percent additive. Error bars indicate measurement variation.
The tensile strength of the block specimens with 5% pulverised rabbit droppings inclusion increased from 0.114 at 14 days drying to 0.215 at 56 days drying. Like the behaviour for compressive strength, the tensile strength of block specimens with pulverised rabbit droppings inclusion of 5% showed the best performance. It recorded a tensile strength of 0.215 N/mm2 as against the control of 0.183 N/mm2, representing a 17.5% strength gain over the control. The percentage improvement is relatively lower than the 94.7% increase in tensile strength recorded by Naapuo and Danso (2025), who incorporated cow dung in earth mortar. The improved tensile strength of the block specimens can be attributed to the fibrous nature of the rabbit droppings, which act as a bridge between the matrix of the laterite soil (Danso et al., 2015).
The tensile strength of the block specimens, like the compressive strength, recorded a decline after it peaked at 5% inclusion of pulverised rabbit droppings. The decline in strength can be a result of the weakening of the bond in the block specimens as the quantity of the pulverised rabbit droppings was high beyond the acceptable level. Danso et al. (2015) found that the fibres overlap each other as the quantity increased instead of mixing with the soil matrix. To determine whether the differences in the tensile strength of the block specimens were significant, one-way ANOVA was performed after the normality and homogeneity of variances were established using Shapiro–Wilk test and Levene’s test, respectively. The results in Table 2 indicate a statistically significant difference among the treatment values, with a p-value <0.001. A Tukey pairwise comparison at 5% level of significance was performed to identify the pairs of the treatment where a significant difference existed. The results showed a significant difference among the pairs, except the 7.5% vs. 10, 10% vs. 15, 0% vs. 7.5, and 5% vs. 2.5.
One-way ANOVA of the tensile strength test.
Treatment
N
Source of variation
DF
SS
MS
F
p
0%
5
Between subjects
4
0.001
0.011
2.5%
5
Between treatments
5
0.081
0.016
115.945
<0.001
5%
5
Residual
10
0.014
0.001
7.5%
5
Total
17
0.085
0.005
10%
5
15%
5
N (number of specimens); DF (degrees of freedom); SS (sum of squares); MS (mean square); F (F ratio); p (significant level at 0.05).
The relationship between tensile and compressive strength is presented in Figure 9. A positive linear relationship was found between the tensile and compressive strengths of all the experimental block specimens. The coefficient of determinant (R2) results observed are 0.7568, 0.8718, 0.8365, 0.9820, 0.9995, and 0.9907, respectively, for 0%, 2.5%, 5%, 7.5%, 10%, and 15% pulverised rabbit droppings inclusion in the blocks. This suggests that as the tensile strength of the block specimens increased, the compressive strength also increased, which also implies that the pulverised rabbit droppings explained between 75.68% and 99.95% of the variance in the compressive and tensile strengths of the block specimens. There was a strong positive correlation between the tensile and compressive strengths of the block specimens stabilised with pulverised rabbit droppings. A similar trend was found by Danso et al. (2025) who explored the use of recycled glass particles and lime in CEBs and obtained an R2 of 0.7362–0.9547. Moreover, Danso and Manu (2020) also established a good correlation between the tensile and compressive strengths of burnt bricks.
Relationship between tensile strength and compressive strength of block specimens.
Scatter plot showing the relationship between tensile strength and compressive strength in newtons per square millimeter for different percentage groups, each represented by distinct markers and colors: 0 percent (red triangles), 2.50 percent (green diamonds), 5 percent (blue squares), 7.5 percent (blue x’s), 10 percent (purple plus signs), and 15 percent (yellow circles).Physical properties
The physical properties of the block specimens were evaluated using dry density and water absorptions test results. The average density of the block specimens is depicted in Figure 10. The result shows that the density of the block specimens with varied pulverised rabbit droppings exhibited different and irregular characteristics along the various drying periods. Block specimens with 10% pulverised rabbit droppings achieved superior density consistently for 14-, 21-, and 28-day drying but were superseded by 2.5%, 5%, and 15% after 56-day drying, with the 5% pulverised rabbit dropping inclusion showing density superior to the other treatments.
Average dry density of block specimens.
Bar chart comparing average density in kilograms per cubic meter for different percentages of an additive (ranging from zero percent to fifteen percent) across four drying periods: fourteen, twenty-one, twenty-eight, and fifty-six days. Bars indicate variation in density by percentage and time, with higher values tending at lower percentages and longer drying periods. Error bars are present for each data point.
It is clear from the result that most of the block specimens showed higher densities as the days of drying increased. However, for block specimens with 5% and 10% pulverised rabbit droppings, the highest densities of 1770 kg/m3 and 1800 kg/m3, respectively, were achieved for 14 days of drying. Block specimens with 7.5% pulverised rabbit droppings inclusion recorded the highest density of 1713 kg/m3 at 28 days drying. The average densities of the various percentage inclusions over the drying period showed that 10% pulverised rabbit droppings inclusion had the highest average density of 1765 kg/m3, followed closely by 5% inclusion with density of 1718 kg/m3. The lowest average density of 1666 kg/m3 was recorded for block specimens with 15% pulverised rabbit droppings inclusion.
Density measures how closely packed the particles of a substance are. For compressed earth blocks and other building materials, higher density has a positive effect on the strength of the material. The current finding is similar to those of Bogas et al. (2018), who recorded densities between 1740 kg/m3 and 1810 kg/m3 in CEBs with partial incorporation of recycled aggregate and stabilised with cement and lime. According to Deboucha and Hashim (2011), an acceptable range of densities for CEBs is 1700–2200 kg/m3, which the findings of the current study fall within. Deboucha and Hashim (2011) further indicated that low density CEBs have the advantage of being better thermal insulators than high density ones. This requirement also favours the current study’s findings as they fall within the lower bracket of the range of acceptable densities.
The water absorption result of the block specimens is presented in Figure 11. It can be observed from these results that the water absorption rate of the block specimens reduced as the pulverised rabbit droppings increased up to 5% inclusion; that is, 5.01%, 3.34%, and 2.70% water absorption for 0%, 2.5%, and 5% pulverised rabbit droppings inclusion, respectively. Beyond 5% pulverised rabbit droppings inclusion, the water absorption rate increased, with increasing pulverised rabbit droppings at 4.39%, 5.88% and 6.64% water absorption for 7, 5, 10.0% and 15% inclusions, respectively. Water intake in earth blocks is not desirable as the presence of water causes weakness them and in some cases causes erosion of the material. Hence, the lower the water absorption rate, the better. The highest water absorption rate of 6.64% was recorded at 15% inclusion of pulverised rabbit droppings, compared with 2.7% absorption for the 5% inclusion rate, which was the lowest. Comparing the control block specimens, which recorded water absorption of 5.01% with the 5% inclusion with 2.70% absorption, this represents a reduction in water absorption of 46.10%. These findings show superior outcomes to those of Uche (2007), who recorded absorption rates of 9.82%–13.26% for laterite stabilised with donkey dung inclusion and those of Kurpińska et al. (2022), who also recorded 8% higher water absorption than control in a composite material with natural fibres.
Average water absorption of block specimens.
Bar chart showing water absorption percentages on day 28 of drying for six samples with increasing percentages: 0, 2.5, 5, 7.5, 10, and 15. Water absorption rises from about 3 percent to 6.5 percent as the percentage increases, with slight error bars for each column.Durability property
The durability of the block specimen was evaluated using an erosion test. The results of the erodibility test on the block specimens are presented in Table 3. The block specimens with 0% pulverised rabbit droppings inclusion recorded an erosion depth of 7.5 mm, followed by the 3.5 mm recorded by the samples with 2.5% pulverised rabbit droppings inclusion. The absence of rabbit droppings or the presence of just a little witnessed some degree of erosion. There were, however, no signs of erosion on the samples with inclusion rates of 5% and beyond. It can be inferred from the results that the inclusion of the pulverised rabbit droppings improved the resistance of the block specimens to erosion, possibly due to the fibre content of the rabbit droppings, which helped in blocking the ingress of water. Poor resistance to water is one disadvantage of earth buildings, and it is for this reason that raw earth products need stabilisation in order to improve their properties. Uche (2007) recorded erosion rates of 1 mm, with CEBs stabilised with donkey dung at 15% inclusion, up from 18 mm at 0% inclusion using the abrasion test. Similarly, Bogas et al. (2018) also recorded erosion of 4.3 mm for unstabilised CEBs while recording no erosion in the stabilised CEBs with partial incorporation of recycled aggregates. Naapuo and Danso (2025) also recorded an erosion depth of 5 mm and width of 4 mm for control specimens, while no erosion was recorded for the specimens, which incorporated cow dung in the earth mortar.
Erosion test result of block specimens.
Pulverised rabbit droppings inclusion
Average depth of erosion (mm)
Erodibility index
Rating
0%
7.5
3
Erosive
2.5%
3.5
2
Erosive
5%
0
2
Non-erosive
7.5%
0
2
Non-erosive
10%
0
2
Non-erosive
15%
0
2
Non-erosive
Microstructural analysis
The microstructural property of the block specimen with 5% pulverised rabbit droppings was analysed with SEM imaging at 100× magnification (Figure 12). Close observation of the image reveals important insights about the surface morphology and internal structural composition of the block specimen. The image shows elongated fibrous and layered fragments mixed with the soil matrix, which is an indicative reinforcement in the block specimen. This contributed to the improved mechanical and durability performance of the block specimens at the optimum (5%) pulverised rabbit droppings inclusion. The inter-spatial relationship created between the soil matrix and the fibres also contributes to the improved properties of the blocks (Danso et al., 2017b). Micro-gaps and loose binding between particles can also be observed, implying porosity, which can affect properties such as moisture retention, microbial colonisation, and decomposition rates. This accounted for the decline in the mechanical and durability performance of the block specimens with high quantities (7.5%–15%) of pulverised rabbit droppings. A similar result was found by Danso et al. (2017b), who evaluated the mechanisms by which natural fibre inclusion improves the properties of soil blocks.
SEM image of block specimen with pulverised rabbit droppings.
Scanning electron microscope image shows a fibrous and fragmented material with irregular particles and dense clusters, magnified one hundred times. Scale bar indicates one hundred micrometers. Instrument settings and date stamp appear below.Summary and conclusion
This study assessed the potential of pulverised rabbit droppings as a stabiliser in CEBs. Its findings can be summarised as follows.
The maximum compressive strength (1.369 N/mm2) of the block specimens with 5% pulverised rabbit droppings recorded an 8.1% strength increase over the control strength of 1.265 N/mm2. The difference was found to be statistically significant, with a p-value < 0.001.
The highest tensile strength of 0.215 N/mm2 of the block specimens with 5% pulverised rabbit droppings as against the control of 0.183 N/mm2 represented a 17.5% strength gain over the control; the difference was found to be statistically significant, with a p-value < 0.001.
A strong positive linear relationship was found between tensile and compressive strength, with a coefficient of determinant (R2) between 0.7568 and 0.9995.
The average densities of the block specimens showed that 10% pulverised rabbit droppings inclusion had the highest average density of 1765 kg/m3, followed closely by 5% inclusion with density of 1718 kg/m3.
The 5% pulverised rabbit droppings inclusion in the block specimens recorded 2.7% water absorption compared with the control of 5.01%, representing a reduction in water absorption of 46.1%.
The SEM image at 100× magnification revealed elongated fibrous and layered fragments mixed with the soil matrix, which is an indicative reinforcement in the block specimen.
The study therefore concludes that the pulverised rabbit droppings inclusion in the CEBs significantly improved the mechanical, physical, and durability properties of the block specimens. Consequently, the use of pulverised rabbit droppings has great potential as a soil stabiliser in CEBs. The findings greatly support the utilisation of pulverised rabbit droppings as an eco-friendly by-product for manufacturing CEBs as sustainable materials for housing applications. It is recommended that CEB manufacturers use 5% pulverised rabbit droppings as a stabiliser for producing CEBs. Considering the low strength values recorded, its use should be limited to low-rise buildings and non-load-bearing walls. As the current study focused on the mechanical, physical, and durability properties of the block specimens, it is recommended that future studies investigate the thermal, fire-resistance, chemical composition, and long-term durability properties of CEBs stabilised with pulverised rabbit droppings.
Data availability statement
The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.
Author contributions
AAT: Conceptualization, Data curation, Methodology, Project administration, Writing – original draft. HD: Conceptualization, Formal Analysis, Investigation, Methodology, Supervision, Validation, Writing – review and editing. FA: Formal Analysis, Methodology, Software, Supervision, Writing – review and editing. PM: Data curation, Formal Analysis, Investigation, Software, Supervision, Writing – review and editing.
Conflict of interest
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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The author(s) declared that generative AI was not used in the creation of this manuscript.
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Edited by:Hosam Saleh, Egyptian Atomic Energy Authority, Egypt
Reviewed by:Wahib Arairo, University of Balamand, Lebanon
Viviana Mora-Ruiz, Universitaria de Investigación y Desarrollo, Colombia