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Article

Evaluation of the Potential of Natural Mining By-Products as Constituents of Stabilized Rammed Earth Building Materials

by
Miguel Angel Martin-Antunes
1,2,*,
Céline Perlot
2,3,
Pedro Villanueva
1,
Rafik Abdallah
2 and
Andrés Seco
1
1
Institute of Smart Cities (ISC), Department of Engineering, Public University of Navarre (UPNA), 31006 Pamplona, Spain
2
Department of Building and Public Works, Université de Pau et des Pays de l’Adour, E2S UPPA, SIAME, 64600 Anglet, France
3
Institut Universitaire de France, 75231 Paris, France
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(9), 5167; https://doi.org/10.3390/app15095167
Submission received: 14 March 2025 / Revised: 4 May 2025 / Accepted: 5 May 2025 / Published: 6 May 2025
(This article belongs to the Section Civil Engineering)
Browse Figures
Versions Notes

Abstract

:
In this investigation, different natural by-products were used to modify the Particle Size Distribution (PSD) of a soil to evaluate their potential in Stabilized Rammed Earth (SRE) building. Three different mixes were manufactured: (i) a mix composed entirely of a clayey soil, (ii) a mix consisting of mining by-products and clayey soil and (iii) a mix entirely based on mining by-products. Unstabilized and stabilized samples of the mixes were manufactured using two cement dosages (2.5% and 5%), and the samples were tested for Unconfined Compressive Strength (UCS), soaked UCS, and wetting and drying tests. Mining by-products demonstrated significant potential in SRE building, as their addition to the clayey soil resulted in higher UCS values compared to the UCS obtained from clayey soil alone. Unstabilized samples lost their integrity during exposure to water. The inclusion of mining by-products also showed potential as, although the mixes did not fully meet the requirements for soaked UCS and the wetting and drying tests, the mix containing both mining by-products and clayey soil retained its integrity in water, unlike the samples composed solely of clayey soil. M3C5 successfully met the requirements for soaked UCS and the wetting and drying tests, further highlighting the great potential of mining by-products in SRE building.

1. Introduction

Earth offers significant advantages as a construction material, including its widespread availability, cost-effectiveness, versatility, low environmental footprint, minimal heat transfer and high heat storage capacity [1,2,3]. Due to these properties, earth has been one of the most widely used building materials throughout human history.
Among the known earth construction techniques, the most widely used method worldwide is Rammed Earth (RE) [4,5]. This technique involves the systematic compaction, using a manual or pneumatic rammer, of a soil–water mixture into layers [6,7,8,9]. The traditional form of RE, known as unstabilized RE, relies solely on soil and water as construction materials, with clay acting as a natural binder. The fact that clay is the only binding material makes the Particle Size Distribution (PSD) and the type and amount of clay present in the soil crucial factors in assessing the suitability of a soil for RE building [9]. Despite this, there are no standardized regulations defining the specific types of soil that can be used for RE building. Instead, researchers often rely on recommendations such as those proposed by Houben et al. [9]. Houben et al. suggested PSD zones that are frequently referenced in the RE literature; however, these zones should not be considered strict rules, as practical experience has shown that soils outside these recommended zones have still performed well in practice, while some that met the criteria have not [10,11,12]. In some cases, the reason for not achieving the desired properties is related to the clay content or type. In this situation it is common practice to stabilize the mix by adding a material that can act as a supplementary binder to enhance its performance, resulting in what is known as Stabilized Rammed Earth (SRE). Various researchers have also observed that modifying the soil’s PSD by adding other granulometric materials can enhance the properties of the soil in SRE building [13,14,15]. This is particularly relevant as it allows for the use of mining by-products to adjust the soil’s PSD, as has been achieved in other construction methods [16,17,18]. In this way, large quantities of mining by-products or waste that currently end up in landfills could be valorized. In fact, the mining industry is one of the largest contributors to global waste production [19], generating approximately 100 billion tons per year worldwide [20]. In the European Union, waste from this industry accounts for around 22.7% of the total waste generated [21]. Therefore, finding a practical application for these by-products is of significant interest, in order to develop sustainable solutions that preserve a healthy environment [22].
Thus, in this research, different mining by-products were used to modify the PSD of a soil to evaluate their potential in SRE building. A laboratory experimental campaign was conducted, in which three different mixes were manufactured (a mix composed entirely of clayey soil, a mix consisting of mining by-products and clayey soil, and a mix entirely based on mining by-products), along with specimens of both unstabilized and stabilized mixes using two cement dosages (2.5% and 5%). The testing methodology was carried out following the new methodology to characterize SRE materials explained in [23]. The Standard Proctor (SP) test was employed to determine the Optimal Moisture Content (OMC) of each combination. Unconfined Compressive Strength (UCS) tests were conducted at 7, 28, and 90 days to study the evolution of the mechanical properties of the mixes. To assess the durability of the combinations, two different durability tests were performed: a UCS test at 28 days under soaked conditions to analyze the sensitivity of the mixes to liquid water, and a wetting and drying test at 28 days to determine the erosion withstanding capability of the combinations.

2. Materials and Methods

2.1. Materials

In the present study, three different soil mixtures were used. The first (M1) was composed entirely of a clayey soil found in Pamplona (Spain). The second mixture (M2) consisted of a blend of this clayey soil with three differently sized gravel and sand by-products to enhance the dry density achieved by the mixture. The by-products employed were the following: a gravel (<12 mm) and a sandy gravel (<4 mm) calcium carbonate that came from the mining of magnesium carbonate rock for refractory material manufacturing, and a foundry-recycled sand (<1 mm). Based on a previous study [24], the mixture was composed of 17.9% gravel, 26.4% sandy gravel, 31.8% sand and 23.9% clayey soil. The third mixture (M3) was composed entirely of by-products, maintaining the same proportion of by-products as in mixture 2, but with the clayey soil replaced by another by-product, which had the role of fines. These fine by-products were composed of sludges from the cleaning process of the magnesium carbonate extracted in the magnesite mine. Figure 1 shows the PSD of the materials and Figure 2 shows the mineralogy obtained by XRD for the considered materials.
Table 1 summarizes of the PSD (in accordance with UNE-EN 933-1:2012 [25]), bulk density (in accordance with UNE-EN 1097-3:1999 [26]), and mineralogy obtained by XRD for the materials considered. More detailed information regarding these materials can be found in articles [24,27].
Table 2 shows the Liquid Limit (LL), Plastic Limit (PL), and Plasticity Index (PI) of the sludge and the clayey soil, as well as their Unified Soil Classification System (USCS) classifications.
The cement (CEM) used in this study was produced in compliance with the UNE-EN 197-1:2011 standard [28] and marketed under the trade name CEM-II-BL-32.5-R. Table 3 provides the bulk density (in accordance with UNE-EN 459-2 [29]) and a summary of the chemical properties of the CEM.

2.2. Methods

Samples of the mixtures were manufactured, either unstabilized or stabilized with CEM at two different dosages of 2.5% or 5% by mass, as these are the two most commonly used dosages in SRE [23]. The combinations were identified as follows: first, the type of mixture used (M1, M2 or M3) was indicated, followed by the amount of CEM added in each case. “C0” was used when no CEM was added, “C2.5” when stabilized with 2.5% CEM, and “C5” when 5% CEM was used. Table 4 shows the identification of the combinations, their mixture compositions and their stabilizer dosages.
The manufacturing, curing, and testing conditions were carried out following the new methodology to characterize SRE materials explained in [23].
The samples were prepared as follows. First, impurities in the sand were removed by passing it through a 1 mm sieve, discarding any material retained. All materials were then oven-dried at 60 °C until they reached a constant weight (i.e., less than 0.1% mass variation). Next, the mixing process was carried out. This step was not necessary for mix M1, but for mixes M2 and M3, the required amounts of each material were weighed in their dry state and mixed for one minute until homogenized. To ensure M1 soil sample representativeness, strategic sampling points were selected to uniformly cover the entire study area, considering the natural variations in the terrain (such as slopes, land use types, and vegetation). Additionally, an adequate volume was collected to ensure homogeneity and avoid biases. Afterward, water was added according to the OMC of each combination. The OMC was determined by performing an SP test on each mixture following the UNE 103500:1994 Standard [30], and the results are presented in Section 3.1. Once water was added, the mix was blended for five minutes to ensure complete homogenization. The homogeneous mixture was then compacted into three layers using a 2.5 kg manual rammer with a 102 mm diameter in a 122 mm high mold (the same mold and rammer used in the SP test). After demolding, the specimens were wrapped in plastic to prevent dehydration and ensure proper cement hydration. Before each test, the specimens were dried in an oven at 60 °C until they reached a constant weight (i.e., less than 0.1% mass variation) to homogenize their moisture content. This temperature was selected to prevent the loss of non-evaporable water through chemical reactions (cation exchange, flocculation, and pozzolanic reactions).
UCS tests were performed on three samples of all combinations at 7, 28, and 90 days, following the UNE-EN 13286-41:2022 standard [31]. Durability against environmental exposure was assessed by conducting soaked UCS tests at 28 days on three samples of each combination. This test involved curing the specimens, drying them in an oven at 60 °C, immersing them in water for 24 h, and then testing them for UCS under the same standard used for dry conditions. Durability against erosion was evaluated using the wetting and drying test according to the ASTM D559M standard [32], which was conducted on two specimens for each combination at 28 days. This standard consists of 12 cycles in which the specimens undergo 5 h of water immersion, 41 h of oven drying, and 26 brush strokes per cycle.

2.3. Limitations and Future Studies

The absence of well-defined criteria for evaluating SRE poses significant challenges for researchers in this area [33]. This issue is compounded by the ambiguity surrounding which standards should be applied, as well as the wide range of variables that can impact mechanical performance, such as specimen geometry and fabrication methods. As a result, comparing outcomes across studies is often problematic. For example, Maniatidis and Walker [34] found that cylindrical samples of reconstituted soil exhibited higher compressive strength than prismatic ones. They linked this discrepancy to the angular features of the prismatic molds, which likely hinder compaction during preparation, thereby reducing unconfined compressive strength (UCS). Additionally, Raju and Reddy [35] studied how the thickness of soil layers affects compaction and concluded that 100 mm was the optimal thickness under their conditions; greater thicknesses led to lower UCS values. Further, research by Los et al. [36] and Zamanian et al. [37] showed that curing conditions could significantly influence compressive strength in lime- and alkali-stabilized SRE. They noted that elevated curing temperatures accelerated both pozzolanic and geopolymerization reactions. Due to the influence of these factors, a study is needed to define the standards and specimen molds that should be used in the SRE building sector to achieve consistency among the results obtained by different authors. Since such a study is currently lacking, the present research was conducted following the steps and specifications outlined in the new methodology to characterize SRE materials explained in [23], as this methodology aims to standardize the results obtained by researchers working in the SRE sector.

3. Results and Discussion

3.1. Optimal Moisture Content

Table 5 shows the OMC and the Maximum Dry Density (MDD) achieved for all the combinations during the SP test.
In Table 5, an indirect relationship between MDD and CEM dosage can be observed, along with a direct relationship between OMC and CEM dosage. This is related to the fact that an increase in the cement content in the mix led to an increase in fines in the sample, resulting in a higher content of material with a lower bulk density than the aggregates and leading to a lower MDD. The increase in OMC was due to the fact that a higher content of cementitious material increased the amount of fine materials, requiring a greater amount of water to hydrate these fines and reach the OMC. Additionally, the inclusion of mining by-products increased the MDD of the mixtures, as M2C0 achieved a significantly higher MDD compared to M1C0. This was due to the higher bulk density of the added mining by-products compared to the clayey soil, which directly increased the overall density.

3.2. Unconfined Compressive Strength

Figure 3 shows the UCS values obtained for the tested combinations at 7, 28 and 90 days with three replicates (standard deviations are provided on the curves).
The unstabilized samples achieved the same UCS values at all ages, as no chemical reactions occurred in the unstabilized combinations. M1C0, M2C0 and M3C0 achieved 0.6 MPa, 1.5 MPa and 1.4 MPa, respectively. The results obtained for M1C0 were similar to those reported by Vikas et al. [10] for clayey soil. However, Ngo et al. [11] achieved higher values (1.6 MPa) with clayey soil. The values obtained by Ngo et al. [11] were reached by M2C0, which demonstrates that adding by-products to the clayey soil improved the UCS values. In fact, M2C0 showed an improvement of 250% compared to the mixture without by-products (M1C0). Additionally, the clayey soil contributed to greater cohesion in the mix, as combination M2C0 achieved a higher UCS value than combination M3C0.
In the CEM-stabilized specimens, a direct relationship was observed between UCS values and CEM dosage. This was related to the fact that a higher cement dosage allows for the generation of a greater amount of cementitious gel, and therefore, stronger specimens are obtained [38]. Additionally, a direct relationship was found between UCS values and curing time, with a generally faster increase in UCS between days 7 and 28 compared to the period between days 28 and 90. This was related to the rapid hydration of the cement to generate hydration products, in accordance with the literature [11,39]. M1C2.5 achieved 2.1 MPa, 2.3 MPa and 2.8 MPa at 7, 28 and 90 days, improving the UCS value of the unstabilized M1 mix (M1C0) by 383% at 28 days, in accordance with the literature [12,39]. The improvement in combination M1C5 was greater, achieving UCS values of 4 MPa, 4.1 MPa and 4.2 MPa at 7, 28 and 90 days respectively, which represented a 700% increase compared to the values of M1C0 at 28 days. These values were consistent with the literature, where similar UCS values are reported for cement-stabilized SRE samples [12,39,40]. The UCS values obtained for combinations M1C2.5 and M1C5 exceeded the typical requirements found in the literature, which are between 1.3 MPa and 2 MPa [9,41].
Combination M2C2.5 achieved 4.3 MPa, 4.5 MPa and 5.9 MPa at 7, 28 and 90 days respectively, improving the UCS values of M2C0 by 300% at 28 days. Similarly, M2C5 reached 7.9 MPa, 9.3 MPa and 9.6 MPa at 7, 28 and 90 days, respectively, representing a 620% improvement over M2C0 at 28 days. Additionally, both M2C2.5 and M2C5 outperformed combinations M1C2.5 and M1C5 at 28 days by 196% and 227%, respectively. This demonstrated that the addition of by-products with gravel- and sand-sized PSD to a clayey soil enhanced the UCS of the SRE mixtures. As cement generated calcium silicate hydrate gels, these gels were capable of binding the by-product aggregates, resulting in a stronger specimen than if only clay were used [23,24]. Both combinations M2C2.5 and M2C5 achieved higher values than those reported in previous studies [12,39,40]. This was attributed to the fact that the soil had not been improved in those studies, whereas in the case of Mixture 2, the clayey soil was modified by adding by-products that modified and enhanced the mix’s properties.
Combination M3C2.5 achieved 5.5 MPa, 6.2 MPa and 6.5 MPa at 7, 28 and 90 days respectively, improving by 443% over combination M3C0 at 28 days. Combination M3C5 reached 9.7 MPa, 11.8 MPa and 12.5 MPa at 7, 28 and 90 days, respectively, representing an 842% increase over M3C0 at 28 days. These two combinations achieved the highest UCS values for the same cement dosage and curing age in the present study. Combination M3C2.5 outperformed combination M1C2.5 by 269% at 28 days and combination M2C2.5 by 137% at 28 days. Similarly, combination M3C5 exceeded the UCS values of combinations M1C5 and M2C5 by 288% and 126% at 28 days, respectively. These results demonstrated that, although mixture M2 initially showed higher UCS values than M1 (since in the unstabilized samples the clayey soil provided more cohesion than the sludge), once stabilized with cement, the sludge exhibited superior compressive performance. This highlights the potential of by-products in SRE building, as a mixture completely based on by-products obtained the highest UCS results in this study.

3.3. Soaked Unconfined Compressive Strength

During the soaked UCS test, all unstabilized samples lost their integrity during immersion in water, which was consistent with observations reported in the literature [10,14,42]. This loss of integrity was attributed to the limited ability of both the clayey soil and the sludge to maintain the cohesion of the sample. Figure 4 shows sample M3C0 losing its cohesion during water immersion.
M1C2.5 and M2C5 also lost their integrity when submerged in water, whereas M2C2.5, M2C5, M3C2.5 and M3C5 maintained their structural integrity. This difference was due to the fact that in mixtures containing M1, which consisted solely of clayey soil, CEM was unable to establish strong bonds between the soil particles, leading to a loss of integrity when exposed to water. In contrast, the inclusion of gravel- and sand-sized by-products in M2 and M3 enabled the CEM to bind these coarser particles together, creating a more durable matrix that could withstand water exposure and maintain its integrity.
Table 6 shows the results obtained for the M2C2.5, M2C5, M3C2.5 and M3C5 combinations in the soaked UCS test. The results for combinations M1C0, M1C2.5, M1C5, M2C0 and M3C0 are not presented, as these combinations lost their integrity and no data could be recorded.
M2C2.5 and M2C5 achieved 0.9 MPa and 1.8 MPa in soaked UCS values at 28 days. The soaked UCS/dry UCS ratios obtained for these two combinations were 0.21 and 0.20, demonstrating a significant reduction in UCS after water immersion. However, the values obtained were better than those reported by Vikas et al. [10], who observed a complete loss of integrity in specimens stabilized with 2% of CEM. They also noted an improvement in the ratio when increasing the CEM content to 4% and 6%, achieving ratios of 0.24 and 0.47 respectively. Nevertheless, the ratios obtained for M2C2.5 and M2C5 remained below the 0.33 threshold suggested by Heathcote [43], meaning these combinations would not meet the desired requirements. However, an improvement in M2 compared to M1 was observed, attributed to the use of by-products that allowed CEM to develop cementitious gels that bound these aggregates, forming stronger specimens.
Combinations M3C2.5 and M3C5 achieved ratios of 0.26 and 0.40, respectively. While combination M3C2.5 did not meet Heathcote’s requirements, combination M3C5 did. Moreover, both combinations achieved higher ratios than M2 with the same CEM dosages. This demonstrated that a mix composed entirely of by-products performs better against water exposure than a clayey soil or a clayey soil mix improved with by-products.

3.4. Wetting and Drying

In this test, the samples also had to be submerged in water, so all combinations that lost their integrity in the soaked UCS test also failed to maintain their integrity in this test.
Figure 5 illustrates the mass loss experienced by combinations M2C2.5, M2C5, M3C2.5 and M3C5 over the 12 cycles of wetting and drying at 28 days.
As shown in Figure 5, M2C2.5 and M2C5 experienced significant mass loss during the initial cycles. In fact, by cycle 6, the mass loss of M2C2.5 had already exceeded 10%, leading to the decision to stop further cycles, as the degradation was excessive. Combinations M2C5, M3C2.5 and M3C5 experienced mass losses of 4.6%, 7.1% and 2%, respectively. For this test, EM 1110-2-1913 [44] suggests a maximum allowable mass loss of 6%. Therefore, combination M3C2.5 did not meet this requirement, whereas combinations M2C5 and M3C5 did. These results align with the findings of Mustafa et al. [42], who observed that at low cement contents, the maximum mass loss requirements were not met, but with higher cement dosages, compliance was achieved. Similar conclusions were drawn by Zami et al. [12], who observed a reduction in weight loss as the cement content increased.
Figure 6 presents the condition of specimens from combinations M2C2.5, M2C5, M3C2.5 and M3C5 after six cycles for M2C2.5 and twelve cycles for M2C5, M3C2.5 and M3C5.
As observed in Figure 6, M2C2.5 suffered a huge loss of mass after the 6th cycle, which is further evidenced by the mass loss shown in Figure 5. However, specimens M2C5, M3C2.5 and M3C5 maintained their structural integrity. The final condition of the samples also revealed that sample M3C2.5 experienced greater mass loss than M2C5 and M3C5, as a higher presence of coarser particles was observed on the surface of M3C2.5 compared to M2C5 and M3C5. This suggests that M3C2.5 experienced a substantial loss of fines due to the wetting and drying cycles, which exposed the coarser particles. In contrast, the cementitious gels formed in M2C5 and M3C5 successfully preserved the integrity of the fines within the sample, enhancing their resistance to mass loss during the cycles and offering better protection to the coarser particles from the test’s effects.
Table 7 shows the unit price and carbon footprint of each material used in this work, as well as those of transportation. The carbon footprint data were obtained from [45].
Taking into account the unit price and carbon footprint of each material, the cost per ton was calculated for each of the construction materials manufactured in this study, as well as their carbon footprint. Figure 7 shows the price per ton of construction material and the carbon footprint of the materials.
Figure 7 shows a direct relationship between price and amount of cement for each of the mixes. It can also be seen that, for the same cement content, mix M1 has the highest price, followed by M2 and M3. This is because mix M3 contains the highest proportion of by-products, which are cheaper than the clay used in mixes M2 and M1. The prices obtained are similar to those reported by Pakand and Toufigh [46], who found costs of 4.16 USD/t and 4.81 USD/t for SRE materials stabilized with 2.5% and 5% cement, respectively. Regarding the carbon footprint, it is again observed that an increase in cement content leads to a rise in the carbon footprint for all mixes. Although the data on price and carbon footprint are interesting, it is more relevant to analyze the price/UCS ratio and carbon footprint/UCS ratio in order to make a direct comparison between the combinations. Figure 8 shows the price/UCS ratio and the carbon footprint/UCS ratio for all the combinations studied in this research.
Figure 8 showed that, for each mix, the price/UCS ratio decreased significantly from the unstabilized combination to the one stabilized with 2.5% cement, and then leveled off, in accordance with the observations made by Avila et al. [47]. For mix M1, the M1C0 combination had a price/UCS ratio of 4.41 EUR/tMPa, which dropped to 1.63 EUR/tMPa for M1C2.5 and to 1.51 EUR/tMPa for M1C5. In the case of mix M2, this reduction was smaller, as the M2C0 combination already had a much lower ratio of 1.44 EUR/tMPa. M2C2.5 and M2C5 reached ratios of 0.73 EUR/tMPa and 0.66 EUR/tMPa, respectively. M3C0, M3C2.5, and M3C5 showed values of 1.05 EUR/tMPa, 0.56 EUR/tMPa, and 0.46 EUR/tMPa. As observed, the combinations that used the by-product-based mix (M3) achieved the lowest price/UCS ratios among all the combinations studied in this experiment and they also obtained a lower ratio compared to other studies [47], demonstrating the potential of this material for SRE building. A similar pattern was observed for the carbon footprint/UCS ratio, where combinations using mix M1 showed a higher carbon footprint/UCS ratio compared to those with M2 and M3. Combinations M3C2.5 and M3C5 had the lowest carbon footprint/UCS ratios, just as they did for price/UCS ratio.

4. Conclusions

In this study, different granulometric mining by-products were used to modify the PSD of a clayey soil to evaluate their potential in SRE building. Within this research, the following conclusions were obtained:
  • Both curing time and CEM dosage had a direct correlation with improvement in UCS. Mining by-products demonstrated significant potential in SRE building, as their addition to clayey soil resulted in higher UCS values compared to the UCS obtained from clayey soil alone. Moreover, the mix composed entirely of mining by-products achieved the highest UCS values.
  • Unstabilized samples lost their integrity during exposure to water. CEM stabilization proved to be an effective solution for enhancing the water resistance of the mixes. The inclusion of mining by-products also showed its potential, as although the mixes did not fully meet the requirements in the soaked UCS and wetting and drying tests, the mix containing both mining by-products and clayey soil retained its integrity in water, unlike the samples composed solely of clayey soil. M3C5 successfully met the requirements in the soaked UCS and wetting and drying tests, further highlighting the great potential of mining by-products in SRE building.
  • Cost–benefit and carbon footprint analyses showed that the combinations which performed best when evaluating both price and carbon footprint in relation to their mechanical properties were those using the mix composed entirely of by-products. This highlighted the potential of these by-products in the SRE building sector.
This study highlights the potential of mining by-products for use in SRE building. These by-products exhibited excellent performance, as a mix entirely composed of mining by-products, combined with 5% CEM, met all established requirements. Additionally, they proved beneficial in enhancing the properties of a local soil. Further research would be valuable to explore the use of different stabilizers in combination with these by-products.

Author Contributions

Conceptualization, M.A.M.-A., C.P. and A.S.; methodology, P.V., R.A. and A.S.; validation, C.P. and A.S.; formal analysis, M.A.M.-A. and R.A.; investigation, M.A.M.-A.; data curation, M.A.M.-A. and P.V.; writing—original draft preparation, M.A.M.-A., P.V. and R.A.; writing—review and editing, C.P. and A.S.; visualization, M.A.M.-A., C.P. and A.S.; supervision, C.P. and A.S.; project administration, P.V. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Universidad Pública de Navarra via a doctoral grant to Miguel A. Martin-Antunes (1204/2022) in collaboration with Université de Pau et des Pays de l’Adour.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.

Acknowledgments

This research has been made possible thanks to the cooperation with the company Magnesitas Navarras S.A.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
CEMCement
LLLiquid Limit
MDDMaximum Dry Density
OMCOptimal Moisture Content
PIPlastic Index
PLPlastic Limit
PSDParticle Size Distribution
RERammed Earth
SPStandard Proctor
SREStabilized Rammed Earth
UCSUnconfined Compressive Strength
USCSUnified Soil Classification System

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Applsci 15 05167 g001
Figure 1. PDS of the gravel, sandy gravel, sand, sludge and clay.
Figure 1. PDS of the gravel, sandy gravel, sand, sludge and clay.
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Figure 2. XRD mineralogy of the considered materials.
Figure 2. XRD mineralogy of the considered materials.
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Figure 3. UCS values of the tested combinations at 7, 28 and 90 days. (a) M1 mix, (b) M2 mix, (c) M3 mix.
Figure 3. UCS values of the tested combinations at 7, 28 and 90 days. (a) M1 mix, (b) M2 mix, (c) M3 mix.
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Figure 4. M3C0 sample losing its cohesion during water immersion.
Figure 4. M3C0 sample losing its cohesion during water immersion.
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Figure 5. Mass loss experienced by combinations M2C2.5, M2C5, M3C2.5 and M3C5 over the 12 cycles of wetting and drying at 28 days.
Figure 5. Mass loss experienced by combinations M2C2.5, M2C5, M3C2.5 and M3C5 over the 12 cycles of wetting and drying at 28 days.
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Applsci 15 05167 g006aApplsci 15 05167 g006b
Figure 6. Condition of specimens after wetting and drying cycles. (a) M2C2.5 after 6 cycles, (b) M2C5 after 12 cycles, (c) M3C2.5 after 12 cycles and (d) M3C5 after 6 cycles.
Figure 6. Condition of specimens after wetting and drying cycles. (a) M2C2.5 after 6 cycles, (b) M2C5 after 12 cycles, (c) M3C2.5 after 12 cycles and (d) M3C5 after 6 cycles.
Applsci 15 05167 g006aApplsci 15 05167 g006b
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Figure 7. Price per ton of construction material and the carbon footprint of the materials: (a) Price per ton and (b) carbon footprint.
Figure 7. Price per ton of construction material and the carbon footprint of the materials: (a) Price per ton and (b) carbon footprint.
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Figure 8. (a) Price/UCS ratio and (b) carbon footprint/UCS ratio for all the combinations.
Figure 8. (a) Price/UCS ratio and (b) carbon footprint/UCS ratio for all the combinations.
Applsci 15 05167 g008
Table 1. Summary of the properties of the mixture constituents.
Table 1. Summary of the properties of the mixture constituents.
GravelSandy GravelSandSludgeClayey Soil
PSD (%)
Gravel (x > 2 mm) (%)92.876.9000
Sand (2 mm > x > 0.063 mm)6.922.895.51.82.3
Fines (0.063 mm > x)0.30.34.598.297.7
Bulk Density (g/cm3)1.621.491.500.871.21
XRD mineralogyMagnesiteMagnesiteQuartzMagnesiteCalcite
DolomiteDolomite DolomiteQuartz
QuartzHalloysite
Albite
Table 2. LL, PL, PI and USCS of the sludge and the clayey soil.
Table 2. LL, PL, PI and USCS of the sludge and the clayey soil.
SludgeClayey Soil
LL (%)25.038.4
PL (%)21.222.8
PI (%)3.815.6
USCSMLCL
Table 3. Bulk density and chemical properties of CEM.
Table 3. Bulk density and chemical properties of CEM.
CEM
Bulk Density (g/cm3)1.08
Oxides (%)
SiO214.1
CaO70.8
Fe2O34.1
Al2O33.4
SO34.2
MgO1.2
Others2.2
Table 4. Identification of the combinations, mixture compositions and stabilizer dosages.
Table 4. Identification of the combinations, mixture compositions and stabilizer dosages.
Mixture (% Dry Mass)Stabilizer
GravelSandy GravelSandSludgeClayey SoilCEM (%)
M1C0----100-
M1C2.5----1002.5
M1C5----1005
M2C017.926.431.8-23.9-
M2C2.517.926.431.8-23.92.5
M2C517.926.431.8-23.95
M3C017.926.431.823.9--
M3C2.517.926.431.823.9-2.5
M3C517.926.431.823.9-5
Table 5. OMC and MDD of all combinations.
Table 5. OMC and MDD of all combinations.
OMC (%)MDD (g/cm3)
M1C018.51.76
M1C2.519.81.72
M1C521.41.65
M2C07.12.27
M2C2.57.62.24
M2C58.42.22
M3C06.92.29
M3C2.57.32.25
M3C57.72.21
Table 6. Soaked UCS and soaked UCS/dry UCS ratio results obtained for M2C2.5, M2C5, M3C2.5 and M3C5 combinations in the soaked UCS test.
Table 6. Soaked UCS and soaked UCS/dry UCS ratio results obtained for M2C2.5, M2C5, M3C2.5 and M3C5 combinations in the soaked UCS test.
Soaked UCS (MPa)Dev. (s)Soaked UCS/Dry UCS RatioDev. (s)
M2C2.50.90.20.210.06
M2C51.80.10.200.01
M3C2.51.60.10.260.01
M3C54.70.20.400.02
Table 7. Unit price and carbon footprint of the materials.
Table 7. Unit price and carbon footprint of the materials.
Unit Price (€/t)CO2e (kg)/Material (kg)
Gravel3.542.10
Sandy Gravel3.542.28
Sand0.002.66
Sludge0.003.90
Clay3.142.81
CEM98.49256.30
Water0.010.02
Transport0.080.11
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Martin-Antunes, M.A.; Perlot, C.; Villanueva, P.; Abdallah, R.; Seco, A. Evaluation of the Potential of Natural Mining By-Products as Constituents of Stabilized Rammed Earth Building Materials. Appl. Sci. 2025, 15, 5167. https://doi.org/10.3390/app15095167

AMA Style

Martin-Antunes MA, Perlot C, Villanueva P, Abdallah R, Seco A. Evaluation of the Potential of Natural Mining By-Products as Constituents of Stabilized Rammed Earth Building Materials. Applied Sciences. 2025; 15(9):5167. https://doi.org/10.3390/app15095167

Chicago/Turabian Style

Martin-Antunes, Miguel Angel, Céline Perlot, Pedro Villanueva, Rafik Abdallah, and Andrés Seco. 2025. "Evaluation of the Potential of Natural Mining By-Products as Constituents of Stabilized Rammed Earth Building Materials" Applied Sciences 15, no. 9: 5167. https://doi.org/10.3390/app15095167

APA Style

Martin-Antunes, M. A., Perlot, C., Villanueva, P., Abdallah, R., & Seco, A. (2025). Evaluation of the Potential of Natural Mining By-Products as Constituents of Stabilized Rammed Earth Building Materials. Applied Sciences, 15(9), 5167. https://doi.org/10.3390/app15095167

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