The identification and location of the major sandpits in the region was done mainly through inquiries from contractors, builders and quarry workers in the areas. The sandpits (sources) identified were the Noun sandpit, Mifi sandpit, Baleng quarry, Batié quarry and the Bandjoun quarry. A mobile GPS was used to record the geographical coordinates and the ArcMap software was used to bring out the map of the location of the sandpits.

At each sandpit, samples were collected from just removed sand placed in hips beside the pit and the samples were collected at different spots from the hips to ensure the samples were representative of the overall sand deposit. Twenty (20) litres of sand were collected from each pit and placed in labeled bags. A small portion of each sample was then placed in an airtight plastic container to prevent moisture loss for the determination of moisture content. The samples were then transported from the pits to the geotechnical laboratory for testing and analysis.

Laboratory tests and analysis were conducted on the sand samples collected from the various sandpits to determine their geotechnical properties. The standard geotechnical testing methods that were employed to determine these properties included the natural moisture content, grain size analysis, specific gravity, apparent density, and sand equivalent test. The requirements, procedure and analysis for the various tests followed established French Norm (AFNOR), European Standards (EN), and equivalent International Standards (ISO) to ensure the reliability and reproducibility of the results. The geotechnical analysis was carried out at the Société BUNS laboratory at Santa, Mezam Division, working on the rehabilitation of the Babadjou-Bamenda road.

Quartering was done at the start of every test conducted to ensure accuracy. Quartering is a technique in which a representative sample is reduced to a convenient size for laboratory tests. It ensures that the sample is reduced to a convenient quantity having all the representatives of the material. The NF EN 932-1 standard outlines the methods for sampling including the quartering method.

The natural moisture content was determined according to NF P94-050, the grain size distribution and finesse modulus (FM) according to NF P94-056, the specific gravity according to NF P 94-054, the apparent density according to NF EN ISO 17892-2, and the sand equivalent (SE) according to NF EN 933-81.

Since the fineness modulus is an important parameter in concrete mix design, concrete was formulated using the various sands to directly evaluate their performance in practical applications. This approach allowed the assessment of how the fineness modulus reflects the actual quality and suitability of each sand for concrete production. Concrete with characteristics resistance of 25 MPa at 28 days (C25 class of concrete) was formulated using the Dreux-Gorisse method and the NF P18-305 which provides the guidelines for the production and conformity of concrete. Dreux-Gorisse method permits to determine the optimal quantities of materials (water, E; cement, C; sand, S; fine gravel, g; coarse gravel, G) necessary for the confection of one metre cube of concrete in accordance with the specifications. The concrete dosage with the different sands was 350 Kg/m³ with sand to gravel ratio of 1:2 in general. The testing of the concrete was done according to NF EN 12390 which provides guidelines for the curing and preparation of concrete specimens for compressive strength testing.

The classification of the various sands was done following the limits specified by the EN, ISO, and ASTM. The key parameters considered for the classification include grain size distribution, finesse modulus, specific gravity and sand equivalent.

From the grain size analysis, depending on the gradation, sands can be classified as poorly or uniformly graded (short range of sizes) and well graded (good range of sizes). The coefficient of uniformity Cu and curvature Cc provide quantitative information about the gradation and particle size distribution of the sands according to [6] . Sand with Cu > 4 is well graded and Cu < 4 is poorly or uniformly graded, while sand with 1 ≤ Cc ≤ 3 is well graded and Cc < 1 and Cc > 3 is poorly graded.

The fineness modulus (FM) is a numerical value that provides a measure of the coarseness or fineness of a sand or aggregate material. It is calculated by adding the cumulative percentages retained on a series of standard sieves and dividing the sum by 100. The specific sieves for calculating fineness modulus of sand as defined in the AFNOR standards are 0.16 mm, 0.315 mm, 0.63 mm, 1.25 mm, 2.5 mm, and 5 mm concrete. The classification of sands based on fineness modulus according [7] is as follows:

The sand equivalent (SE) classification is an important consideration in the selection and quality control of sand used in concrete, mortar and other construction materials as it helps ensure the desired performance and consistency of the final product. The sand equivalent is a measure of the relative proportion of fine dust or clay-like materials in the sand. According to the EN ISO 14688-2 [7] standard, the classification of sand based on sand equivalent (SE) is as follows:

The sand equivalent classification provides information about the cleanliness and quality of the sand, which can impact the performance of concrete and other construction materials. Very low and low SE sands have a higher content of fine, clay-like materials, which can negatively affect concrete workability, strength, and durability. Medium SE sands have a balanced amount of fine materials, making them suitable for general construction purposes. High and very high SE sands have a low content of fine materials, resulting in cleaner and higher-quality sand that is preferred for more demanding applications.

The specific gravity is an important parameter in the classification of sand, as it provides information about the density and composition of the sand particles, which can affect the properties and performance of the material in various applications. This classification system helps engineers and construction professionals to select the appropriate sand for their specific requirements, such as concrete production, soil stabilization, or fill material, based on the desired density and particle characteristics. According to the [7] standard, the classification of sand based on specific gravity is as follows:

The Unified Soil Classification System (USCS) uses a two-letter classification system to identify materials. The first letter represents the broad category (G for gravel, S for sand, M for silt and C for clay), and the second letter represents the gradation (W for well-graded, P for poorly-graded, M for silty and C for clayey). The classification of sands in the USCS is primarily based on the gradation and the amount of fines. In general, a material is considered as sand when 50% or more of coarse fraction is smaller than Number 4 (4.75 mm) sieve size. The USCS classifies sands into the following main categories:

The Noun sand is sourced from the Noun River basin in Manki II, known locally as the Mvi River, in the Malantouen Subdivision of the Noun Division. The sand source, called Kougbamé in the local language, is located about 3 km from the National Road N6. This sand, derived from alluvial deposits, is fine and rounded due to prolonged water transport, which explains its relatively poor grading and lower strength performance in concrete.

The Mifi sand, also referred to as black sand because of its dark coloration, is obtained from the alluvial deposits along the Mifi River near Boya and Ndjinga in the Bafoussam II Subdivision. The river expands during the rainy season, making access difficult. Like Noun sand, its alluvial origin results in smooth, rounded particles that reduce inter-particle friction and thus the mechanical strength of concrete.

The Baleng sand originates from the highlands of Sansang in Baleng, the chief town of Bafoussam II Subdivision, approximately 17 km from Baleng town. The highlands consist primarily of andesite rock masses that are manually excavated and sieved. The resulting sand has more angular particles and a better grain distribution, enhancing interlocking and mechanical resistance compared to river sands.

The Batié sand is extracted from mountainous areas in Bachepan, Batié Subdivision, Hauts Plateaux Division, about 10 km from Batié town and 1 km off the National Road N5. The parent material is mainly granite with silica and feldspar components. This geological origin produces coarse, angular, and well-graded sand, which contributes to its excellent performance in structural concrete.

The Bandjoun sand comes from the Bandjoun quarry, a basaltic rock deposit in the Koung-Khi Division. The basaltic rocks are blasted and crushed mechanically to produce the sand. Owing to its crushed, angular nature and dense mineral composition, the Bandjoun sand exhibits superior strength characteristics and grading, making it particularly suitable for high-quality concrete production.

A map showing the locations of the various sandpits is presented in Figure 1 .

The natural moisture content of the sands ( Figure 2 ) ranged from 6.98% to 12.90%, with Bandjoun sand having the lowest and Noun sand having the highest. The range is slightly different from that of the North West sands (8.07% to 15.17%) as investigated by [8] .

The coefficient of uniformity (Cu) and curvature (Cc) of the sands ( Figure 3 ) obtained from: grain size distribution curves of the various sands ( Figure 4 ) ranged

from 2.43 to 12.86 and 0.83 to 1.74 respectively. Noun sand had the lowest coefficient of uniformity and Baleng sand had the highest, while Mifi sand had the lowest coefficient of curvature and Batié sand had the highest. According to the USCS, Batié and Bandjoun sand were classified as well graded (SW) with Bandjoun sand having a relative amount of fines (silt) similar to studies carried out by [9] and [10] . Noun, Mifi and Baleng sands were classified as poorly graded (SP) with Baleng sand having a relative amount of fines (silt) similar to studies carried out by [11] [12] .

The fineness modulus of the sands ( Figure 5 ) ranged from 2.40 to 3.78, with Mifi sand having the lowest and Batié sand having the highest. This range is wider than that of the North West sands (2.63 to 2.93) as investigated [8] , due to the mixture of river and quarry sands in the West region. Studies carried out by [12] reported a fineness modulus of 2.35 for Mifi sand which is slightly different from 2.40 obtained. [9] had a fineness modulus ranging from 2.30 to 2.45 for Batié sand which is different from 3.78 obtained. This difference could be as a result of the improvement in the gradation of the quarry sand over time. From the [7] classification ( Table 1 ), all the sands are coarse grained sands which are suitable for structural applications, where higher strength and durability are required.

The specific gravity of the sands ( Figure 6 ) ranged from 2.394 to 2.586 g/cm³ with Mifi having the lowest and Noun sand having the highest. This range is similar to that of the North West sands (2.486 to 2.548 g/cm³) as determined by [8] . [12] [13] had 2.64 for Mifi and 2.65 g/cm³ for Noun sand respectively. Based on the [7] standard, all the sands had low specific gravity ( Table 2 ) and would produce concrete of relatively low density and moderate strength, suitable for general-purpose.

The apparent densities of the sands ( Figure 7 ) ranged from 1.456 to 1.713 g/cm³, with Mifi sand showing the lowest value and Baleng sand the highest. These variations can be attributed to differences in particle size distribution, mineral composition, and particle shape among the samples. Sands composed of heavier minerals or more compact, angular grains tend to exhibit higher apparent densities compared to those with lighter minerals or more rounded particles. Apparent density is a key geotechnical parameter that directly influences both material handling and concrete performance. It is particularly useful in estimating the bulk weight of aggregates during batching and storage. In concrete production, sands with higher apparent density generally contribute to denser mixes, resulting in improved compressive strength and reduced voids. Conversely, sands with lower apparent density yield lighter concretes, which can be advantageous in non-load-bearing or lightweight applications where reduced self-weight is desired. The apparent density values obtained in this study fall within the typical range of 1.4 - 1.8 g/cm³ for natural sands used in construction, indicating that all the sands investigated are suitable for practical use, with variations reflecting their geological origin and degree of compaction.

The sand equivalent of the sands ( Figure 8 ) ranged from 53.80% to 94.90% with Baleng having the lowest and Bandjoun sand having the highest. [8] reported a range of 65.20% to 91.46% for the North West sands and [10] had 85% for Bandjoun sand. The cleanliness of the sands ranged from dirty to very clean according to the [7] standard ( Table 3 ). Very low and Low SE sands have a higher content of fine, clay-like materials, which can negatively affect concrete workability, strength, and durability. Medium SE sands have a balanced amount of fine materials, making them suitable for general construction purposes. High and very high SE sands have a low content of fine materials, resulting in cleaner and higher-quality sand that is preferred for more demanding applications.

As seen in Table 4 , according to the USCS, Batié and Bandjoun sand were classified as well graded (SW: Cu > 4 and 1 ≤ Cc ≤ 3) with Bandjoun sand having a relative amount of fine silt (SM). This is similar to studies carried out by [9] and [10] . Noun, Mifi and Baleng sands were classified as poorly graded (SP: Cu < 4 and 1 ≥ Cc ≥ 3) with Baleng sand having a relative amount of fine silt (SM) which is similar to studies carried out by [11] [12] .

The compressive strength of concrete with the various sands ( Figure 9 ) and summarized in Table 5 ranged from 9.78 to 14.85 MPa at 3 days with Baleng sand producing the lowest and Noun sand producing the highest. The compressive strength at 7 days ranged from 14.87 to 22.56 MPa with Baleng sand having the lowest and Bandjoun sand having the highest. The compressive strength obtained at 28 days ranged from 20.14 to 33.62 MPa with Baleng sand having the lowest and Bandjoun sand having the highest. The Batié and Bandjoun sand gave resistances equal to and greater than 25 MPa respectively while the Noun, Mifi and Baleng sand gave resistances less than the desired 25 MPa at 28 days due to their poor gradation and low specific gravity. The Bandjoun sand gave the best resistance because of the improved interlocking and bonding characteristics of angular quarry sand particles [14] . The Baleng sand gave the least resistance due to its high fine content.