Contribution to the Physico-Mechanical Characterization of Career Sands in the Western Region in Cameroon

-The objective of our study is the physico-mechanical characterization of quarry sands in the West Cameroon region with a view to their rational use in civil engineering works. This work was done in two ways: • In the field we took samples • In the laboratory we did some tests. Laboratory studies focused on: ✓ Physical characterization which is an intrinsic property: water content, specific weights, density, sand equivalent, dry particle size analysis, sedimentation, granularity. ✓ Mechanical characterization: Proctor test, CBR test and concrete formulation. The study concludes that representative samples of the sand analyzed have physical and mechanical properties such that: the specific gravity is 2.46 g / cm3, the apparent density is 1.9 g / cm3, the sand equivalent is 67.2 %, The modulus of fineness (Mf) is 3.3, The Immediate CBR is 10.37, the Normal Proctor test shows a maximum dry density of 1.68g / cm3 for an optimal Moisture content of 12.18 %, the Modified Proctor test also stands out a maximum dry density of 1.74 g / cm3 for an optimal Moisture content of 14.8 and the compressive strength of Concrete at 28 days is 25.08 MPa.


1-INTRODUCTION
Aggregates are inert materials derived from rock erosion or grinding, which agglomerated by a binder constitute the skeleton of concretes and mortars. Aggregates can be rolled and deposited by erosion agents (wind, volcano, and water) or crushed (angular and quarried). Aggregates are of great importance because they are at the base of mortars, hydraulic concretes, as well as hydrocarbon concretes (bituminous concretes). They also serve as ballast (crushed granulate of size between 25 and 50mm) without fines used in particular in the structural structures of the civil engineering structures. Their use is more and more important and in great mass. The aggregates are said: ✓ Natural when they come from loose or massive rocks and which undergo no treatment other than mechanics. These aggregates come from quarries, gravel pits, sand pits and borrow pits. ✓ Artificial when they come from the transformation of both thermal and mechanical rocks. Most of them are only used for lightweight insulating and low-resistance filling concrete. A lot of work has been done (huge work has been done on the use of sand) in the manufacture of concrete and mortars. Granites are famous rocks for their hardness and resistance contributing to the construction of buildings. However, none analysis was conducted on the sands of Career of the MiFi in the Western Region Cameroon. In addition granites and its alteration products have been carefully studied by several researchers such as : Fetgo B. [28] (2002) who carried out the geotechnical characterization of alteration products sector of Bafou by limiting itself to the intrinsic parameters of the material. Kouayep Lawou S. [13] (2003), during the study of mass movements in the Bana massif, contributed to the geotechnical characterization of the granites of the massif. Keyangue T. J. H. [15] (2007) has briefly studied the physical properties of sand from the alteration materials of Batié granites (West Cameroon) and made proposals for improving their quality for the manufacture of concrete. Goodwill [16] (2011) did a study on the sand properties of some quarries of Bamenda (especially the sands of Ndop, Woum, Mbattu) with particular interest the equivalent of sand; and made an analysis of their impact in the manufacture of concrete.

2-MATERIALS AND METHODS
To better characterize the aggregates of western Cameroon for appropriate use in civil engineering, a suitable methodology must be applied to conduct field work, laboratory and for the calculation of various parameters.

2.1-Materials
The main materials are here represented by rocks, soils and aggregates from which we take our different sand samples. For this we used the following equipment and tools: • A topographic map to position the different sampling sites; • A Mercedes vehicle (truck) with a load capacity of twenty tonnes for the movement and transport of samples • Pickaxe, shovel and hoe to dig trenches to collect samples and load them into bags; • Polystyrene bags used to collect samples; • A decameter for taking measurements of different variants; • PPE (Personal Protective Equipment) for personal safety; • Pens and notepads for taking data on site; • A camera for shooting ✓ Location of the study site In the locality of West Cameroon, several sand quarries are open. An inventory of these last ones during many descents in the field made it possible to make a choice related to the geotechnical studies of the aggregates coming from these different sites: localization between the parallels 5 ° 25 'and 5 ° 28'00' 'of Latitude North and the meridians10 ° 20 'and 10 ° 25'00' '.

Sampling
In order to have the most representative samples, the approach of <shovel in butte> was necessary, it was necessary to mix the materials which one made of a bleeding on the whole height of the face of size . Then, the quarterly sampling method made it possible to determine our operation by retaining the quantities necessary for laboratory work. The reworked samples taken from each sand were packaged in polystyrene bags and labeled. They were used for mechanical identification of each of these sands (CBR, concrete formulation, optimum water content, etc.). Laboratory work was carried out on the various sand samples at the Laboratory of Engineering and Industrial and Environmental Systems (URISIE) of the University Institute of Technology FOTSO Victor Bandjoun associated with the Laboratory of Mechanics and Modeling of Physical Systems (UR2MSP).

2.2-Experimental methods
In this part, the experimental methods will be presented for the determination of the different characteristics of the material. Among others: ➢ Physical characteristics: Water content, density, specific gravity, sand swell, absorption coefficient, degree of surface cleanliness or equivalent of sand, loss of mass.

Water content
The water content of the materials studied was determined by the method of steaming according to the prescription of standard NF P 94-050 (1995).

Density (apparent density)
The measurement of the density was carried out according to the standard NF EN 1097 -6; NT 21-193.

= ℎ *
With: Mech: Mass of the sample gram (g) and Mliq: Mass of the liquid (water) gram and ρliq: Density of the liquid in (g / cm3)

Specific mass (absolute or real density)
The determination of the specific gravity of the studied materials was carried out with the use of the method of the water pycnometer according to the prescriptions of standard NF P 94-054. The absolute density sought is: With ρw: Density of water taken conventionally equal to 1 g / cm3

Measurement of the cleanliness of sands: equivalent of sand
Sand cleanliness is routinely assessed using the sand equivalent test. It is carried out on the fraction of sand passing by 5mm sieve, following the prescriptions of the standards NF EN 933-8 and NT 21 -26. The value of the equivalent of the desired sand is obtained using the expression: Where ESV and ESP are respectively the equivalent of visual sand and the equivalent of sand measured at the piston Sand blasting The abundance of materials has been studied on the basis of the principle described by standard NFP 18-558. This test consists of the fineness module and the state of the material (water content) through the abacus to determine the expansion coefficient Determination of the expansion coefficient

Absorption coefficient
The absorption coefficient of the materials studied was evaluated by the method described in standard ; EN 1097 -6. The water absorption coefficient (in %) of the sand was determined by the formula: With: Mh the final dry mass and MS the initial dry mass of the sample under test.

Mass loss control test (NF P 20-049)
The loss of mass of the materials was studied on the basis of the principle and the procedure described by the standard NFP20-049. The latter states that the weight loss coefficient is defined by: With: M0 is the initial mass of the sample and Mf is the final mass after execution of the test. ➢ Geometric characteristics: The granular composition, the fineness modulus, and the flattening coefficient Sieve analysis by dry sieving (NF P 94-056) Particle size analysis of the various materials was carried out by the dry route. It makes it possible to determine the size and the respective weight percentages of different families of grains constituting the soils. The fineness module, quantifying the more or less fine character of the sands corresponds to the sum of the percentages of the accumulated refusals brought back to the unit for the sieve of the modules 23, 26, 29, 32, 35, and 38. It is given by the following expression: = (% 5 + % 2,5 + % 1,25 + % 0,63 + % 0,315 + % 0,160 ) 100 Where % Ri is the percentage of the cumulative rejection on the separate sieve on the opening sieve i (in mm). It is important to note that when the material passing through the 63 mm sieve has more than 50% refusal of 0.080 mm, the uniformity (Cu) and curvature (Cc) coefficients can be calculated using the expressions following: Or dy: dimension of the sieve corresponding to y% of passing.

Particle size analysis by sedimentation (NF P 94-057)
The objective of the test is to determine the particle weight distribution of a soil with the largest dimension equal to 80 μm and the smallest larger than 1 μm. This test completes the sieving analysis. with η the viscosity of the liquid ➢ Mechanical characteristics: CBR, concrete formulation, optimal water content, optimal density.

Proctor Trial
The Proctor Normal or Modified test is used to find the optimum water content that leads to the best compaction of the material. The compaction of a sample of material is done in a standardized mold, using a standardized lady, according to a process defined by NFP 94-093.

CBR test
The Californian Bearing Ratio (CBR) is a load bearing test (ability of materials to withstand the loads) of embankments and compacted layers of road structures. It consists in experimentally determining the bearing indices (IPI, CBR). According to NF P94-078 standard.

Formulation of concretes
The purpose of concrete formulation is to determine, according to the handling and resistance criteria defined by the specifications, the nature and the quantities of materials necessary for the manufacture of a cubic meter of concrete. is to define, according to the type of work to be done, the parameters necessary for the implementation of the concrete and the short and long term stability of the structure 3-RESULTS AND DISCUSSION   ➢ The sand has a water content of 10.8 which results in a low content of fine particles, which makes it possible to affirm that this soil is in a compact or dense state and therefore has a lower vacuum index.

3.1-RESULTS
➢ The apparent density of the sand is greater than 1.4 g / cm3 which confirms that the studied material is a granulate and its specific mass varies from 2 g / cm3 to 3 g / cm3 which means that we are in presence of a common granulate. ➢ The sand equivalent of sand has a sand equivalent value of between 60% and 70%, therefore, it is recommended for the realization of a concrete of standard quality which can present a slightly strong withdrawal. The cement used must necessarily be Portland type. ➢ The dry density at sand OPM varies from 1.53 t / m3 to 1.74 t / m3, its water content at OPM is 14.8% and this shows that the material is recommendable for the preparation of the base layers of pavements. ➢ Sand with a CBR Index between 8 and 12 which leads to a soil class S2. ➢ After plotting the grain size curve and various calculations, the sand has a curvature coefficient Cc < 1 and the coefficient of uniformity Cu < 4 this indicates that we are in the presence of a badly graduated gravity. Furthermore, According to the value of its fineness module, which is 3.3, the sand is qualified as coarse. ➢ We can therefore conclude that concrete formulated with sand is a quality concrete, the resistance obtained is equal to the desired resistance. Therefore are common concretes.

-CONCLUSION AND PESPECTIVES
CONCLUSION At the end of our study, we were talking about performing a Physico-Mechanical Characterization of the MiFi Career Sands in the MiFi River Basin for use in Civil Engineering. For this reason, we have this characterization of the physico-mechanical parameters that have been presented and interpreted. From this results the physical and mechanical properties of the material taken from the site. In the end, the results obtained during this study lay the foundations of a Physico-Mechanical Database of the Care Sands of the MiFi in the Western Region of Cameroon.

PROSPECTS
• For the cement field, it is necessary to make a quantitative and qualitative mineralogical study, because the resistances depend on it. • For the field of mechanical tests on hardened concrete, the tests (compression and tensile splitting) must be made. Non-destructive testing must also be done with sclerometrics. • The effects of dimensional variations have not been taken into account for modeling swelling and shrinkage. It would be of paramount importance to study them because of them depend the complex phenomena of setting and the hardening of mortars and concretes. • For the study of Pathologies, it is necessary to make a study to complete the detailed visual inspection of the Structures, to assess the quality of the materials in place and to characterize the current mode of operation of the structure.