This paper deals with the physical characterization and the optimization of fineness moduli of some natural sand samples for their appropriate valorization in construction in North Cameroon. Five sands samples (SN5, SB1, SB2, SB3 and SB4) were selected from various locations. Tests conducted include Particle size analysis, Organic impurities, Sand Equivalent and Bulk density. Fineness Modulus (FM), Mean grain, Sorting index (Si), Skewedness index and Uniformity coefficient have been deducted mathematically. Results shown that the particle size distribution curves of the studied sands have an "S" shape. The sand equivalent values vary between 91.1 and 96.8 %, characteristic of very clean sand. The fineness moduli values vary between 1.9 and 3.4 except for samples SB1 and SB2 which are coarser with values of 3.4 and 3.3 respectively. Others results shown that all the sands are pure (impurity level less than 0.5 %), well classified Sorting index Si < 0.35) and Coefficient of uniformity (Cu < 2). Studied sands are globally coarse (skewedness index between -0.35 at -0.79F). Only SB4 and SN5 satisfy the NF EN 933-1 gradation limits. Combinations of SB3 (FM = 2.1) with SB1 (FM =3.4) or SB2 (FM= 3.3) were carried out to get desired sand gradation (2.2 to 2.8), SB4 and SN5 having already good fineness moduli of 2.6 and 2.8 respectively.
Clayey materials from Sekandé and Gashiga localities in the northern part in Cameroon traditionally used for pottery were studied. Eight samples were collected and investigated by XRD, IR, XRF, physical and firing properties from 900, 1000 and 1100 °C. In term of mineralogy, studied clays are rich in smectites, illite, kaolinite, quartz, feldspar and mica. Physicochemically, results show large particle size variations with high plasticity (18–30%). Clay fraction (<2 μm) ranges from 18 to 38% and sand fraction from 40 to 53%. Si0
2
(46–55%) and Al
2
O
3
(19–21%) are major chemicals oxides, followed by Fe
2
O
3
(6.68–10.82%) and alcali and alcali-earth elements (8–10%). These characteristics govern their behavior on firing with temperature development. The color of specimens was predominantly red after firing. Between 900 and 1100 °C, their color ranged from reddish brown, red yellow or brown red to red. The linear shrinkage values vary from 0.5% to 7%, weight loss from 4% to 9% and bulk density from 1.74 to 2.21 g/m
3
. These values increased gradually for specimens fired from 900 to 1100 °C. The water absorption decreased from 17% to 14%. The evaluation of the studied clays based on their mineralogical, physicochemical and ceramic properties revealed that they are suitable for the manufacture of earthenware products like fired bricks.
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