In recent years, the construction industry has been faced with a decline in the availability of natural sand due to the growth of the industry. In the present study, effect of gneiss powder as fine aggregate replacement on the compressive strength of concrete was investigated. The percentage of gniess powder added by weight was 0%, 25%, 50%, 75% and 100% as a replacement of river sand used in normal concrete. Tests were performed for compressive strength tests for all replacement levels of gneiss sand at different curing period (7 days, 28 days and 90 days). The results revealed that all the concrete made with different replacement present the good mechanical performance. At 90 days, the maximal values of compressive strength are obtained for conventional concrete CN (37.07 MPa), followed by CG75 concrete made with 25% of river sand and 75% of crushed gneiss (35.09 MPa). Then it is suggested that sand with a partial substitution of 75% can be effectively used in concrete production without affecting the strength and durability properties of the concrete.

No abstract

The present work consists of a statistical study of the properties of the soils of the locality of Monatele used for the confection of compressed and stabilized earth bricks by calcination. This study is based on sixteen (16) samples taken from four (04) sites, namely, Nkolossananga, Nkol-Medock, Avoh, and Enieg. The results of the chemical and mineralogical tests show that the soils sampled are composed of quartz, Kaolinite, Hematite, Muscovite, Calcite, Rutile, Pyroxene, Montmorillonite, and Illite, with variable proportions. The water content of these soils varies from 10.32 to 26.35%. The granulometric analysis supported by Methylene Blue reveals dominant proportions of clay ranging from 32.8 to 53.7%. The plasticity test shows that the studied soils are almost essentially medium plasticity clays and high plasticity clays depending on the case. The HBR classification identifies them as clayey and silty soils belonging to classes A-7-6 and A-5. The physical-mechanical tests carried out on the fired brick specimens show that the density decreases with the increase of the temperature, while the water absorption, the flexural strength, and the compressive strength increase under the same conditions. The statistical study of the studied properties shows good correlations between the different granular classes present in the studied soils. In particular-0.79 between the proportions of gravels and silts and-0.68 between sands and clays. The values of methylene blue and plasticity also show interesting correlations with the percentage of silt, namely, 0.52 and 0.54, respectively. The Pearson correlation matrix also reveals that mechanical strength, water absorption, density, and firing temperature show good correlations with each other. These allow for the establishment of predictive models for compressive strength with a correlation coefficient R 2 = 0.83.