Abstract
The present work consisted in carrying out a study on the effective formulation of concrete for an optimal resistance to compression (fc28) between 20 and 30 MPa for the sites animated by the actors of the informal and semi-informal sectors of the construction. Studies have been carried out on projects under construction, by taking samples of fresh concrete in order to evaluate their real compressive strengths. These surveys show that there is a problem in the concrete formulation, as nearly 2/3 of the results show the lack of technical knowledge on concrete formulation practices. Indeed, on eight sites surveyed and whose fresh concrete samples were taken, only two sites (7 and 8) report fairly consistent results. Their 28-day compressive strength values are respectively 35.36 and 22.18 MPa. In addition, various formulations proposed with aggregates from different quarries or extracts from the bed of the Congo River, were determined in the laboratory. This study allowed us to obtain fairly objective results overall, which is characteristic of concretes of required quality. Of the six (06) formulation proposals, average resistances of 19.6 MPa at 07 days and 25.28 MPa at 28 days were obtained. These results at 28 days are in the range of 20 to 30 MPa, set as objective in this study. These formulations can be a reliable source for concrete manufacturers in these construction sectors. Similarly, the statistical study based on principal component factor analysis tests has shown that the most appropriate formulation, in terms of mechanical resistance, is that proposed with sand extracted from the Congo River (formulation 3). This is justified by the fact that this sand is consistent and has a good granular distribution.
Highlights
The act of building has become much more intense nowadays because of phenomena related to the accelerated urbanization of cities, and in order to meet a pressing need, that of the building of basic infrastructure by public authorities or private partners, for the benefit of the population
Studies have been carried out on projects under construction, by taking samples of fresh concrete in order to evaluate their real compressive strengths. These surveys show that there is a problem in the concrete formulation, as nearly 2/3 of the results show the lack of technical knowledge on concrete formulation practices
If the formulation of a concrete can be understood as the process of selection of constituents and their proportions optimal to manufacture a complex possessing certain required properties, it is true to note that this is still done for the most part empirically, whereas there are more rational scientists [3]
Summary
The act of building has become much more intense nowadays because of phenomena related to the accelerated urbanization of cities, and in order to meet a pressing need, that of the building of basic infrastructure by public authorities or private partners, for the benefit of the population. If the formulation of a concrete can be understood as the process of selection of constituents (aggregates, cement, additives) and their proportions optimal to manufacture a complex possessing certain required properties (consistency, resistance, durability...), it is true to note that this is still done for the most part empirically, whereas there are more rational scientists [3]. In these sectors of construction where self-construction predominates, the quality assurance of the works is not often appropriate, due to the lack of control of the appropriate technology for the realization of the works. This measures the importance of the study on the formulation of concrete, all the more necessary as the required characteristics are demanding
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