This research work focuses on the study of the durability of composite cements based on coal bottom ash powder produced by SONICHAR in Niger. After a physicochemical and environmental characterization of the coal bottom ash powder, mortar test specimens were made. In these specimens, 10%, 15% and 20% of cement were replaced by identical mass percentages of coal bottom ash powder. Durability studies focused on the determination of the chloride ions apparent diffusion coefficient, the measurement of the depth of carbonation and the accelerated ammonium nitrate leaching. The influence of carbonation and leaching were examined using the following parameters: pore distribution, gas permeability, porosity accessible to water, capillary absorption and electrical resistivity. The results show that the incorporation of coal bottom ash powder into CEM I leads to an increase in the depth of carbonation. This increase is more significant when the substitution rate exceeds 10%. In the leaching test, the partial substitution of coal bottom ash powder in CEM I up to 20% does not significantly affect the durability parameters of the composites compared to the control mortar. Diffusion test shows that for mortars containing less than 15% substitution, there is no significant influence on the chloride diffusion coefficient. A slight decrease is observed for mortar containing 20% substitution.

This paper presents the feasibility of using locally available limestone Tuff in Burkina Faso as a partial replacement for CEM I artificial Portland cement. To this end, standard tests were carried out in the laboratory on mortars containing variable proportions of Tuff in partial substitution of CEM I cement. These include heat of hydration, setting time, total shrinkage, compressive strength, capillary absorption and resistance to acid attack. The experimental results obtained show that Tuff can be used as a natural pozzolan. It is also noted that the incorporation of Tuff into cement has virtually no influence on the transfer properties of mortars. However, at a rate above 15% partial substitution of CEM I, the mechanical strength of mortars is considerably reduced. This is probably linked to the finesse of the Tuff used. A finer shredding improved the mechanical activity index. However, we note a better resistance to acid attack (sulphuric acid that can come from acid rain) of mortars containing Tuff compared to mortar based on artificial Portland cement. All these results have shown that the Tuff used in this work can be a solution for reducing CO 2 emissions in cement production and also in reducing the price of cement in Burkina Faso.

CBA (coal bottom ash) is an industrial waste generated by coal fired thermal power plant. In this work, we investigate the utilization as an additive material in composite cement of CBA resulting from the firing of the coal extracted in Tefereyre mine (TCBA) in a thermal power plant in Niger. Our investigations are carried out by using compressive mechanical tests on 40 × 40 × 160 mm 3 mortar specimens. These mortar specimens are made with a partial substitution of the cement by TCBA at levels of 0%, 5%, 10%, 15%, 20% and 25% by mass. The tests were performed on the specimens at 7, 14, 28, 45 and 56 days of age. The results were used to evaluate the pozzolanic activity index as the ratio of the compressive strength of mortar containing 25% of coal bottom ash on that of the control mortar containing 100% of cement, according to ASTM C618. From these data, the maximum rate of TCBA addition in Portland cement was derived. It was found that TCBA has a pozzolanic activity index of about 71% at 28 days and displays a maximum substitution rate of 15% in Portland cement. These results strongly support the development of composite cement using TCBA.