Ecological concrete by partially substitution of cement with Cameroonian corn stover ash

This study focuses on the influence of the partial substitution of cement by Cameroonian corn stover ash (CCSA) on the physical and mechanical behavior of concrete. For this, as materials used, one has first the corn stovers coming from the Bandjoun town in the Koung-khi division, in the West region of Cameroon, which are used to obtain the ashes, while the sand used, came from the Sanaga River in the coastal region of Cameroon. In order to obtain the CCSA, the corn stover is calcined in an oven at 600 °C for 6 h and then characterized; the characterization included infrared spectrometry, X-ray fluorescence spectrometry, fineness of grinding, and absolute density. Four concrete formulations were prepared, according to the amount of CCSA (that is at 0 %, 5 %, 10 % and 15 %), in order to carry out tests in the fresh state (slump test, compactness) and in the hardened state, i.e. mechanical tests (compression and bending tests) and physical tests (density test, water absorption, and porosity) after 7, 14, 28 and 60 days. The results of the chemical analyses carried out on the CCSA show that it contains 73.97 % of SiO₂ + Al₂O₃ + Fe₂O₃, giving it a pozzolanic character in accordance with ASTM C618 standard. The mechanical behavior at an early age (0-28 days) showed a general decrease in strength for concretes containing CCSA. Replacing 10 % of the cement with CCSA showed the best mechanical performance (compressive and flexural strength) in the long term (60 days) as compared to the control concrete (with 0 % of CCSA). At the same substitution rate the lower absorption and porosity rates were obtained, which are close to those of the control concrete, with relative differences of ±2.43 % and ±3.06 % respectively.