BEHAVIOR OF R.C. COLUMNS CONTAINING ALKALI WASTES OF OIL AND CELLULOSE PAPER INDUSTRIES AND EXPOSED TO SULFATE AND CHLORIDE ATTACK UNDER AXIAL STATIC LOADS

Abstract

The underground R.C. structures especially footings, piers, piles and column necks are always subjected to aggressive environmental conditions during their exploatation. These conditions are represented by the aggressive sulfate and chloride attack from surrounded soil or underground water. Which implies to deterioration of concrete cover and penetration of sulfate and chloride ions to the interior of concrete elements. According to that, the actual strength of R.C. elements decreases and corrosion damage of embedded steel bars accompanied with large deformations of concrete and steel increases. Consequently, a higher reduction of the construction durability occurs. So, the need for using an effective and economic admixtures for the protection of concrete elements against sulfate and chloride attack is required. Therefore, the main purpose of the project described in this paper is to study experimentally the mechanism effect of the suggested economic admixtures, which fabricated from alkali wastes of oil and cellulose paper industries, on the behavior of normal strength R.C. columns,subjected to external sulfate and chloride attack, under axial static loads. The main variables studied in this research on fifeteen R.C. columns were: three different types of plasticizing organic admixtures(SM-S, CM-B &SM-O), which contain in their compositions amount of alkali wastes from secondary products of oil and cellulose paper industries plus a control plasticizing admixture (Addicrete DM2), and three different concentrations of external surrounded sulfate and chloride solutions (2%Na2SO4+1%CaCL2 -Group A, 4% Na2SO4+2%CaCL2 - Group B, and 6% Na2SO4+3% CaCL2 - Group C). The experimental results showed that, Ultimate loads, stiffness, deformations, mode of failure and properties of the failure zone of the different groups of R.C. tested columns are significantly affected by the suggested admixtures and the concentration of sodium sulfate and calcium chloride solutions. R.C. columns modified with these admixtures(SM-S, CM-B &SM-O) and hardened in 6% Na2SO4+3% CaCL2 until 7 months showed a higher increment in their ultimate and working loads by about 51, 41, & 15% , a large increase of their energy absorption and ductility index of about 90, 47 & 33% over than that of the control column and a decrease of their ultimate longitudinal concrete strain by about 40, 24 & 18%, respectively compared to the control tested column without admixtures