This thesis studies three sources of black liquor in Egypt and their effect on concrete workability, compressive and tensile strength, and their effect as set retarder. Firstly a review on pulping processes and black liquor treatment techniques is submitted, also the previous work on black liquor as concrete admixture is discussed. Afterwards the test program is proceeded by analyzing the black liquors, studying the effect of various concentrations and different doses of black liquors on concrete mixes and the effect of ages of black liquor during a year on the concrete performance. Our main target is to obtain the optimum dose, concentration and kind of black liquor from those produced in Egypt as they are without treatment to obtain the optimum conditions as admixture. The effect of black liquor as set retarder and the effect of silica fume additives are studied. Finally recommendations on temperature, validity date and storage tanks are applied.