The influence of partial substitution of raw materials with heavy ash on the main properties of portland cements

Abstract

The use of wastes in cement industry have impact both from economic and environmental point of views. Wastes can be used in clinker manufacture (to substitute raw materials or as alternative fuel) as well as supplementary cementitious materials in cement. This paper presents results regarding the use of heavy ash (bottom ash) as component of raw mix used for the clinker manufacture. Two types of cements were obtained by the milling of clinker produced with/without heavy ash (HA) as component of raw mix and gypsum (2%). The compressive strengths of these cements was assessed on plastic mortars (water:binder = 1:2 ratio and binder:aggregate = 1:3 ratio), cast in prismatic moulds (14x14x160 mm3), hardened different periods of time comprised between 1 to 28 days. The hydration and hardening processes which occur in the cementitious systems with/without waste content were assessed on pastes with water to binder ratio of 0.5, hardened for 1 up to 90 days. X-ray diffraction (XRD) and complex thermal analysis (DTATG) were used for pastes' characterization. The composition of clinker was assessed by XRD and microstructure by scanning electron microscopy (SEM). The results obtained in the framework of this research do not show any important difference between the clinkers' characteristics produced with alternative raw material (heavy ash) as compared with the ones produced with natural raw materials. Also, the properties of cements produced of these clinkers are similar.