An alternative raw material for Portland cement clinker preparation: Meta-schist

Abstract

This study investigates the use of meta-schist as an alternative base material to cement clay in clinker production. First, the mineralogical differences between the reference cement clay, rich in silica but poor in iron and aluminium and the meta schist, rich in aluminium and iron and relatively poor in silica, were revealed by the XRD method. Two raw meal samples were prepared, one with ordinary raw materials (limestone and clay) ((RM)/Ref) and the other with meta-schist ((RM)/M) as a reference sample. The effects on the reactivity of the raw mix samples were evaluated on the basis of the unreacted lime content in the samples sintered at 1200, 1300, 1350, 1400 and 1450 °C. Then, two different clinker samples were produced by sintering the two raw mixtures at 1450°C. The relationships between the internal structures of the clinker samples determined by polarizing microscope (amount of porosity, distribution, grain structure of silicate phase crystals and variation of equivalent crystal diameters) were investigated. In addition, setting time, compressive strength and expandability properties of cement mortars produced with both clinker samples were tested. The microstructures of the mortar samples were examined on the 2nd, 7th and 28th days by scanning electron microscopy. It was observed that the meta-schist clinker contains less free CaO than the reference clinker at different temperatures. Both clinkers have similar proportions of alite and microstructures of alite and belite are identical in terms of crystal size and composition. At the same time, the distribution of the liquid phase is more uniform in the reference cement. Using meta-schist, low-temperature and low-cost Portland cement clinker can be produced without additional regulatory materials and blending.

Effect of Thermal Activation on the Mineralogical Structure of Magnesium Slag

“…Because of this, small periclases are formed. Clinker cooling conditions have a significant impact on the mineralogical composition of clinker [15,16]. According to various cooling degrees, The C3S percentage reached 59.8% in slow cooling, 65.2% in rapid cooling and 70% in rapid cooling [15].…”

“…Clinker cooling conditions have a significant impact on the mineralogical composition of clinker [15,16]. According to various cooling degrees, The C3S percentage reached 59.8% in slow cooling, 65.2% in rapid cooling and 70% in rapid cooling [15]. Clinker comprises oxides in its composition, which form calcium silicate and aluminium silicate compounds under specific stoichiometric values and kiln temperature conditions.…”

“…The Bogue Method fails to consider the incorporation of foreign ions into the structures or forming different solid solutions. Previous research has indicated that the Bogue calculation typically underestimates the alite content and overestimates the oxide content compared to quantification by point counting and optical microscopy techniques [4,15]. Quantitative X-ray diffraction techniques (QXRD) can yield results comparable to quantitative optical microscopy for alite and belite phases.…”

Full-Scale Testing of an Alternative Energy Converting Installation

“…The use of metashale in Portland cement clinker is being investigated due to the application of nuclear technology and protection from atomic radiation with harmful environmental effects such as gamma rays. Methods are proposed to reduce the sintering temperature of clinker materials and reduce emissions, which helps reduce the greenhouse effect [7,8]. The authors also propose to use production waste to achieve energy saving and thus do not waste energy on burning cement clinker [6].…”