Effect of alternative fuels on the microstructure and strength development of cement paste

Official URL: http://risc01.sabanciuniv.edu/record=b1615023 (Table of Contents)

The object of this study was to investigate the effect of using alternative fuels in the cement production process on the microstructure and strength development of the output cement. Five different samples were produced using different alternative fuels in a cement kiln. The samples were prepared respectively with all kinds of alternative fuels (in the dirty kiln), petrocoke (in the clean kiln), waste plastics, a mixture of waste plastics and sewage sludge and lastly sewage sludge. The microstructure of the cement clinkers was studied with scanning electron microscopy (SEM). The results showed that the distribution of main phases of alite, belite, aluminate and ferrite varies in the samples prepared with different fuels. The alite/belite ratio varied between 5.2 and 1.5 among the samples. The phase distribution measurements using x-ray diffractometry (XRD) showed good agreement with the SEM results. Chemical composition of the clinkers was analyzed using energy dispersive x-ray spectroscopy (EDS) and x-ray fluorescence (XRF) methods. The sulfur and phosphorous amounts were higher in the samples with higher belite content. Hydrated cement paste samples were prepared with water to cement ratio of 0.3 and 0.5 by mass. The strength of the hydrated cement samples was measured in the compression tests for several curing ages up to 28 days. Results showed that alternative fuel usage affected the compressive strength values of hydrated cement samples, particularly the sample produced with all alternative fuels. The reactivity of hydrated phases was investigated using SEM and XRD analyses.