Date

2002

Author

Erdoğdu, Korhan

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As limestone is a new widely used mineral addition in cement, understanding the effects of this material on cement properties and hydration in a detailed manner is of substantial importance for efficient and proper usage. Consequently, the current study is designed. In the experiemental study, three different limestones were used. The aim of using different limestones is to reach broad generalisations by crosschecking the results and compare the effects of limestones with different structures. These limestones are a marble waste, an ordinary limestone aggregate for concrete and a chalky limestone. All limestones were added to portland cement clinker in 5, 10, 20 and 30 %, by weight, and cements are produced mby intergrinding. During the intergrinding process, grindability measurements were also conducted. In the study, standard physical and mechanical properties of the cements, particle size distributions, microstructure of 2 and 28 day pastes, early heat of hydration up to 72 hrs and flow values were investigated. The grindability results showed that grinding energy requirement to reach certain Blaine fineness decreases sharply with the usage of any limestone. In addition, limestone usage changes the particle size distribution of cements remarkably. Limestones are not suitable additions for separate grinding as this method results in inefficient energy consumption in grinding. Hydration studies yielded that limestone is not simply an inert filler material in cement and interferes with the hydration process. By heat of hydration studies of portland limestone cements, increase in initial heat of hydration rate, increase in peak rate and lenghtening of peak rate period as a result of limestone usage were exhibited. Limestones decrease the water requirements of cements as proved by normal consistency and flow tests. This is attributed to internal friction decrease emerged with usage of limestones due to smooth surface and nonporous structure of limestones. Setting times increase with usage of limestones. This provides with the possibility of using limestone as gypsum replacement material for set retarding. Compressive strengths of portland limestone cements were found to be similar to that of PC at 5 and 10 % addition amounts. However, further increase in addition amount brings about the need for more grinding to overcome the reduction in strength.

Subject Keywords

Cement, Portland cement, Limestone, Calcium carbonate, Limestone addition, Portland limestone cements, Grindability, Particle size distribution, Standard physical and mechanical properties, Hydration, Microstructure

URI

https://hdl.handle.net/11511/12793

Collections

Graduate School of Natural and Applied Sciences, Thesis