Calcined Marl and Condensed Silica Fume as Partial Replacement for Ordinary Portland Cement
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The main objective of this investigation is to replace calcined marl (0, 10, 20%) and condensed silica fume (SF, 0, 7, 10%) partially for ordinary Portland cement (OPC). Marl, a calcium-based supplementary cementitious material (SCM) calcines at a considerably lower temperature (750 °C) than OPC (up to 1480 °C). The calcined marl contributes in prolonged pozzolanic reactions and represents characteristics of latent cement chemistry. To approach the major conclusions, 27 mixes were designed based on the three ratios of water to the total binders (W/B) of 0.38, 0.42 and 0.45. The calcined marl and SF proportioned in mixes with “0, 10 and 20%” and “0, 7 and 10%”, respectively. After the ages of 7, 28 and 90 days all mixes improved, mechanically. In particular, the hardened concretes containing 10 and 20% of calcined marl show stronger reaction for substitution of OPC. In the lower limit of W/B ratio (0.38) mixes with 20% calcined marl exhibit a remarkable increase of some 2.4-fold strengths from 7 to 90 days. Also, the results obtained by tensile strength and modulus of rupture for concrete mixes containing 10 and 20% calcined marl highlight the mechanical progress of hardened concrete after 28 days. Collectively, both SCMs replaced OPC in a considerable amount (up to 30%). However, long-term enhancement in mechanical strength and durability indices are typically supported by calcined marl.
KeywordsCement Calcined marl SF Mechanical strength Durability indices
The authors would like to acknowledge Shahid Rajaee Teacher Training University (SRTTU), Tehran, Iran, for technical laboratory equipment and experimental materials provided for performing this research.
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