Assessing the Synergistic Effect of Limestone and Metakaolin
The effect of simultaneous addition of limestone and metakaolin on the properties of blended cements after 2 and 28 d of curing were investigated using a multi method approach. Hardened properties after 2 d of hydration are largely independent from the limestone to metakaolin ratio. After 28 d of curing, a strong influence of the quality of metakaolin used as well as the ratio of metakaolin to limestone on the hardened properties is observed. High quality metakaolin leads to higher compressive strength values. In the present experimental matrix the highest compressive strength values are obtained with a limestone to metakaolin ratio between 1 and 0.33. A positive effect between limestone and metakaolin is found, which leads to a refinement of the pore microstructure and consequently to higher compressive strength values. The absence of limestone leads to the destabilisation of ettringite, which transforms into monosulphate, and the formation of significant amounts of strätlingite if high quality metakaolin is used.
KeywordsCompressive Strength Mercury Intrusion Porosimetry Blended Cement High Compressive Strength Compressive Strength Testing
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