Abstract
At present, sustainability is of major importance in the cement industry, and the use of additions such as silica fume as clinker replacement contributes towards that goal. Special foundations, and particularly micropiles, are one of the most suitable areas for the use of sustainable cements. The aim of this research is to analyse the effects in the very long-term (for 600 days) produced by sulphate attack in the microstructure of grouts for micropiles in which OPC (ordinary Portland cement) has been replaced by 5% and 10% silica fume. This line of study is building on a previous work, where these effects were studied in slag and fly ash grouts. Grouts made using a commercial sulphate-resisting Portland cement were also studied. The non-destructive impedance spectroscopy technique, mercury intrusion porosimetry, and Wenner resistivity testing were used. Mass variation and the compressive strength have also been analysed. Apparently, impedance spectroscopy is the most suitable technique for studying sulphate attack development. According to the results obtained, grouts for micropiles with a content of silica fume up to 10% and exposed to an aggressive sulphate medium, have a similar or even better behaviour in the very long-term, compared to grouts prepared using sulphate-resisting Portland cement.
Highlights
The use of additions as clinker replacement in cement manufacturing has become very common [1,2,3,4,5]
The microstructure of 5% and 10% silica fume cement grouts exposed to sodium sulphate medium was more refined than that noted for sulphate-resisting Portland cement grouts during the entire studied period
The pore network of the grouts became more refined as the percentage of silica fume increased
Summary
The use of additions as clinker replacement in cement manufacturing has become very common [1,2,3,4,5]. Among the benefits provided by the additions, it is important to emphasise their contribution to cement industry sustainability, because they reduce the CO2 emissions generated during the cement production. Some of them are active additions, which means that they can react with water or with Portlandite that has been produced as a product of hydration reactions of clinker. This reaction forms new hydrated products that boost the cement-based materials’ properties [6,7,8,9,10]. The most popular active additions are fly ash, silica fume, and ground granulated blast furnace slag
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