Abstract
Nowadays, one of the most popular ways to get a more sustainable cement industry is using additions as cement replacement. However, there are many civil engineering applications in which the use of sustainable cements is not extended yet, such as special foundations, and particularly micropiles, even though the standards do not restrict the cement type to use. These elements are frequently exposed to the sulphates present in soils. The purpose of this research is to study the effects in the very long-term (until 600 days) of sulphate attack in the microstructure of micropiles grouts, prepared with ordinary Portland cement, fly ash and slag commercial cements, continuing a previous work, in which these effects were studied in the short-term. The microstructure changes have been analysed with the non-destructive impedance spectroscopy technique, mercury intrusion porosimetry and the “Wenner” resistivity test. The mass variation and the compressive strength have also been studied. The impedance spectroscopy has been the most sensitive technique for following the sulphate attack process. Considering the results obtained, micropiles grouts with slag and fly ash, exposed to an aggressive medium with high content of sulphates, have shown good behaviour in the very long-term (600 days) compared to grouts made with OPC.
Highlights
Nowadays, the sustainability has a major importance in the cement industry, and the main aim in that regard is to reduce the CO2 emissions produced during cement manufacturing
The pore network of slag and fly ash cement grouts exposed to sodium sulphate medium was more refined than that observed for CEM I ones during the entire period of time studied
All the grouts showed a progressive pore refinement, independently of cement type used, which has been related to the development of cement and slag hydration and fly ash pozzolanic reactions, which produce new solid phases
Summary
The sustainability has a major importance in the cement industry, and the main aim in that regard is to reduce the CO2 emissions produced during cement manufacturing. Some of them can react directly with water or with portlandite formed during the cement hydration, producing new hydrated products which improve the properties of cement-based materials [6,7,8]. They are called active additions, and fly ash and ground granulated blast furnace slag are two of the most popular ones. Many studies show that cementitious materials with ground granulated blast furnace slag and fly ash develop a denser pore structure of concrete at later ages [4,8,9] and they show very good durability
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