HIGH PERFORMING INNOVATIVE SOLUTIONS FOR SUSTAINABLE CONCRETE

The increasing demand for energy caused by the exponential population growth is responsible for the climate change. Portland cement production is an energy-intensive process which accounts for about 8 per cent of the anthropic CO2 emissions. One of the most promising initiatives for cutting down the contribution of concrete to climate change is the increasing use of alternative materials to produce Portland cement and concrete, such as fly ashes, ground blast furnace slag, calcined clays, pozzolanas and limestone. This strategy, which is aimed at limiting the environmental impact of cementitious materials by reducing the energy-intensive clinker fraction, has the main limitation of unacceptable reduction of early and final compressive strength. The science and technology of admixtures is quickly changing from merely performance-based admixtures to sustainability performing solutions, developing new products capable to reduce or eliminate the drawbacks and limitations arising from the use of large quantities of latent and non-hydraulic materials in the production of Portland cement and concrete. A significant step forward in the pursuit of this goal is the development of composites based on nanosized metal silicate hydrates, which are emerging as essential ingredients of concrete admixtures to meet the requirements and objectives of sustainability and durability of concrete structures. In the present paper, the chemical and microstructure characteristics of these new class of admixtures are presented. Secondary nucleation, which is the basis of their mechanism of action, their role in promoting the activation of SCMs and their contribution in improving performance and durability of “low-carbon” concrete are discussed