NANOSTRUCTURAL SUPERPLASTICIZERS FOR IN-LINING CONCRETE IN UNDERGROUND PROJECTS

摘要

Nanostructural superplasticizers allow the production of cement mixtures characterised by high early age mechanical strength development. These polymers are incorporated in the first cement hydration products and, thanks to their molecular structure, optimise the ettringite morphology, by reducing the average dimension of the crystallites at the nanometric scale. It is believed that the reduction of the ettringite crystallite dimensions could be the reason for the earlier development of the mechanical strength. Their behaviour has been studied in comparison to traditional polycarboxylate superplasticizers in terms of morphological analysis of the cement hydration products, hydration rate and development of mechanical strength. The use of nanostructural superplasticizers improve the productivity of precast concrete industry by reducing or even eliminating the steam curing cycle and the time for the moulds reuse. In the present paper, the application of these innovative superplasticizers for the production of precast segments for in-lining concrete in underground projects is described.