Physical and Chemical Effects in Blended Cement Pastes Elaborated with Calcined Clay and Nanosilica

Divino Gabriel Lima Pinheiro; Matheus Ian Castro Sousa; Fernando Pelisser; João Henrique da Silva Rêgo; Amparo Moragues Terrades; Moisés Frías Rojas

doi:10.3390/ma16051837

Physical and Chemical Effects in Blended Cement Pastes Elaborated with Calcined Clay and Nanosilica

Materials (Basel). 2023 Feb 23;16(5):1837. doi: 10.3390/ma16051837.

Authors

Divino Gabriel Lima Pinheiro¹, Matheus Ian Castro Sousa¹, Fernando Pelisser², João Henrique da Silva Rêgo¹, Amparo Moragues Terrades³, Moisés Frías Rojas⁴

Affiliations

¹ Department of Civil and Environmental Engineering, University of Brasília (UnB), Brasília 70910-900, Brazil.
² Department of Civil Engineering, Laboratory of Application of Nanotechnology in Civil Construction (LabNANOTEC), Federal University of Santa Catarina (UFSC), Florianópolis 88040-900, Brazil.
³ Department of Civil Engineering: Construction, Polytechnic University of Madri, Calle del Prof. Araguren, 3, 28040 Madrid, Spain.
⁴ Eduardo Torroja Institute (CSIC), Spanish National Research Council, 28033 Madrid, Spain.

Abstract

Supplementary cementitious materials (SCMs) are commonly used in the manufacture of commercial cements with lower clinker content and carbon footprints, enabling environmental and performance improvements. The present article evaluated a ternary cement combining 23% calcined clay (CC) and 2% nanosilica (NS) to replace 25% of the Ordinary Portland Cement (OPC) content. For this purpose, a series of tests were performed, such as compressive strength, isothermal calorimetry, thermogravimetry (TG/DTG), X-ray diffraction (XDR), and mercury intrusion porosimetry (MIP). The ternary cement studied, 23CC2NS, presents a very high surface area, which influences hydration kinetics by accelerating silicate formation and causes an undersulfated condition. The pozzolanic reaction is potentialized by the synergy between the CC and NS, resulting in a lower portlandite content at 28 days in the 23CC2NS paste (6%) compared with the 25CC paste (12%) and 2NS paste (13%). A significant reduction in total porosity and conversion of macropores in mesopores was observed. For example, 70% of pores in OPC paste were macropores that were converted in the 23CC2NS paste into mesopores and gel pores.

Keywords: calcined clay; hydration kinetics; microstructure; nanosilica; ternary cements.

Grants and funding

This research was funded by Federal District Research Support Foundation (FAPDF) for supporting research through the project Edital 04/2017/FAP/DF, No. 0193.001641/2017-1. We also thank the National Council for Scientific and Technological Development (CNPq), the Coordination for the Improvement of Higher Education Personnel (CAPES) and the Federal Institute of Education, Science and Technology of Goiás (IFG) for the financial support for conducting research in the Postgraduate Program in Structures and Civil Construction at the University of Brasília (PECC/UNB).