TY - JOUR

T1 - Microstructural and mechanical properties of (Ca, Na)-poly(sialate-siloxo) from metakaolin as aluminosilicate and calcium silicate from precipitated silica and calcined chicken eggshell

AU - Tchuente, Flore Mpombo

AU - Tchakouté, Hervé K.

AU - Banenzoué, Charles

AU - Rüscher, Claus H.

AU - Authority, Local Materials

AU - Andreola, Fernanda

AU - Leonelli, Cristina

N1 - Funding information: Hervé Tchakouté Kouamo gratefully acknowledges the Alexander von Humboldt Foundation , Germany for financially support this work under the grant N° KAM/1155741 STP. The authors would like to thank Mr Valerie Petrov for SEM observations.

PY - 2019/3/20

Y1 - 2019/3/20

N2 - The aim of this work is to investigate the influence of the amorphous calcium silicate on the microstructural, physical and mechanical properties of (Ca, Na)-poly(sialate-siloxo) networks. The calcium silicate with molar ratio CaO/SiO 2 equal to 1.0 was prepared from the precipitated silica and calcined chicken eggshell. The X-ray patterns and infrared spectra of the synthesized calcium silicate indicate that it mainly constitutes of the amorphous calcium silicate hydrate. The X-ray patterns of geopolymer cements indicate that the prepared amorphous calcium silicate hydrate does not include in the network. The compressive strengths of the geopolymer mortars decrease from 28.92 to 12.03 MPa with increasing the replacement level of metakaolin (from 0 to 25% by mass). Whereas, the values of the apparent densities increase with increasing the replacement level of metakaolin. It seems that the amorphous calcium silicate hydrate in the structure of calcium silicate affects negatively the mechanical properties of the (Ca, Na)-poly(sialate-siloxo) network. The heterogeneous structure of geopolymer mortars containing 25% of calcium silicate could be related to the higher calcium content and the amorphous structure of calcium silicate hydrate. It was typically found that in the absence of significant levels of dissolved calcium, the precursors such as silicate and aluminate condense to form (Ca, Na)-poly(sialate-siloxo) networks. This implies the homogenous structure and the higher values of the compressive strengths of geopolymer mortars containing 0, 5, 10 and 15% of calcium silicate. Whereas those from the replacement level of metakaolin by 20 or 25% of calcium silicate contain significant levels of dissolved calcium and amorphous calcium silicate hydrate in their structure which hinder the formation of the precursors and therefore impede the formation of the (Ca, Na)-poly(sialate-siloxo) networks.

AB - The aim of this work is to investigate the influence of the amorphous calcium silicate on the microstructural, physical and mechanical properties of (Ca, Na)-poly(sialate-siloxo) networks. The calcium silicate with molar ratio CaO/SiO 2 equal to 1.0 was prepared from the precipitated silica and calcined chicken eggshell. The X-ray patterns and infrared spectra of the synthesized calcium silicate indicate that it mainly constitutes of the amorphous calcium silicate hydrate. The X-ray patterns of geopolymer cements indicate that the prepared amorphous calcium silicate hydrate does not include in the network. The compressive strengths of the geopolymer mortars decrease from 28.92 to 12.03 MPa with increasing the replacement level of metakaolin (from 0 to 25% by mass). Whereas, the values of the apparent densities increase with increasing the replacement level of metakaolin. It seems that the amorphous calcium silicate hydrate in the structure of calcium silicate affects negatively the mechanical properties of the (Ca, Na)-poly(sialate-siloxo) network. The heterogeneous structure of geopolymer mortars containing 25% of calcium silicate could be related to the higher calcium content and the amorphous structure of calcium silicate hydrate. It was typically found that in the absence of significant levels of dissolved calcium, the precursors such as silicate and aluminate condense to form (Ca, Na)-poly(sialate-siloxo) networks. This implies the homogenous structure and the higher values of the compressive strengths of geopolymer mortars containing 0, 5, 10 and 15% of calcium silicate. Whereas those from the replacement level of metakaolin by 20 or 25% of calcium silicate contain significant levels of dissolved calcium and amorphous calcium silicate hydrate in their structure which hinder the formation of the precursors and therefore impede the formation of the (Ca, Na)-poly(sialate-siloxo) networks.

KW - (Ca, Na)-poly(sialate-siloxo)

KW - Apparent density

KW - Calcium silicate

KW - Compressive strengths

KW - Hardener

KW - Metakaolin

UR - http://www.scopus.com/inward/record.url?scp=85059532162&partnerID=8YFLogxK

U2 - 10.1016/j.conbuildmat.2018.12.219

DO - 10.1016/j.conbuildmat.2018.12.219

M3 - Article

AN - SCOPUS:85059532162

VL - 201

SP - 662

EP - 675

JO - Construction and Building Materials

JF - Construction and Building Materials

SN - 0950-0618

ER -