Effects of Naphthalene Sulfonate-type and Polycarboxylate-type Superplasticizers on the Fluidity of Belite-rich Cement Concrete

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  • 高ビーライトセメントコンクリートの流動性に及ぼすナフタレンスルホン酸系高性能減水剤およびポリカルボン酸系高性能AE減水剤の影響

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Belite-rich cement (BRC) is thought to be suitable for highly fluid concrete like self-compacting concrete. In this study, the reason why BRC is suitable for highly fluid concrete is investigated. The analysis of the fluidizing mechanisms of superplasticizers was carried out on the basis of the fluidity tests for a combination of two types of cements, normal portland cement (NPC) and BRC, and two types of superplasticizers, β-naphthalene sulfonate type (NS) and polycarboxylate type (PC).<br>　For each superplasticizer added, 0.48mass% of NS and 0.20mass% of PC, the increase to NPC's paste flow was the same. However, NS produced lower flow in BRC than in NPC, and PC produced higher flow in BRC than in NPC.<br>　The sulfate ion reduced the PC adsorption on cement particles. Therefore, PC showed higher fluidity in the paste of BRC, with lower alkaline sulfate content, than in NPC paste with higher alkaline sulfate content. In the case of NS, it was necessary to use more to achieve the same fluidity as PC because NS tended to make the specific surface area of paste larger than PC and the dispersing ability was less than PC. There was suitable sulfate content for NS, which was around 0.9mass% as Na2SO4, for a high fluidity of paste because NS sorbed onto C3A competitively with sulfonate ion. Because BRC had a lower alkaline sulfate content, 0.28mass% as Na2SO4, BRC paste with NS snowed lower fluidity than NPC paste whose alkaline sulfate content was 0.96mass% as Na2SO4.

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