Study on performance prediction of concrete damaged by secondary ettringite formation

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14802
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 22010:Civil engineering material, execution and construction management-related
• Research Institution: University of Yamanashi
• Principal Investigator: Sato Kennosuke 山梨大学, 大学院総合研究部, 助教 (20821606)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: エトリンガイト / 二次生成 / C-S-H / 硫酸塩劣化 / DEF / ASR

Outline of Final Research Achievements

The purpose of this study was to clarify the mechanism by which hydration products such as C-S-H promote secondary ettringite formation, which leads to the expansion of hardened cement paste, and to clarify the accompanying changes in the mechanical properties of hardened cement paste. The results of mixing and hydrating synthesized monosulfate with C-S-H and other substances in a sodium sulfate solution showed that ettringite was rapidly formed in the presence of C-S-H and continued to increase with the age of the cement. In addition, when DEF (delayed ettringite formation) was caused in actual hardened cement, the compressive strength decreased with increasing expansion, and it was inferred that the compressive strength decreased due to the formation of coarse pores caused by the progress of DEF expansion.

Free Research Field

セメント化学、コンクリート工学

Academic Significance and Societal Importance of the Research Achievements

エトリンガイト二次生成および、それに伴う膨張発生のメカニズムについては長年議論されてきたが、未だ未解明な点が多い。本研究は、純薬合成したセメント水和物を用いて単純化した実験を行うことによって、C-S-Hの影響およびASR生成物の影響を直接的に把握した。また、これまで実験的に評価した例が極めて少ないDEFが生じたセメント硬化体の力学性能について、その経時変化を明らかにした。これは、今後のエトリンガイト二次生成に起因する、セメント・コンクリート硬化体の膨張現象の全貌を理解し、ひいては力学特性や耐荷性能を適切に予測することにも繋がることから、本研究成果は学術的意義、社会的意義が高いと考える。