エトリンガイトの生成量および生成起源が長期間硫酸塩に浸漬した高炉セメント系材料の耐硫酸塩性に及ぼす影響

Abstract

Sulfate attack is known as one of the deterioration phenomena of concrete structures. Sulfates react chemically with hydration products of cement pastes and lead expansion or weakening of cement matrix. Deterioration cases of this phenomenon have been reported in a variety of environments all over the world. However, most of studies about sulfate resistance of hardened cementitious materials were mainly considered at 23℃ in Na₂SO₄ solution immersion. Thus, this study was conducted to investigate the effect of sulfate species (Na₂SO₄ and MgSO₄) and high temperature (40℃) on the mechanisms of sulfate attack of cementitious materials containing Ordinary Portland Cement (OPC) with Blast Furnace Slag (BFS), Anhydrite (AH) and Limestone Powder (LSP), and to evaluate the expansion characteristics of specimens immersed sulfate solutions considering “Amount of ettringite”, “Ettringite generation rate” and “Ettringite generation origin”. From the results of sulfate immersion test, the expansion was caused due to Na₂SO₄, however not only expansion but also mass decrease were caused due to MgSO₄. This was considered that hydration products in each sulfate solution were different because of pH differences of sulfate solutions were occurred by the difference of sulfate species. And the expansion characteristics of the specimens were not evaluated by only simple amount of ettringite, however it became able to evaluate considering the ettringite generation rate and ettringite generation origin. In addition, the paste specimen of 70% BFS-cement with 10% AH and 10% LSP (BFS 59.5%-OPC 25.5%-AH 10%-LSP 10%) was proposed a material design against sulfate attack. 本研究は、普通ポルトランドセメントに高炉スラグ微粉末-無水せっこう-石灰石微粉末を用いた高炉セメント系材料について、硫酸塩種および温度条件が硫酸塩劣化機構に及ぼす影響を明らかにすること、さらにエトリンガイトの生成量、生成速度および生成起源に着目して検討することにより、膨張性状の評価を行うことを目的とした。その結果、硫酸塩種によって溶液のpHに差が生じ、水和生成物が変化することで劣化形態が異なるものと考察した。また、単純なエトリンガイト生成量だけでは膨張性状を評価できなかったが、単位週当りのエトリンガイト生成量や、特に生成起源別エトリンガイト量を考慮することによって、膨張性状評価が可能となることが示唆された。