セメント系材料の水理・力学特性の変遷に関する研究(III); 概要

Study on the Alteration of Hydrogeological and Mechanical Properties of the Cementitious Material (III); Summary Report

武井 明彦*; 藤田 英樹*; 原澤 修一*

Takei, Akihiko*; Fujita, Hideki*; Harasawa, Shuichi*

処分環境におけるセメント系材料の長期変遷挙動を評価した。1) セメント系材料に対する海水系地下水の影響に関する検討 模擬海水による通水劣化試験を実施し,イオン交換水を通水したブランク試験と比較することで,化学的性質の変化と水理特性および力学特性の変化に及ぼす海水成分の影響を評価した。2) 硬化セメントペーストで取得したデータのモルタル・コンクリートへの拡張 これまで劣化試験に用いてきたペーストに加え,コンクリートおよびモルタルにおいても,同条件で透水係数や力学特性といったデータを取得し,これらの関係を求めた。3) セメント系材料のひび割れ自己修復性の検討 模擬ひび割れを導入したセメント試料に重炭酸イオン成分を含む溶液を通水することで,地下水成分とセメント成分の反応による,ひび割れの自己修復の可能性を検討した。④ セメント系材料の変遷に対するアンモニアの影響に関する検討 アンモニアおよび硝酸ナトリウムが初期に共存した場合のセメント系材料へのより長期的な影響を評価した。また,硝酸ナトリウム-アンモニア混合系の通水試験に供したものと同様のセメント試料に対して,硝酸ナトリウム水溶液のみの通水を実施し,透水係数の変化とともにその絶対値を求め比較することで,アンモニアの影響を検討した。

We experimentally investigated the influence of several phenomena at the disposal environment, to evaluate the long-term alteration of cementitious material. The results are shown below. (1)Hardened cement paste specimens were altered and characterized after artificial seawater permeation. The calcium dissolution was accelerated, and secondary minerals containing magnesium were deposited. The permeability became one to three orders of magnitude smaller than data from specimens altered by deionized water permeation. It was estimated that secondary mineral formations reduced the permeability. These results meant that seawater and pure water differ remarkably from each other in influence to alteration of cementitious material. (2)Two type mixture proportions concrete, two type mixture proportions mortar and a cement paste under same W/C ratio 55% were characterized, to apply the accumulated data of paste to concrete or mortar. Compressive strength of paste was lower than that of concrete and mortar. It was contrary to the previous report. The behavior of Young's modulus and Poisson's ratio could be explained well using amount of aggregate. The data of permeability meant that boundary between aggregate and cement paste didn't become path of water flow, and that aggregate disturbed permeation. (3)Self-sealing property of cracked specimen of cementitious material were investigated by the water permeation test using sodium bicarbonate solution. The permeability decreased in two orders of magnitude, and possibility of sealing was suggested. By the morphology, the deposits in the cracks might be portlandite and C-S-H, and be not calcium carbonate. (4)Alteration of characteristics of cementitious material in sodium-nitrate and ammonia solution was evaluated by the water permeation test. Alteration degree of the nitrate and ammonia solution case showed similar trend to that of the sodium nitrate solution case. This result meant that ammonia solution would not ...