焚化底渣/氟化鈣污泥熔渣混凝土耐久性之研究

Abstract

本研究採熔融技術，將垃圾焚化底渣與氟化鈣污泥進行共同熔融處理，並將水冷所得之熔渣作為取代水泥之摻料，探討熔渣本身之卜作嵐性質及其對混凝土之耐久性影響。本實驗總共分成三階段，第一階段為尋求焚化底渣與氟化鈣污泥共同熔融之最低熔流溫度；第二階段為水冷熔渣之基本性質分析；第三階段則是將熔渣粉體取代部分水泥後，利用各種試驗，如抗壓試驗、超音波速試驗、電阻係數試驗、快速氯離子滲透試驗(RCPT)、鋼筋銹蝕試驗及XRD、MIP、SEM等分析，探討其對熔渣混凝土耐久性之影響。 實驗結果顯示，當焚化底渣/氟化鈣污泥配比為7：3時，CaO/SiO2約為1.4時，具有最低之熔流溫度1081℃，此配比經熔融水淬後所得之熔渣為非晶質，比重約3.15，成分為與C級飛灰接近之卜作嵐材料。將熔渣依不同水泥取代率添加至水泥砂漿中，經由抗壓試驗及燒失量、MIP及SEM分析結果，顯示養護齡期之晚期具卜作嵐作用之效應，水泥取代率可由3%至20%。但由熔渣混凝土耐久性加以評估，綜合超音波速、電阻係數及RCPT等試驗結果則顯示最適水泥取代率宜為3%，此取代率將有助於增加混凝土內部的緻密性，使耐久性提高。以電阻係數評估熔渣混凝土之耐久性，本研究顯示養護齡期對熔渣混凝土之影響遠大於水泥取代率。由氯離子滲透試驗結果顯示，水泥取代率與電荷通過量之關係有一明顯折點，此折點可做為選擇最適取代率之指標。另外，由鋼筋銹蝕試驗亦發現，熔渣會與侵入氯離子形成佛來第鹽類，具有抑制氯離子移動之防蝕濳力。

The purpose of this research was to study the effects of co-melting slags produced from municipal solid waste incinerator bottom ash and industrial calcium fluoride sludge on pozzolanic reaction and durability in cement-based composites materials. The co-melting slag was water-quenched with room temperature. Experiments were conducted to (1) determine the lowest pouring temperature of co-melting ash and sludge at different proportions. (2) analyze the physical and chemical characteristics of the pulverized slag, such as specific gravity, particle size, chemical composition, TCLP, XRD patterns and strength activity index (SAI). (3) incorporate the slag as mineral admixtures in the cement-based composites materials in place of a fraction of the cement, and evaluate the influence of the replacement ratio on performance of the cement-based composites materials in terms of setting times, compressive strengths, electrical resisitivity, the rapid chloride penetration test (RCPT) , etc. The results showed that the lowest pouring temperature was 1081℃ when the co-melting ash and sludge were in the ratio of 7:3. The molten slag was then water-cooled and examined its properties. It was observed that the water-quenched slag was amorphous and had a specific gravity of 3.15 which was close to Class C fly ash. The results of compressive strength, degree of hydration, MIP and SEM indicated that the slag was a latent pozzolans and it could replace 3% to 20% cement in mortar. It was also observed that 3% replacement of cement with slag would enhance concrete properties with denser microstructure based on pulse velocity, resisitivity and RCPT results. Furthermore, resisitivity test results showed that the influence of curing time on concrete durability is more important than that of cement replacement on concrete duability. The relationship between cement replacement and cumulative charges from RCPT results shows that there existed a critical point which could be employed as the indicator for choosing a suitable replacement ratio. In addition, the aluminate phase of the slag could bind chlorides to form Fredel’s salt resulting from reinforced concrete corrosion test. It implied that blending cement with slag would decrease the diffusivity of chloride in the concrete and improve its durability.