以矽酸鈉活化還原碴製作無水泥混凝土

本研究利用鹼劑將電弧爐-還原碴加以活化，依不同設計強度(fcr′)拌製無水泥混凝土；以爐石粉與還原碴完全取代水泥作為膠結材料使用，並利用矽酸鈉為鹼劑活化其膠結性質，骨材則採用煉鋼過程之副產物氧化碴石及氧化碴砂來拌製不使用天然材料之綠色環保混凝土。研究流程首先進行爐石粉、還原碴、氧化碴砂及氧化碴石的基本物、化性質試驗分析，比較傳統純水泥(OPCC)及完全使用爐石粉(100S)與還原碴取代20%爐石粉(20RS)之三種不同膠結材料之配比，設計28天齡期分別為140、175及210 kgf/cm^2之三種目標強度混凝土，進行坍度、抗壓、質量成長等試驗。試驗結果顯示所有組別皆能達到所設計三種抗壓強度，且應用還原碴和爐石粉的組別在7及28天齡期之抗壓強度就和純水泥組近似或高，而56天齡期即可比純水泥組高，最高可比OPCC組增加達28%，且使用鹼劑活化還原碴，可有效降低膨脹率，還原碴取代20%爐石粉組比純水泥組降低膨脹率約14%。

關鍵字

還原碴粉末；鹼活化；矽酸鈉；混凝土

並列摘要

This study used alkali-activated reduced electric arc furnace (EAF) slag, a byproduct of steelmaking, to prepare cement-free concrete of various designed strengths, in which granulated blast furnace (BF) slag and reduced EAF slag fully replaced cement as cementing materials. Sodium silicate was used as the alkali agent to activate the cementing properties of the alternative materials. The aggregate was prepared by mixing granulated and ground oxidized EAF slag, which are also byproducts of steelmaking. Environmentally friendly concrete consisting fully of steelmaking byproducts and no natural materials was thereby produced. In the research process, the basic physical and chemical properties of granulated BF slag, reduced EAF slag, and granulated and ground oxidized EAF slag were first tested and analyzed. In accordance with the different mixture designs of the three cementing materials, three types of concrete with different target strengths (140, 175, and 210 kgf/cm^2) and an age of 28 days were designed, namely conventional cement, a new type of cement composed entirely of granulated BF slag, and a new type of cement in which 20% of BF slag powder was replaced by EAF slag. Based on the Chinese National Standards, the slump, compressive strength, and mass growth of these three types of concrete were measured and compared. The results showed that both new types attained the designed compressive strengths without cement. Measurements of the new concrete types with reduced EAF slag and granulated BF slag approximated or exceeded those of pure cement at ages of 7 and 28 days, respectively. All measurements of the new types surpassed those of pure cement at 56 days by a maximum of 28%. In addition, the type containing alkali-activated reduced EAF slag exhibited a significantly lower coefficient of expansion. Specifically, the concrete in which 20% of BF slag powder was replaced by reduced EAF slag attained a coefficient of expansion approximately14% lower than that of the concrete with pure cement.