爐石海砂混凝土工程性質研究

Abstract

在國內砂石來源匱乏之際，向廣大海洋尋找可供利用的砂石資源為一重要方向。以海砂作 為細骨材，具有粒形良好的優點，且在相同水灰比下，海砂與河砂的抗壓強度相差不多； 在水泥的使用量上，細度模數1.1以上的各種海砂與河砂均大致相同。而爐石具有優異的 後續強度發展性，低水合熱，提升混凝土的耐久性、化學抵抗性，故嘗試以海砂作為細骨 材、爐石取代部分水泥，試驗其各項工程性質。本研究以除鹽的桃園觀音海砂及中鋼生產 的爐石粉為材料，固定絕對細骨材率為0.4及坍度為15公分，變動水膠比(0.5、0.6、0. 7 、0.8)及爐石粉取代量(0%、20%、30%、40%、50%、60%)以瞭解其各項工程性質。經研究 發現：添加爐石後，拌合用水量皆明顯下降。同水膠比者，取代量越多，用水量越少，但 相差並不大。在相同取代量下，隨著水膠比的提升，爐石水化所需時間亦延長，對含爐石 者的強度判定齡期應予延長。對強度而言，最佳取代量有隨水膠比增高而增高的現象，水 膠比0.5、取代量20%，水膠比0.6、取代量30%，水膠比0.7、取代量30%及水膠比0.8、取 代量40%為各組的最佳強度，在經濟性的分析中亦有相同的結論。依強度增加速率來看， 取代量越多、水膠比越高，強度增加率越大(60%除外)。取代量60%在各種水膠比及齡期表 現皆不佳。使用爐石具有延緩凝結的效果且對於抗硫酸鹽有隨取代量的增加而增加的情形 。 Based upon the exhausted usage of river sand gradually in Taiwan and tremendou s coverage of offshore sand because of Taiwan geography condition. It is impor tant to find out usable materials to replace river sand. The benefits to utili ze washed offshore sand to be fine aggregates are well particle shape, less di fference compressive strength at the same W/C ratio, and almost same amounts o f cement with fineness modulus over 1.1 compared with river sand. The advantag es of slag are excellent subsequent strength development, low heat-liberation, high durability and chemical resistibility of concrete. As these reasons, the purpose of the paper is to use offshore sand as fine aggregates and replace p art of cement with slag to study the properties of engineering.This research u sed the washed offshore sand from Taoyuan to be fine aggregates and the slag p roduced by Chinese Steel Company as materials. By fixing the S/A ratio as 0.4 and the slump as 15 cm, we changed the W/C ratio from 0.5 to 0.8 and the subst itution of slag from 0% to 60%. We found out that the amount of water per cubi c meter decreased after adding slag, that is, at the same W/C ratio, more subs titution of slag, less usage of water. On the other side, at the same substitu tion of slag, the one with higher W/C ratio, the longer hydrated time was need ed. So, we should prolong the age of concrete for estimating its compressive s trength. As strength was concerned, the optimum substitution of slag was incre ased as the W/C ratio increased. The maximum strength of each W/C ratio is : t he substitution is 20% while W/C ratio is 0.5; the substitution is 30% while W /C ratio is 0.6 and 0.7; the substitution is 40% while W/C ratio is 0.8. Also, we got the same results in analysis the economic benefits. However, except th e substitution as 60%, the larger rate of strength increased with higher W/C r atio and more substitution of slag. The properties of the substitution as 60% were poor within different kinds of W/C ratio and different ages. By the way, we got longer setting time and higher resistibility of sulfate attack on concr ete when adding slag.