以TFT-LCD廢玻璃混合轉爐石燒製之輕質骨材拌製輕質混凝土研究

Abstract

本研究以TFT-LCD廢素玻璃混合轉爐石經旋窯燒製結構用輕質骨材，依不同的水灰比拌製結構用輕質混凝土，在不同的養護齡期做抗壓強度測試，建立輕質混凝土水灰比與強度之關係。並根據不同水灰比、齡期之試體抗壓試驗結果進行分界強度(Dividing Strength)分析，以探討輕質混凝土的力學變化情形。最後進行骨材與水泥砂漿交界處之微結構分析，研究本實驗製作之結構用輕質骨材與水泥砂漿相互作用情形及交界處對混凝土強度的影響。 試驗結果顯示，本實驗製作之結構用輕質骨材混凝土，在水灰比0.7、0.5與0.3時，28天抗壓強度分別為26.95、43.78與49.89 MPa，且在水灰比0.3時，將達到輕質混凝土之極限強度約50 MPa。當水灰比較高且養護齡期較短時，輕質混凝土之強度取決於界面過渡區之結構強度。界面過渡區之寬度隨養護齡期增加而縮小，惟在養護齡期固定時，隨水灰比增加而變寬。當水灰比由0.7減至0.3時，水泥砂漿強度與界面強度皆增高，故脆弱面由界面過渡區轉至骨材，使得輕質骨材強度之影響將趨於顯著。 以TFT-LCD廢素玻璃混合轉爐石所製造之輕質混凝土，其密度及抗壓強度皆符合ASTM對結構輕質混凝土之規範，而混凝土密度主要取決於骨材本身的密度而水灰比及養護齡期則影響不大。輕質混凝土於水灰比0.3時，其分界強度為48.79 MPa，故混凝土的設計強度小於48.79 MPa時，單位水泥用量對混凝土強度貢獻較高，屬較環保及經濟之設計，且輕質混凝土之結構效率因子皆優於常重混凝土而具有商轉之市場競爭力。 綜上所述，本研究以TFT-LCD廢素玻璃混合轉爐石所製造之輕質骨材，其機械性能優良，在混凝土設計強度50 MPa以內皆適合作為結構用輕質混凝土之骨材使用。

In present study, lightweight aggregate (LWA) was produced by a mixture of thin-film transistor liquid-crystal display (TFT-LCD) waste glass, basic oxygen furnace (BOF) slag using a rotary kiln. The resulted lightweight aggregate was used to prepare lightweight concrete in different water to cement ratios. Compressive strength analyses at different curing ages were carried out to study the effects of W/C on compressive strength. In addition, to understand transformation of stress distribution in the lightweight concrete under compressive strength test at different curing ages, a linear regression analysis was performed to find out dividing strength. Finally, interaction between mortar and aggregate and its effect on compressive strength of concrete were identified by observing the interfacial transition zone (ITZ) of the microstructure. The results indicate that compressive strength of the lightweight concrete were 26.95 MPa (W/C=0.7)、43.78 MPa (W/C=0.5) and 49.89 MPa (W/C=0.3) at 28 days. When the w/c ratio was 0.3, lightweight concrete reaches its ceiling strength which was 50 MPa. The strength of lightweight concrete depended on the structure of ITZ at a high W/C and early curing age. But the lightweight concrete strength may turn to depends on coarse aggregate strength because the strength of mortar and ITZ can increases with increasing curing ages and reducing W/C. Concrete density primarily depended on the aggregate density. All of the investigated lightweight concrete densities in present work were below 1800 kg/m3. Both density and compressive strength met ASTM C330 (standard specification for lightweight aggregate for structural concrete). The dividing strength of the lightweight concrete is 48.79 MPa. According to the concept of dividing strength, the designed compressive strength of concrete should be smaller than its dividing strength. It ensures that the use of amounts of cement would be more economic. Structural efficiency factor of the lightweight concrete was higher than the normal weight concrete even though the w/c ratio was low. According to above discussions, lightweight aggregate which was made of TFT-LCD waste glass and basic oxygen slag has good mechanical behavior. The good compressive strength of lightweight concrete gave it potential for application in structural lightweight aggregate. It would be a good structural lightweight aggregate when designed concrete strength was below 50 MPa.