爐石水泥改良高嶺土之強度特性

Strength Properties of Slag Cement Stabilized Kaolinite

洪晨瑋(Chen-Wei Hung)

指導教授 ： 葛宇甯

國立臺灣大學/工學院/土木工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201603021

摘要

軟弱黏土的低強度與高壓縮性造成應用上很大的困難，工程上通常透過水泥遇水而進行的水化作用，以及其與黏土之間發生的卜特蘭作用之固化產物，填充土壤間的孔隙，取代孔隙間原本存在的水或是空氣，抑或提供膠結性，黏結土壤顆粒，增加整體土體的強度、勁度與耐久性，減少可壓縮性與滲透性，其中強度的增加為本研究主要探討的現象。由於環保意識的提升以及經濟成本的掌控，近年來開始使用工業廢棄物(例如：爐石、飛灰等)取代部分水泥用量，可得到相似的結果，且進一步降低結構體的重量，達到輕量化的效果，此些取代物同時也能降低水化熱，減少溫度裂縫生成的機會。
本研究主要透過一系列的無圍壓縮試驗，探討高嶺土在不同爐石水泥含量，以及不同含水量的情況下，對強度的影響程度。選取5種不同的水泥含量，C/S ratio = 15%、20%、25%、50%、75%，分別搭配3種含水量，ωi = 1.8LL、2.0LL、2.2LL，以及5種養護天數，curing time = 3、7、14、28、56天，進行配比調配。C/S ratio為乾水泥與乾黏土的重量比，當C/S ratio越大，即表示在相同黏土重量下之水泥含量越多；含水量部分則以高嶺土的液限做為參考指標，以其液限的1.8倍、2倍與2.2倍的高含水量情況，模擬軟弱黏土的狀況。而文獻中極少提到試體品質的控制，本研究針對試體品質也做了討論，並以單位重做為試體品質衡量的準則，認為當單位重誤差越大，單位重越小，代表試體內部大部分氣泡尚未排除，可能有低估材料強度的疑慮，實驗數據不夠可信。
實驗結果顯示，材料強度會隨著養護天數增加而隨之成長，而高爐石水泥含量的試體，其強度成長趨勢又比其他配比更明顯。不僅是材料強度會增加，其勁度也會隨著爐石水泥含量增加而更大。因此，爐石水泥可謂是一種有效的、具有經濟性的，且對環境保護有貢獻的一種良好的地盤改良材料。

關鍵字

爐石水泥改良高嶺土 ； 無圍壓縮試驗 ； 品質控制 ； 單位重 ； 無圍壓縮強度

並列摘要

Due to low strength and high compressibility, soft clay should be improved to increase its strength, stiffness and durability, and decrease the permeability and the ground settlement for a better construction condition. Nowadays the sustainability is much more important, so recycled materials such as fly ash and slag have been widely used in soft ground improvement. Through replacing part of the cement, the slag-cement material could provide a lighter weight and lower hydration heat. In this research, the soft clay defined as kaolinite with high water content was mixed with slag-cement.
In this thesis, a series of unconfined compression tests were carried out on the slag-cement stabilized clay. The specimens were prepared under three different initial water contents, ωi = 1.8LL, 2.0LL, 2.2LL, and five different cement content, C/S = 15%, 20%, 25%, 50%, 75%. All specimens were stored in a saturated environment to be cured for 3, 7, 14, 28, and 56 days before testing.
The variation of the unit weight could be controlled within 1.5%, and the variation of the duplicated tests was also compared in this research. Therefore, the quality control of the specimens could be understood clearly.
The results showed that the unconfined compressive strength increases when the curing time increases. It also indicated that the higher the slag-cement content, the greater strength and stiffness of the improved clay. Based on the test results, slag-cement is an effective, economic and environment friendly additive for soft ground improvement.

並列關鍵字

slag-cement stabilized clay ； unconfined compression test ； quality control ； unit weight ； unconfined compressive strength

參考文獻

Ali, F. H., Adnan, A., & Choy, C. K. (1992). Geotechnical properties of a chemically stabilized soil from Malaysia with rice husk ash as an additive. Geotechnical & Geological Engineering, 10(2), 117-134.

ASTM D4318-10 (2010). Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils, ASTM International, West Conshohocken, PA, www.astm.org

ASTM D2487-11 (2011). Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), ASTM International, West Conshohocken, PA, www.astm.org

ASTM D2166 / D2166M-13 (2013). Standard Test Method for Unconfined Compressive Strength of Cohesive Soil, ASTM International, West Conshohocken, PA, www.astm.org

ASTM C191-13 (2013). Standard Test Methods for Time of Setting of Hydraulic Cement by Vicat Needle, ASTM International, West Conshohocken, PA, www.astm.org