以超微細水泥 - 奈米二氧化矽溶膠灌漿材料改良砂土之強度

Abstract

本研究旨在探討灌漿材料地盤改良領域中的應用，尤其是材料的選擇對工程性能的影響。其動機係基於傳統水泥和矽酸鈉的局限性，由於傳統水泥的濾層效應、阻塞現象以及矽酸鈉的不穩定性限制了其在改良材料上的應用。本研究提出以水泥-矽酸鈉為發展的力學材料，其係以超微細水泥－奈米二氧化矽溶膠作為新型改良材料，以提升地盤改良的效果及穩定性。 首先進行超微細水泥－奈米二氧化矽溶膠之配比試驗，包括凝固試驗、泌水試驗與黏滯度試驗，當水灰比為2時，固定加入1 %減水劑的條件下，添加5、10、15和20 % 的奈米二氧化矽溶膠；100 % 之奈米二氧化矽溶膠於配比試驗之結果顯示，提升奈米二氧化矽溶膠的含量可以有效降低凝固時間與泌水率。而製作超微細水泥時，建議採用高速攪拌器，且其攪拌轉速應超過1000 rpm，而本研究使用1500 rpm攪拌5分鐘。 在無圍壓縮強度、動態三軸與變水頭滲透之試驗中，選擇相對密度為50 % 之渥太華20－30級配標準砂作為基材，選擇三種不同的配比製成改良漿液，分別為水灰比為2，添加1 % 減水劑；同樣水灰比和減水劑含量，添加為20 %奈米二氧化矽溶膠；100 % 奈米二氧化矽溶膠加入12 % 之氯化鈉溶液使之促凝劑的漿液。於無圍壓縮強度試驗之結果顯示，超微細水泥漿液添加20 % 奈米二氧化矽溶膠在灌漿後經過28天養護，提升抗壓強度至將近3 MPa；動態三軸試驗中，含有超微細水泥之改良試體，超額孔隙水壓激發過程較為緩慢；變水頭試驗中，砂土之滲透係數為7.121×10-2 cm/sec，經改良後其滲透係數範圍降低10-6至10-7 cm/sec。總結本研究改良材料之結果，證實能改善其土壤力學性質與穩定性，顯示其在地盤改良的潛力。

This research investigates the application of a grouting improvement which focuses on the impact of grout material selection. The study addresses the limitations of traditional cement and sodium silicate grouts, such as the filtration and clogging phenomena associated with cement and the instability of sodium silicate. To overcome these challenges, the research introduces microfine cement and colloidal silica as the grouting materials. Experimental grouting materials tests, which included setting, bleeding, and viscosity tests, used a water-cement ratio equal to 2 with incremental additions of 5%, 10 %, 15 %, and 20 % colloidal silica, as well as a pure colloidal silica solution. These tests demonstrated that increasing the colloidal silica content effectively reduced setting time and bleeding rates. For optimal performance, high-speed mixing at speeds exceeding 1000 rpm is recommended; in this study, a speed of 1500 rpm was employed for a duration of five minutes. Advanced tests were also conducted using Ottawa 20-30 graded standard sand with a relative density of 50%. These tests included cyclic triaxial tests, unconfined compressive stress tests, and falling head permeability tests. The paste formulations tested were pure microfine cement, microfine cement with 20 % colloidal silica and pure colloidal silica paste. The results showed that grouts containing 20 % colloidal silica in microfine cement paste significantly increased compressive strength after 28 days of curing and decreased permeability, without inducing an increase in the pore pressure ratio, demonstrating the potential of this new grout formulation for enhancing ground improvement.