| 摘要: | 硫鋁酸鈣水泥(CSA)為一種以硫鋁酸鈣（又稱葉綠石，簡寫為C4A3S̅）、矽酸二鈣（又稱貝萊土，簡寫為C2S）及鐵鋁酸四鈣(C4AF)為主要成分組成之特殊水泥，具有早期強度發展快速、凝結時間短、流動性佳及乾縮量小等性質。因材料成本昂貴，故有研究提出將CSA與卜特蘭I型水泥(OPC)複合使用，仍具備早期強度高、凝結快等特徵，以提高經濟性。
本研究分為「OPC-CSA系統之初步工程性質探討」、「OPC-CSA系統水泥砂漿之體積穩定性與抗硫酸鹽能力研究」及「OPC-CSA系統工程性質提升策略探討」三階段。第一階段探討OPC-CSA系統之OPC/CSA佔比（1/9、2/8、3/7、5/5、7/3、8/2及9/1）對工作性質與力學性質之影響；第二階段探討OPC-CSA系統之OPC/CSA佔比（與第一階段配比相同）對體積穩定性及抗硫酸鹽能力的影響，同時進行抗硫能力短期試驗，快速分析配比劣化現象；第三階段將具潛力之OPC-CSA系統（依據前兩階段試驗成果提出），使用不同改良策略（添加矽灰、降低水膠比及高溫養護）進行工程性質改善，最終提出OPC-CSA系統的適當配比設計，並建立非破壞檢測法（反彈錘、超音波及成熟度法）與強度發展之關係。
結果顯示，OPC-CSA系統在強度方面，OPC佔比20 % ~ 50 % 時水化發展最快速，1.5小時強度可達12 MPa以上，28天強度接近60 MPa，強度發展的表現為特早強(Very Rapid Hardening, VRH)之強度表現。其中C30(OPC占比30 %)強度發展最佳，1.5小時強度可達16 MPa，28天強度達62.9 MPa；新拌性質方面，當OPC佔比20 % ~ 50 % 時，終凝時間在10分鐘內，流度低於40 %，不符合ASTM C1600規範要求，其中C30之新拌性質最差，終凝時間僅5分鐘，砂漿流度為0 %；乾燥收縮方面，OPC佔比低於50 % 時CSA可抑制OPC收縮，整體乾縮量可維持至0.02 % 以下，其中C30之收縮量最低，僅0.015 %；OPC佔比高於50 % 時整體乾縮量隨OPC佔比有明顯變化，28天乾縮量達0.047 % ~ 0.064 %，其中C70收縮量最顯著，可達0.064 %；抗硫酸鹽能力方面，OPC佔比10 % ~ 30 % 時具備良好之抗硫酸鹽能力，經168天硫酸鹽溶液浸泡，膨脹量可維持在0.030 % 以下，且無發生明顯外觀變化，其中以C30之抗硫酸鹽能力最佳，膨脹量僅0.025 %，OPC佔比為50 % ~ 90 % 時具高膨脹性特徵，經168天硫酸鹽溶液浸泡，膨脹量達0.049 % ~ 0.101 %，其中以C50之抗硫酸鹽能力最差，膨脹量為0.101 %。
根據前兩階段結果挑選C30（強度高且耐久性佳）、C50、C70（強度高但耐久性差）及C80（強度低但耐久性問題輕微）進行矽灰(SF)取代OPC、降低水膠比及高溫養護改良策略研究。使用SF取代OPC進行耐久性改良，SF取代OPC體積佔比30 % 時的改良效果最佳，C50SF30、C70SF30及C80SF30於改良後其長度皆縮短初始長度之0.01 % ~ 0.03 %，但新拌性質方面因SF使流動性及坍度損失加速，拌合後30分鐘之流動性皆為0 %。力學性質提升方面，依據強度提升成效排序，同時降低水膠比與高溫養護表現最佳，早期強度及晚期強度可分別提升58 % ~ 215 %及21 % ~ 37 %。其次為僅改變水膠比，高溫養護成效最差。配比改良後，C50SF30，水膠比為0.35且經常溫養護或經6小時40℃高溫養護皆能符合超早強水泥工程應用性配比，C50SF30，水膠比為0.35且經常溫養護之1.5小時抗壓強度達21.8 MPa，28天達73.9 MPa；C50SF30，水膠比為0.35且經6小時40℃高溫養護之1.5小時之抗壓強度達28.4 MPa，28天達75.2 MPa，且經抗硫能力短期試驗，長度變化量皆無發生膨脹且外觀無明顯變化，評級為良好。非破壞檢測以成熟度法、超音波波速法、反彈錘法評估水泥砂漿之抗壓強度關係性，R2值皆大於0.7，顯示出非破壞檢測法具良好可行性。
相比於常見抗硫酸鹽能力試驗ASTM C1012因試驗期長達一年，本研究提出抗硫能力短期試驗，透過評估長度變化量和外觀形貌，僅56天即可獲得與ASTM C1012半年試驗之相似結果，依據長度變化量與外觀形貌將耐久性評級定義為「良好」、「差」及「極差」，當耐久性評級為「差」與「極差」，表示配比之抗硫酸鹽能力差，該檢測適用於OPC佔比50 % ~ 90 % 之OPC-CSA系統。
;Calcium sulfoaluminate cement (CSA) is a special type of cement mainly composed of calcium sulfoaluminate (also known as ye′elimite, abbreviated as C4A3S̅), dicalcium silicate (also known as belite, abbreviated as C2S), and tetracalcium aluminoferrite (C4AF). It is characterized by rapid early strength development, short setting time, good fluidity, and low drying shrinkage. Due to the high cost of the materials, research has proposed using CSA in combination with Portland I type cement (OPC) to maintain features such as high early strength and fast setting while improving economic feasibility.
This research is divided into three stages: "Preliminary Study of the Engineering Properties of the OPC-CSA System," "Study on the Volume Stability and Sulfate Resistance of OPC-CSA System Cement Mortar," and "Investigation of Strategies to Improve the Engineering Properties of the OPC-CSA System." The first stage examines the effect of OPC/CSA ratios (1/9, 2/8, 3/7, 5/5, 7/3, 8/2, and 9/1) on workability and mechanical properties. The second stage investigates the impact of OPC/CSA ratios (same as the first stage) on volume stability and sulfate resistance, including short-term sulfate resistance tests for rapid analysis of deterioration phenomena. The third stage uses promising OPC-CSA systems (based on results from the first two stages) and applies different improvement strategies (adding silica fume, reducing water-to-cement ratio, and high-temperature curing) to enhance engineering properties, ultimately proposing an appropriate mix design for the OPC-CSA system and establishing the relationship between non-destructive testing methods (rebound hammer, ultrasonic, and maturity methods) and strength development.
The results indicate that the OPC-CSA system exhibits the fastest hydration development with an OPC ratio of 20% to 50%, achieving a strength of over 12 MPa in 1.5 hours and nearly 60 MPa in 28 days, demonstrating Very Rapid Hardening (VRH) performance. Among these, C30 (30% OPC) shows the best strength development, reaching 16 MPa in 1.5 hours and 62.9 MPa in 28 days. In terms of fresh properties, when the OPC ratio is 20% to 50%, the final setting time is within 10 minutes, and the flow is below 40%, not meeting ASTM C1600 specifications. Among these, C30 has the worst fresh properties, with a final setting time of only 5 minutes and mortar flow of 0%. For drying shrinkage, when the OPC ratio is below 50%, CSA can inhibit OPC shrinkage, maintaining the overall drying shrinkage below 0.02%, with C30 showing the lowest shrinkage of only 0.015%. When the OPC ratio is above 50%, the overall drying shrinkage significantly changes with the OPC ratio, reaching 0.047% to 0.064% in 28 days, with C70 showing the most significant shrinkage at 0.060%. Regarding sulfate resistance, when the OPC ratio is 10% to 30%, the system shows good sulfate resistance, with expansion maintained below 0.030% after 168 days of immersion in sulfate solution, and no significant appearance changes. Among these, C30 has the best sulfate resistance, with an expansion of only 0.025%. When the OPC ratio is 50% to 90%, the system exhibits high expansion characteristics, with expansion reaching 0.049% to 0.101% after 168 days of immersion, with C50 showing the worst sulfate resistance at 0.101%.
Based on the results of the first two stages, C30 (high strength and good durability), C50, C70 (high strength but poor durability), and C80 (low strength but minor durability issues) were selected for improvement strategy research using silica fume (SF) to replace OPC, reducing the water-to-cement ratio, and high-temperature curing. Using SF to replace OPC for durability improvement, the best effect is achieved when SF replaces 30% of the OPC volume. After improvement, C50SF30, C70SF30, and C80SF30 all show a length reduction of 0.01% to 0.03% of the initial length, but the fresh properties deteriorate due to accelerated fluidity and slump loss caused by SF, with zero fluidity 30 minutes after mixing. In terms of enhancing mechanical properties, the combination of reducing the water-to-cement ratio and high-temperature curing showed the best performance, improving early and late strength by 58% to 215% and 21% to 37%, respectively. Next was only changing the water-to-cement ratio, with high-temperature curing being the least effective. After mix improvement, C50SF30 with a water-to-cement ratio of 0.35 and cured at room temperature or for 6 hours at 40℃ meets the ultra-rapid hardening cement engineering application requirements. C50SF30 with a water-to-cement ratio of 0.35 and cured at room temperature reaches a compressive strength of 21.8 MPa in 1.5 hours and 73.9 MPa in 28 days. C50SF30 with a water-to-cement ratio of 0.35 and cured for 6 hours at 40℃ reaches a compressive strength of 28.4 MPa in 1.5 hours and 75.2 MPa in 28 days, showing no expansion and no significant appearance changes in short-term sulfate resistance tests, rated as good. Non-destructive testing using the maturity method, ultrasonic pulse velocity method, and rebound hammer method to evaluate the compressive strength of cement mortar shows R2 values greater than 0.7, indicating good feasibility of non-destructive testing methods.
Compared to the common sulfate resistance test ASTM C1012, which has a test period of up to one year, this study proposes a short-term sulfate resistance test. By evaluating length changes and appearance morphology, similar results to the ASTM C1012 six-month test can be obtained in just 56 days. Based on length changes and appearance morphology, durability ratings are defined as "good," "poor," and "very poor." When the durability rating is "poor" or "very poor," it indicates poor sulfate resistance of the mix, and this test is suitable for OPC-CSA systems with OPC ratios of 50% to 90%. |
