| 摘要: | 本研究為探討環境溫度對於預拌型超早強混凝土用於剛性鋪面的影響，並擬定對低溫環境可供強度穩定發展之策略。本研究依據現地作業模式制定模擬運輸的流程，初步試驗以砂漿試驗方式，探討各水泥用量以及不同水灰比的配比與溫度之相關性，主要試驗以混凝土測試熱養護策略對於提供低溫環境強度發展的有效性，以及建立成熟度與早期強度之相關性，並以現地試鋪驗證熱養護之成效，現地驗收方式採用反彈錘試驗法，並輔助以成熟度建立之相關性進行驗證，現地驗收對早強效果要求為4-6小時達到目標強度210 kgf/cm2。
在初步試驗以水泥用量500及600 kg/m3及水灰比為0.27、0.29、0.31設計配比，並在23、32、50°C環境溫度養護。結果顯示，抗壓強度隨者水灰比增加而降低，並以23°C環境溫度之抗壓強度為基準值，相同配比的養護溫度由23°C提升至32°C可增加約35%的強度增長，由23°C提升至50°C可增加約55%的強度增長。養護溫度對0.27水灰比的強度增長較少。反之，在0.31水灰比時，養護溫度增長使強度增長趨勢則更為明顯，可推測養護溫度對高水灰比的影響較高。抗壓強度及成熟度與齡期呈現正比關係，但不同水泥用量及水灰比的趨勢略有不同，可推測為水泥漿體的組成不同，使組間成熟度與抗壓強度增長趨勢不同。
在主要試驗以500kg/m3水泥用量及0.31水灰比之配比進行試驗，結果顯示環境溫度在26°C至32°C對混凝土的坍度及坍流度無明顯差異，坍度均可在22±2cm，但隨著溫度增加會增加新拌料黏稠度，需控制運輸過程中混凝土溫度的過度增加；拌和10分鐘及50分鐘時的坍度及坍流度均可符合現場施作之工作性需求。減少細粒料含泥量，將可減少配比用水量及增加抗壓強度。在強度發展方面，可發現溫度為影響早期強度之主要因素，當環境平均溫度達32℃時，4小時之抗壓強度可達目標強度210 kgf/cm2；當環境平均溫度達26℃時，6小時抗壓強度可達目標強度210 kgf/cm2；當環境平均溫度不足26℃時，熱養護為有效提供強度發展之策略，以連續澆熱水及覆蓋電熱毯的方式可提供較穩定的熱能，同時防止熱量散失。並且在使用熱養護情況下，成熟度依舊可良好推估抗壓強度，可作為現地早期強度的評估方式，或輔助反彈錘試驗法驗證抗壓強度之正確性。
現地成效方面，現地環境溫度為20°C並使用50°C熱水養護，分別以成熟度法以及反彈錘試驗法進行成效驗收，兩者均可在5小時達到目標強度210 kgf/cm2，符合對超早強條件的需求，並且最大誤差約為9%，可符合施工綱要規範要求誤差，並且出場及現場工作性均可符合施工需求。經由現地實驗可驗證，熱養護為有效穩定強度增長的策略，並且成熟度法可做為輔助驗收強度的方法。;This study is about the effect of temperature on the use of ready-mixed ultra-early-strength concrete for rigid pavement, and a strategy to stabilize the strength improvement in a low-temperature environment is drawn up. The experiment will formulate a process based on on-site work. The preliminary tests will use mortar to explore the relationship between the amount of cement and the water-cement ratio and temperature. The main experiment will use concrete to test the effectiveness of thermal curing strategies in providing strength development in low-temperature environments, and to find the correlation between maturity and early strength, and verify the performance of thermal curing by field work. According to the experimental results, the performance of on-site work was verified. The performance of on-site work was tested by rebound hammer and maturity. The target strength for on-site acceptance was set at 210 kgf/cm2.
In preliminary tests, it is found that the compressive strength decreases as the water-cement ratio increases, and the compressive strength increases as the curing temperature rises, but the curing temperature has less influence on the low water-cement ratio.Conversely, when the water-cement ratio is higher, the increase in curing temperature will increase the strength more significantly. Compressive strength and maturity have a positive relationship with age, but cement content and water-cement ratio will affect the growth rate of strength. It can be inferred that the composition of cement paste is different, which reduces the correlation between different groups.
In the main test, the mixing design is tested with a cement content of 500kg/m3 and a water-cement ratio of 0.31. It can be found that there is no significant difference in the slump and slump fluidity of concrete between 26°C and 32°C. In the compressive strength, it can be found that temperature is the main factor affecting the early strength. When the ambient temperature is 32℃, the compressive strength of 4 hours can have the target strength of 210 kgf/cm2; When the ambient temperature is 26℃, the compressive strength for 6 hours of age has the target strength of 210 kgf/cm2. When the ambient temperature is less than 26°C, thermal curing is an effective strategy to provide early strength development. Hot water curing can provide a stable heat source while preventing heat loss. And in the case of using thermal curing, the maturity can evaluate the compressive strength well, and verify the correctness of the compressive strength of the rebound hammer test. |
