| 摘要: | 對於設計適用於剛性路面維護應用的現場混凝土，文獻回顧指出，
混凝土應採用早強劑並在適當溫度下固化。加速劑通過影響水泥材料與水 之間的反應速度，提高水化速率。因此，在水泥漿、灰漿和混凝土中使用 加速劑可以減少凝結時間和/或提高早期強度發展。此外，固化溫度對混凝 土的早期抗壓強度發展有顯著影響。
因此，為了找到適合於現場混凝土廠使用的早強水泥材料的適當劑 型和固化方法，本研究論文提供了商業加速劑的歷史和技術概述，以及它 們對水泥水化加速的機制和目前的商業加速劑特性。研究結果表明，使用 凝結加速劑和硬化加速劑的組合比單一類化學品更有效。在早期抗壓強度 的最佳組合是 2.0% KBr、1.0% Ca(HCOO)2 和 0.05% TIPA，在 23°C 固化 8 小時後達到 33.8 MPa 的抗壓強度，符合剛性路面維護要求。因此，在台灣 氣溫超過 23°C 時，我們可以使用 2.0% KBr、1.0% Ca(HCOO)2 和 0.05% TIPA 的加速劑組合進行剛性路面維護。然而，在冬季氣溫下降時，需要進 行詳細的實驗，以評估低於 23°C 溫度下混凝土早期抗壓強度的發展。此外， 本論文還指出，在台灣低於 23°C 的天氣日，使用熱固化方法(固化方法 50C)可以確保所需的抗壓強度。熱固化方法顯著提高了早期抗壓強度，但不影響灰漿試件的乾縮、吸水率、長期抗壓強度和氯離子滲透性。然而， 加速劑組合的使用減少了灰漿試件的氯離子滲透性，同時增加了乾縮問題， 這可能會降低對化學襲擊的抵抗力，並在惡劣條件下影響耐久性。
本論文還應用非破壞性方法來評估混凝土的早期抗壓強度，如超聲 波脈沖速度(UPV)測試、反彈錘測試和成熟度法。結果顯示，反彈錘測 試和 UPV 測試能夠預測混凝土的早期抗壓強度。然而，在施工現場使用熱 固化方法時，反彈錘測試的準確性降低，可能不適合。成熟度法在預測混 凝土早期抗壓強度方面表現良好，具有高準確性和高效應用(易於操作， 抗壓強度偏差小於 8%)，即使在使用或不使用早強劑組合時，它仍能在 不同環境溫度下保持可靠。;To design a suitable ready-mixed concrete for rigid pavement maintenance applications, the literature review indicates that concrete should be mixed with early strength accelerators and cured at an appropriate temperature. Accelerating admixtures improve the hydration rate by affecting the reaction speed between cementitious materials and water. As a result, using accelerators in cement paste, mortar, and concrete can reduce setting time and/or improve early strength development. Additionally, curing temperature can significantly affect the early-age compressive strength development of concrete.
Hence, aiming to find suitable admixtures and curing methods for high early strength for cementitious materials used in ready-mix plants, this research dissertation provides a historical and technical overview of commercial accelerators, as well as their mechanism for cement hydration acceleration and current commercial accelerator characteristics. The results found that the use of a combination of setting accelerators and hardening accelerators is more effective than using a single type of chemical. The optimal combination for early age
compressive strength is 2.0% KBr, 1.0% Ca(HCOO)2, and 0.05% TIPA, achieving compressive strengths of 33.8 MPa after 8 hours of curing at 23°C, which meets rigid pavement maintenance requirements. Therefore, we can use the accelerator combination with the ratios 2.0% KBr, 1.0% Ca(HCOO)2, and 0.05% TIPA for rigid pavement maintenance during times when the temperature exceeds 23°C. However, in winter when temperatures drop, detailed experiments are needed to assess the early compressive strength development of concrete at temperatures below 23°C. Additionally, this dissertation also indicates that using a heat curing method (curing method 50C) can be a way to ensure the required compressive strength during days when Taiwan’s temperature is below 23°C. The use of heat curing significantly enhances early age compressive strength without affecting the drying shrinkage, water absorption, long-term compressive strength, and chloride permeability of mortar specimens. However, the use of accelerator combinations reduces chloride permeability while increasing the drying shrinkage of the mortar specimens. These issues may decrease resistance to chemical attacks and impact durability in harsh conditions.
This dissertation also applies nondestructive methods to evaluate the early compressive strength of concrete, such as the UPV (Ultrasonic Pulse Velocity) test, rebound hammer test, and Maturity method. The results show that the rebound hammer test and UPV test have the capability to predict the early compressive strength of concrete. However, the accuracy of rebound hammer test reduced and may not be suitable for applications using the heat curing method in the construction site. The Maturity method proves effective in predicting the early compressive strength of concrete on-site with high accuracy and efficient application (easy and achieves less than 8% compressive strength deviation) even when using or not using early strength accelerator combination, and it remains reliable under varying environmental temperatures. |
