本研究由材料觀點針對透水性鋪面滲透係數、熱學性質、入滲及保水等性能進行綜合評估分析與探討；於實驗室先行針對面層材料熱學性質、滲透性能之量測分析其基本性質，並藉由現地透水性鋪面施作案例，量測實際鋪面熱行為及保水量，並以統計分析方法評估其性能。 由實驗室量測之結果，傳統密級配瀝青混凝土熱傳導係數約1.3~1.8W/mK，而多孔隙瀝青混凝土量測結果由於孔隙率增加至20%，使得熱傳導係數降低至0.4~0.9 W/mK，但多孔隙瀝青混凝土與密級配瀝青混凝土皆由相同材料組成，孔隙的增加使熱容量降低、表面積增加，當獲得熱能時，溫度會有迅速升高之情形，於實驗室模擬及現地量測之結果顯示，多孔隙瀝青混凝土表面溫度較密級配瀝青混凝土高約4~6℃，由於多孔隙瀝青混凝土熱傳導係數低，其熱容量亦較低，因此白天吸收的熱能量較少，夜晚平均熱輸出量亦較密級配瀝青混凝土少，於鋪面下方4公分夜晚溫度較密級配瀝青混凝土約低1℃。 面層多孔隙瀝青混凝土材料之滲透係數，車轍試體滲透係數高於馬歇爾試體約10~40%，顯示尺寸大小或壓實方式對滲透係數有所影響，而模擬坡度10%對滲透係數之影響最大約減少10%的滲透能力；本研究中提出以鋪面材料基本性質包括各層厚度、孔隙率、滲透係數及鋪面各層中最低之滲透係數，並利用區域降雨強度公式，可使工程師利用簡易計算方式概估保水量及延緩表面逕流時間；利用實驗區模擬降雨進行保水量簡易計算公式驗證，總雨量、降雨延時及保水量，與簡易公式計算結果較符合。 實驗區透水瀝青混凝土鋪面歷經9年使用後進行鋪面更新，並於更新過程中針對鋪面各層滲透係數進行量測，結果顯示於面層下方各層滲透係數與初始鋪設之狀態並無太大差異，僅於面層產生孔隙阻塞現象，針對鋪面更新前之面層孔隙率，利用電腦斷層掃瞄分析結果顯示，孔隙阻塞約於表面至下方20mm，最低空隙率降至3%，使原始滲透係數2.2*10-1cm/sec降低至1.2*10-3cm/sec；針對鋪面更新前、後之面層多孔隙瀝青混凝土以電腦斷層掃瞄進行孔隙分布分析，發現滾壓可能造成表面至深度20mm孔隙率降低約4%之現象。 由於面層之滲透能力與排除降雨量有直接關係，而且鋪面各層中最低之滲透係數影響長期的直接滲透保水量，因此影響透水性鋪面滲透及保水能力主要因素為面層滲透係數及鋪面各層中最低之滲透係數。 The objective of this study was to assess the permeability and the thermal conductivity in porous asphalt concrete. PACs mixed in the laboratory and paved on the test section were evaluated. The thermal conductivity performed in the laboratory in PAC with 20% of porosity in comparison with parallel dense-graded asphalt concrete were 0.4-0.9 W/mK and 1.3-1.8 W/mK, respectively the temperature profile performed in the laboratory and field show a similar trend that the temperature in the surface portion of PAC was 4-6℃ higher than that of DGAC. This can attribute that the higher porosity in PAC was reducing the capacity of heat transfer across materials and thus the heat was accumulating on the surface of pavement structure. The field data also show that the temperature in 4cm underneath the surface in PAC was 1℃ lower than that of DGAC. It has to be noted that both PAC and DGAC were designed and mixed with same sources of aggregates and binder. The permeability performed in the laboratory between Marshall compacted and wheel track specimens were evaluated and the wheel track specimen show 10-40% higher in that by the constant head permeability test. Additionally, a modified permeability test with 10% of pavement cross slope was found 10% reduction in permeability. The field permeability performed in the test section show a reduction from 2.2*10-1 to 1.2*10-3 cm/sec after nine years of service. The analysis in conjunction with X-ray Computed Tomography indicate that the clogging of PAC occurred in 20mm depth topdown where the porosity was reducing down to 3%. It was also found that the effect of roller compaction can cause 4% reduction in porosity on the same depth topdown. The test section was then excavated and it was found that permeability of base and subbase layers remained the same capacity in comparison with that in nine years ago. Hence, it can conclude that the porosity of surface layer can be the dominant parameter in term of overall capability of permeable pavement.
