酸(acid)作為瀝青的改質劑能夠改善瀝青的溫感性，擴大瀝青使用的溫度範圍，增加瀝青的勁度(stiffness)以防止瀝青混凝土鋪面產生車轍；最近有研究指出添加磷酸(Phosphoric Acid)能夠增加瀝青在高溫時的勁度，但是與其他的改質劑相比，目前關於酸改質劑(acid modification)的資訊與研究還是相當有限。
本研究以AC-20為基底瀝青，磷酸作為改質劑，研究添加磷酸對瀝青膠漿性質的影響，並以磷酸改質瀝青製作馬歇爾試體，研究添加磷酸對瀝青混凝土成效的影響。
由試驗結果得知，添加磷酸確實能有效的增加瀝青膠漿的勁度，但是也會加速瀝青膠漿的老化；由於添加磷酸對瀝青膠漿有加勁的效果，所以添加磷酸後，瀝青混凝土的承載力、抵抗車轍變形能力、抗張強度和抗磨損能力都有所提升。然而添加磷酸也會降低瀝青混凝土抗水侵害的能力，磷酸的添加量越多，瀝青混凝土水侵害的情形越嚴重，所以根據試驗結果，建議磷酸可以添加到2%左右。

Acid can be used to improve asphalt temperature susceptibility, expand the temperature range that the asphalt uses, increase the asphalt stiffness in order to prevent rutting of the asphalt concrete. Recent studies showed that add the Phosphoric Acid could increase the asphalt stiffness at high temperatures, but the information and research of acid modification was still quite limited at present.
This study used AC-20 as the basis asphalt and Phosphoric Acid was used as a modifier to evaluate effect of Phosphoric Acid on the properties of asphalt, Marshall samples were fabricated with Phosphoric Acid modified asphalt to study effect of Phosphoric Acid on the performance of asphalt concrete.
According to result of tests, adding the Phosphoric Acid would increase asphalt stiffness, but would accelerate the asphalt aging. Because adding the Phosphoric Acid would increase asphalt stiffness, the resistance of rutting, tensile strength and the resistance of wearing of asphalt concrete were all improve. But the resistance to moisture damage was reduced. Results of the tests, showed that Phosphoric Acid could be added about 2%.

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