級配離析為粗與細粒料不均勻分佈於瀝青混凝土鋪面，配比設計、粒料的儲放、拌合廠拌合流程、運料卡車的進出料及鋪築過程都可能發生離析現象，而離析會降低鋪面之使用年限。為判斷離析，多藉由鑽心試體之篩分析來確認，然無法進行現地品質監控，而國內則是以目視來判斷，因此本研究藉由發展一個離析量化模式來判斷離析的存在及嚴重程度。
　　本研究分為現地試驗與實驗室試驗兩部份，現地試驗包含現地離析類型的觀測及以電磁式密度儀進行現地密度量測，實驗室試驗則在現地取得鑽心試體後進行紋理深度、間接張力強度、孔隙率、瀝青含量與粒料級配等試驗。
　　由現地試驗發現國內道路的離析類型多為「連續分佈」及「粒料於運輸卡車後之離析」，使用非破壞性電磁密度儀(PaveTracker)可用來判斷離析程度，尤其在中度及重度離析時。隨著離析程度的增加，離析區域的電磁密度值與控制區的差異越大。根據線性迴歸分析的結果，經過平移與旋轉校正後之電磁密度值與試體密度值之相關係數R為0.74。
　　由實驗室試驗發現，紋理深度隨離析程度增加而增加，重度離析之紋理深度達一般正常鋪面的2.9倍，中度及重度離析試體之間接張力值較控制區少8至9%，中度與重度離析的孔隙率約為控制區的1.2倍，將控制區與離析區域的篩分析結果進行統計分析，於中度離析區域8號篩過篩百分率有顯著差異的機率為83%；於重度離析區域8號篩過篩百分率有顯著差異的機率為77%。
　　本研究利用複線性迴歸模式來發展離析量化模式，以校正後電磁密度值作為依變數，紋理深度、孔隙率、4號篩的過篩百分率差異值、瀝青含量及鑽心試體密度值作為自變數，其相關係數R為0.884。

Segregation refers to the areas of non-uniform distribution of coarse and fine aggregate particles in hot-mix asphalt pavements. In general, segregation is caused by mix design, improper handling of asphalt mix and paving operation. Furthermore, occurrence of segregation reduces pavement service life. Segregation could be confirmed by performing gradation tests on aggregate extracted from cores. However, the extensive time required for lab testing would prohibit immediate adjustment of the paving operation. The identification of segregation has been typically based on visual observations in Taiwan. Hence, one of the objectives of this study is to develop a quantitative model to detect presence or severity of segregation.
Field and laboratory tests were conducted. At each test section, segregation patterns were identified and field density tests were performed using non-nuclear density gauge. After field tests, cores were taken and sent to laboratory to determine texture depth, indirect tensile strength, percent air voids, asphalt content and gradation curve.
It is found that “continuous” and “end of the load” are the most frequently observed segregation types in Taiwan. The non-nuclear density gauge, PaveTracker, is non-destructive and can be used to identify segregation in medium and heavy segregated areas. The density difference between segregated area and control area increases with increasing severity of segregation. The correlation coefficient R is 0.74 based on the result of linear regression analysis between the calibrated PaveTracker density and core density.
The results of laboratory tests indicated that the texture depth increases when the segregation level increases. The texture ratio of heavy segregated area and control area is 2.9. Indirect tensile strength in medium and heavy segregated area is 8-9% lower than that in the control area. The air voids in medium or heavy segregated area increase by 20% compared to the air voids in the control area. Results of statistical comparisons between segregated and control areas showed that if a statistical difference in PaveTracker density exists, the chance of aggregate gradation difference in percent passing No.8 sieve for medium and heavy segregation is 83% and 77%, respectively.
A multiple linear regression model was developed to quantify segregation. The correlation coefficient of the statistical model is 0.88. The dependent variable is calibrated PaveTracker density value. The independent variables are texture depth, air voids, the difference in percent passing No.4 sieve, asphalt content, and core density.

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