ABSTRACT

This research recommends a mathematical modelling approach to determine flow time (FT). The scope of the work includes the collection and analysis of the static creep test data for asphalt mixtures produced using two different nominal maximum aggregate size (NMAS) values and two base binder grades. Modifiers of styrene butadiene styrene (SBS), polyphosphoric acid (PPA) and combination of them are selected to consider a wide range of testing times from 120 to 30,000 s. The FTs of the mixtures are determined using three techniques: the method developed in national cooperative highway research programme (NCHRP) Report 465, the Francken model, and the proposed mathematical model which is based on the ordinary tangent function. The results show that the NCHRP method is sensitive to the user-selected size of logarithmic scale unit of time, causing difficulties in the FT computation. It is also shown that the Francken model, often used to fit the dynamic creep curves, cannot completely fit the static creep test data, and so is not capable of estimating FT, properly. However, based on the limited data available in this study, the proposed tangent model performs very well in characterising all the three stages of the static creep curve and estimates the accurate value of FT in a reasonable time. Because of the simplicity, computational speed and accuracy of the proposed tangent model, it can be considered as an alternative to the NCHRP method to determine FT.

摘要

本研究建议采用数学建模方法来确定流动时间 (FT)。工作范围包括收集和分析使用两种不同标称最大骨料尺寸 (NMAS) 值和两种基础粘合剂等级生产的沥青混合物的静态蠕变试验数据。选择苯乙烯丁二烯苯乙烯（SBS）、多聚磷酸（PPA）及其组合的改性剂，以考虑从120到30,000秒的广泛测试时间。混合物的 FT 使用三种技术确定：国家合作公路研究计划 (NCHRP) 报告 465 中开发的方法、Franken 模型和基于普通正切函数的建议数学模型。结果表明，NCHRP方法对用户选择的对数尺度单位时间大小敏感，导致FT计算困难。还表明，通常用于拟合动态蠕变曲线的 Francken 模型不能完全拟合静态蠕变试验数据，因此无法正确估计 FT。然而，基于本研究中可用的有限数据，所提出的切线模型在表征静态蠕变曲线的所有三个阶段方面表现非常出色，并在合理的时间内估计了 FT 的准确值。由于所提出的切线模型的简单性、计算速度和准确性，它可以被视为 NCHRP 方法的替代方法来确定 FT。基于本研究中可用的有限数据，所提出的切线模型在表征静态蠕变曲线的所有三个阶段方面表现良好，并在合理的时间内估计了 FT 的准确值。由于所提出的切线模型的简单性、计算速度和准确性，它可以被视为 NCHRP 方法的替代方法来确定 FT。基于本研究中可用的有限数据，所提出的切线模型在表征静态蠕变曲线的所有三个阶段方面表现良好，并在合理的时间内估计了 FT 的准确值。由于所提出的切线模型的简单性、计算速度和准确性，它可以被视为 NCHRP 方法的替代方法来确定 FT。