State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics & Civil Engineering, China University of Mining & Technology, Xuzhou, China.
PLoS One. 2022 May 11;17(5):e0268105. doi: 10.1371/journal.pone.0268105. eCollection 2022.
Since the recycling of waste original cement-stabilized macadam (OCSM) base has important environmental and economic significance, the addition of emulsified asphalt to OCSM to form emulsified recycled OCSM (ER-OCSM) can improve the flexibility of recycled mixtures. However, the influence of emulsified asphalt on the mechanical performance of such mixtures remains to be investigated. This study presents a gradation design and ER-OCSM established using the step-by-step filling method and investigated the mechanical properties of the ER-OCSM mixture. The apparent characteristics, crushing value and needle-like particle content of the OCSM milling material were tested. Based on step-by-step filling theory, the appropriate test method to achieve a uniform and dense state according to the characteristics of different aggregates was selected, and the dense skeleton gradation design method for recycled cement macadam was obtained. The mechanical properties of the ER-OCSM were analyzed by performing indoor physical laboratory tests. The natural gradation of the OCSM milling material exceeded the gradation range recommended in the Technical Guide for the Promotion of Science and Technology of the Construction Project of the Main Highway in Jiangsu Province (Trial), but the designed gradations were basically within the range. At the same age and temperature, the flexural strength and dynamic elastic modulus of the ER-OCSM decreased gradually with an increase in the emulsified asphalt content. Because ER-OCSM had temperature-sensitive characteristics, the adhesiveness of the asphalt between particles in the mixture decreased with increasing temperature, which was manifested as the unconfined compressive strength, flexural tensile strength and dynamic elastic modulus decreasing with an increase in temperature (the decrease was slight within 5-25°C but noticeable within 25-60°C). Furthermore, a higher emulsified asphalt content caused a more noticeable decrease. The flexural strength of the tested ER-OCSM showed noticeable correlations with the splitting strength, unconfined compressive strength and dynamic elastic modulus. The proper addition of emulsified asphalt can reduce the rigidity of ER-OCSM. However, the emulsified asphalt content should be strictly controlled; otherwise, the mechanical properties of the material will decrease greatly, adversely impacting the comprehensive road use performance.
由于废旧水泥稳定碎石基层（OCSM）的回收具有重要的环境和经济意义，因此在 OCSM 中添加乳化沥青形成乳化再生 OCSM（ER-OCSM）可以提高再生混合料的柔韧性。然而，乳化沥青对这种混合物力学性能的影响仍有待研究。本研究提出了一种级配设计和采用逐步填充法建立的 ER-OCSM，并研究了 ER-OCSM 混合物的力学性能。测试了 OCSM 铣刨料的表观特性、压碎值和针状颗粒含量。基于逐步填充理论，根据不同集料的特性选择了合适的测试方法，以达到均匀密实的状态，获得了再生水泥稳定碎石的密实骨架级配设计方法。通过室内物理实验室测试分析了 ER-OCSM 的力学性能。OCSM 铣刨料的天然级配超出了《江苏省高等级公路建设项目科技推广技术指南（试行）》推荐的级配范围，但设计级配基本在范围内。在相同龄期和温度下，随着乳化沥青含量的增加，ER-OCSM 的抗弯强度和动态弹性模量逐渐降低。由于 ER-OCSM 具有温度敏感性，混合料中颗粒之间沥青的粘性随温度的升高而降低，表现为无侧限抗压强度、抗弯拉强度和动态弹性模量随温度升高而降低（5-25°C 范围内降低幅度较小，但在 25-60°C 范围内较为明显）。此外，较高的乳化沥青含量会导致更明显的降低。测试的 ER-OCSM 的抗弯强度与劈裂强度、无侧限抗压强度和动态弹性模量有明显的相关性。适当添加乳化沥青可以降低 ER-OCSM 的刚性。但是，乳化沥青的含量应严格控制；否则，材料的力学性能会大大降低，对综合道路使用性能产生不利影响。
