水泥就地冷再生基层的级配优化设计

Optimum Design of In-Situ Cold Regenerated Base Layer

现行规范中无机结合料稳定冷再生混合料级配范围过宽,对设计者的指导意义较弱。本文采用N法、I法和K法对水泥就地冷再生基层级配进行研究,然后利用贝雷法CA、FAc、FAf三参数进行级配优化,结合混合料在击实和现场压实过程中的压碎情况,对理论级配范围进行修正,得到了工程上适用的级配范围。在黄河堤顶道路郑州段旧路基层为水泥稳定碎石的沥青路面进行了实体验证,在工程级配范围内设计了粗、中、细3组级配,经室内7 d无侧限抗压强度、劈裂强度、抗弯拉强度、刚度、干缩和温缩等路用性能验证,得到最佳配比为中级配,即10~30 mm碎石、石屑、铣刨料比例为20%、6%、74%,水泥剂量为4.5%,最佳含水率为6.5%。考虑到就地冷再生路拌法施工的实际情况,现场将水泥剂量增加1%,即采用5.5%,最佳含水率为8.2%,最大干密度为2.169 g/cm3,经试验段检测各项指标均较好地满足规范要求。

In the current specification, the range of grading of the inorganic binder stabilized cold reclaimed mixture is too wide and the guid ance to the designer is weak.In this paper, the N-method, I-method and K-method were used to study the grading of cold regenerated base layer in cement. Then Bailey method CA, FAc and FAf three parameters were used for grading optimization. Combined with the crushing of the mixture during compaction and on site compaction, the theoretical grading range was corrected and the applicable grading range was obtained. The physical verification was carried out at the cement stabilized macadam base of the old road in the Zhengzhou section of the Yellow River embankment asphalt pavement. In the grading range, three sets of coarse, medium and fine grading were designed and the road performance of 7 d unconfined compressive strength, splitting strength, bending strength, stiffness, dry shrinkage and temperature shrinkage were verified. The best ratio was the medium grade, i.e. the ratio of 10-30 mm gravel, stone chip and milling material was 20%、6 % and 74%, cement dosage was 4.5% and the optimal moisture content was 6.5%. Taking into account the actual situation of the local cold reclaimed road mixing method, the cement dosage was increased by 1% on site, i.e. 5.5%, the optimum moisture content was 8.2% and the maximum dry density was 2.169 g/cm3. All the indicators tested by the test section can meet the requirements of the specification.