Investigation of the Flow and Mechanical Performances of Foamed Concrete Used for Filling Cracks in the Base Layer of Asphalt Pavement

Addressing the challenge that traditional flowability criteria cannot accurately characterize the grouting filling efficacy of foam concrete (FC) for cracks and voids in the base layer of asphalt pavement, this paper established a flowability evaluation method tailored for road grouting. Firstly, FC with varying flow performances were prepared by controlling the water–cement (W/C) ratio and water-reducing agent (WRA) dosage. Secondly, the flow cone method and micro-slump meter on a smooth flow degree pan method (MSM) characterized their flow performances. The porous Marshall specimens were constructed to simulate the crack–void structure of the base layer, and grouting plumpness was calculated using sectional image processing methods. Building upon this, gray relational analysis and regression analysis were employed to establish quantitative relationships between multiple factors and grouting plumpness. The results show that increasing W/C ratio and WRA dosage could improve the flow performance of FC, but reduce the compressive strength. Specifically, when the W/C ratio increased from 0.40 to 0.45, flow time decreased by 72.2% and flow diameter increased by 25%. Increasing WRA dosage from 0.3% to 0.5% could reduce flow time by 16% and increase flow diameter by 10%. Gray relational analysis revealed the strong correlations between flow indexes and grouting plumpness. The gray relational degree was 0.87 between grouting plumpness and flow diameter. In addition, the gray correlation between grouting plumpness and flow time was 0.65. Therefore, flow diameter should be first selected to measure the flow performance of FC. Furthermore, it was found that flow diameter should be higher than 230 mm to ensure that the average grouting plumpness of FC was above 80%. The results of this study provide a reliable basis for evaluating the flow performance of FC for filling cracks in the base layer of asphalt pavement.