Introduction. The quality of asphalt concrete mixture compaction in the road pavement layer is assessed by the compaction coefficient. The compaction coefficient refers to the ratio of the average density of cores to the average density of samples reformed from them.
Problem Statement. During sample preparation for reforming, there is a separation of cut mineral materials, which can affect the composition of the asphalt concrete mixture and lead to significant differences compared to the actual composition. The analysis of foreign sources revealed that the compaction coefficient is determined by the ratio of the average density of cores to the average density of samples made from the mixture used for constructing the road layer. A historical review of regulatory documents shows that the domestic method for determining the compaction coefficient has been in use for over 40 years. Additionally, a literature review found that this issue has not been adequately addressed. Thus, there is a need to study the effect of cut mineral material separation on the properties of reformed samples and the value of the compaction coefficient.
Objective. To improve the method for determining the compaction coefficient of asphalt concrete mixture.
Materials and Methods. The asphalt concrete mixture with a maximum nominal aggregate size of 20 mm, type A, continuous grading. Cores were taken from the road pavement layer constructed with the aforementioned asphalt concrete mixture. Testing methods include determining soluble bitumen content, aggregate grading, average density, water saturation, and the compaction coefficient.
Results. The soluble bitumen content changes significantly depending on the core preparation method. The separation of cut mineral materials leads to an increase in soluble bitumen content in the test sample. When using cores to determine soluble bitumen content, the deviation from the content in the asphalt mixture is negligible. The separation of cut mineral materials also significantly affects the grading of the aggregate, resulting in an increase in the amount of material passing through sieves with certain hole sizes. The separation of cut aggregates does not affect the average density of reformed samples and, accordingly, the compaction coefficient but has a significant impact on the water saturation, which differs significantly from the water saturation of samples made from the asphalt concrete mixture.
Conclusions. The current method of core preparation for reformed sample creation significantly affects the soluble bitumen content and the aggregate grading in the test sample. During core preparation, an increase in soluble bitumen content and the amount of material passing through sieves with specific hole sizes occurs. The average density of samples made from the asphalt concrete mixture and the average density of reformed samples are identical, allowing for the improvement of the compaction coefficient determination method by using the average density of samples made from the asphalt concrete mixture.
