GRADE COMPOSITION DESIGN AND MECHANICAL PROPERTIES OF COMPACTED MAGNESIUM SLAGS FOR ROAD PAVEMENT BASES

Abstract

Gradation composition is crucial to the performance of pavement bases, and differently structured pavement bases vary greatly in pavement performance. However, the gradation range recommended in the relevant code is large without specific provision for the gradation range of low-strength aggregates, such as magnesium slags, which easily leads to a wide selection range of synthetic gradation and weak guiding significance to practical projects. To solve the optimization problem of magnesium slag aggregate gradation design, skeleton-dense type gradation was constructed using the Bailey and Stone asphalt concrete (SAC) gradation methods with magnesium slag materials as the base aggregate. Then, the design gradation was optimally adjusted through compaction tests in combination with the fragile nature of magnesium slag materials. On this basis, the applicable gradation range of magnesium slag aggregates in engineering was obtained, and the gradation optimization design method for this kind of material was formed. Finally, the compaction characteristics and California bearing ratio (CBR) of magnesium slag aggregates with design gradation and those with local specification recommended gradation were analyzed. The test results show that the compaction process significantly influences the target gradation of magnesium slag aggregates, and the cumulative change rate of aggregate gradation of the median design gradation is 37.12%. The bearing capacity of the design gradation is excellent, and the CBR values of the upper limit and the gradation's lower limit are greater than 60%, meeting the paving requirements of different traffic load grades and structural layers. The CBR value of the design gradation is better than that recommended by the specification, which verifies the reliability of the gradation algorithm proposed in this study. This study can provide a theoretical reference for the gradation calculation of low-strength aggregates applied to roads. Keywords: road engineering, magnesium slag, gradation design, skeleton-dense type gradation, CBR