Experimental study on dynamic resilient modulus of subgrade with circulating fluidized bed combustion ash as filler

•With increasing f-CaO and SO3 content, the DRM of CFBCA increased.•With increasing compaction and moisture content, the DRM of CFBCA increased.•With increasing f-CaO and SO3 content, total porosity and macropore of CFBCA decreased.•Impact of dry-wet cycles on DRM is more pronounced than that of freeze–thaw cycles. Using circulating fluidized bed combustion ash (CFBCA) as roadbed filler can solve the problem of secondary utilization, and dynamic resilient modulus (DRM) can match the dynamic performance of roadbed filler under driving load. In order to explore the dynamic performance of the subgrade with CFBCA as filler under driving load, based on the dynamic triaxial test and mercury intrusion porosimetry test, the DRM of the sample under different curing ages, compaction, moisture content, stress, dry-wet and freeze–thaw cycle conditions were studied, and the pore distribution characteristics of the sample were analyzed. The results show that the DRM of CFBCA samples increases significantly in the 0 ∼ 7d age curing period, and increases slowly in 7 ∼ 28d; with the increase of f-CaO and SO3 content, the DRM of CFBCA samples increased; after the dry-wet cycle and freeze–thaw cycle, the DRM of the CFBCA sample decreased, and the decrease was more obvious under the dry-wet cycle. With the increase of f-CaO and SO3 content, the total porosity and macropore of CFBCA samples decreased; with the decrease of moisture content, the total porosity and macropore of CFBCA samples increased, the DRM becomes smaller. Under different moisture content and compaction, the DRM fitting of the CFBCA sample shows that the prediction results of the three-parameter theoretical model with volume stress and octahedral shear stress as variables are compared with the test results with a high correlation (R2 > 0.96), it can effectively predict the DRM of the subgrade with CFBCA used as filler.