Interlayer Aggregates Embeddedness Index and Its Characterization for Interlayer Bonding Quality of Roller-Compacted Concrete

Abstract

Interlayer bonding is one of the critical principles of roller-compacted concrete (RCC) construction. The fundamental premise of ensuring interlayer bonding quality is embedding interlayer aggregates (IAs) into the lower layer of the RCC during vibratory compaction. This paper demonstrated the relationship between the RCC bonding quality and the embedding value (EV) of IAs of various sizes by first theoretically analyzing the failure model of the interlayer strength of the RCC, and then defining an index called the interlayer aggregates embeddedness index (IAEI) to characterize the overall influence of the size and EV of IAs. An experiment scheme was designed to examine the characterizing comprehensiveness of the IAEI for interlayer bonding strength of RCC. In the experiment scheme, IAs of three different sizes were placed on the bedding surface of RCC and two different vibration times were set on the upper layer of the RCC when molding to produce different EVs of different size IAs. The EVs of the IAs in the RCC were measured using computed tomography (CT) scanning and inert stain dying, and the interlayer bonding quality was measured using the direct shear test. The results showed an increase in the EV led to an improvement in the interlayer shear strength. With an adequate vibration time of two times the vibrating compacted (VC) value, the shear strength of the RCC grew as the particle size of the IA increased. For placed IAs, the EV of the IAs increased with the growth of particle size. For natural IAs, the number grew with vibration time increasing, and the particle size distribution was mainly below 2.5 cm. Compared with other embedding-related indices, IAEI showed the best liner correlation with the interlayer shear strength, with a determination coefficient of 0.89, which verified the characterizing comprehensiveness of IAEI for interlayer bonding quality of RCC. This study revealed the interlayer bonding mechanism of RCC from the meso perspective of interlayer aggregate embedding.