Effects of coarse aggregate content on mechanical and durability properties of high-performance concrete for jacking prestressed concrete cylinder pipe

The prestressed steel cylinder concrete jacking pipe (J-PCCP) combines the structural advantage of prestressed concrete cylinder pipe (PCCP) with jacking construction, offering broad prospects for deployment in marine engineering. To ensure the mechanical property and long-term durability of J-PCCP in marine environments, high-performance concrete (HPC) was developed to replace the pipe core and protective layer. Based on the modified Andreasen and Andersen model (MAA model), four HPC mixes with coarse aggregate (CA) volume fractions of 42%, 32%, 22%, and 12% were designed, and the current C50 ordinary concrete (NC) mix served as the control. The effects of CA content on workability, mechanical property, durability, and microstructure under standard and steam curing were systematically investigated. The results indicated that reducing CA content mitigates the frictional resistance and interlocking between fine and coarse aggregates, enhancing workability. Steam curing effectively activated the reactivity of mineral admixtures and promoted secondary hydration in HPC. As CA content decreased, the gap between the mechanical and durability properties between steam-cured specimens and standard-cured specimens widened. The mix with 22% CA content (CA-22%) exhibited the best combination property. Under standard and steam curing, the compressive strength of CA-22% increased by 41.7% and 71.7% at 28 days, respectively. The flexural strength increased by 48.4% and 107.1%, respectively. Meanwhile, the chloride ion migration coefficient decreased by 97.1% and 98.6%, respectively. The water permeability coefficient decreased by 76.6% and 84.0%, respectively. Microstructural analysis indicates that reducing CA content decreases calcium hydroxide content, lowers porosity, and promotes densification of the interfacial transition zone. The superior performance of CA-22% is consistent with the predictions of the MAA model. Finally, verification results based on a multi-objective evaluation model further confirmed the practicality of CA-22%. CA-22% mix provided key material support for jacking prestressed high-performance cylinder pipe and created potential for subsequent lightweight design.