Mechanical and durability properties of reactive powder concrete exposed to acid, sulfate, and fire

Reactive powder concrete (RPC) is an ultrahigh-performance concrete with exceptional mechanical strength and very low permeability, making it a promising material for infrastructure elements exposed to harsh environments. However, its high cement content may increase vulnerability to chemical attacks such as acid and sulfate exposure, while its dense microstructure can lead to internal vapor pressure problems under elevated temperatures. To address these challenges within a single RPC system, this study investigated two complementary modification strategies: using blast furnace slag (BFS) as a partial cement replacement to improve chemical durability against acid and sulfate attacks, and incorporating polypropylene (PP) fibers to enhance resistance to spalling under high-temperature conditions. Three RPC mixtures with varying BFS contents (0%, 10%, and 20%) and three mixtures with different PP fiber dosages (0%, 0.25%, and 0.5%) were prepared. Specimens were exposed to sulfuric acid, sodium sulfate, and direct flame to simulate aggressive environmental conditions that can simultaneously occur in infrastructure applications. Unit weight, compressive strength, and microstructural analyses were conducted to assess deterioration mechanisms and the effectiveness of the modifications. The results showed that moderate BFS replacement can help reduce cement content but may increase susceptibility to chemical attack if used excessively, while PP fibers effectively mitigate internal vapor pressure and reduce spalling at high temperatures. This study demonstrates an integrated approach for optimizing RPC performance under combined chemical and thermal hazards, supporting its safe and sustainable use in critical infrastructure.