Properties and microstructure of reactive powder concrete having a high content of phosphorous slag powder and silica fume

• Phosphorous slag powder was utilized to produce reactive powder concrete (RPC).
• Mechanical strength, freeze–thaw and sulfate resistance of RPCs are investigated.
• The content of phosphorous slag could be as high as 35% (by the weight of binder).
• RPCs prepared herein have excellent mechanical and durability properties.
• The diameter of the most probable pore in RPC samples is less than 10 nm.

Reactive powder concrete (RPC) specimens whose content of phosphorous slag powder (PS) and silica fume was about 50% (by the weight of binder) were produced after they had been cured in 95 °C steam for a given duration. The test results of strength (compressive and flexural), freeze–thaw and sulfate resistance verified the excellent mechanical and durability properties of RPC containing a high content of PS. The investigation of selected RPC compositions by Thermogravimetric Analysis, Mercury Intrusion Porosimetry and Scanning Electronic Microscope made it possible to better understand their mechanical and durability properties depending on their microstructure. Thermogravimetric Analysis and Scanning Electronic Microscope demonstrated the sequential hydration effect of cementitious composites during heat treatment. Mercury porosimetry results showed that RPC had very low porosity and the diameter of the most probable pore was less than 10 nm. These microstructural characteristics would enable RPC to have excellent mechanical and durability properties.