Coupled effects of cement type and water quality on the properties of cemented paste backfill

• We tested cemented paste backfill (CPB) properties by using different types of cement and mixing water.
• Water quality affected the coagulation time of CPB.
• Zn2 + delayed CPB coagulation.
• Cement type influenced unconfined compressive strength of CPB.

The significant coagulation delay and poor strength performance of cemented paste backfill (CPB) are two of the biggest challenges faced by the backfilling system in Chihong mine. These factors significantly affect the mining and backfill cycle. Hence, CPB property tests (e.g., slump, coagulation, and strength) were conducted to investigate the influence of different cement types and mixing water qualities (tailings pore water and distilled water). Results of the tests for slump, initial coagulation time (ICT), and unconfined compressive strength (UCS) of the CPB samples are as follows: (i) slump variation of different CPB samples is insignificant. (ii) The ICT changing trends of the CPB samples are in line with the ICT of their mixing cement slurry. In addition, zinc ions in the tailings pore water are detrimental to CPB coagulation. (iii) Cement has an obvious influence on the UCS of CPB, and water quality barely affects the UCS of CPB. These results indicate that cement choice and water chemical components are important factors in CPB design and mine operations.