Use of sludge produced from reject brine as a supplementary cementitious material with enhanced carbonation capability

TY - JOUR

T1 - Use of sludge produced from reject brine as a supplementary cementitious material with enhanced carbonation capability

AU - Mi, Tangwei

AU - Li, Yongqiang

AU - Yang, En-Hua

AU - Unluer, Cise

N1 - © 2025 The Authors.

PY - 2025/7

Y1 - 2025/7

N2 - Sludge obtained from reject brine via a novel two-step approach involving precipitation and filtration was used as a supplementary material in reactive magnesia cement (RMC) and Portland cement (PC) mixes. Detailed evaluation of the performance and microstructure of the resultant cement pastes revealed the underlying mechanism. Incorporating 25 % (of the binder content) sludge in RMC mixes significantly increased the compressive strength under ambient and carbonation-based curing, which was more than doubled under the latter condition. While the strength of PC mixes decreased with the use of sludge, it still exceeded 30 MPa under carbonation. Increase in hydration heat observed in sludge-containing mixes was attributed to the presence of brucite acting as nucleation sites. ∼30 % reduction in CO2 emissions and ∼25 % reduction in energy consumption was achieved by simply incorporating sludge in the designed mixes. Furthermore, sludge enhanced carbonation in RMC and PC mixes by increasing the amount of CO2 sequestered at 28 days by 25.9 % and 41.1 %, respectively. Overall, the feasibility of re-purposing reject brine by directly using the produced sludge was demonstrated, offering a sustainable alternative for concrete production with a significantly reduced environmental impact.

AB - Sludge obtained from reject brine via a novel two-step approach involving precipitation and filtration was used as a supplementary material in reactive magnesia cement (RMC) and Portland cement (PC) mixes. Detailed evaluation of the performance and microstructure of the resultant cement pastes revealed the underlying mechanism. Incorporating 25 % (of the binder content) sludge in RMC mixes significantly increased the compressive strength under ambient and carbonation-based curing, which was more than doubled under the latter condition. While the strength of PC mixes decreased with the use of sludge, it still exceeded 30 MPa under carbonation. Increase in hydration heat observed in sludge-containing mixes was attributed to the presence of brucite acting as nucleation sites. ∼30 % reduction in CO2 emissions and ∼25 % reduction in energy consumption was achieved by simply incorporating sludge in the designed mixes. Furthermore, sludge enhanced carbonation in RMC and PC mixes by increasing the amount of CO2 sequestered at 28 days by 25.9 % and 41.1 %, respectively. Overall, the feasibility of re-purposing reject brine by directly using the produced sludge was demonstrated, offering a sustainable alternative for concrete production with a significantly reduced environmental impact.

KW - Reject brine

KW - Sludge

KW - MgO

KW - Blended cement

KW - Carbonation

KW - Waste management

U2 - 10.1016/j.cemconcomp.2025.106051

DO - 10.1016/j.cemconcomp.2025.106051

M3 - Article

SN - 0958-9465

VL - 160

JO - Cement and Concrete Composites

JF - Cement and Concrete Composites

M1 - 106051

ER -