Durability, workability, and setting time of cementitious systems containing chloride-rich oil and gas production wastewater

Abstract

The application of alternative non-potable water sources can be leveraged to build infrastructure components that support sustainable industrial operations in regions that experience high frequency of freshwater shortages. This study examines how the use of highly saline produced water (as mixing water) in portland cement mortar impacts workability, setting time, electrical resistivity, pore formation, and microstructure. The results show that produced water decreases both mortars setting time by 30% and workability by 20%. Alkali solubility and pore solution conductivity are also influenced by the produced water-increasing pore solution conductivity by approximately 100 mS/cm. The produced water reacts with the cementitious material to form small deposits of Friedel's salts and calcite that primarily fill the smaller pores in the matrix-thus primarily influencing the pore structure of low w/c mortar systems. In the low water/cement (w/c) produced water mortar systems (0.4), both the pore formation factor (∼2X) and resistivity (∼1.5X) are significantly higher than the control (tap water mortar systems), but in the high w/c systems (0.6) both are slightly lower. The produced water mortar systems also tend to retain more moisture during dry cycling which leads to significantly lower resistivity than the control in air-dried conditions. Diluting the produced water with tap water will reduce moisture retention during dry cycling and increase resistivity.