Mechanical properties of fly ash and silica fume based geopolymer concrete made with magnetized water activator

Using of magnetized water (MW) in the manufacturing of Portland cement concrete has shown promising effects in recent decades. This research investigates the effect of using alkaline activator (AA) solution prepared with MW on producing fly ash (FA) and silica fume (SF) based geopolymer concrete. The MW was prepared by passing tap water (TW) through two permanent magnetic fields of 1.4 and 1.6 Tesla intensities. Sodium hydroxide (SH), potassium hydroxide (PH), and sodium silicate (SS) solutions were the AA used. In total, 28 geopolymer concrete mixes were produced and tested in this study. Half of the mixes was made with the proposed MW (activator and added water), and compared with the other half that made with TW (activator and added water). Variables like; water type (TW or MW), SF content (10%-100%), AA type (SH+SS or PH+SS), AA concentration, AA to cementitious materials (AA/C) ratio, and water to cementitious materials (W/C) ratio were applied in this study. Physical and chemical properties of the utilized water and AA were measured. Concrete fresh and hardened mechanical properties were measured including workability, compressive strength, tensile strength, flexural strength, bond strength, and water absorption. Ultrasonic pulse velocity non-destructive testing was also conducted on the produced concrete. Scanning electronic microscope (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) analyses were carried out on selected mixes to closely investigate the microstructure of the introduced geopolymer concrete. The results showed that compared with TW, utilizing MW in preparing the AA of geopolymer concrete caused notable increase in the concrete slump with an average of 14%, compressive strength increase by up to 64%, tensile strength increase by up to 60%, flexural strength increase by up to 41%, bond strength increase by up to 40%, and water absorption decrease by up to 38%.