Synthesis of one-part activators for geopolymer concrete utilizing SiO2 rich waste materials

Nathan Slawinski

Investigation was undertaken into the syntheses of one-part activators (OPA) for production of geopolymer concrete utilizing SiO2 rich waste materials. Waste glass powder (WGP), baghouse dust (BHD) and lithium alumino-silicate reside (LAR) were added to sodium hydroxide of varying molar ratios to dissolve available SiO2. The mixtures were heated at 85-90oC and continuously stirred for a period of 6hrs to allow for dissolution to occur. Resulting solutions were utilized to produce fly ash based geopolymer mortars, with mortars tested for compressive strength at 7, 14, and 28 days. Initial results exhibited very low early (7 day) strength with use of 100% one-part activators with MPa values of < 1MPA in some cases. The addition of 20% sodium silicate to the mixture improved early strength of samples by up to 1600%, likewise the addition of 5% Ca improved early strength by up to 3200%. The evaporation rate during production of one-part activators was shown to have a direct correlation with compressive strength and increases in MPa were noted in line with increases in evaporation. Mortar samples made using 100% one-part activator and 100% fly ash returned the highest compressive strength values when evaporation rate was 50%. Waste glass powder one-part activators achieved 28-day maximum strength of 24.53 MPa, baghouse dust one-part activators achieved 28-day maximum strength of 24.75 MPA and samples made with lithium alumino-silicate one-part activators achieved 28-day maximum strength of 24.76 MPa. Samples produced with one-part activators and the addition of 20% sodium silicate and 5% Ca produced the highest compressive strengths at 52.35 MPa and 45.86 MPa respectably. Samples were compared against control samples produced using commercial sodium silicate and NaOH for activation. Control groups were made using NaOH with molar values of 10M, 12M and 14M. These samples returned the highest 28-day compressive strength averages from all samples produce with MPa values of 66.60, 57.23 and 48.04 respectively.

Synthesis of one-part activators for geopolymer concrete utilizing SiO2 rich waste materials

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