Study on the Effect of Alkali Activator and Curing Conditions on the Strength of Waste Concrete-Based Geopolymer
The waste concrete powder was utilized as source material to prepare geopolymer.The effect of NaOH solution concentration,water glass content,mass ratio of alkali activator to waste concretepowder,and curing con-dition(curing temperature,curing time,curing method and age)on the unconfined compressive strength of waste concrete-based geopolymer were studied.The results indicate that increasing the NaOH solution concentration,water glass content and mass ratio of alkali activator to waste concretepowder were all leading to enhance the un-confined compressive strength of waste concrete-based geopolymer.The optimum NaOH solution concentration corresponded to 14 mol/L,water glass to NaOH solution mass ratio of 1.5 and alkali activator to waste concrete-powdermass ratio of 0.4.A maximum 7-day unconfined compressive strength of 14.32 MPa was achieved by seal-ing curing at 70 ℃ for 24 hours.The low activity and high calcium content are the causes for the low strength of waste concrete-based geopolymer.
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