This study is to improve crushed rock with fly ash geopolymer for maintenance on the base layers to be effective strength and increased service life.The use of fly ash from power plants BLCP Power Ltd. in Map Ta Phut Industrial Estate, Rayong Province.The proportions of crushed rock with fly ash geopolymer (CR:FA) are 100:0 95:5 90:10, and 80:20.A liquid alkaline activator is a mixture of sodium silicate (Na2SiO3) solution and sodium hydroxide (NaOH) at 5 molar concentration.The compressive strength and C.B.R. value higher proportion of fly ash and Alkaline Activator geopolymer catalysts that curing time 7 days, more than the compressive strength standard Department of Rural Road (DRR.244-2556(2013)) at 17.5 ksc. And the Department of Highways (DOH.203/2556 (2013)) at 24.5 ksc. As well, The ability to compressive strength and loading capacity increasing.Such materials, when used in the maintenance would last longer than ever before.When considering the cost of maintenance per square meter.The proportion CR:FA 5%. The Na2SiO3:NaOH ratio of 40:60 is appropriate to bring in maintenance.Due to the maximum compressive strength of 65.10 ksc.,and the cost of maintenance 287.60 baht per square meter. This compared with crushed rock mixed fly ash geopolymer in other proportion to lowest price,Therefore, concluded that the compressive strength of crushed rock with fly ash geopolymer has increased from quantity fly ash mixture, the type and concentration of Alkaline Activator and the curing time. In terms of price, Fly ash has a high price. If considered in terms of the value of the investment, the higher compressive strength of base material is considered to be a good choice for road maintenance.