Does concrete gain strength by drying out?
No. Concrete is made by mixing cement, aggregates and water together. When the water comes in contact with the cement a chemical reaction starts to take place. This chemical reaction is called hydration. Hydration is the reaction between the chemicals in water and the chemicals in cement. This reaction forms new compounds and crystals interlocking themselves and the aggregates together. A majority of this reaction takes place over the first month after placing the concrete. Small amounts of additional reaction and strength gains could take place for years as long as moisture is still present to cause more hydration. Actually, when the concrete does finally dry out, it stops gaining strength.
