Strength properties of high-strength concrete on the basis of a mixture of high-calcium ash and cement crushed to a specific surface of 600 m2 / kg in the presence of a superplasticizer were investigated. It was established that at the initial stages of hardening of the binder, its strength strongly depends on the dosage of fly ash and it depends little on the water/binder ratio. After 28 days of hardening, the strength of concrete, depends more on the water-binder ratio, rather than on the ash content of the cement-ash binder. There was concluded that minerals of fly ash affect on strength of the cement-ash binder in later periods, and at the initial stages, its hardening is provided by hydration of the cement clinker. It was established that in high-strength concretes was no decrease in strength in later periods when using finely grinding ash containing a significant amount of free CaO.
Keywords: high-strength concrete, fly ash, free CaO, cement-ash binder, strength, dump strength