Abstract: In order to meet the needs of the development of the cementing,aiming at the problem of early strength of the lowdensity flyash cement slurry,authors of the paper analyze and discuss the action mechanism in the course of hydrating reaction of fly ash in low density composite material cement.A new kind of highly efficient early strengthening agent DY is developed,and this production is efficient for early strength of fly ash in the low temperature environment.Increased early strength of light weight fly ash cement slurry in low temperature is principally based on interaction between cement and fly ash.The authors analyze both the positive and negative experimental results.The results indicate the development of pozzolanic reaction and stone strength of fly ash is based that Ca²⁺ and OH^- which is hydration product composition of well cement released to slurry as many as possible.This study is useful for cementing in the long isolation section of large borehole and lost circulation and blowout environment.

Key words: cementing, cement slurry, fly ash, early strengthening agent, low density