Study On The Cement Of Fly Ash Activated By Phosphoric Acid

The utilization of fly ash is a severe problem that people have paid attention for a long time Since fly ash have potential activation, domestic and international researcher have found many ways to utilize it effectively. But according to the present results of study and state of using, various kinds of way to excite the activation of fly ash generally have the same problem that the exciting rate is slow and the exciting degree is low. To solve this problem,the thesis use acid (phosphoric acid ) to excite the activity of fly ash. Taking this way, fly ash can get gelation rapidly and wins higher intensity within a short time.The binder produced with phosphoric acid and fly ash is called the cement of fly ash activated by phosphoric acid. The thesis study on the fundamental character of this cement mainly. Since the cement has high heat of hydration and short setting time, The thesis study it's development of compressive strength and setting time mainly. It is shows that compressive strength of this cement changes with proportion of material, adging days, curing conditions, kind of fly ash, admixtures. But the kind of fly ash is the most important factor influencing the strength. The factors which influence the setting time are proportion of material, kind of fly ash, admixtures etc. The thesis studied several effective ways to retard setting, including adding retarder of borax, adding borax with some kind of phosphate and pretreatment fly ash with dilution of phosphoric acid.The mechanism of reaction of the cement is analysed through X-ray diffraction and SEM research. Then the thesis discussed it's application in engineering and production through researching other characteristics of this cement. Finally it is concluded that the cement of fly ash activated by phosphoric acid is a new type of cement with extensive prospect.