Research On Effects Of Wet-discharging On Pozzolanic Reactivity Of Fly Ash

The fly ash, as the admixture of concrete, had been widely used because of notonly its good effect on improving several properties of concrete but also its goodbenefits to both economy and environment. Today the dry fly ash has played the keyrole in the concrete construction. But because of its high costs of storage andtransportation, it has often become a economic burden of the power plants and theconstruction units. Because the wet fly ash is superior to the dry one in storage andtransportation, the attention has been paid to how it will go on after wet-dischargingwith its hydration ability. It has been proved that the high calcium fly ash will lose itsreactivity after reaction with the water. While it is fiercely disputed that what willhappen to the low calcium fly ash after wet-discharging.Although a lot of researches had been carried out on the properties and the effecton the concrete of the wet fly ash, it can hardly been found that what happened to theproperties of the wet fly ash, without the comparisons with the fly ash. That is why sofar few things have been reported about the properties and the effect on the concrete ofthe wet fly ash at home and abroad.Through the simulation experiments, this paper discusses the effect ofwet-discharging on the fly ash, especially the changes of its reactivity with the timegoing on and the influence factors, and finally investigate what has happened to theconcrete properties.It has been found that: ①The wet-discharging has an effect on the uniformity ofthe fly ash. ②After wet-discharging, the water demand of the fly ash will increase, butthe soundness will be better. ③The reactivity of the fly ash will become worse andworse with the time going on; In the early phase, the velocity of loss of reactivitydeceases quickly; in the later, it goes slowly. ④The amount of the calcium, thetemperature and the PH values of the ash-immersing water contribute greatly to thechanges of the reactivity of the wet fly ash. ⑤The water reduction ability of the wet flyash is worse than that of the dry ash. Otherwise, the improvement of the slump loss ofthe wet fly ash is better than that of the dry one. Also the wet fly ash is friendly with thewater-reducing agent. ⑥The compressive strength of the concrete with the wet fly ashis a little lower than that with the dry ash. But there are not remarkable differencesbetween their impermeability and carbonization.