Study On Preparation Factors And Properties Of Autoclaved Materials Prepared With Nickel Residue

Nickel laterite residue from aciding leaching method is a kind of industry solid wastes. It’s usually disposed by yarding and landfilling which was harmful to the environment of soil and groundwater. This paper provide a way to comprehensive utilization of nickel residue by preparing the autoclaved products. The effect of the content of hydrated lime, cement and sand, molding condition of green body and autoclaved schedule on the compressive strength, softening coefficient have been studied through compressive strength testing, XRD, SEM and so on. The results showed, the samples can obtain better performance when m(nickel residue):m(hydrated lime):m(cement)=70:15:15. The compressive strength of samples was about 40MPa and softening coefficient was 0.78 when water-binder ratio was 0.2, the moulding pressure of green body was 20MPa, autoclave temperture was 170℃, holding time was 6h. At the same condition, when water-binder ratio ≥ 0.2, the compressive strength of samples ≥ 35MPa evenif the moulding pressure of green body was 10MPa; when moulding pressure of green body≥ 20MPa, the compressive strength of samples≥ 35MPa evenif the water-binder ratio was 0. The results showed that compaction rate of green body had direct influence on compressive strength of samples. The proper moulding condition of green body as following:water-binder ratio = 0.2; moulding pressure = 20MPaUnder the condition of basic formula, water-binder ratio was 0.2, moulding pressure was 20MPa, autoclave temperature was 110℃ and holding time was 2h, adding sand was helpful to improving the compressive strength of samples. The effect of sand content on the compressive strength was as following:the mechanism of sand> river sand> fine artificial sand mechanism; the effect of sand content on the softening coefficient was as following:artificial sand> fine artificial sand> river sand.This paper studied the physiochemical process of nickel residue autoclave materials under different conditions, especially the hydration process of nickel residue with slaked lime. The results showed:in the condition of autoclave curing, calcareous materials, magnesia material and ferrous material have reacted with siliceous material, and many kinds of hydration products have formed, such as hydrated calcium silicate, hydrated magnesium silicate and so on. It is worth noting that this system could obtained hydration products at autoclave temperature of 30-50℃ (e.g. C-S-H or C-A-S-H). Material particles were cemented together by hydration products, and the sample pore between particles has been filled with hydration products so that the samples have higher density and strength.