Abstract
It is difficult to treat dredged sludge with high organic matter content by solidification. A new solidification of dredged sludge with high organic matter content was developed, using cement, fly ash, slag, and phosphogypsum as a solidifier and strong oxidant KMnO4and GH as additives, to improve the engineering performance of dredged sludge and make it as a roadbed material possible. The properties of the solidified samples were determined in terms of unconfined compressive strength, products of hydration, toxicity characteristics, water stability, freeze-thaw resistance, and volume stability. The microstructure and hydration products of the dredged sludge after solidification were evaluated by X-ray diffraction analysis, scanning electron microscopy, and thermogravimetry-differential scanning calorimetry analysis. Experimental results showed that the strength of the solidified samples has been significantly improved after treatment by strong oxidants. The effect of GH is better than that of KMnO4. Hydration products (ettringite) were well formed. After solidification by using the binders and strong oxidant GH, the samples had sufficient strength and good water stability performance, freeze-thaw resistance performance, and volume stability performance. The leach liquid of the dredged sludge solidified body meets the standard requirements. So, the dredged sludge after solidification can reach the requirement of the roadbed material.
Highlights
Increasing amount of dredged sludge has become an unavoidable environmental issue
Different strong oxidants (KMnO4 and GH) were chosen as additives to improve the solidification performance. ere are two points to evaluate whether the dredged sludge can be used as a roadbed material after solidification: good mechanical properties and no harm to the environment. erefore, the following tests were performed after the solidification: (1) unconfined compressive strength tests, (2) water stability tests, (3) freeze-thaw cycle tests, (4) expansion tests, and (5) leaching tests. e microstructure and hydration products of the dredged sludge after solidification were evaluated by X-ray diffraction analysis, scanning electron microscopy, and thermogravimetry-differential scanning calorimetry analysis
E raw dredged sludge was taupe gray and possessed a somewhat unpleasant smell due to the presence of organic matter. e physical properties of the dredged sludge are shown in Table 1. e content of organic matter was determined by the method of burning loss. e dredged sludge was dried to a constant weight at 105–110°C for 4 h and grounded finely for chemical composition analysis. e dried dredged sludge composition was analyzed by X-ray fluorescence (XRF)
Summary
Increasing amount of dredged sludge has become an unavoidable environmental issue. The dredged sludge is disposed via incineration, landfilling, or ocean disposal [2]. Dredged sludge are very soft soils (Cu < 50 kPa) and the moisture content of dredged sludge is higher than its liquid limit [3]. Solidification is one of the best ways to deal with dredged sludge [4]. It can improve mechanical properties and engineering properties of dredged sludge and its environmental properties [5]. Solidification is a simple, convenient, and flexible technology which is suitable for handling large quantities of dredged sludge
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