Micro-mechanisms of dredged sludge solidified with reactive MgO-fly ash
WANG Dongxing1，2，WANG Hongwei2，WANG Ruihong3
(1. Hunan Provincial Key Laboratory of Key Technology on Hydropower Development，Zhongnan Engineering Corporation Limited，PowerChina，Changsha，Hunan 410014，China；2. School of Civil Engineering，Wuhan University，Wuhan，Hubei 430072，China；3. Key Laboratory of Geological Hazards on Three Gorges Reservoir Area，Ministry of Education，China Three Gorges University，Yichang，Hubei 443002，China)
Abstract：The macro-efficiency and intrinsic mechanisms of low-carbon and environmental-friendly reactive MgO-fly ash blend，which is innovatively introduced into solidification of dredged sludge from Wuhan Eastlake，China，are deeply discussed. Based on unconfined compressive strength，X-ray diffraction，scanning electron microscopy，thermogravimetric and mercury intrusion porosimetry tests，a systematical study has been performed to analyze the strength，hydration products，structural morphology，thermal stability and microscopic pores of reactive MgO-fly ash solidified sludge. The test results indicate that the unconfined compressive strength of reactive MgO-fly ash solidified sludge increases with curing time，MgO-fly ash content and MgO/fly ash mass ratio. The formation of Mg(OH)2 and M-S-H(magnesium silicate hydrate) gel is the main reason why the strength property of solidified sludge is obviously improved. The increase in reactive MgO-fly ash content and MgO/fly ash mass ratio leads to an intensified diffraction peaks of Mg(OH)2 and M-S-H，an increase in thermogravimetric weight loss，a transformation of inter-aggregate pores to inter-particle pores. This induces a denser microstructure and better integrity，which promotes greatly the strength gain of solidified sludge. The obtained result further deepens the understanding of macro- and micro-characteristics of reactive MgO-fly ash solidified sludge，and establishes a full microscopic reaction model of reactive MgO-fly ash to clarify the intrinsic micro-mechanisms for the property improvement of solidified soils. The research results provide a theoretical basis for the application of green and low-carbon reactive MgO-fly ash blends in the practical engineering such as sludge solidification.
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2019, Vol. 38 
