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To explore the reaction mechanism of sludge, slag, lime, and fly ash in high temperature environments, the unconfined compressive strength (UCS) test was hereby implemented to study the effect on curing age, curing temperature, slag content and fly ash content about the strength of sludge. Scanning electron microscopy (SEM) was used to observe the microscopic composition of the substance, and X-ray diffraction (XRD) was used to analyze the mineral composition at the micro level to further disclose its reinforcement mechanism. The experimental results demonstrate the difference in the strength measured by different dosage of curing agent, and results indicate that the strength of high temperature curing sample was obviously higher than that of low temperature curing sample. When the curing temperature rises, the pozzolanic reaction and hydration reaction between materials are accelerated, and a certain amount of gel products are produced, playing a precipitation and bonding role between particles. The 28 days and 90 days strengths of the sludge samples with 20% fly ash and 80% slag dosing at 40°C were 1139 KPa and 1194 KPa, which were 1.4 and 1.1 times of that of pure cement solidified sludge. At 60°C, the strength of 14 days, 28 days and 90 days were 802 KPa, 1298 KPa and 1363 KPa, which were 1.1, 1.5 and 1.3 times of that of pure cement solidified sludge. Under the influence of an alkaline environment, the silicon-aluminum grid structure was interconnected into a denser network structure, and the compressive strength of lime-activated fly ash-slag was thus continuously enhanced. Affected by the high temperature, lime-activated fly ash-slag solidified sludge could significantly improve the middle and late strength of the sample. The research showed that the new solidification material can replace partly the concrete curing agent, thereby alleviating the carbon emission and environmental pollution problems arising from cement solidified sludge. [ABSTRACT FROM AUTHOR]

To reveal the mechanism of the influence of the curing temperature on the strength of lime activated fly ash-GGBS cured silt soil, the curing of dredged silt was carried out by using fly ash and GGBS as the curing agent and lime as the activator. Unconfined compressive strength (UCS) experiments were carried out, and the micro-analysis of the cured silt was carried out by experimental methods including scanning electron microscope (SEM) tests, X-ray diffraction (XRD), etc. to reveal the mechanism of the curing temperature on the dredged silt. According to the test results, the hydration reaction and pozzolanic reaction between lime-fly ash-GGBS and silt soil were promoted with the increase of the curing temperature. when the curing temperature of the sample reached 40 ℃, a large amount of gel products such as hydrated calcium aluminate (C–A–H) and hydrated calcium silicate (C–S–H) were generated, which enhanced the bonding force between soil particles and filled up the inter-particle pore space, thereby improving the UCS of the sample. The results of SEM confirmed that C–A–H and C–S–H were the main substances for the construction of cured silt skeleton. C–S–H and C–A–H were detected by XRD. The results of the study fill the gap in the effect of curing temperature on the direction of lime-activated fly ash-GGBS cured silt soil. [ABSTRACT FROM AUTHOR]