Experimental Research on the Carbonation Granulation Method for Silty Drilling Residue and Its Strength Growth Mechanism

To enhance the low-carbon and diverse utilization of silty drilling residue, this study proposed a self-designed temperature and humidity-controlled carbonation reactor, and presented systematic experimental investigations into the granulation carbonation method for silty drilling residue and its strength growth mechanism. Firstly, the silty drilling residue, from bridge pile foundation construction, were modified with hydrated lime to produce granular billets with a 12 mm diameter. Subsequently, the reactor was filled with CO? and the granular billets were carbonation cured at constant temperature and humidity (60 °C, 80% humidity) for 8 hours to obtain high-strength pellets from silty drilling residue. After that, thermal gravimetric analysis (TG), X-ray diffraction (XRD), and pellet strength tests were carried out, providing insights into the strength augmentation mechanisms inherent in carbonated pellets with 7 different amounts of hydrated lime. The experimental results demonstrate that this process yields a remarkable carbonation rate exceeding 80%, primarily resulting in the formation of calcium carbonate crystals of the calcite variety. The strength of carbonated pellets exhibits a discernible dependency on the quantity of hydrated lime, showing a two-stage progression. It presents an initial gradual increase followed by a rapid surge. Specifically, with hydrated lime contents below 12%, the strength of carbonated pellets gradually increases. When exceeding this threshold, a substantial quantity of calcite functions as a binding agent, which interlocks soil grains and forms a coherent structural framework. During this process, the crystal particle size of calcite diminishes progressively that expands and fills into pore spaces, and the pellets strength enters an accelerated period, which can surpass 3. 0 MPa. Moreover, the water stability assessments reveal that when hydrated lime content exceeds 16%, carbonated pellets display an exceptional A-grade water stability performance. Remarkably, carbon emissions analysis indicates a noteworthy reduction in C02 emissions by 42. 7% to 52. 6% when compared to ceramsite, underscoring substantial carbon reduction advantages. This study provides a technical solution for the green disposal of silty drilling residue and its utilization in scenarios, such as road base fillers and bridge abutment subgrade fillers. © 2024 Chang'an University. All rights reserved.