Abstract
Effective foundation reinforcement treatment is essential for modern large and complex infrastructure, while it is significant for developing new green high-performance materials for foundation reinforcement. This study investigates a new green concrete by using high volume fly-ash and coal gangue aggregates, which is expected to apply for foundation treatment of modern infrastructure with high loading-bear ability. In this experiment, 12 mix proportions of fly ash coal gangue mixture (the material name, abbreviated FGM) were designed, and its mechanical properties and durability performance were investigated. The mechanical properties of FGM include compressive strength, dynamic elastic modulus, dynamic shear modulus, Poisson’s ratio, and the stress–strain behaviors. The durability performance was evaluated by the parameters of acid resistance, which simulated an acid circumstance. After that, the environmental effects about carbon emission of this material were also investigated. Results show that the FGM with 84.6% wastes utilizing rate is a cost-effective material for foundation reinforcing treatment. Its compressive strength at 28 days and 60 days can reach more than 8 MPa and 10 MPa, respectively. After being immersed in the acid environment for 140 days, the mass loss (%) of the material could be under 3.5%. The greenness shows that the e-CO2 indices of FGM are lower than 20 kg/MPa·m3, and the e-energy indices are at below 150 MJ/MPa·m3. FGM has the advantages of acid resistance, waste recycling, and lower carbon emissions than the previous methods for foundation improvement.
Highlights
The foundation improvement can uniformly disperse surface load into the original soft soil foundation and effectively reduce railway settlement [1]
With much more strict requirements for high-speed railway construction, the technology for ground improvement has been being developed: (I) At the first stage, lime and cement were used to improve marine clay [2,3]; (II) water glass and other chemical grouting materials could be injected with arbitrary curved intrusion pass into soft foundation to enhance properties [4]; (III) In the third stage, cement-fly ash-gravel mixture (CFG)
The lower binder amount means the fewer content of hydrated silicate calcium gel, calcium hydro-oxide crystals, and ettringite formed, which contribute to the strength development [43]
Summary
The foundation improvement can uniformly disperse surface load into the original soft soil foundation and effectively reduce railway settlement [1]. CFG materials can enhance the subgrade (to the extent of more than 10 MPa), and provide an opportunity to consume industrial waste solid (fly-ash), which will reduce the engineering cost by more than 50% and promote environmental protection after. Because of the shortage of natural sand and limestone [8], utilizing recycle aggregates or solid wastes can be confirmed to replace the concrete’s gravel or sand [9]. It has been recognized as an economical and environmentally friendly method that brings many social benefits
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