Unraveling pH evolution driven by multi-component synergy and plant feedback in cement-based vegetation substrate

Area of Science:

• Environmental Engineering
• Materials Science
• Soil Science

Background:

• Cement-based vegetation substrates (CBVS) offer ecological restoration and slope stabilization benefits.
• High substrate alkalinity in CBVS inhibits plant survival, necessitating effective pH regulation strategies.

Purpose of the Study:

• To investigate pH evolution in a vegetation-compatible cementitious system with silica fume and a composite ecological regulator (CER).
• To elucidate multi-component alkaline-regulation mechanisms and plant-substrate feedback loops.

Main Methods:

• Utilized Scanning Electron Microscopy (SEM) and vegetation experiments.
• Analyzed the impact of cement content, silica fume, and CER on substrate pH.
• Quantified pH changes induced by plant growth over 100 days.

Main Results:

• Initial substrate alkalinity was primarily controlled by cement content.
• CER reduced alkalinity by 11.2% through ion neutralization, humate complexation, and microbially induced precipitation.
• Silica fume (2%) decreased pH by 5.2% by consuming portlandite and forming low-alkalinity C-S-H gels, enhancing matrix strength.
• Tall fescue reduced system pH by 15.7%, confirming a plant-material feedback loop.

Conclusions:

• The developed vegetation-compatible cementitious system effectively mitigates alkalinity.
• Composite ecological regulators and silica fume are key to reducing initial substrate pH.
• Plant growth significantly contributes to long-term pH regulation, establishing a beneficial feedback loop for ecological restoration.