Preparation And Application Of Loess Based Geopolymer Composites

Open-structure and collapsibility of loess have resulted landslides,soil erosion and other geological disasters,which seriously harm the normal production and life of people.However,loess with aluminosilicate as the main component is also a natural inorganic material with abundant resources,cheap,easy to obtain and eco-friendly.Therefore,the exploitation and utilization of loess resources have gradually attracted the attention of more and more researchers.Moreover,geopolymers prepared with aluminosilicate as the main material have the characteristics of lightweight porous structure,excellent mechanical properties and stability,making them inorganic polymer materials with broad application prospects.In this paper,loess-based porous geopolymers were prepared using cheap and eco-friendly loess particles as the main raw material,and activated by two different（acid and alkaline）activators,respectively.Furthermore,they were respectively compounded with agricultural waste（corn,wheat straw powder）and green functional polymer materials,and after loading urea to were prepare a series of eco-friendly and nutrient slow-release loess-based geopolymer composites.The application of composite materials in promoting plant growth and stabilizing loess slopes was investigated.The paper includes the following parts:Chapter 1,firstly,the main components and geological characteristics of loess,as well as the modification methods and application fields of loess were expounded.Secondly,the preparation methods and characteristics of geopolymers and their composite materials were introduced.Finally,the research progress of application of geopolymer and solid soil slope protection were summarized.Chapter 2,Alkali-activated loess-based geopolymers（ALPGs）was prepared using loess particles（Lo Ps）as raw materials,activated by Na₂Si O₃-Na OH and saponified by siritch.Subsequently,corn stalk powder（Co S）was compounded with ALPGs and loaded with urea,and then acrylic acid（AA）was used as the polymerization monomer,MBA was used as the cross-linking agent,and KPS was used as the initiator to prepare a loess-based geopolymer composite loaded with urea（N@Co S-PAA/ALPGs）through in-situ graft polymerization method.The microstructure,morphology and properties of the composites were characterized and analyzed by FT-IR,SEM,EDS,BET,XRD and TG.The swelling properties and water retention properties of the composites were investigated.The N slow-release properties of the composite were studied by leaching experiments,and the release kinetics models were established to explore the release mechanism.The effect of composite material on maize growth was investigated by pot experiment.The results showed that the maximum swelling ratios of N@Co S-PAA/ALPGs in distilled water and 0.9 wt.%Na Cl solution were 263.16 g/g and 62.5 g/g;2 wt%soil addition amount of N@Co S-PAA/ALPGs was added to the soil,the soil water holding capacity reaches 25 d.In addition,N@Co S-PAA/ALPGs released 60.6%of nutrients at 30 d,which could effectively promote the germination and growth of maize.Chapter 3,The prepared N@CoS-PAA/ALPGs was applied in the field of loess slope stability and soil and water conservation.The effects of composite on the compressive strength,heat resistance,freeze-thaw resistance and p H value of loess;on the solidification,water erosion resistance and wind erosion resistance of the slope surface;and on the germination rate of grass seeds were investigated,respectively.The effect of composite materials on the fixation and soil and water conservation of loess slope was studied through the simulated loess slope test.The results showed that the compressive strength of loess sample increased from 0.89 MPa to 1.82 MPa with the soil addition of N@Co S-PAA/ALPGs increased from 0 wt%to 5 wt%.N@Co S-PAA/ALPGs not only improved the heat resistance,freeze-thaw resistance and p H value of loess,but also had good slope curing effect and corrosion resistance,providing a suitable growth environment for vegetation.In addition,N@CoS-PAA/ALPGs could effectively promote the germination and growth of grass seeds and effectively fix the loess slope.Chapter 4,Acid-activated loess-based geopolymers（PALPGs）was prepared using Lo Ps as raw materials,activated by H₃PO₄,and emulsified by OP-10;then,wheat straw powder（Wh S）,sodium humate（SH）and PALPGs were compounded and loaded with urea;finally,AA and 2-acrylamido-2-methylpropanesulfonic acid（AMPS）were further used as polymerized monomers.A urea loaded PALPGs composite（N@WS-PAM/PALPGs）was prepared by in-situ graft polymerization using MBA as crosslinking agent and KPS as initiator.It was characterized and analyzed by FTIR,SEM,EDS,BET,XRD and TG.The swelling and water retention properties of the composites under different conditions were investigated,and their N sustained release properties were studied by leaching experiments.In addition,the effect of promoting the growth of vegetables was explored through cultivation experiments.The results showed that:N@WS-PAM/PALPGs not only had good swelling rate;the maximum swelling rate in distilled water and 0.9 wt%NaCl solution is 322.58 g/g and 166.67g/g;but also,can increase the water holding capacity of soil,reached 27 d.In addition,N@WS-PAM/PALPGs had good N slow-release performance,which’s releasing rate of nutrients could reach 66.2%within 30 d,and could effectively promote the germination and growth of vegetables.Chapter 5,The N@WS-PAM/PALPGs were used as soil stabilizers and applied to loess slopes to improve soil quality.After the composite material was mixed with loess,the compressive strength,heat resistance,freeze-thaw resistance of loess;surface curing,erosion resistance,wind erosion resistance and other properties of loess slope surface was studied;Moreover,the effect of composite on soil p H and germination rate of grass seeds had also been investigated.The results showed that N@WS-PAM/PALPGs could not only improve the compressive performance and corrosion resistance of loess,but also effectively improve soil quality and promote grass germination.All in all,this paper focuses on the effective utilization of loess and agricultural waste resources and the widening of the application field of geopolymer.Eco-friendly geopolymer matrix composites were successfully prepared by selecting cheap and green materials and adopting simple preparation technology.As a slow-release fertilizer,the composite material not only had good swelling and water retention performance,but also increases the ability of soil moisture absorption and moisture retention,which could provide excellent living conditions for plants.It also released nutrients for a long time to promote germination and growth.In addition,as a soil stabilizer,composite materials could not only improve soil quality,but also achieved long-term effect of soil fixation and slope protection under the synergistic action of physical,chemical and biological methods.Therefore,this low-cost and eco-friendly composite material is expected to be used in agriculture and slope protection,thus benefiting soil and water conservation!...