Preparation And Performance Research Of The Composite Foamed Concrete Insulation Material

Compared with the traditional organic insulation materials,high-volume fly ash foamed concrete is a new kind of more ideal inorganic thermal insulation materials owned to its non-combustible,lightweight and anti-aging characteristics.However,low strength is the most obvious shortcomings of foamed concrete,and sometimes,low strength foamed concrete cannot meet the needs of the actual project.With the development of materials science,it has been found that concrete materials could be enhanced obviously by nanotechnology and this also provided new thought to improve the performance of foamed concrete.Nano-montmorillonite?nMMt?is a kind of functional materials composed of two layers of silicon-oxide tetrahedron with aluminum-oxide octahedron.Because of its great specific surface area and lower prize,it was widely used in materials science,and a lot of literature also indicated that nMMt has obvious effect on cement-based material.Therefore,it was considered to use nMMt to modify the microstructure of high-volume of fly ash foamed concrete to improve the performance of foamed concrete,and prepare a kind of new composite foamed concrete with the enhancement of anti-crack polypropylene fibers?PP fibers?.In this paper,a kind of composite foamed concrete was prepared with the modification of nMMt and the enhancement of PP fibers.Effects of the raw materials on the mechanical properties and thermal properties was analyzed,and then the modification mechanism of nMMt and interface performance of PP fibers was also analyzed in details.The main conclusions are summarized as follows:?1?Uniform design was used to investigate the optimal mixture as following:70%class F fly ash,30%Portland cement,1%sodium Alpha-Olefin Sulfonate,2%Alcohol Ethoxylate,0.75%Sodium Phosphate and 1%nano-montmorillonite.28d compressive strength is 3.23MPa and the thermal conductivity is 0.074 Wm^-1K^-1which could meet the needs of the actual project.?2?It was found through the strength prediction modules that fly ash and AOS was side effect to the strength and the nMMt was good for it.It also found through the detail analysis of the interaction between raw materials that hydration of Portland cement was promoted by nMMt,Sodium Phosphate could enhance the effect of AOS and AEO but it would inhibit the hydration of cement.?3?It was indicated through changing the content of nMMt that the optimal nMMt content in this study was 3%,and the strength increased about 18%,this might been owned to the filler effect and pozzolanic effect of nMMt.When the content was over 3%,the strength was decreased and this might be owned to the strong water absorption and expansibility.Because of the strong water absorption,actual cement water ratio of the cement hydration and surface tension of bubbles will be affected which will influence foaming performance and is bad for its insulation property.Compared with the other content of nMMt,1%content is suitable which will balance the contradictive relationship between the compressive strength and insulation property.?4?It was suggested that 0.4%volume content of PP fibers with 3mm length was the best combination to increase rupture strength and anti-crack performance obviously.The coupling-effect of different raw materials on composite foamed concrete was guessed through the element analysis between the interfaces of PP fibers and concrete matrix,and based on this,the synergistic effect between PP fibers,surfactant and nMMt was established with the comparison of relative literature.