| Foamed concrete is a kind of lightweight concrete which is made of foam,cement,water,aggregate and so on,and foam is the preparation of foaming agent into foam by physical method.Foamed concrete has excellent characteristics such as light weight,high fluidity,small thermal conductivity,and good fireproof sound insulation,because there are a large number of tiny closed pores inside.Foamed concrete is widely used in construction engineering,municipal road engineering,underground engineering,port water conservancy engineering,filling engineering and other fields.Therefore,the application of foamed concrete to the roadbed filling project can not only give full play to the performance advantages of foamed concrete,but also play an important role in promoting the development of traffic construction materials to green environmental protection,energy conservation and emission reduction.At present,the application of foamed concrete in the direction of roadbed filling has been reported,but many engineering application schemes only study one or a few proportioning schemes.Theoretical analysis on the influence of foamed concrete mix ratio on the performance of foaming liquid and concrete for roadbed filling.And detailed experimental research is still rare.Based on this issue,this paper firstly analyzes the foaming mechanism of surfactant foaming agent and the rheological process of foam from the theoretical aspect.A lot of experiments were carried out from three aspects:foaming agent,water-cement ratio and aggregate.The performance improvement of foamed concrete for roadbed filling is studied,and the optimum proportion and performance parameters of roadbed filling are determined.(1)The properties of the foaming agent and the microstructure of the foam were studied by adding xanthan gum as a foam stabilizing agent to the anionic surfactant foam solution.Foamed concrete specimens with a designed dry density of 600kg/m~3were prepared with foam prepared by foaming agent for concrete test.The results of foam test showed that the surface tension of the foaming liquid,after adding xanthan gum,can be reduced,and the expansion ratio can be increased.With the increase of the amount of xanthan gum,the stability of foam have been improved.The concrete test shows that the foamed concrete made of foaming liquid after adding xanthan gum has uniform pore diameter and less pores.(2)The research on the influence of different water-cement ratios on the foamed concrete performance shows that,in terms of mechanical properties,the peak values of compressive strength,splitting strength and axial compressive strength are mainly concentrated in the water-cement ratio between 0.50 and 0.60.With the increase of water-cement ratio,the fluidity of foamed concrete slurry increases.The water-cement ratio of foamed concrete is in the range of 0.50～0.60.The effect of water-cement ratio on the crack resistance of foamed concrete is studied by using the outer circle eccentric restraint mold.It is found that the cracking time of foamed concrete is obviously accelerated with the increase of water-cement ratio.Combined with the SEM image,when the water-cement ratio is 0.55,the roundness of the bubble is better,and the bubble penetration rate is small,and the thickness of the hole wall structure is large and uniform.(3)The results of the preparation of the rubber aggregate as a foamed concrete show that,when the rubber aggregate content is 10%,the fluidity is reduced from the initial 189mm to 165mm.In terms of mechanical properties,with the increase of rubber aggregate content,the strength of foamed concrete generally increased first and then gradually decreased,and reached a peak when the dosage was about 4%.In addition,in terms of concrete crack resistance,as the rubber aggregate content increases,the cracking time of the foamed concrete gradually increases.When the rubber aggregate content was 10%,the cracking time was extended to 111.7 h. |
