Development Of Foaming Agent For Air-foam Treated Lightweight Soil And Soil Tests On Its Engineering Properties

Air-foam treated lightweight soil is a new type of geotechnical material made of soil,cement,air bubbles and water.It has the advantages of lightweight,adjustable density and strength,good fluidity and self-standing.The foaming agent is an important reagent that has great influence on air-foam treated lightweight soil.It is always one of the important research targets to develop a new foaming agent with higher foaming ratio and better foam stability.In this paper,gelatin was used as raw material to carry out the development and test of compound protein foaming agents.The soil tests of samples were carried out to conduct a comprehensive evaluation of foaming agents.The main works and results are as follows.(1)The hydrolysis tests of gelatin were carried out in this paper.The results show that enzymatic can significantly improve the rate of hydrolysis compared with the traditional way.The hydrolysis time can be shortened from 4 to 10 hours to about 1 hour.It is most suitable for 10 g gelatin to heat it with 0.1g alkaline protease,200 g water and 0.2g calcium hydroxide at 50? for 40 minutes.(2)The foaming agent concentrate was compounded with surfactants in a series of experiments.The results show that the performance of foaming agent concentrate cannot improved by triethanolamine,CDEA and Arabian gum powder,but it can be improved by LAS and AES.(3)The single factor repeated tests for the dosages of gelatin,LAS and AES were respectively carried out.The significance test on the test results was carried out.The results show that when the significance level is 0.1,the foam stability and foaming ability can be significantly improved by both LAS and AES.But when the dosages of LAS and AES reach 32 g and 18 g respectively,the effect will be weakened obviously.The foaming ability of the foaming agent,instead of the foam stability,can be significantly improved by gelatin.(4)The factor levels were set as LAS(26g?32g?38g),AES(26g?32g?38g),gelatin(10g)in the comprehensive tests.The significance test on the test results was carried out.The comparative analysis of the 9 kinds of homemade foaming agent and 3 kinds of commercially available foaming agent was carried out in the comprehensive tests.The results show that in a mixed system of LAS,AES and gelatin,the order of influence on the performance of the foaming agent should be: interaction between LAS and AES>AES>LAS> gelatin.The comprehensive performances of nine kinds of homemade foaming agent are all better than 3 kinds of sold foaming agent.(5)The existing shortages about evaluation standard and methods of the foaming agent were analyzed.It is recommended to characterize the foam stability of the foaming agent by 1h defoaming ratio,and to characterize the foaming ability of the foaming agent by expansion ratio in this paper.A comprehensive index as-(9)ba)1(was proposed to evaluate the comprehensive performance of the foaming agent,where a is expansion ratio of the foaming agent,and b is 1h defoaming ratio of the foaming agent.Its physical meaning is the amount of remained bubbles after the bubble emitted by the unit volume of foaming agent was at rest for 1 hour under certain conditions.(6)Air-foam treated lightweight soil samples were respectively prepared by using 9 kinds of homemade foaming agents and 3 kinds of commercially available foaming agents.The tests of density,strength and volume water absorption of the samples were carried out.The results show that the evaluation results based on the water absorption rate and the strength of the samples should be opposite to those based on the sample density.Considering that lightweight is the most important characteristic of air-foam treated lightweight soil,the sample density was taken as the basic basis for evaluating the effect of the foaming agent.(7)After the comprehensive consideration of foaming agent performance evaluation result and sample density evaluation result,the optimum comprehensive properties of foaming agent were determined as homemade foaming agent F-6 and F-7.Their formulas were respectively 38 g LAS + 18 g AES + 10 g gelatin and 26 g LAS + 22 g AES + 10 g gelatin.