Preparation And Performance Study Of High-performance Air-entraining Agent And Defoaming Agent For Concret

Concrete air-entraining agents and defoamers can effectively improve the working performance of concrete,especially improving the frost resistance of concrete.To address the problems of commercially available air-entraining agents with insufficient air-entraining and foam-stabilizing properties and poor compatibility with other concrete admixtures,as well as the loss of concrete strength caused by commercially available defoamers.The first work of this paper aims to synthesize sulfate-based baryonic polyether air-entraining agents and to test and analyze their performance,specifically by converting fatty alcohol polyoxyethylene ethers into baryonic intermediates and modifying them by sulfation.The second work aims to prepare a polyether-modified silicone defoamer and to test and analyze its performance.The specific work consisted of the esterification of allyl polyethylene glycol(APEG)and allyl alcohol polyether F-6 with propionic anhydride for capping.Then,the capped two polyethers were subjected to a silicon-hydrogen addition reaction with hydrogencontaining silicone oil to obtain polyether-modified silicones.Finally,the polyethermodified silicone is compounded with silicone paste,emulsifier,and thickener to obtain polyether-modified silicone defoamer.The main contents of this thesis are:1.Synthesis and characterization of air-entraining agentThe fatty alcohol polyoxyethylene ether and ethylene glycol diglycidyl ether or butylene glycol diglycidyl ether were synthesized as baryonic polyether intermediates;the intermediates were sulfated and modified with sulfamic acid and urea to synthesize sulfate-based baryonic polyether air-entraining agents G3-2,G7-2,G9-2,G3-4,G7-4and G9-4,and their NMR hydrogen spectra and elemental analyses were performed to verify the product structures.At the same time,single-chain sulfate polyethers S3,S7,and S9 were synthesized by direct sulfation modification of fatty alcohol polyoxyethylene ethers.2.Air-entraining agent performance testFirstly,the surface tension,foaming performance,and foam stabilization performance of the air-entraining agents synthesized in this paper were tested and analyzed.Then,the effects of G3-2,G3-4,S3,and commercially available airentraining agent Y49 on the net cement flow,air content,slump,expansion,and compressive strength of concrete were investigated.The results showed that compared with Y49,the net slurry flow loss of G3-2 was smaller and the concrete performance test results were close to those of Y49,indicating that the G3-2 air-entraining agent synthesized in this paper has the potential to act as an air-entraining agent for concrete.3.Preparation of defoamerAPEG and F6 were capped with propionic anhydride,and then silicone hydrogen addition was carried out with silicone to produce polyether-modified silicone.The polyether-modified silicone was compounded with silicone paste,emulsifier,and thickener to produce APEG-F6 defoamer(DX01).The effects of feeding ratio,catalyst dosage,reaction time,and reaction temperature on the conversion rate of silicahydrogen bonding were explored to optimize the synthesis process.Meanwhile,the effects of silica paste and polyether-modified silicone mass ratio,emulsifier type and dosage,thickener type,and dosage on defoaming performance were also explored to optimize the compounding process.4.Defoamer performance testTo investigate the effect of the homemade defoamer DX01 and the commercially available defoamer X3,X5,and X12 on the net cement flow rate,air content,slump,expansion,and compressive strength of concrete.The results showed that compared with the commercially available defoamer,DX01 can effectively improve the concrete’s compatibility,reduce the air content,and have less effect on the net cement flow and hardened concrete strength,which has better application and development prospects.