Research On Rheological Properties Of Foam Concrete

The good working performance of foam concrete is a precondition for achieving the intended quality objectives,and a important part of that is the rheological properties of foam concrete,which directly determines the selection for water-cement ratio,the stability of the foam,the development of pore structure and so on.At present,the research on the rheological properties of foam concrete is deficient,it is necessary to develop the systematic research.In this thesis,rheological parameters of foam concrete with different composition were determined by rotational viscometer and the applicable rheological model for foam concrete was fitted by regression analysis.The thesis adopted a certain factor method to study the effect of the reference paste,the type of cement,water-cement ratio,adding volume of foam,different mixing amounts of polycarboxylic and naphthalene series water reducing agent,different mixing amounts of class I fly ash,silica fume and GGBS,different mixing amount of HPMC on the rheological properties of foam concrete.The research shows that the optimal rheological model of foam concrete is Herschel-Bulkey(H-B)model,the rheological parameters are yield stress,viscosity coefficient,rheological index,with the yield stress and viscosity coefficient characterizing the rheological properties of slurry,the rheological index characterizing the shear behavior of slurry.The Bingham rheological model common used by ordinary concrete is not applicable for foam concrete.The rheological properties of foam concrete are affected by the rheological properties of the reference paste.The rheological properties would differ from the varities of cements.Water-cement ratio has a great influence on the rheological properties of foam concrete,and the rheological properties of the slurry increase with the augment of water-cement ratio.The adding volume of foam has an impact on the rheological properties of foam concrete,and the rheological properties of the slurry increase with the augment of the adding volume of foam.The effect on the rheological properties of foam concrete by the reference paste,the type of cement,water-cement ratio is similar to that of ordinary concrete.Water reducing agent can significantly improve the rheological properties of foam concrete and different types of water reducing agent have different improvementeffect.The slurry mixed with hydroxypropylmethylcellulose(HPMC)is thixotropic and the thixotropy increases with the augment of HPMC content.HPMC can improve the rheological properties of foam concrete.The effect on the rheological properties of foam concrete mixed with different kinds of water reducing agent is similar to that of ordinary concrete,but the effect of HPMC is different,and HPMC would inhibit the rheological properties of ordinary concrete.The admixture also has an impact on the rheological properties of foam concrete.In which of that,ClassⅠfly ash can improve the rheological properties of foam concrete,as the mixing amount increased,the improvement impact enhanced,but the mixing amount should not be too large.Silica fume could inhibit the rheological properties of foam concrete,the larger the mixing amount of silica fume,the greater the inhibition impact.GGBS would improve the rheological properties by reducing the yield stress of the foam concrete slurry.The impact and mechanism of three kinds of admixture on the rheological properties of foam concrete is similar to that of ordinary concrete.