The Researches Into The Influence Of Different Plasticizers On The Performance Of Low Cement Castable

Adding appropriate plasticizers into low-cement castable can effectively improve its usability. Existing researches mostly use all kinds of polyphosphate-type plasticizer, while there are few researches on influencing difference of naphthalene, sulphamate and polycarboxylate series of plasticizers which have been extensively applied in Portland cement concrete on performance of low cement castable. This paper conducted a systematic comparative research on influencing rules and mechanisms of plasticizer like sodium tripolyphosphate, sodium hexametaphosphate, naphthalene, sulphamate and polycarboxylate on rheological properties, physical properties and high-temperature performance of castable. Main research achievements are as following:(1)Absolute value of ζ-potential of matrix slurry added with comb-like structure polycarboxylate plasticizer was only 20-30 mV, electrostatic repulsion was small, mainly being steric hindrance repulsion, the slurry presented good plasticity, pseudo-plasticity and dilatant fluid status; Mixing polyphosphate plasticizer could make matrix slurry form thick diffused double electric layer, absolute value of ζ-potential was high, reaching 70-100 mV and mainly being electrostatic repulsion,the slurry presented good plasticity fluid state; Absolute value of ζ-potential of matrix slurry mixed with naphthalene and sulfamate plasticizer was 30-60 mV, both electrostatic repulsion and steric hindrance repulsion were quite weak, and good flow conditions of slurry could be reached only by increasing dosage of plasticizers.( 2) Apparent viscosity of matrix slurry added with comb-like structure polycarboxylate plasticizer was low while fluidity of slurry good. When mixing amount was 0.10%~0.12%, water consumption of castable mixture would be low with the good workability, the influence on fluidity of matrix slurry and influence on mixture workability were consistent; Apparent viscosity of matrix slurry mixed with polyphosphate plasticizer was high, fluidity of slurry was good, when mixing amount was 0.15%, water consumption of castable mixture was relatively low with relatively good workability, and the influence on fluidity of matrix slurry and influence on mixture workability were consistent; Apparent viscosity of matrix slurry mixed with sulfamate and naphthalene plasticizer was the highest with good fluidity of slurry., when mixed amounts respectively reached 0.18% and 0.75%, water consumption of castable mixture was high with poor workability, the influence on fluidity of matrix slurry and influence on mixture were inconsistent.(3)Water consumption of castable mixed with 0.10%~0.12% polycarboxylate plasticizer was 5.4%~5.8%, after hardening, bulk density, cold crushing strength and bending strength of castable were high; Water consumption of castable mixed with 0.15% polyphosphate plasticizer was 5.6%, and bulk density, cold crushing strength and bending strength of castable after hardening were slightly lower than those of that mixed with polycarboxylate plasticizer; water consumptions of casables which were respectively mixed with 0.18% and 0.75% sulfamate and naphthalene plasticizer reached as high as 6.3% and 6.5%, and bulk density, cold crushing strength and bending strength of castable after hardening was the lowest.(4)Linear change rate of castable mixed with polycarboxylate plasticizer was low, that of castable mixed with tripolyphosphate and sodium hexametaphosphate was relatively low, and that of castable mixed with sulfamate and naphthalene plasticizer was high.(5)The pore size distribution in the castable mixed with the polyphosphate plasticizer has a strong peak and a second-strongest peak,average pore size is small,the pore size distribution is uneven, but it can improve castable thermal shock stability to some extent; The pore size distribution curve in the castable mixed with the polycarboxylate plasticizer has only one strong peak,the pore size distribution is even,the thermal shock stability of the castable mixed with the polycarboxylate plasticizer is increased by 10% than that of the polyphosphate plasticizer;Average pore size of the castable mixed with the amino sulfonate and naphthalene plasticizer is large,the porosity is high, and the thermal shock stability is the worst.(6)SEM microstructure analysis shows tha through dring at 110 °C for 24 h, the specimen of castable with tripolyphosphate contains large spherical particles with a few floc structure, The specimen of castable with polycarboxylate plasticizer KS-JS70 has finer particles that are dispersed better, thereby illustrating that KS-JS70 has a better dispersion effect;Through handling at 1000 C for 3h, large pores formed in castable structure,gradually crystals form needle-like and sheet-like structure. Through handling at 1400 C for 3h, the castable was fully sintered, and two calcium aluminate(CA2), mullite(A3S2), anorthite(CAS2) phases were produced,which improved bulk density and cold crushing strength.