Optimization Research On Graduation And Composition Of Chloride Resistance Portland Cement

The chloride ion has the negative affect on the durability of steel reinforced concretestructures in the chloride environment.The anti-chloride concrete has been widely used inmany projects due to the good resistance to chloride ion penetration. Nowadays the mainmeasures used inthe anti-chlorine concrete are low water to binder ratio (w/b) and highdosage of mineral admixtures. Such concrete is generally manufactured by mixing Portlandcement and mineral admixtures in concrete mixing station or on site. Before manufacture theanti-chloride concrete should be tested a lot in laboratory to optimize the cementitiousmaterialin the initial period of the project, which consumes time and labor,the methodrequires construction units to purchase variety of raw materials, during the constructionprocess it’s difficult to guarantee the quality of anti-chlorine concrete andthe heat of hydrationof cementitious material is high under the low w/b, especially for the temperature deformationof mass concrete. To solve the above problems, the special cement has been usedin somemajor project in recent years.But the studies on the chloride resistant special cement transferpreparation cementitious materials place mainly, not on the optimization of graduation and thecomposition of cementitious materials.The optimization research on graduation and composition of chlorideresistant Portlandcement are studied in this.article.Different sizes limestone powdersare used to simulatecementitious materials to study the law of particle size distribution firstly, mixing differentfineness limestone powders by different proportions, analyzing accumulation porosity/wetporosity and flowability to evaluate limestone powders’ particle size distribution.And then theoptimizedparticle size distribution of chloride resistant Portland cement is studied on the baseof the law of the particle size distribution. After that theoptimized compositionof chlorideresistant Portland cement is studied by comparison experiment. Under the experimentalcondition in this paper,the results are as followings:(1) By analyzing the porosity and flowability of different size limestone powder, the“standard analysis curve”of limestone powder is got,this article uses RRSB distributions toexpress “standard analysis curve”.(2) On the base of the optimization graduation laws of the limestone powder, by mixingslag, fly ash, ultrafine powders (beads, silica fume, WS, NS) and other blending materials,analyzing lower accumulation porosity/liquid limit and plastic limit porosity and quickerflowability to evaluate the performance of chloride resistant Portland cement, and thegraduation of chloride resistant Portland cement is studied. From the results the optimal dosage of fly ash is15%~30%, the optimal dosage of slag is30%~50%, the optimal dosage ofultrafine powder is less than15%.(3) By modifing “standard analysis curve”of limestone powder the “standard analysiscurve”of cementitious materials is got. It can be divided into two conditions by weatheradding slag, and the “standard analysis curve” equations with slag(portland cement-slagsystem/portland cement-fly ash-slag system/portland cement-slag-ultrafine powder system)“standard analysis curve” equations without slag(portland cement-fly ash system/portland cement-ultrafine powders system/portland cement-fly ash-ultrafine powderssystem).(4) On the base of optimized particle size distribution,the composition of chloride resistantPortland cement is studied; by mixing ultrafine powders the anti chloride performanceofchloride resistant Portland cement is improved greatly. The ultrafine powders haveinsignificant effect on the strength performance but have significant effect on the anti chlorideperformance by max to50%because the “additive effect” of ultrafine powders.Differentultrafine powders have different optimize dosage, which the microbeads, the WS limestonepowder, and the silica fume are7%.