摘要
A superplasticizer is a type of chemical admixture used to alter the workability(viscosity)of fresh concrete.The workability of fresh concrete is often of particular importance when the water-to-cement(w/c)ratio is low and a particular workability is desired.Reactive Powder Concrete(RPC)is a high-strength concrete formulated to provide compressive strengths exceeding 130MPa and made of primarily powders.RPC materials typically have a very low w/c,which requires the use of a chemical admixture in order to create a material that is easier to place,handle and consolidate.Superplasticizer are commonly used for this purpose.Superplasticizers are developed from different formulations,the most common being Polycarboxylate Ether(PCE),Polymelamine Sulfonate(PMS),and Polynaphthalene Sulfonate(PNS).This study investigates the effect of various PNS based superplasticizers on the rheological performance and mechanical(compressive strength)performance of a RPC mixture.Six distinctive types of PNS based superplasticizers were used;three of various compositional strengths(high,medium,low range)from a local provider,and three of the same compositional strengths(high,medium,low)from a leading manufacturer.The properties investigated were the individual superplasticizers’viscosity,the concrete workability,determined through a mortar spread test,the concrete viscosity,and the compressive strength of the hardened RPC mixtures measured at 7,14,and 28 days.Two separate RPC mixtures were prepared,which contained two different water-to-cementitious ratios,which consequently increases the dosage of superplasticizer needed,from 34.8L/m3 to 44.7L/m3.The results show that the name brand high range composition produced the overall highest spread,lowest viscosity,and a highest compressive performance.However,the local provider outperformed the name brand in the mid and low range compositions.Lastly,the rheology assessment also confirmed that the name brand high range,and RPC fabricated with the name brand high range,developed the lowest viscosities.
