The effect of mineral and chemical admixtures on viscosity and consis -tency of paste using the FlowCyl (modified Marsh cone) and mini slu -mp tests

The production of high strength concrete (HSC)، high performance concrete (HPC) and self consolidating concrete (SCC) at the end of 20th century، made a revolution in the field of concrete technology. Paste (matrix) plays an important role in these concretes. In addition to cement، a variety of mineral additives such as silica fume and fly ash used as pozolans and limestone powder، micr- onized quartzite and fine siliceous sand as fillers are frequently in the paste of these concretes. For reduction of water cement ratio، a variety of chemical admixtures and superplastisizers with different properties has been introduced to the market. In order to optimize mix proportion design of HSC/HPC/SCC، the study of compatibility of these mineral and chemical admixtures with cem -ent and the performance of their combination in the mix is essential and inevitable. The flow properties of the paste can be established by using only a few liters of the material، while providing the designer with useful information for predicting the flow behavior of mortar and concrete. A modified version of Marsh cone test called FlowCyl، was utilized to quantify the viscosity of paste. The result of automated FlowCyl test is not operator dependent and has a good repeatability index. Al -so، using a miniature slump cone، the spread diameter of the paste، which is related to its yield stress، was measured. From these data، the effect of various parameters on fresh properties of paste was studied. The saturation dosage of super plasticizer (SP) for paste، a value beyond which an increase in the SP dosage does not significantly improve the flowability، was investigated. Also the reduction of viscosity one hour after mixing was studied.