Cement-superplasticizer compatibility and flow properties of binder paste and mortar using marsh cone and flow table method

Abstract

Flow behavior of the binder paste renders a fair idea about the properties of high-performance concrete, especially, in the fresh state. Optimisation of the cement matrix phase or the paste phase in terms of fluidity is an important step in the development of high-performance concrete. It is, therefore, imperative to have a simple, effective, and reliable methodology to assess the flow behavior of the paste. Marsh cone test is often employed for this purpose, and limited review of the prior art indicates no standardization of the quantity of the paste corresponding to which the flow time should be measured and the saturation dosage of superplasticizer to be assessed. Rate of flow through the cone orifice may not remain same, and rather decreases with time. This paper investigates the flow time for different quantities of the paste with an aim to assess the optimum quantity to be used with Marsh cone test for the determination of saturation dosage of superplasticizer. The effect of mixing time upon the flow behavior of the paste is next evaluated with the help of Marsh cone test. Further, the mix design of high-performance concrete of compressive strength in the order of 100 MPa often excludes the coarse aggregates, and hence, resulting in a significant increase in the cost of concrete production. This paper also investigates the flow behavior of the mortar prepared with a low sand-to-cement ratio of 0.62, which is typically the case with ~100 MPa concrete utilizing coarse aggregates. Marsh cone test may not be feasible in such a case on account of low water-cement ratio. Conventional flow-table test is indigenously extended for this purpose to make inference on the fluidity of paste and the saturation of superplasticizer dosage. Finally, results of the paper, in principle, enable assessment of the cement-superplasticizer compatibility. Three different brands of cements are used throughout the test program with a well-known brand of superplasticizer.