Possibilities and challenges of constant shear rate test for evaluation of structural build-up rate of cementitious materials

The rapid development of additive manufacturing technologies in the construction industry has heightened interest in the accurate estimation of the structural build-up rates of cementitious materials, especially in in-situ conditions. For this purpose the constant shear rate (CSR) test performed by rotational rheometers using the single-batch approach can be applied. The paper at hand presents possibilities in improving the methodology of experiments and data analysis in the CSR test, for particular rheometers, and discusses both the features and limitations of the test. The breaking criterion is proposed for the CSR tests to prevent excessive deformation in a single sample measurement. Evaluation of the elastic properties of cementitious materials by the CSR test is assessed; two approaches for the characterisation of structural build-up rate based on proportionality limit and flow onset points are compared. The findings are illustrated for the examples of cement paste and cementitious mortars tested using two different types of rotational rheometers.