Probabilistic functions of mechanical properties of plain cement pastes determined by a reduced-size test

Autores: Fábio C. Oliveira; Marcos P. Kassab; Natalia V. Silva; Sérgio C. Angulo; Luís Marcelo Tavares;  David A. Lange

Revista: Construction and Building Materials (doi)

Disponível online: 7 de Junho de 2021

Resumo: Knowledge of the mechanical properties of plain cement pastes, as well as their variability, is important to predict the properties of concretes. Pastes are very susceptible to critical defects that not only reduce the mechanical strength but also increase the variability. The paper proposes a method to evaluate the tensile strength and the elastic modulus of cement pastes, based on the Point Load Test and the Hertz Contact Theory, from experiments on reduced-size cubic samples (~10 mm). Three cement pastes with w/c ratios of 0.30, 0.50 and 0.70 were produced and 40 samples were cast for each paste. A simple method of estimating the chemically combined water and the effective w/c ratio (after bleeding in the stationary stage) of each sample was proposed. Being an expedite method, it allowed obtaining more than 100 valid mechanical results in about 8 h of testing using less than 250 g of cement, with values of tensile strength and elastic modulus that approached the macroscale reference values from the literature. The tensile strength of cement pastes varied considerably, but in the range informed in the literature, whereas the elastic modulus was less variable. Probabilistic functions for the characteristic values of the mechanical properties were provided.