Evaluation of the influence of the viscosity modifying admixture on the properties of self-compacting concrete

ABSTRACT

The properties of Self-Compacting Concrete (SCC) are ensured by the high flowability, the ability to pass through obstacles without being blocked and the resistance to segregation. However, such fluidity can cause effects of aggregate segregation and water exudation, which can be controlled with the incorporation of viscosity modifying admixtures. The present study evaluated quantitatively the influence of chemical admixtures, focusing on the viscosity modifying admixture. Two types of polycarboxylate-based Superplasticizer Admixtures (SP) were used to produce five different self-compacting concretes, one of these admixtures was incorporated into the composition of the reference concrete of this study. A water-soluble polyethers-based Viscosity Modifying Admixture (VMA) with a high molecular weight was added to the mixes of the other four concretes in the contents of 0.5% and 1.5% of the weight of the cement. Also, another concrete was produced with the use of an experimental polycarboxylate-based admixture that acts as superplasticizer and viscosity modifier. To reach the scope of this study and to evaluate the properties of fresh concrete, the slump flow test, the L-box test and V-funnel test were performed. It was set as a specification for each concrete the value of 0.85± 0,05 for the HP parameter, which is determined by the L-box test. To characterize the suspension stability of the chemical admixtures, the zeta potential test was performed. In the hardened state, the simple compressive strength test was performed at the ages of 7, 14 and 28 days. In addition, other tests were performed at the age of 28 days such as the diametrical compression test and water absorption by immersion test. In addition, to evaluate hydration products, thermogravimetric analysis was performed on cement pastes with the contents of chemical admixtures of each SCC. The results of this research showed that the viscosity modifying admixture along with the Superplasticizer Admixtures (SP) produced traces with variable fresh properties. The use of the VMA influenced the cement hydration process and, therefore, the mechanical properties of the concrete.

Keywords
Self-Compacting Concrete (SCC); Viscosity Modifying Admixture (VMA); Superplasticizer Admixture (SP)