Viscosity Modifiers to Enhance Concrete Performance

The hazard rate function for concrete structures often is portrayed as a “bathtub”-shaped curve, with a finite ever-decreasing probability of early-age failures being followed by a life with a relative low, constant probability of failure that ultimately increases dramatically as the end of service is reached. Ideally, new concrete technologies should reduce the failures occurring at both ends of this service life spectrum. VERDiCT (Viscosity Enhancers Reducing Diffusion in Concrete Technology) is one such technology, having the potential to reduce the propensity for early-age cracking, while also reducing long-term transport coefficients of deleterious ions such as chlorides. In this paper, the performance of a typical VERDiCT admixture, a viscosity modifier/shrinkage-reducing admixture, is investigated in mortars and concretes, both as an addition to the mixing water and as a concentrated solution used to pre-wet fine lightweight aggregates. A reduction in early-age cracking is achieved by eliminating autogenous shrinkage stresses that typically develop in lower water-to-cementitious materials ratio concretes. By substantially increasing the viscosity of the pore solution in the concrete, the resistance to ionic diffusion is proportionally increased relative to a control concrete without the VERDiCT