Title: Chloride Binding Capacity of Pastes and Scaling Resistance of Concretes with Natural and Non-Traditional Pozzolans (NNPs) Exposed to Different Types of Chloride Solutions

Author(s): Tokpatayeva

Publication: Web Session

Volume: ws_S22_Tokpatayeva.pdf

Issue:

Appears on pages(s):

Keywords:

DOI:

Date: 3/28/2022

Abstract:
The first part of this work focused on evaluating the chloride binding capacity of cement pastes in which 25% of the weight of cement was replaced by one of the 11 different NNPs (3 calcined clays (CC), 3 natural pozzolans (NP), 2 fluidized bed combustions ashes (FBC) and 3 ground bottom ashes (GBA)). The hydrated pastes containing these materials were exposed to three different chloride solutions (3%NaCl, 3%CaCl2 and 3%MgCl2) while also being subjected to up to 50 freezing and thawing (FT) cycles in the temperature range from -20°C to + 20°C. After FT exposure the paste samples were analyzed by using the TGA, DSC and QXRD techniques. The purpose of these investigations was to determine the influence of chloride and FT exposure on the relative (with respect to the control paste (i.e. plain OPC paste) quantities of Ca(OH)2 and AFm/AFt phases as well as on the formation of any new, chloride-binding phases (e.g. Friedel’s or Kuzel salts). The results of these analyses were correlated with the chemical composition of the NNPs, especially with the alumina content. In addition, the concrete salt scaling test (ASTM C672) was performed on concrete slabs containing four different NNPs (one per each group of NNPs) using 3% CaCl2 solution. The NNPs used to prepare the concrete scaling test slabs were the least reactive from each group. Comparison of the results from both groups of specimens, i.e., pastes and concretes revealed that the materials with low chloride binding capacity showed poor scaling resistance.