Critical Chloride Content in Reinforced Concrete: A Review

Durability of concrete — Degradation phenomena involving detrimental chemical reactions

Chloride threshold values to depassivate reinforcing bars embedded in a standardized OPC mortar

Chloride threshold level for corrosion of steel in concrete

Samples of the capillary pore solution, associated with hardened cement pastes containing various proportions of silica-fume and sodium chloride, have been expressed at different stages of curing and analysed to determine concentrations of dissolved ions. The results indicate that partial replacement of Portland cement by increasing percentages of silica-fume causes a regular decrease in alkalinity of the pore solution and a reduction in the chloride-binding capacity of the material. Possible implications regarding the level of corrosion protection afforded to embedded steel are considered.

Pore solution composition and chloride binding capacity of silica-fume cement pastes

THE TESTS DESCRIBED IN THIS PAPER WERE DESIGNED TO: IDENTIFY THE MECHANISM BY WHICH CORROSION OF STEEL IS INITIATED, PROVIDE QUANITATIVE INFORMATION ABOUT THE EFFECTS OF CHLORIDES, AND DETERMINE IF A PREDICTABLE THRESHOLD OF CORROSION EXISTS LABORATORY STUDIES ARE REPORTED ON THE CORROSION OF BARE STEEL RODS IN ENVIRONMENTS SIMULATING POROUS CONCRETE CONTAMINATED WITH CHLORIDES THE INITIATION OF CORROSION IS SHOWN TO REQUIRE FREE OXYGEN AT THE STEEL SURFACE AND A RATIO OF CHLORIDE TO HYDROXYL ION ACTIVITY OF AT LEAST 06 A PROBABILITY MODEL IS USED TO EXPLAIN THE CHLORIDE EFFECT AND TO PREDICT THE THRESHOLD VALUE CAUSING CORROSION /AUTHOR/

Steel corrosion in concrete -- how does it occur?

By increasing the density of interfaces in NiAl-CrMo in-situ composites, the mechanical properties can be significantly improved compared to conventionally cast material. The refined microstructure is achieved by manufacturing through electron beam powder bed fusion (PBF-EB). By varying the process parameters, an equiaxed or columnar cell morphology can be obtained, exhibiting a plate-like or an interconnected network of the (Cr,Mo) reinforcement phase which is embedded in a NiAl matrix. The microstructure of the different cell morphologies is investigated in detail using scanning electron microscope (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT). For both morphologies, the mechanical properties at elevated temperatures are analyzed by compression and creep experiments parallel and perpendicular to the building direction. In comparison to cast NiAl and NiAl-(Cr,Mo), the yield strength of the PBF-EB fabricated specimens is significantly improved at temperatures up to 1027 °C. While the columnar morphology exhibits the best improved mechanical properties at high temperatures, the equiaxial morphology shows nearly ideal isotropic mechanical behavior, which is a substantial advantage over directionally solidified material. This article is protected by copyright. All rights reserved. 

D A Hausmann

Papers

Steel corrosion in concrete -- how does it occur?

Using selective electron beam melting to enhance the high‐temperature strength and creep resistance of NiAl‐28Cr‐6Mo in‐situ composites