The availability of separately ground granulated iron blast-furnace (GGBF) slag, as a separate cementitious material or supplement, has prompted new research on its effects on concrete properties. One area in which GGBF slag has particular promise in concrete is its ability to alter the permeability characteristics of concrete to the extent that its resistance to chloride intrusion is significantly improved. This paper discusses the ability of GGBF slag-cement mixtures to reduce the potential detrimental effects of chloride intrusion into concrete. Three test methods for chloride penetration were used and the results of each are discussed. The following conclusions were developed. 1. Significant reductions in permeability are achieved as the replacement level of the slag increases from 40 to 65% of total cementitious material by mass. 2. The permeability of concrete containing GGBF slag is less affected by increases in water-cement ratio than concrete containing regular portland cement alone. 3. The detrimental effects of accelerated curing on the permeability of concrete are virtually eliminated with cement blends containing GGBF slag greater than 50%. 4. Concrete containing GGBF slag may require less depth of cover to protect the reinforcing steel than those concretes using portland cement alone.

SP102 As a designer you need the wealth of information presented in "Corrosion, Concrete and Chlorides -- Steel Corrosion in Concrete: Causes and Restraints," a compilation of 11 papers covering the corrosion phenomenon. Prompted by the nationwide corrosion problem with concrete, there have been extensive field and laboratory investigations into the specific phenomena that induce corrosion, methods for identifying the magnitude and extent of corrosion in structures, techniques for stabilizing corrosion once it has begun, and design of structures and concretes so that corrosion will not occur. Presenting an in-depth analysis into a variety of aspects dealing with corrosion, this state-of-the-art publication includes such topics as: the marked influence of chloride in causing corrosion, ways for controlling corrosion by using chloride-free accelerators, the reduction of chloride penetration through the use of pozzolanic blast-furnace slag as an admixture in concrete, and the conductive coating aspects of cathodic protection. "Corrosion, Concrete and Chlorides" provides important answers to a complex problem.

Strength-increasing effects of achloride-free accelerating admixture are investigated on various portland cement pastes, mortars and concretes with or without other admixtures. Although the test results are preliminary in nature, the available experimental evidence shows that this chloride-free accelerator increases significantly the strengths of a wide variety of cementitious compositions including portland cement, epoxy, pozzolans and combinations of these.

The wide variety of disciplines involved with the corrosion of steel in concrete has caused difficulties in communication. Each discipline has its own terminology; at times two disciplines use conflicting terms or explanations for the same phenomenon. This paper addresses some areas of such confusion, and presents chemical mechanisms to explain half-cell potentials and causes for chloride-induced corrosion. Examples of such corrosion are presented.

A method for evaluation of the corrosion potential of chemical admixtures is presented. The method allows the direct measurement of the macrocell corrosion current between two layers of electrically connected reinforcing bars embedded in concrete. By ponding the specimens with chloride-free water, the potential of the chemical admixture to instigate corrosion can be evaluated. By using a chloride-containing ponding solution, in particular a 15% NaCl solution, it may be possible to assess the potential corrosion inhibiting effects of certain chemical admixtures. The test method was used to compare the corrosion activity in reinforced concrete slabs containing a normal dosage rate of calcium chloride, plain concrete and concrete containing two dosage rates of a multicomponent calcium nitrate based non-chloride accelerator. Only the slabs containing calcium chloride exhibited corrosion when ponded with tap water. When subjected to cyclic ponding with the salt solution, both the plain concrete and the concrete slabs containing the two dosage rates of the non-chloride accelerator exhibited corrosion. However, the slab containing the higher dosage rate of the non-chloride accelerator exhibited only 25% of the corrosion activity of the other two slabs. It is speculated that this reduction may be the result of corrosion-inhibiting effects of the non-chloride accelerator when it is added at sufficient rates.