Presents results of expansion tests carried out on concretes immersed in 1/10-M and 1-M sodium chloride solutions. The concretes were prepared using two reactive aggregates, cristobalite and a natural aggregate from the southwest of the U. K. Tests were carried out both at alkali levels which were known to induce expansion due to alkali-silica reaction (ASR) and alkali levels which would not normally induce expansion due to ASR. The concretes were, at the ages of one, three, and six months, immersed in a sodium chloride solution. The concretes were stored at 38 C, 20 C, and externally. For the concretes containing the natural aggregate, it was shown that immersion in a 1-M salt solution had no major adverse effects upon long-term expansion. This is attributed to the low available reactive silica content within the concretes. In the case of concretes containing cristobalite, it was shown that the immersion in 1-M salt solution had an adverse effect upon long-term expansion. This is attributed to the high available reactive silica content of the concrete.

Mechanisms of stratlingite (C 2ASH 8) formation in high-alumina cement (HAC)-siliceous material systems were investigated. Different siliceous materials (silica fume, fly ash, ground granulated blast furnace slag) and chemical admixtures (sodium silicate, sodium sulfate) were employed. Reactions between CAH 10 or C 2AH 8 and dissolved silica occur. Acceleration of silica dissolution by addition of chemical admixtures promotes the formation of stratlingite. The pH value of the HAC-siliceous materials system was also studied. The intrinsic relationship between the pH value and stratlingite formation is discussed in this paper. Mechanisms of stratlingite formation in preference to hydrogarnet (C 3AH 6) in HAC products are postulated. A method for prevention of strength reduction of HAC products due to the conversion of thermodynamically unstable hexagonal calcium aluminates to cubic hydrogarnet is described.

Silica fume has been available commercially in the United States for over 10 years. Until recently, there has not been a well-accepted consensus specification for it. This paper deals with the question of a specification for silica fume for use in concrete by reviewing the following areas. 1. ASTM and AASHTO efforts to develop a specification for silica fume are described. The author's comments on these documents are presented. 2. The status of international efforts to develop silica fume specifications is reviewed. Work from Australia, Canada, Norway, RILEM, South Africa, and other European countries is reviewed to indicate the direction that is being taken outside the United States. 3. Recommendations, based upon the author's experience with silica fume since its introduction to the United States, for what a specification for silica fume for use in concrete should include are presented. The use of silica fume is increasing every year. Some engineers, particularly those in public agencies, have been hesitant to use the material because of the lack of a standard specification. Most engineers wanting to use silica fume have developed their own specification for silica fume with provisions that may have little or no relationship to the performance of the material in concrete. A consensus needs to be established to increase the confidence of specifiers wanting to use silica fume.

The Japanese economy has been highly developed through foreign trade. Port facilities have been supporting this economic growth; many concrete port structures have been constructed and maintained during the past few decades. Recently, various social and economical demands have required port facilities to be multi-functional. New facilities are being constructed to meet this trend. These changes include new types of breakwaters, revetment, and undersea tunnels which improve aesthetics and reduce cost, labor, and construction time. Fresh concrete used in the construction of these new types of structures is often required to have high flowability and to be self-compactible because of the complicated shape and densely arranged reinforcements of these structures. To meet these demands, the authors have developed super workable concrete using viscous admixture (segregation-reducing admixture) and super plasticizer. In this paper, the mix design and material properties of this supe rworkable concrete and examples of its application to new port concrete structures are presented.

In this paper, corrosion-inhibiting admixture systems are classified as active, passive, or passive-active, depending on the mechanism(s) by which corrosion inhibition is achieved. Also, a simple analytical equation that relates chloride ion contents in treated concretes to that in companion untreated concrete is presented. Using this equation, chloride ion content versus screening efficiency curves have been for passive and passive-active inhibitor systems. If chloride ion threshold and chloride screening efficiency data are available, these curves can be used to determine and "equivalent chloride ion threshold" for passive and passive-active inhibitor systems and to compare directly the effectiveness of passive and passive-active inhibitor systems on time-to-corrosion relative to active inhibitor systems. Corrosion test data have been used to show the validity of this analytical procedure. The data show that the procedure can be used to rank the effectiveness of corrosion-inhibiting admixtures in delaying the time-to- corrosion of steel in concrete and that passive and passive-active inhibitor systems can delay the onset of corrosion longer than active inhibitor systems. In combination with corrosion rate data, the relative overall effectiveness of corrosion-inhibiting admixtures can be determined.