SP-153 In 1995, CANMET, in association with ACI, U.S.A. Electric Power Research Institute, Canadian Electrical Association, and several other organizations in Canada and the United States, sponsered the Fifth International Conference on fly ash, ferrous and nonferrous slags, and silica fume was held. The two volume proceedings of the Fifth CANMET/ACI Conference contains 62 papers from 23 countries.

Describes chemical attack caused by a high concentration CaCl 2 solution and its preventive measures by the addition of a mineral admixture. Changes which occur in mechanical strengths and chemical properties in mortars with and without fly ash, blast furnace slag, and silica fume when immersed in a 30 percent CaCl 2 solution at different temperatures were investigated. Portland cement mortars seriously deteriorated at early ages of exposure to a high concentration CaCl 2 solution, its deterioration being associated with cracking and spalling on the surfaces of specimens. On the other hand, 10 percent silica fume and 50 percent blast furnace slag mortars showed a good resistance to calcium chloride attack, although 30 percent fly ash mortars slightly deteriorated at late ages of exposure. X-ray diffraction and differential thermal analysis indicated that the deterioration of portland cement mortars cause by the chemical attack of a high concentration CaCl 2 solution was attributed primarily to both the dissolution of calcium hydroxide and the simultaneous formation of a complex salt in the mortar. Thus, the combined effect of a decrease in calcium hydroxide content and a reduced chloride ion permeability by the addition of a mineral admixture effectively improved the resistance of mortar to calcium chloride attack.

The strength development of blends of five cements with various levels of a fly ash, two blast furnace slags, a ground limestone, and a dried chalk dust was determined using EN 196 mortars and, for selected materials, concretes. Three of the cements were based on normal portland cement (OPC) clinkers and two on a high-early-strength (HES) mineralized clinker. At the same specific surface area and SO 3 content, the HES clinker gave cements with strengths 5 to 10 MPa higher than those based on equivalent normal clinker at all ages from one to 56 days. This allows the use of significant levels of fly ash, slag, or other less reactive materials in blends giving similar early strengths to normal portland cements. The early strengths of the blends with the ground limestone and the lower surface area HES cement were higher than expected. The finer chalk dust gave significant contributions to strengths with all the base cements, particularly at early ages. The effect was greater with the lower surface area cements and those based on HES clinker. It is concluded that the acceleration of hydration by the fine calcium carbonate is particularly strong with cements based on the mineralized clinker.

Three reactive aggregates from New Brunswick, Canada, a greywacke, a gneiss, and a meta-volcanic rock were evaluated for their potential alkali reactivity (AAR) in concrete mixtures incorporating 420 kg/m 3 of cementitious materials. The concrete mixtures consisted of the control made with CSA Type 10 low- and high-alkali cements and mixtures incorporating ASTM Class F fly ash at 20, 30, and 56 percent replacement levels of the high-alkali cement. The susceptibility of the concretes to AAR was evaluated by casting test prisms and subjecting these to various accelerated curing conditions in the laboratory. For comparison purposes, mortar bars were also made and tested according to the ASTM C 1260-94 Accelerated Mortar Bar Test procedure. The AAR concrete prism tests performed in this study have shown that none of the test prisms cast from concrete mixtures incorporating 20, 30, and 56 percent fly ash showed significant expansion after two years of testing at 38 C and relative humidity >95 percent. These results were in good accordance with those obtained in the accelerated mortar bar test. Some alkaline immersion tests results would indicate, however, that concrete incorporating 20 percent fly ash might not offer adequate protection against potential deleterious expansions with highly reactive aggregates.

The water-to-cementitious materials ratio (W/CM) is recognized as an important variable in understanding and controlling the quality of concretes containing pozzolan powder additives, such as fly ash. This paper presents part of a study to determine a correct way to evaluate the contribution of fly ash to concrete strength as is usually indicated by the W/CM ratio. A rational mathematical model of the form W/CM = W/(C + K * FA) is presented, in which W, C and FA are water, cement, and fly ash contents per m 3 of concrete, respectively. K is a pozzolan efficiency factor based on comparing the compressive strength of two concretes having the same workability and the same amount of cement. An experimental program was conducted to demonstrate the use of the proposed W/CM ratio model and corresponding K values. The variables studied were class and addition level of fly ash and slump, strength, and age of concrete. Results show that the model describes and considers the influence of fly ash on the rheological properties of fresh concrete and on the strength of hardened concrete. The model is also suitable for use as an equivalent to Abram's law to account for modern day powder additives.