Presents results of investigations carried out on high fly ash content concrete (HFCC) cores removed from several structures constructed in the U.K. since 1979. Structures investigated included a road pavement, a major road viaduct, water-retaining and industrial structures, and a slipway subjected to marine exposure. Concrete properties measured after 10 years of service include compressive strength, depth of carbonation, permeability, and chloride and sulfate penetration profiles. In addition, petrographic analysis of thin sections was also undertaken. The HFCCs studied were designed considering the fly ash to be just a further ingredient in the concrete rather than as a cement replacement. This led to higher fly ash contents and lower cement contents than is generally normal practice. The structures examined were in excellent condition after 10 years. Results show a durable concrete exhibiting increases in compressive strength beyond 28 days, little evidence of carbonation, low to average permeability, and resistance to chloride penetration. In this respect, it is significant that at the marine exposure sites, the chloride concentrations decreased significantly with depth. No evidence of alkali-silica reaction was detected in spite of reactive aggregates being present in some of the concretes.

Compressive strength, flexural strength, and fracture energy of ordinary portland cement concrete with and without fly ash have been determined over a 6-month period. Specimens were cured in water at various constant temperatures ranging from 7 to 80 C. Flexural strength and fracture energy were measured on notched specimens subjected to a constant rate of deformation. The influence of temperature on strength is complex, and does not always follow the trend of a higher initial rate and lower ultimate value as the curing temperature is raised. Compared with strength, fracture energy is less sensitive to curing temperature. For all concretes, general expressions are presented for relating flexural and compressive strengths, and facture energy and flexural strength. These expressions are independent of age and temperature, and suggest that approximate estimates of strength and fracture energy can be made only from a knowledge of strength of ordinary portland cement concrete cured at 20 C.

When heated at 800 C for 5 hr, Indonesian laterites showed good pozzolanic activity. The kaolin content of the material is the main cause of pozzolanicity, as indicated by the lime reactivity. Blended portland cements containing 20, 30, 40, and 50 percent of calcined laterite admixture were studied. Concretes were made with such cements and placed in aggressive solutions: seawater, acetic acid, and sulfuric acid. The best results were obtained with a cement containing 30 percent of calcined laterite admixture.

In Japan, fly ash has been generally used as a material of low-heat cement for mass concrete, such as dams. As an alternative material for low-heat cement, granulated blast furnace slag can be considered. In this study, moderate heat portland cement, in which the fineness is 300 m¦/kg, and granulated blast furnace slag, in which the fineness is 300, 400, 500, and 600 m¦/kg, were made. The slag content in cement is 50, 60, 70, and 80 percent. Tests for setting and heat of hydration in cement, and for setting, compressive strength, freezing and thawing, adiabatic temperature rise, carbonation, and drying shrinkage in concrete, were carried out. The following results were obtained: 1) as the slag content increases, the time of setting increases; 2) the compressive strength of concrete increases with the increase of fineness of slag; 3) concrete with slag has a satisfactory resistance to freezing and thawing; 4) the adiabatic temperature of concrete is affected by the slag content and the fineness; 5) the depth of carbonation increases with the increase of slag content; 6) there is no great difference in drying shrinkage between concretes with slag and fly ash. From the test results, it is concluded that, by properly determining the slag content and fineness, it is possible to manufacture cement with similar or better quality compared to conventional moderate heat fly ash cement.

Ten blended slag-cement concretes made with typical slags from four countries are compared with a control ordinary portland cement concrete. The slags replaced 30 to 70 percent of cement by mass. Concretes are compared on the basis of equal mass proportions of cementitious materials, aggregates, and water. Average strength, elasticity, and creep are quantified relative to the corresponding properties of the control concrete. The influence of type of slag on concrete properties is inconsistent and small. The influence of replacement level on strength and creep is time-dependent. For water-stored mature concrete, slag enhances the secant modulus of elasticity, but the opposite occurs for dry-stored concrete. Compared with OPC concrete, slag-cement concrete has a similar or greater long-term strength, similar shrinkage, lower basic creep, and similar or lower total creep.