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Recently, in Japan, application of the roller compacted dam concrete (RCD) method has increased in the construction of concrete gravity dams. The concrete for the RCD method (RCD concrete) features a very stiff consistency with low water content, which enables the use of a vibration roller for compaction. Most of the cement used so far for RCD concrete has used a combination of fly ash with moderate heat portland cement. However, the supply of high-quality fly ash for use in concrete has recently lessened in Japan. One admixture replacing fly ash is granulated blast furnace slag. In this study, properties of RCD concrete made with slag cement featuring blends of moderate heat portland cement and granulated blast furnace slag were examined. The effect of fineness of the individual slag cement components on compressive strength and adiabatic temperature rise were studied. The unit cement content in the concrete was 120 kg/m 3. The maximum size of the coarse aggregate was 150 mm. The results show that concrete with moderate low-heat slag cement can provide the same or better performance as fly ash cement concrete by employing a rational combination of fineness and slag content. Also, the advantages of slag cement at longer ages were confirmed. The results obtained in this study are now being applied to an actual dam construction.

Results of a laboratory test series are reported concerning the effect of cement type, class of fly ash, and fineness of fly ash on the strength development of mortars. Thirty percent by weight of portland cement was substituted by fly ash. The following materials were used in various combinations: Type I and Type III portland cements, Class F fly ash before and after grinding, Class C fly ash before and after grinding, a silica fume, a superplasticizer, and an accelerating admixture. More than 60 different compositions were tested in all. Standard flow, compressive strength, and pulse velocity measurements were performed in the standard manner at 1, 7, and 28 days. The obtained results show the effects of fineness of fly ash, along with other characteristics of mortar composition, on the flow and strength development, as well as the interactions between fineness and cement type. For instance, as expected, ground Class F fly ash with Type I cement produced lower strengths at 1 day than the same fly ash with its original fineness and Type III cement; however, at 7 and 28 days, the fly ash mortars with Type I cement showed higher strengths. The results of the pulse velocity tests showed the same trend as the strength results.

A reliability-based approach is used to recommend allowable edge loads for precast hollow core slabs. Full-scale test results are used to predict the statistical parameters of the resistance at the edge. The study indicated that the allowable load is a function of dead-to-live load ratio and concrete strength. The analysis is extended to include system reliability of the whole slab due to different failure modes. The failure modes include flexure at midspan and total shear at the ends, in addition to local failure at the edge. The system modeling is composed of a series system made up of three partially correlated elements. A numerical example is also included for illustration. The approach will help engineers make a rational selection of allowable edge loads that occur around large floor openings.

In recent years, highway agencies and constructors have used improved construction techniques and materials for better pavement quality. However, newly constructed portland cement concrete pavement surfaces are not always being built to the desired level of ride quality; thus, there is a need for an improved smoothness specification to insure the best riding quality. This paper documents the development and evaluation of end-result smoothness specifications for portland cement concrete pavements in Texas. Based on available equipment and prior studies, the California Profilograph was selected as the instrument for use in developing the specification. Because there are several types of California profilographs, the study team compared two instruments by two different manufacturers. This paper presents the results of this comparison, along with a methodology for defining a recommended specification.

The customary criterion for establishing grades of structural concrete is the crushing strength measured in an arbitrary manner on a standardized specimen stored in a stipulated fashion for approximately a month after making. In some parts of the world, the specimen is a cube, and in other parts of the world, the specimen is a cylinder. There have been debates as to how the strength at 28 days can be predicted from procedures performed at early ages, especially 24 hr, on the grounds that a month is not soon enough. The intent of this paper is to suggest that the only time that really is "soon enough" to know that the grade of the concrete in any batch is correct is before the concrete is discharged from the concrete mixer into the forms. It is suggested, therefore, that effort would preferably be expended upon insuring that the materials used are those intended and the proportions in which they are used are those that were intended. If this is the case, the grade of concrete will be proper at all ages, and testing at any age is merely confirmation.