A new partially prefabricated elevated slab has been recently introduced in two different industrial buildings, to propose a viable alternative to the classical double tee deck with the addition of an in-situ RC topping. The solution is characterized by an adjustable spacing in the orthogonal direction, 40 mm thick FRC plates used as predalles and a cast-in-place FRC finishing, designed according to a continuous slab resting on the simply-supported beams. The proposed deck is a structural solution that tries to fit different issues like construction speed, transport and cost reduction, structural optimization, high fire resistance (R120) and quality performance. All elements are made of SFRC, characterized by different mix designs. This paper presents a design investigation on this kind of floor element, aimed at optimizing the global structural solution by minimizing the whole floor weight. Longitudinal and transverse bending, as well as vibration limit state, were considered in the design. The optimization strategy will be here presented, through the discussion of the parameters considered in the design, the variables taken into account and the constraints adopted within the procedure. A Model Code 2010 design approach was followed.

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Abnormal early hydration resulting from "incompatibilities" of common concrete materials can result in erratic set and strength gain behavior and associated finishing, curing, and cracking issues. Contributing influences include high temperatures, cement sulfate levels, Class C fly ash content, chemical admixture use, and design approaches for retardation of hot-weather concrete. Simple, expedient test methods are needed to identify potentially incompatible materials and conditions and to verify appropriate modifications to concrete proportions. Thermal measurements of the early heat development of materials mixtures in the laboratory (semi-adiabatic calorimetry) have been shown very useful toward this end. Abnormal set and strength development of field concrete was reproduced in laboratory paste and mortar mixtures and studied using thermal measurements, verified by parallel mortar cube strengths. Sensitivities of various contributing influences were documented in extensive testing. Changing one or more of the key material or mixture characteristics was usually successful in restoring normal behavior. Recommendations are presented for avoiding related field issues and for the use of calorimetry testing programs for diagnosis of such problems.

An experimental program which aimed at investigating the behavior of SCC containingClass F fly ash has been carried out. The fresh state properties of the concrete wereassessed using methods of segregation and flow. The rheology of the paste matrix wasalso characterized and compared with a previously developed paste rheology model. Inaddition, compressive strength, chloride permeability, and mold-finish were evaluated. The results indicate that it is possible to develop a SCC containing Class F fly ash that is high performing in its fresh state. Furthermore, the addition of fly ash was shown toreduce superplasticizer dosage, increase workability, and increase overall chloride permeability resistance. In addition, it was determined that the difference of densities between the aggregate and matrix influence the results of a previously developed pasterheology model.

The Citadel in Charleston, South Carolina is steeped in tradition down to the buildings at the campus. Currently under construction is a replacement for the Padgett-Thomas Barracks, which was demolished in 2001. The new structure will be identical to the original barracks. It will showcase a classic fortress design that requires intricate forming and careful planning in the proportioning and placement of the concrete mixtures, in order to minimize/eliminate cost over-runs that have been experienced in previous construction projects at the campus. Through a cooperative effort involving all parties in the construction of the new barracks, self-consolidating concrete (SCC) is now being used in lieu of the originally specified regular slump concrete. The use of SCC in the construction of the narrow 150mm (6 in.) thick walls have significantly increased placement/construction efficiency. It has also resulted in a greatly enhanced surface finish and sharper edges. This paper chronicles the project from the pre-construction meetings and trial placements to the placement efficiencies that have been realized due to the use of SCC. About 7646 cubic meters (10,000 cubic yards) of SCC are going to be used for this project, which is scheduled for completion in 2004. Data on the properties of the SCC mixture from the field and companion laboratory studies are presented and discussed.