In this paper we present theexperimental analysis of samples of concrete where portion of the natural aggregate were replaced with recycled aggregate originating from concrete (RCA). Experimental analysis to obtain the shrinkage properties (basic and dried) of the concrete containing recycled concrete aggregate (CRCA) was performed. The percentages of replacement of natural aggregate with RCA were 0%, 15%,30%, 60% and 100% with test conditions of 50% RH and 20°C. The results of these trials are compared with reference concrete tests, at an age of 270 days. The results demonstrated an increase in the shrinkage of the CRCA that is proportional to the am- of RCA used as a replacement for the natural aggregate. When compared to the derence concrete, the drying shrinkage showing significant changes; however, their evolution over time is similar to standard concrete.

The durability and perme&i&y of concrete are of special concern in the Arabian Gulf due to the prevailing aggressive weather conditions. Very few practical examples showing the ability of the local ready-mixed industry to adapt to extreqie hot weather, characteristic of this region of the world, have and analyzed. The following paper describes extreme concrete properties in two particular projects in Saudi Arabia demonstrating how the local concrete industry has used specific measutes to produce high-performance concrete in very hot weather. In the first project concrete was hauled for 8 hours in hot weather using high dose of standard retarders and superplasticisers and following rigorous measures to control the mix temperature. In the second project high-strength high-performance concrete was hauled for 45 minutes at an ambient temperatup of 40" C and achieved 24 hours strength in excess of 50 MPa. It is concluded that controlling the temperature of fresh concrete in hot weather should be primarily based on parameters related to cost, workability retention and long-term strength. Besides, the cited examples'demonstrated how the use of admixtures in hot weather could be very beneficial even if the dosage considered did not comply with ASTM C 494 requirements and the manufacturer standard recommendations.

High-strength concrete shows particular characteristic behavior at ele- vated temperatures, such as explosive spalling, that is rarely observed in normal-strength concrete. This behavior has been attributed to the very dense concrete matrix usually associated with high-strength concrete. This paper presents the effect of fiber reinforcement on mitigation of explosive spalling and residual properties of high-strength concrete under elevated temperatures (600°C). The experimental work has been carried out on the influ- ence of three parameters associated with fire resistance. These three parameters are an addition of polypropylene fibers andor polymer beads, the moisture content of the concrete and the water to cement ratio. The experimental results showed that the internal temperature elevation was mitigated in the test specimens, that contained the fibers or beads, that were melted by heating, by low cement-water ratio and by high moisture content. The accompanying strains due to heating at these conditions were reduced in the test specimens.

Completion of the Central A r t e r y b e l Project inchdes development of more that 20 distinct parcels along the original, elevated artery corridor. This paper presents challenges encountered during the design of Parcel 6, which is located between New Chardon and Sudbury Streets in Boston, Massachusetts. The Parcel 6 lid will cover five adjacent cast-in-place concrete boat section ramps. The final use of the lid is not yet known; however, since construction of the ramps is currently underway, the walls were re-designed to accommodate either a landscaped deck, or a five-story building. Design included both wind and seismic lateral analyses of the two types of potential lid structures, with the reinforcing in the ramp walls modified to accommodate both options in order to minimize impacts or retrofits requkd in the future. Changes to the original design included modifying wall heights and reinforcing, and inclusion of interim backwalls for temporary earth support. The landscaped option included preliminary designs of four separate deck structures, skewed portal beams, overhead impact attenuators, and a merge gore area. The building option presumed asymmetrical column loadings and locations, with a comparative analysis of column base shears used to determine maximum loading on the existing ramp walls.

Test results of four composite RCS beam-column-slab subassemblies under cyclic loading are presented in this paper. The specimens were designed for beam plastic hinging and controlled joint deformations through the use of a deformation-based design model for RCS connections. Tho types of simple connection details were used in the specimens, one with overlapping U-shaped stirrups passing through the steel beam web, and the other with steel band plates wrapping around the column just above and below the steel bem flanges. The performance of the test specimens was evaluated in terms of load-displacement response, beam rotations, joint deformations and energy dissipation capacity. The accuracy of the deformation-based joint model was also evaluated. Excellent response was observed for all specimens, with large beam rotations, minor to moderate joint damage, and significant energy dissipation capacity, indicating that RCS frame construction is adequate for use in zones of high seismicity. Good agreement was also found between predicted and experimental shear force vs. shear deformation response in RCS connections.