This paper presents the experimental research regarding the physical-mechanical properties and the bending and shear behavior of the ultra high performance concrete. The cementitious composite with 2% volume of steel fibers was tested for the following characteristics: the compressive and tensile strength, the stressstrain characteristic curve for compression strength and flexural strength. Furthermore, a series of reinforced elements were tested and analyzed in terms of maximum crack width, deformations and maximum compressive strain. The specimens subject to 90°C thermal treatment for 5 days displayed an increase of compressive strength up to 180 MPa at the age of 6 days. The experimental data obtained on specimens with a thermal curing regime are evaluated by comparison with specimens with a water-curing regime.

Concrete is usually the most common element in a building and over the years, many solutions were developed in order to improve its qualities. We conducted a comparison between ordinary Portland cement concrete and high volume coal fly ash concrete, with the fly ash used as a substitute for the cement. Generally accepted, the total binder in a green concrete is composed of 50% cement and 50% fly ash, which is less than 200 kg/m 3 in our case (P. Kumar Mehta -High Performance, high-volume fly ash concrete for sustainable development. University of California, Berkeley, USA). We investigated concrete mixes containing 40% and 50% fly ash as partial replacements of the cement. A C20/25 class concrete was tested at 7, 28, 90 and 365 days of age for: compressive and tensile strength, modulus of elasticity, freeze thaw resistance, water permeability, and shrinkage and bond strength. We found that concrete made with fly ash is a good choice for a medium concrete class with increased durability properties.

No abstract

No abstract

No abstract