Reactive Powder Concrete Containing Basalt Fibers: Strength, Abrasion and Porosity
The paper presents the test results of basalt fiber impact on a compressive and flexural strength, resistance to abrasion and porosity of Reactive Powder Concrete (RPC). The reasons for testing were interesting mechanical properties of basalt fibers, the significant tensile strength and flexural strength, and in particular the resistance to high temperatures, as well as a relatively small number of RPC tests performed with those fibers and different opinions regarding the impact of those fibers on concrete strength. The composition of the concrete mix was optimized to obtain the highest packing density of particles in the composite, based on the optimum particle size distribution curve acc.…
The role of nanoparticles in decreased washout of underwater concrete
Abstract The paper presents research results of the influence of SiO2 nanoparticles on the washout of underwater concrete and hardened concrete. Based on infrared spectroscopy (FTIR) and thermogravimetric (TGA) analyses of the applied anti-washout admixture (AWA), its chemical structure was determined. A beneficial effect of SiO2 nanoparticles on the reduction of the mix washout was demonstrated and the most probable reason for that phenomenon was given, taking into account the AWA chemical structure and its behaviour in the concrete mix environment. It was found that a dosing method of AWA and nanoparticles to the concrete influenced the washout.
Effect of Cu-Zn coated steel fibers on high temperature resistance of reactive powder concrete
Abstract Even though many studies have reported about the impacts of shape, length and distribution of steel fiber reinforcement on global concrete properties, there is a lack of information about the influence of coating type of steel fibers on high temperature resistance of concrete. This paper describes the effect of Cu-Zn coated steel fibers on selected properties of reactive powder concrete (RPC) after exposure to elevated temperatures. The initial corrosion of zinc in Cu-Zn surface layer is found to be already activated by the alkaline environment of the fresh concrete. The RPC samples reinforced with Cu-Zn coated steel fibers are heated to 600 °C and 1000 °C, and the influence of the…
Hydric, thermal and mechanical properties of self-compacting concrete containing different fillers
Abstract Water vapor diffusion coefficient, water absorption coefficient, water permeability, thermal conductivity, compressive strength and freeze resistance properties of two self-compacting concretes (SCC) containing limestone filler and fly ash are determined in the paper. The results indicate that strength development is faster in the material containing limestone filler but after 90 days the strength values in both materials are almost the same. Liquid water transport and heat transport are faster in SCC with limestone filler while the water vapor transport is faster in the material containing fly ash. This corresponds well with the much better freeze resistance of the material with f…
Effect of superplasticizers on the rheological properties of fly ash suspensions containing activators of the pozzolanic reaction
Rheological studies have been carried out on the effect of a superplasticizer from the sulphonated melamine formaldehyde (SMF) group upon the properties of fly ash suspensions containing a small quantity of mineral admixtures such as cement, lime and gypsum. The superplasticizers' efficiency has appeared to depend greatly on the admixture used. The highest liquefaction degree was found in fly ash suspensions containing both cement and gypsum together and the next it was, when only cement was added. These suspensions exhibit features of a newtonian fluid of low plastic viscosity, when the water to solid ratio (w/s) is 0.3 and a superplasticizer has been used. However, fly ash suspensions wit…
Mechanical and Basic Physical Properties of High-Strength Concrete Exposed to Elevated Temperatures
In this paper, the effect of elevated temperatures on the mechanical and basic properties of two different newly-designed high-strength concretes is studied. The studied materials were prepared from Portland cement, steel fibers, reactive finely milled quartz powder and quartz sand, silica fume, plasticizer, and with a relatively low water/cement ratio of 0.24. The samples were stored in water environment for the first 28 days of hydration to achieve better mechanical properties. Then, after pre-drying at 105 °C to constant mass, the materials were exposed to elevated temperatures of 600 °C and 1000 °C where they were kept for 2 hours. The basic physical properties, such as matrix density, …
Effect of content and particle size distribution of high-calcium fly ash on the rheological properties of cement pastes
Abstract The Theological properties of high-calcium fly ash cement pastes were investigated. An increase both in yield value and plastic viscosity with fly ash content was found. It was also observed that the pastes became more fluid with the higher fly ash fineness. A more important relation was shown between the fine fractions (