# Experimental Study and Modelling on the Structural Response of Fiber Reinforced Concrete Beams
## 2 Materials and Methods  
### Concrete Mix Materials  
Mix design of FRC matrix implies combining Portland cement with multi-fractional aggregates and reactive pozzolanic admixtures, such as fly ash, silica fume and nano-silica. When selecting raw materials for production of a concrete matrix, preference was given to the locally available mineral materials and cement. The composition of the developed concrete mixture and the exact concentration of the ingredients. In the current research, the following components were used as FRC mix materials:  
1. Portland cement CEM I 42.5N.
2. Sikament(r) 56, a third generation (polycarboxylate based) superplasticizer admixture. It was used to provide flowability of the mix and dispersion of microparticles. Basic properties: light yellow and highly flowable liquid, density--1.08 \(\pm\) 0.02 kg/dm\({}^{3}\), pH--4.5 \(\pm\) 1, solid content--37 \(\pm\) 1%. Recommended dosage: in the range of 0.1-2.0 % by weight of cement.
3. Stabilizer AkzoNobel Cembinder 50. A commercial colloidal nano-silica product Cembinder 50 was used. Nano-silica is a new generation of reactive silicon dioxide admixtures. Its high reactivity is explained with chemical purity and extremely high specific surface (>30,000 m\({}^{2}\)/kg) and particle size <100 nm. The size of the silica fume particle corresponds up to 1000 nano-silica particles and, comparing with the size of cement particles, one cement particle corresponds to approximately one billion of nano-silica particles. This determines high chemical reactivity of the admixture and its accelerated effect on the cement hydration.
4. Coarse aggregates. Crushed limestone (fractions 2/6 mm) was used as a coarse aggregate. The shape of the rough aggregate has a significant influence on the workability of a concrete mix, because water quantity depends on the type of aggregate, particle size distribution, the shape and texture of grains and the quantity of fines.
5. Fine aggregate Saulkalne. Fine aggregate of three grades was used: washed quartz-based sand, fractions 0/0.4 (fine), 0/1 (medium), and 0.4/1.2 mm (coarse).
6. Silica fume or Micro-silica, a very fine pozzolanic material composed of amorphous silica produced by electric arc furnaces as a by-product of production of elemental silicon or ferro silicon alloy. Addition of micro silica to cementitious systems can improve the strength by controlling the structure of C-S-H. Silica fume is high-purity amorphous silicon dioxide with >92% SiO\({}_{2}\) content. Silica fume particles are characterized by spherical shape and diameter in the range of 0.05-0.5 \(\upmu\)m or 50-500 nm.
* Fly ash. This pozzolanic admixture is produced as a by-product of coal combustion in the power plants, it is usually collected with electrostatic filters. Good quality conventional fly ash offers such advantages as improvement of concrete workability properties, improvement of structural tightness, reduction of hydration heat, increase of resistance to chemical aggression, participation of ash in cement binding reactions, higher resistance of concrete over long period and reduction of production costs of the concrete mixture. Commercially used fly ash with the cumulative content of oxides SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\) + Fe\({}_{2}\)O\({}_{3}\) was equal to 84.7% thereof. It was classified as class F fly ash in accordance with ASTM C618 [49].