Hydrogen-bonding patterns in 5-fluorocytosine–melamine co-crystal (4/1)
The asymmetric unit of the title compound comprises two independent 5-fluorocytosine molecules and one half-molecule of melamine. The 5-fluorocytosine molecules are linked through two different homosynthons; one is formed via a pair of N—H⋯O hydrogen bonds and the second via a pair of N—H⋯N hydrogen bonds. The 5-fluorocytosine and melamine molecules interact via N—H⋯O, N—H⋯N and N—H⋯O, N—H⋯N, C—H⋯F hydrogen bonds.
Melaminium maleate monohydrate.
In the title compound, 2,4,6-triamino-1,3,5-triazin-1-ium maleate monohydrate, C3H7N6+.C4H3O4-.H2O, containing singly protonated melaminium residues, maleate(1-) anions and water molecules, the components are linked by hydrogen bonds into a three-dimensional framework structure. The melaminium residues are connected by two pairs of N-H...N hydrogen bonds into chains in the form of stacks, with a distance of 3.26 (1) A between the triazine rings, clearly indicating pi-pi interactions. The maleate anion contains an intramolecular O-H...O hydrogen bond and the anions interact with the water molecules via O-H...O hydrogen bonds, forming zigzag chains, also in the form of stacks, in which the almost-planar maleate anions are separated by 3.26 (1) A. The experimental geometries of the ions are compared with molecular-orbital calculations of their gas-phase geometries.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.