Concrete--Permeability

Three vital factors, namely environmental protection, savings in costs, and
strength/durability benefits, make it advantageous to incorporate fly ash of controlled
quality and composition in all concrete made from construction demolition (C&D)
recycled aggregate. The specific objective of this research was to compare the
performance characteristics of High-Volume-Fly-Ash (HVFA) structural concrete
containing C&D aggregate with that of normal recycled aggregate concrete containing no
fly ash.
A coordinated experimental program was undertaken which comprised of ( 1)
Compressive and Split Tensile strength tests; (2) ASTM durability tests by measuring
resistance to chloride-ion penetration; and (3) Flexural strength tests on reinforced
concrete beam specimens. Three mix designs were used, all of which had the same
water/cement ratio of 0.45 and the same amount of recycled aggregate/yd^3. Mix 1
contained cement and no fly ash, Mix 2 contained 16% replacement of cement by weight, and Mix 3 contained 40% replacement of cement, called a HVF A mix. Results
indicate that fly ash increases compressive strength, improves both moment carrying
capacity and tension resistance, and increases resistance to chloride-ion attack.

Three vital factors, namely environmental protection, savings in energy, and technical benefits, make it advantageous to incorporate fly ash of controlled quality and composition in all concrete construction. The specific objective of this research was to compare the performance characteristics of fly ash-modified concrete with that of normal concrete in the coastal environment. To make this comparison, a series of tests using appropriate ASTM standards were conducted. First, the compressive strength development of five mixes was studied. Reinforced beam specimens were then subjected to varying periods of accelerated corrosion with sea water as electrolyte. These were tested under flexure and impact. An attempt was made to predict remaining life. Finally, permeability tests were carried out. Results indicate that fly ash increases compressive strength, improves both moment carrying capacity and impact resistance, and increases watertightness.