Assessment of Durability of Reactive Powder Concrete Using Oxygen Permeability Index
-Durability of concrete is very important parameter for using natural resources effectively and reducing the cost of reconstruction, maintenance and repair of structure. This paper focuses on need of much of the need for concrete repair can be eliminated, if sufficient consideration and attention is given to control of surface quality of concrete at the construction stage. A South African approach is used to measure the oxygen permeability index testing and concluded that the method is applicable to actual project and is durability index is a parameter to evaluate the durability of RPC and cover zone concrete. RPC shows a good OPI value indicating impermeable concrete and its use can be justified for special purpose.
THE USE OF FLY ASH, SILICA FUME, SLAG AND OTHER MINERAL BY-PRODUCTS IN CONCRETE
Portland cement is a highly energy-intensive product, and therefore, in an energy-hungry world considerable efforts are being made to find substitute materials for the partial replacement of cement in concrete. Some of the most promising substitutes or supplementary cementing materials are high- and low-calcium fly-ashes, ferrous- and non-ferrous slags and condensed silica fume. This paper presents a state-of-the-art review on the use of these mineral by-products in concrete, and the role of these materials in the less developed countries. The physical and possolanic properties of the supplementary cementing materials are outlined, and their effect on the properties of fresh and hardened concrete discussed. Particular emphasis is placed on the use of condensed silica fume, a relatively new addition to the family of supplementary cementing materials. The contribution of superplasticizers to achieving high-strength concrete incorporating fly-ash and silica fume is mentioned. Reference is made to the currently available specifications for these materials both in North America and Europe, and their limitations discussed. The advantages and limitations in the use of supplementary cementing materials as separately batched ingredients at a ready-mixed concrete plant, versus the use of blended cements are discussed, and North American trends in this field are mentioned briefly. It is emphasized that additional quality control measures are needed when fly-ash, slag and silica fume are incorporated in ready-mixed concrete. This is especially so when chemical admixtures are also incorporated in concrete made with supplementary cementing materials. (Author/TRRL)
A chloride conduction test for concrete
Abstract The paper describes the development of a very rapid test that measures the permeability of concrete to chloride ions. Once sample conditioning has been done, up to 20 concrete samples can be tested in an hour using a single conductivity cell. The test involves saturating a concrete sample with a 5 M NaCl solution, before measuring the conductivity of the sample. By saturating samples with a highly conductive solution, they have virtually the same pore water conductivity. Different concrete samples yield different conductivities primarily because of differences in their pore structure. The measured conductivity is related to the diffusibility ratio as well as to the chloride diffusivity of the concrete.