Corrosion of Embedded Metals in Concrete Corrosion of reinforcing steel and other embedded metals is the leading cause of deterioration in concrete. When steel corrodes, the resulting rust occupies a greater volume than the steel. This expansion creates tensile stresses in the concrete, which can eventually cause cracking, delamination, and spalling (Figs. 1 and 2). …
Causes of Formwork Failures Failure of formwork in general results from various causes: excessive loads, premature removal of forms or shores, inadequacies related to formwork, and human error on the job, whether due to indifference, haste, or lack of knowledge. Hadipnono and Wang (1986) studied the causes of 85 major falsework failures that have been documented …
Concrete repairs have occurred on Reclamation projects since the first concrete was placed in 1903. Unfortunately, even though the best available knowledge and materials were used, many repair failures have occurred during the 112 years since that first concrete was placed. As a first step to increase the likelihood of a successful repair, it is …
Origin and Classification of Aggregates Most of the properties of an aggregate derive from its parental rock chemical and mineral composition which affects strength, stiffness, density, pore structure and permeability. Rocks experience geothermal and weathering processes which can produce granular materials in the form of natural gravels and sands, these types of aggregates can be …
Pervious Concrete Pervious concrete is a type of concrete with a system of interconnected pores allowing water to rapidly drain through. Pervious concrete itself is made up of coarse aggregate that is coated by a thin layer of cement paste, holding the system together. While the compressive strength, void content, and permeability tend to vary …
Flyash Flyash is the by-product of the combustion of pulverized coal and is collected by mechanical and electrostatic separators from the fuel gases of power plants where coal is used as a fuel and the disposal of flyash is one of the major issues for environmentalists as dumping of flyash as a waste material may …
Admixtures A material other than water, aggregates, or cement that is used as an ingredient of concrete or mortar to control setting and early hardening, workability, or to provide additional cementing properties. Why is admixture used? Over decades, attempts have been made to obtain concrete with certain desired characteristics such as high compressive strength, high …
Formwork materials can be classified as: 1. Timber 2. Metals 3. Plastics 1.Timber a. Lumber: Lumber is commonly available material and has excellent strength, weight and cost factor. Lumber is classified as: • Boards: 1 to 1.5 inches thick, 2 or more inches width • Dimensions: 2 to 4 inch thick, any width. • Timbers: …