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concrete

  • Safety of deteriorated structures

    Safety of deteriorated structures

    By

    Nirmal Raj Joshi
    in ,

    The collapse of various civil engineering structures-such as bridges, dams, and buildings-has become a common occurrence in recent years, often attributed to aging and material degradation (refer to relevant news reports). Many of these structures were constructed decades ago, with assumed service lives typically ranging from 50 to 80 years. For instance, the design life…

  • Use of genetic algorithm for optimum proportioning of concrete

    Use of genetic algorithm for optimum proportioning of concrete

    By

    Nirmal Raj Joshi
    in , ,

    Genetic Algorithms (GAs) have emerged as a robust optimization technique within civil engineering, particularly in the design of concrete mix proportions. Their inherent ability to address complex, multi-objective, and nonlinear optimization problems makes them well-suited for this application. Conventional mix design methodologies often rely on iterative, trial-and-error approaches that are both time-consuming and may fail…

  • Fatigue stress and RC deterioration

    Fatigue stress and RC deterioration

    By

    Nirmal Raj Joshi
    in ,

    Fatigue stress represents a critical factor in the progressive deterioration of reinforced concrete (RC) structures, particularly under conditions involving repeated loading and corrosive environments. The synergistic interaction between fatigue and corrosion, commonly referred to as corrosion-fatigue, significantly intensifies the degradation of structural materials, thereby diminishing overall structural integrity and long-term durability. Fatigue stress originates from…

  • Cavitation effect in concrete

    Cavitation effect in concrete

    By

    Nirmal Raj Joshi
    in

    Cavitation is a physical process that leads to surface pitting caused by the collapse of vapour bubbles, which results in a sudden rise in local pressure. In this article, we explore how this phenomenon can damage concrete. Damages by cavitation Cavitation can damage the concrete in the following ways: Shock Waves Generated by Bubble Implosion:…

  • Durability of concrete in terms of water permeability

    Durability of concrete in terms of water permeability

    By

    Nirmal Raj Joshi
    in ,

    Permeability is one of the main indicator defining the durability of the concrete.  In one hand, the permeability of the concrete can be high from the beginning of concrete life, in which case, the deterioration takes place rapidly during the service life. While in the other hand, the permeability of the concrete may gradually increase…

  • Degradation of concrete by abrasion

    Degradation of concrete by abrasion

    By

    Nirmal Raj Joshi
    in

    Abrasion of concrete is progressive loss of concrete mass due to mechanical degradation such as friction, grinding action, impact, overloading and local crushing. Vehicular movement and pedestrian traffic causes abrasion.  The worst effect of abrasion is caused by vehicle with studded/chain tyres. Similarly, in industrial buildings, the concrete floors are subjected to impact load and…

  • Using microbes for durable concrete

    Using microbes for durable concrete

    By

    Nirmal Raj Joshi
    in ,

    Conventionally, organic matters in concrete were considered to be undesirable. But recent study with selected microbes has shed new light on its usefulness. Both useful and deteriorating microbes has been identified. Metabolic activity of microbes produces acid which degrade concrete. These kinds of deterioration are pronounced in location having high microbial activities such as near…

  • Leaching in water retaining structures

    Leaching in water retaining structures

    By

    Nirmal Raj Joshi
    in

    Cement requires water to undergo hydration. However, after hydration is complete, excess water can dissolve the hydration products, causing leaching and weakening the structure. This issue is particularly critical for water-retaining concrete structures. For example, in dams, hydrostatic pressure and water permeability can cause the rapid leaching of these hydration products. This article examines the…

  • Leaching and Efflorescence of concrete

    Leaching and Efflorescence of concrete

    By

    Nirmal Raj Joshi
    in ,

    In structures such as dam where the flow of water via pores of concrete is high, there could be significant loss of mono-sulfate and ettringite and decalcification of calcium silicate hydrate due to leaching out of these salts to the surface and subsequently washing away. This will lead to reduction in strength of concrete and…

  • Health of reinforced concrete structure based on construction quality

    Health of reinforced concrete structure based on construction quality

    By

    Nirmal Raj Joshi
    in

    Reinforced concrete (RC) structures exhibit significant variability during construction, primarily due to the in-situ casting process. This method introduces numerous factors that can affect quality. As Richard Feynman wisely noted, “The first principle is that you must not fool yourself—and you are the easiest person to fool.” This insight is particularly relevant in the construction…