Creep Of Concrete: Understanding Its Impact On Structural Durability

Concrete is recognised as the most durable and versatile materials used in the construction industry to make buildings, bridges and infrastructure. In doing so, Creep of concrete is such a type of deformation that affects structural integrity. In this blog, we are going to discuss concrete structures, factors like hot and cold weather influencing Concrete creep and its impact on workability and strength. Concrete creep and shrinkage

What is Concrete creep?

Concrete creep can be defined as a phenomenon of slow and continuous deformation of concrete when subjected to a constant load over a certain period of time. Creep in concrete mostly occurs because of internal rearrangement of the concrete matrix especially in cement paste under sustained stress. This is the deformation mostly identified in early stages of concrete curing that leads to structural damages such as deflections, cracking and compromised durability.

Factors influencing Creep in Concrete

Load magnitude and duration

Creep is directly proportional to the magnitude of the sustained load. The higher the load, the greater the potential for creep. Similarly, applying a longer load significantly deforms the structure over a time.

Inappropriate concrete mix composition

Determining susceptibility requires an ideal percentage of concrete mix. However, high water- to- cement ratio resulted in increasing creep because of higher porosity and weaker internal structure. At First Choice Readymix, we have a well-balanced Flowable Concrete Mix containing optimal water and cement that significantly reduces creep.

Using poor aggregates

Inappropriate aggregates used in a concrete mix influencing creep. For example- dense well- graded aggregates provide better resistance to deformation compared to weaker, more porous aggregates. Ensuring quality material from recognised construction chemical suppliers like First Choice Readymix can provide better resistance against creep.

Curing and moisture content

Inadequate curing can lead to higher creep values, as improperly hydrated cement particles tend to be weaker and more prone to deformation. Furthermore, the moisture content in the concrete affects creep, with wet concrete exhibiting higher creep than dry concrete.

Tenure of used concrete

As the concrete ages, the rate of creep decreases significantly. However, it is important to note that creep never completely stops and will continue, albeit at a slower rate, throughout the life of the structure.

Hot weather Concreting

Hot weather Concreting refers to placing and curing of concrete in conditions where high temperatures, low humidity and high wind speed combine to create challenges in concrete's performance. Increasing higher temperature raises the hydration that ensures chemical reaction between cement and water which accelerates the setting time that results in shrinkage and increased concrete creep.

Effects of hot weather on concrete creep and shrinkage

  • Increased creep due to rapid evaporation and increasing internal stress.
  • High temperature makes it challenging for maintaining workability of concrete as Concrete mix loses its retention quickly.
  • Rapid drying can cause surface cracking, which, if unchecked, can propagate deeper into the concrete which affects aesthetic quality of the concrete, structural integrity and increases creep and shrinkage rates

Cold weather Concreting

Cold weathering concreting slows down the speed of the hydration process, delaying the setting and hardening the concrete. As a result, it often produces weak concrete with higher creep and shrinkage rates.

Effects of cold weather on concrete creep and shrinkage

  • Cold weather can significantly delay the curing process, leaving the concrete in a more vulnerable state for longer periods that reduces the strength development.
  • In cold weather, if the concrete freezes before it has gained sufficient strength, it can suffer from cracking, which weakens the structure and increases the likelihood of creep.
  • Cold weather can extend the working time of concrete, allowing more flexibility in placement. It often leads to challenges in mass concreting projects where large volumes of concrete need to be placed at once.

Effect of temperature on concrete workability and strength

Temperature significantly affects the workability and strength of concrete. Both hot and cold weather conditions can negatively impact the fresh concrete mix, altering its hydration process and, consequently, its strength and durability. In hot weather, concrete can set too quickly, reducing the working time and leading to improper finishing, which affects the long-term strength of the structure. In cold weather, concrete sets too slowly, which can delay construction schedules and leave the concrete vulnerable to freezing or inadequate strength development. At FCR, our goal is to maintain an optimal temperature range during concrete curing to ensure that the concrete develops the required strength and durability, with minimal risk of shrinkage, creep, or cracking.

Effect of concrete temperature in mass concreting

In mass concreting, such as in the construction of dams, bridges, or large foundations, the internal temperature of the concrete can rise significantly due to the exothermic nature of the cement hydration process. If the heat generated during curing is not properly controlled, it can lead to thermal gradients within the concrete, causing uneven shrinkage, cracking, and increased creep. To mitigate these risks, using High-Quality Ready-Mix Concrete with a high strength cement mix is crucial. FCR, as one of the leading producers of RMC, suggests cooling techniques, such as using chilled water in the concrete mix, can help control the temperature during the curing process.