How to Estimate The Setting Time of Concrete

This article briefly describes the setting time of concrete, why it is important, and how different weather condition could affect it. We will later review some of existing methods that are used to estimate the setting time of concrete on-site.

Setting Time of Concrete

As ASTM C125-15b, setting is defined as “the process, due to chemical reactions, occurring after the addition of mixing water, that results in a gradual development of rigidity of a cementitious mixture.” As ACI CT-13, initial setting time is defined as “the time required for a freshly mixed cement paste, mortar, or concrete to achieve initial setting.” Final setting time is defined as “the time required for a freshly mixed cement paste, mortar, or concrete to achieve final set.

Setting Time of Concrete

Why is Setting Time of Concrete Important?

The knowledge about the setting time is helpful to estimate the time required for initial curing of concrete, surface preparation, leveling and polishing. This can effectively control the surface cracking at early ages. Hot weather and cold weather can significantly affect the setting time of concrete. Mis-estimating setting time at wintertime can cause delay in effective surface preparation, leveling and polishing. Hot weather can reduce the setting time of concrete; while cold weather can increase the setting time of concrete.

On-site Estimation  of  Setting Time

Beside the standard laboratory test for measuring the setting time of concrete by penetration method (ASTM C 403), the following methods have successfully been utilized in measuring the setting time of concrete:

1- Maturity Method

The maturity method is mostly used to evaluate the strength development of concrete at early ages, specially in wintertime when the development of strength is critical. However, the method has been used by some researchers to predict the setting time of concrete (Min-Cheol Han, Cheon-Goo Han 2010). In this research the very concept of equivalent age was used for estimating the setting time of concrete.maturity-index

 

2- Ultrasonic Pulse Velocity (UPV) Method

UPV method has been used by researchers to study the setting time of concrete. Piyasena et al. (2013) studied the effectiveness of UPV method for estimating the setting time. In their studies, they discovered that the UPV becomes relatively constant near to the setting time.

Peter Taylor and Xuhao Wang (2014) examined the use of UPV method (using shear wave) for evaluating the setting time. Shear waves are reported to be more sensitive to the phase transition between fresh and hardened concretes. The speed of propagation of shear wave within liquid phase is significantly lower when compared to solid phase. Therefore, shear wave may better track the transition from fresh concrete to hardened concrete. This transition results in gradual evolution of shear wave velocity within concrete, helping to precisely find out the setting time of concrete.

3- Electrical Resistivity of Concrete

Zongjin Li et al. (2007) demonstrated the effectiveness of electrical resistivity measurements for predicting the setting time of concrete. Electrical resistivity can be used to track the development of concrete microstructure, setting time, and early age strength.

6 thoughts on “How to Estimate The Setting Time of Concrete

  • “Predicting” set time is a far greater challenge than merely measuring properties that monitor the development of early hydration. Maturity methods would be unreliable if there were variations in admixture doses intended to give a constant set time to cope with day to day ambient conditions. What is very important, is the mix design has appropriate setting performance for the conditions and methods used for placement and finishing. Perhaps even more important, and especially for flat work, is that the finishers time their operations to respond to the concretes performance, not just impose their schedule, but observe and respond to the concrete. For these purposes, poking with a finger or piece or re-bar may outperform many of the theoretical or gadget alternatives.

  • I agree with Kevin on the defficiency of the maturity method to predict setting if admixtures are involved. However, UPV and resistivity (conductivity) measure changes in the structure of the paste and as such should give good corrélations with setting times. You must realise though that the setting times are based on arbitrary values of pressure and may not coincide exactly to the the physical phenomena that are monitored by the two methods.

  • Prediction of concrete setting time depend upon many parameters like quality of aggregates, placing ,heat of hydration , cement composition also depends upon accelerators and retards. Air temperature, ground temperature and weather conditions all play major roles in the rate with which cement hydrates. The setting time of concrete decreases with a rise in temperature, but above 30 degree a reverse effect could be observed. At low temperatures setting time is retarded. Proper curing techniques and site preparation will aid the setting time. However when concrete is being used in times of temperature extremes, i.e. colder weather or in the middle of summer, several admixtures may be used in the concrete mix to aid in the placement of the final product.
    So,Concrete mix design plays major role to predict the setting time of concrete.

  • I have no idea or ever heard of role of mix design in setting time of concrete; but I know its enormous importance in preparation of Ready Mix Concrete( RMC) , particularly in Metros, where travel time may be enormous.
    I feel, not much technology of determining the setting time is available in open source and lie in the secret domains of the manufacturers / producers .Different admixtures for deciding setting time is again the prerogative of various specialised engineers. Initial and Final setting time again , to me, is an unknown fields for many.
    I am doubtful if any benevolent and knowledgable soul will ever respond in such discussions.
    Thanks.

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