The calculation in this concrete temperature calculator works according to the ACI (American Concrete Institute) formula for estimating concrete temperature based on the temperature of its constituent materials.

The graph below shows the change of the concreting type against the change in ambient and concrete temperature. Note that this is only to help understand theoretically how the temperature influences concreting. The ACI, other guidelines, and professional advice should be considered for any practical purposes.

Here’s a detailed breakdown of how the calculation works:

The Formula

The calculator uses the following formula from ACI:

T = (0.22(TcMc + TaMa + TwMw)) / (0.22(Mc + Ma + Mw))

Where:

• T = Final concrete temperature (°F)
• Tc = Temperature of cement (°F)
• Ta = Temperature of aggregate (°F)
• Tw = Temperature of water (°F)
• Mc = Mass of cement
• Ma = Mass of aggregate
• Mw = Mass of water
• 0.22 = Specific heat constant (Btu/lb/°F)

Key Points About the Calculation

1. Proportions: The calculator uses typical concrete mix proportions (by mass):
   
   • Cement: 1 part
   • Aggregate: 3 parts (combined fine and coarse)
   • Water: 0.5 parts
2. Simplification: These are simplifications that provide a reasonable approximation for most concrete mixes.
   

Since the constant 0.22 appears in both the numerator and denominator, it can be mathematically canceled out. The formula effectively becomes a weighted average:

T = (TcMc + TaMa + TwMw) / (Mc + Ma + Mw)

3. Rounding: The result is rounded to one decimal place for practical use.
   

Example Calculation: If cement is at 70°F, aggregate is at 70°F, and water is at 70°F:

T = ((70×1) + (70×3) + (70×0.5)) / (1 + 3 + 0.5)

T = (70 + 210 + 35) / 4.5

T = 315 / 4.5

T = 70°F

4. Two Temperature Options

The calculator offers two modes:

1. Calculated Temperature: Uses the formula above to estimate concrete temperature based on material temperatures.
   
2. Measured Temperature: Bypasses the calculation and lets you input a directly measured concrete temperature from the field.
   

This flexibility allows for a comparison between theoretical and actual temperatures, which can be valuable for quality control and troubleshooting.

The calculated or measured concrete temperature, along with the ambient temperature, is then used to determine the appropriate ACI standard to follow (ACI 306R for cold weather, ACI 305R for hot weather, or ACI 301 for normal conditions).

1.  Hot weather concreting is in the case of either of the two conditions happening:

if (ambientTemp > 90 || concreteTemp > 90) {

  condition = ‘Hot Weather’;

  // Hot weather recommendations…

}

For instance, in scenarios such as:

• The ambient temperature (40°F) is below the hot weather threshold (90°F)
• BUT the concrete temperature (95°F) is above the hot weather threshold (90°F)

Since either condition triggers hot weather procedures, the calculator correctly identifies this as a hot weather scenario requiring ACI 305R guidelines.

This is proper behavior because:

1. Hot concrete (above 90°F) can experience problems regardless of ambient temperature, including:
   
   • Accelerated setting time
   • Increased water demand
   • Potential for thermal cracking
   • Workability issues
2. The high temperature differential between the concrete (95°F) and the ambient air (40°F) creates additional risks:
   
   • Rapid surface cooling while the interior remains hot
   • Thermal shock
   • Increased potential for cracking

The ACI 305R recommendations are appropriate in this unusual case – you’d still need to control the concrete temperature and perhaps use retarding admixtures, even though the air temperature is cold.

In real-world scenarios, you might need to address both hot and cold weather concerns simultaneously in this unusual situation.

Cold weather concreting is defined by the ACI 306R standard as conditions when the ambient temperature falls below 40°F (4.4°C).

2. Cold weather conditions are triggered when:

// Cold weather concrete – ACI 306R

if (ambientTemp < 40) {

  condition = ‘Cold Weather’;

  // Cold weather recommendations…

}

The calculator only uses the ambient temperature to determine if it’s a cold weather situation, not the concrete temperature. This is based on ACI 306R guidelines, where the primary concern is the external environment being cold enough to potentially:

1. Slow down or stop the cement hydration process
2. Cause the concrete to freeze before it reaches sufficient strength
3. Lead to frost damage in fresh concrete
4. Cause thermal stresses due to temperature differentials

Even if your concrete temperature is warm (e.g., 80°F), if you’re placing it in an environment below 40°F, it’s still considered cold weather concreting because the concrete will rapidly cool, potentially causing problems with proper curing and strength development.

The cold weather recommendations activated in the calculator include:

• Heating mixing water and/or aggregates
• Protecting concrete from freezing for the first 24 hours
• Using accelerating admixtures as approved
• Maintaining minimum curing temperatures
• Ensuring the substrate is free from ice and snow

For cold weather concreting, the calculator checks:

if (ambientTemp < 40) {

  condition = ‘Cold Weather’;

}

Cold weather concreting is triggered specifically when:

• The ambient temperature falls below 40°F (4.4°C)
• Regardless of the concrete temperature

This function is called when you click the “Calculate” button. The formula itself is based on the ACI guideline formula for estimating concrete temperature from its constituent materials:

T = (0.22(TcMc + TaMa + TwMw)) / (0.22(Mc + Ma + Mw))

Where:

• T = Final concrete temperature
• Tc, Ta, Tw = Temperatures of cement, aggregate, and water
• Mc, Ma, Mw = Masses of cement, aggregate, and water
• 0.22 = Specific heat constant

The code uses simplified mass proportions (1:3:0.5) to make the calculation more accessible without requiring detailed mix design inputs.

The temperature calculation formula used in the calculator is based on the ACI 305R guideline, which is the “Guide to Hot Weather Concreting.” Specifically, the formula for estimating the temperature of freshly mixed concrete comes from this standard.

The formula is commonly referenced in ACI 305R as a method for predicting the temperature of concrete based on the temperatures of its constituent materials. The equation uses the principle that the final concrete temperature is essentially a weighted average of the component temperatures, with the weights being determined by the mass and specific heat of each component.

It’s worth noting that this same formula or variations of it may appear in other ACI documents as well, including:

1. ACI 306R (Cold Weather Concreting)
2. ACI 301 (Specifications for Structural Concrete)
3. ACI PRC-207.1 (Guide to Mass Concrete)

The formula is a fundamental principle of thermodynamics applied to concrete mixing and is widely accepted across the concrete industry for estimating the temperature of freshly mixed concrete.