Alkali-Activated Fly Ash–GGBFS Binder Mix Design Calculator
This calculator provides an approximate preliminary mix design for alkali-activated mortar or binder systems based on fly ash, GGBFS, alkaline activator, sand-to-binder ratio, NaOH molarity, and curing condition. The predicted compressive strength is an estimated value and must be validated by laboratory testing.
Input Parameters
This ratio shows how much sodium silicate solution is used compared with NaOH solution.
Sodium Silicate-to-NaOH Ratio = Sodium Silicate Solution Mass / NaOH Solution Mass
Example: If NaOH solution = 100 g and sodium silicate solution = 200 g:
Ratio = 200 / 100 = 2.0
A higher ratio may improve strength, but it can also make the mixture sticky and reduce workability.
Liquid activator-to-binder ratio means the mass of total liquid activator divided by the mass of total binder.
Liquid activator = NaOH solution + sodium silicate solution
Binder = fly ash + GGBFS
Liquid Activator-to-Binder Ratio = Total Liquid Activator / Total Binder
Example: If binder = 1000 g and liquid activator = 400 g:
Ratio = 400 / 1000 = 0.40
Extra water-to-binder ratio means the additional water added to the mix divided by the total binder mass.
This is different from the water already inside the NaOH solution and sodium silicate solution.
Extra Water-to-Binder Ratio = Extra Added Water / Total Binder
Example: If binder = 1000 g and extra water = 50 g:
Ratio = 50 / 1000 = 0.05
Extra water can improve workability, but too much water can reduce strength and durability.
Calculated Results
Mix Proportion Table
| Material | Amount | Function |
|---|---|---|
| Click “Calculate Mix Design” to show results. | ||
How the Main Ratios Are Calculated
1. Sodium Silicate-to-NaOH Ratio
This ratio controls the relationship between sodium silicate solution and NaOH solution. Sodium silicate usually improves geopolymer gel formation and strength, but too much sodium silicate can make the mixture sticky and reduce workability.
2. Liquid Activator-to-Binder Ratio
This ratio controls the amount of liquid alkaline activator compared with the total powder binder. The binder is the total mass of fly ash and GGBFS. The liquid activator is the total mass of NaOH solution and sodium silicate solution.
3. Extra Water-to-Binder Ratio
This ratio controls the additional water added separately to improve workability. It does not include the water already present inside the NaOH solution and sodium silicate solution.
Strength Prediction Method Used in This Calculator
The compressive strength prediction in this calculator is a simplified empirical estimate. It is not a replacement for laboratory testing. It is based on the expected effects of GGBFS content, NaOH molarity, sodium silicate-to-NaOH ratio, activator-to-binder ratio, water content, sand content, and curing condition.
In general, increasing GGBFS improves early strength and ambient curing. Increasing fly ash content improves workability but can reduce early-age strength. Higher NaOH molarity and sodium silicate ratio can improve activation, but excessive values may cause sticky mixtures, fast setting, shrinkage, or efflorescence.
Alkali-Activated Fly Ash and GGBFS Mix Design Calculator
Alkali-activated concrete is becoming one of the most important sustainable construction materials for the future. This technology uses industrial by-products such as fly ash and ground granulated blast furnace slag (GGBFS) as the main binder materials instead of relying only on ordinary Portland cement. By using fly ash and GGBFS, engineers, researchers, and construction professionals can reduce cement consumption, lower carbon emissions, and develop high-performance green concrete for modern infrastructure projects.
This Alkali-Activated Fly Ash and GGBFS Mix Design Calculator is designed to help users estimate the basic proportions of alkali-activated binder materials. The calculator allows users to select important mix design parameters such as the sand-to-binder ratio, fly ash percentage, GGBFS percentage, NaOH molarity, sodium silicate-to-NaOH ratio, liquid activator-to-binder ratio, and extra water-to-binder ratio. Based on these inputs, the calculator provides an approximate mix design and an estimated compressive strength for preliminary assessment.
In alkali-activated binders, fly ash and GGBFS have different roles. Fly ash is rich in silica and alumina, which support geopolymer gel formation and long-term strength development. It can improve workability and reduce the heat of reaction. However, mixes with high fly ash content may show slower early strength development, especially under ambient curing conditions. GGBFS, on the other hand, contains more calcium and reacts faster in alkaline environments. It usually improves early-age strength, setting behaviour, and ambient-temperature curing performance. A well-balanced combination of fly ash and GGBFS can produce a strong, durable, and more sustainable binder system.
The alkaline activator is a key part of alkali-activated concrete mix design. The most common activator system includes sodium hydroxide (NaOH) solution and sodium silicate solution. The NaOH solution helps dissolve silica and alumina from the fly ash and GGBFS particles, while sodium silicate provides additional soluble silica to support the formation of binding gels. The ratio between sodium silicate and NaOH is very important because it affects strength, workability, setting time, and durability. A higher sodium silicate-to-NaOH ratio may improve compressive strength, but it can also make the mix sticky and difficult to handle.
Another important parameter is the liquid activator-to-binder ratio. This ratio compares the total mass of liquid activator to the total mass of binder, including fly ash and GGBFS. If the activator content is too low, the reaction may not be strong enough. If the activator content is too high, the mixture may become too liquid, expensive, or more prone to shrinkage and efflorescence. Therefore, this ratio must be selected carefully and checked through laboratory testing.
The extra water-to-binder ratio is also important for practical workability. Extra water can make the mix easier to cast and compact, but excessive water may reduce compressive strength and durability. For this reason, the calculator separates extra added water from the water already present in the NaOH and sodium silicate solutions. This helps users better understand the real liquid content in the mix.
This online calculator is useful for students, researchers, civil engineers, material engineers, and concrete technologists who are working on geopolymer concrete, alkali-activated concrete, fly ash concrete, GGBFS concrete, and low-carbon cementitious materials. It can be used as a preliminary design tool for mortar mixes, binder studies, laboratory trials, and early-stage research planning.
However, the predicted compressive strength shown by this calculator is only an approximate estimate. The actual strength of alkali-activated materials depends on many factors, including the chemical composition of fly ash and GGBFS, NaOH molarity, curing temperature, curing duration, aggregate condition, mixing sequence, activator quality, and specimen testing method. Therefore, all final mix designs must be confirmed by experimental testing, including flowability, setting time, compressive strength, shrinkage, water absorption, and durability performance.
Overall, this alkali-activated fly ash and GGBFS mix design calculator provides a practical starting point for developing sustainable concrete and green construction materials. It helps users understand the relationship between binder composition, activator dosage, water content, and compressive strength, supporting better decision-making in sustainable concrete research and construction practice.