Name: calcium chloride in concrete mixes
Uploaded: 2024-11-07T14:48:38.000Z
Duration: 1 min 17 s
Channel: JoVE

An admixture is an additional substance added to the concrete during mixing to include a unique feature.
Admixtures used to accelerate the hardening of concrete are accelerators; these do not have to affect the setting time of the concrete.
During early hydration, an accelerating admixture should enhance the dissolution of the slowest-dissolving cement components, like silicates.
The most prevalent among the accelerators is calcium chloride. This admixture is often applied in cold weather at 35 to 40 degrees Fahrenheit or when rapid repair requires high early strength post-mixing.
Adding anhydrous calcium chloride at 1 percent of the cement&#39;s mass can accelerate the hardening process as effectively as an 11 degrees Fahrenheit increase in temperature.
Uniform distribution of calcium chloride throughout the concrete mixture is critical, and is most effectively accomplished by dissolving flakes instead of granule admixtures in the mixing water.
Calcium chloride may reduce cement&#39;s sulfate resistance and increase alkali-aggregate reaction risks, as well as shrinkage and creep, but enhances resistance to erosion and abrasion.

accelerators

Accelerators

Accelerators in concrete serve as admixtures to speed up the hardening process, enabling the concrete to achieve early strength faster. Although accelerators do not necessarily impact the time it takes concrete to set, they reduce this time in practice. A common accelerator is calcium chloride, which is particularly useful for hastening early strength development in cold weather or for rapid repair jobs that require quick heat generation after mixing.
The effectiveness of calcium chloride can be compared to raising the temperature of the concrete by 11 degrees Fahrenheit, with a typical addition amount being 1 to 2 percent of the cement&#39;s mass. The distribution of this admixture must be uniform within the mix, achieved by dissolving it in the mixing water.
However, using calcium chloride has drawbacks. It may reduce concrete&#39;s resistance to sulfate attack and increase the risk of alkali-aggregate reaction. Furthermore, it can enhance shrinkage and creep and lower the durability of air-entrained concrete against freeze-thaw cycles. There is also a potential for embedded metal corrosion, such as reinforcing steel. As a result, other chloride-free admixtures like calcium formate are considered for acceleration as they are less likely to cause corrosion. However, their long-term effects on concrete are still being evaluated.

An admixture is an additional substance added to the concrete during mixing to include a unique feature.
Admixtures used to accelerate the hardening of ...

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JoVE Core

Civil Engineering

Unit 1

Admixtures

KEY TERMS AND CONCEPTS

calcium chloride in concrete mixes

Calcium chloride is a concrete admixture that speeds up hardening and helps concrete gain early strength faster. It does not always change the setting time itself, but it can reduce the time needed in practice. This makes it useful in cold weather and in rapid repair work where quick heat generation after mixing is helpful.

A common amount is 1 to 2 percent of the cement mass. Its effect can be compared with raising the concrete temperature by 11 degrees Fahrenheit. To spread it evenly through the mix, the calcium chloride is dissolved in the mixing water.

Calcium chloride also has important limits. It may lower resistance to sulfate attack and increase the risk of alkali-aggregate reaction. It can also increase shrinkage and creep, reduce the freeze-thaw durability of air-entrained concrete, and raise the chance of corrosion in embedded metal, including reinforcing steel.

Because of these concerns, chloride-free admixtures such as calcium formate are also used for acceleration. They are less likely to cause corrosion. Their long-term effects on concrete are still being studied.

Calcium Chloride in Concrete Mixes

Calcium chloride is a concrete admixture that speeds up hardening and helps concrete gain early strength faster. It does not always change the setting time itself, but it can reduce the time needed in practice. This makes it useful in cold weather and in rapid repair work where quick heat generation after mixing is helpful. A common amount is 1 to 2 percent of the cement mass. Its effect can be compared with raising the concrete temperature by 11 degrees Fahrenheit. To spread it evenly through...

retarders

Retarders in Concrete Pouring

Retarders are chemical admixtures used in concrete to slow the setting time. They are especially helpful when one pour must follow another after a delay. By keeping the concrete workable for longer, they can help prevent cold joints and support a more cohesive structure. Retarders can also improve the look of exposed aggregate finishes when they are used in the right amount. Their effect on setting time can be checked with a penetration test. Common retarding substances include sugar,...

plasticizers

Concrete Workability with Plasticizers

Concrete plasticizers are water-reducing chemical admixtures that improve workability and strength. They help concrete use less water while keeping the same flow, reduce cement content without losing workability, or make mixes easier to place in hard-to-reach areas. Plasticizers work by using surface-active agents. These agents create repulsive electrostatic forces between cement particles. The particles disperse more evenly, and the concrete needs about 5 to 15 percent less mixing water. <br...

superplasticizers

Superplasticizers for Stronger Concrete Mixes

Superplasticizers are concrete admixtures that make mixes flow better while using less water. They are strong water reducers, so concrete can be easier to place without losing strength. This makes them useful when concrete must reach tight spaces or heavily reinforced areas without mechanical vibration. These admixtures work through sulfonated melamine or naphthalene formaldehyde condensates. These chemicals give cement particles a negative charge. The particles repel each other and spread out...

additives and fillers in concrete

Concrete Fillers That Improve Performance

Concrete fillers and additives help change how cement paste performs. Pozzolans and blast-furnace slag act as additives or admixtures because they react with calcium hydroxide released during cement hydration. Fine fillers are close in fineness to Portland cement and can improve workability, density, and resistance to capillary bleeding or cracking. Some fillers are hydraulic, which means they can react with water, while others take part in harmless reactions inside the cement paste. A key...

waterproofing and anti-bacterial admixtures in concrete

waterproofing-and-anti-bacterial-admixtures-in-concrete

Concrete Water Resistance and Biological Protection

Concrete can absorb water because of capillary action in the pores of its hydrated cement paste. That movement pulls water into the material. Waterproofing admixtures are added to reduce this penetration and help concrete resist water. The effect of a waterproofing admixture depends on the water pressure acting on the concrete. Rain, capillary rise, and hydrostatic pressure in structures made to hold water can all affect performance. These admixtures make concrete hydrophobic, which means they...

key terms and concepts

Learn how calcium chloride speeds concrete hardening, supports cold-weather repair, and why builders also consider chloride-free alternatives.

Calcium Chloride in Concrete Mixes | JoVE K12

JoVE Core Civil Engineering offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

Calcium Chloride in Concrete Mixes

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