What Goes Into Ready-Mix Concrete? A Look at the Core Ingredients

Concrete is one of the most widely used building materials in the world—and for good reason. It’s durable, versatile, cost-effective, and strong enough to support everything from sidewalks to skyscrapers. But what exactly goes into ready-mix concrete, and why does the mix matter?

At J.J. Kennedy, Inc., we’ve been delivering top-quality ready-mix concrete across Western Pennsylvania since 1946. We know that great concrete starts with the right ingredients—and the right blend. In this post, we’re breaking down the core components of ready-mix concrete and explaining how each one contributes to the strength, performance, and longevity of the final product.

1. Cement (The Binder)

The primary ingredient in concrete is cement, typically Portland cement. Cement acts as the binder that holds everything together. When combined with water, it forms a paste that coats and bonds the other ingredients.

Portland cement is made by heating limestone, clay, and other materials in a kiln to form clinker, which is then ground into a fine powder. It’s this powder that reacts chemically with water in the mix—a process called hydration—to form the hardened material we know as concrete.

2. Water (The Activator)

Water is the catalyst that activates the cement and starts the chemical reaction that causes the mix to harden. Getting the water-to-cement ratio right is crucial. Too much water weakens the mix and leads to cracks and shrinkage. Too little water makes it difficult to pour and finish.

At J.J. Kennedy, Inc., we use precise batching methods to ensure each load has the ideal water content for the job at hand—whether it’s a foundation, a driveway, or a bridge deck.

3. Aggregates (The Fillers)

Aggregates make up the bulk of the concrete mixture—typically 60 to 80 percent of the volume. These include:

• Fine aggregates, like sand
• Coarse aggregates, such as gravel or crushed stone
  

Aggregates provide strength, bulk, and durability to the concrete. Their size, shape, and composition can be adjusted to suit the specific requirements of a project. For instance, smaller aggregate particles are often used for smoother finishes, while larger aggregates are ideal for high-strength applications.

4. Admixtures (The Enhancers)

Modern concrete often contains chemical admixtures—specialized ingredients added in small amounts to modify the performance of the mix. These admixtures can:

• Speed up or slow down the curing process
• Improve workability and flow
• Increase durability
• Reduce water content
• Enhance resistance to freezing and thawing
  

For example, in colder climates like ours in Western PA, air-entraining admixtures are commonly used to create microscopic air bubbles in the mix. These bubbles give expanding ice a place to go, preventing cracking during freeze-thaw cycles.

At J.J. Kennedy, Inc., we work with contractors to select the right admixtures based on the project’s location, weather conditions, and structural requirements.

5. Supplementary Cementitious Materials (SCMs)

In addition to standard cement, many mixes now include SCMs like:

• Fly ash (a byproduct of coal combustion)
• Slag cement (a byproduct of steel production)
• Silica fume
  

These materials improve the strength, durability, and sustainability of concrete by reducing the amount of Portland cement needed. They can also help control temperature during large pours and extend the working time of the mix.

SCMs are a key part of greener building practices and are often used in LEED-certified construction projects.

Why Mix Design Matters

Not all concrete is created equal. The proportions of each ingredient must be carefully balanced to meet the specific requirements of your project. A sidewalk needs a very different mix than a warehouse floor or a bridge.

That’s where the expertise of a trusted ready-mix supplier comes in. At J.J. Kennedy, Inc., we don’t just deliver concrete—we deliver custom-engineered mixes designed for performance, longevity, and efficiency. Our experienced team works with engineers, contractors, and builders to ensure each batch is perfectly suited for its application.

Our Commitment to Quality

Every batch of concrete we produce is made in state-of-the-art plants using high-quality materials and precise computerized batching systems. This ensures consistency, strength, and reliability in every load. Our ready-mix trucks are dispatched with precision and arrive on-site ready to pour—on time and on spec.

With locations across Western Pennsylvania and a long-standing reputation for excellence, J.J. Kennedy, Inc. is proud to be the concrete supplier of choice for residential, commercial, and industrial projects alike.

Ready to Build? Let’s Get Mixing.

Whether you’re pouring a patio, setting a foundation, or paving a highway, understanding what goes into your concrete mix is the first step toward building something that lasts.

Need help choosing the right mix? Contact J.J. Kennedy, Inc. today. We’re here to provide the knowledge, service, and materials you need to get the job done right.