Concrete Basics: Essential Ingredients For A Concrete Mixture

Concrete is and has been for thousands of years, a very popular building material.

Made up of just a few basic ingredients, concrete is the most widely used man-made material on the planet. Humans use more concrete than all other building materials combined.

So what is concrete exactly?

What goes into the most commonly used building material?

Concrete is a mixture of cement, air, water, sand, and gravel–it’s as simple as that!

Not exactly. The typical concrete mix is made up of roughly 10% cement, 20% air and water, 30% sand, and 40% gravel. This is called the 10-20-30-40 Rule–though proportions may vary depending on the type of cement and other factors.

Now let’s discuss each ingredient and the important role they play in your mix.

Concrete mix ingredients and their important roles:

Cement

Though cement makes up the smallest percentage of the mixture, it’s an essential ingredient in concrete. Cement serves as the glue that keeps everything else together. It’s also what allows the ready mix to harden once it’s placed. There are five different types of cement depending on what kind of concrete you’re looking to make:

Type I is used for most residential work
Type II is used in moderate sulfate conditions
Type III is used in climates where freezing is a risk
Type IV is used for special orders like industrial placements
Type V is used in extreme sulfate conditions

Types I and II are the most widely used residentially in the United States due to the relatively moderate climates we experience here.

Air and Water

For a mixture to be effective, some amount of air entrainment (tiny air bubbles) is needed in the concrete. Air-entrained cement ensures that excess water has a chance to expand when it moves through the freeze-thaw cycle. These air bubbles, however, must be microscopically small or else the ‘entrained’ air will turn into ‘entrapped’ air which leads to shrinkage and cracking.

Amongst all of the other essential ingredients involved in creating a mixture, water tends to have the largest impact. As a rule of thumb, the more water that you put into the mixture, the less strength the hardened mixture will have. Shrinkage and cracking are also probable when too much water is involved. Excess water will eventually evaporate out of the hardened concrete, causing the concrete to shrink and eventually crack.

An ideal amount of water can be measured by water to cement ratio, which should vary between .4 and .6. The higher the ratio, the weaker the concrete. A good way to test the solubility of your concrete is to perform a slump test. This will help to determine whether or not your mixture contains too much water.

Gravel and Sand

As you can see, gravel and sand aggregates make up about 70% of the mixture. This high percentage makes the mixture more economical–as gravel and sand are both stronger and more cost-effective than the cement. A good ready mix will include proportionate amounts of both large (gravel) and small (sand).

The reason for this is that the gravel makes up the majority of the ready-mix and the smaller sand particles do a good job of filling in any extra spots that could otherwise be filled by unwanted air pockets.

Well there you have it, the ingredients that combine to create the most widely used building material in the world–concrete. As you can see, each ingredient and its ratio impacts the final ready mix’s quality and type. It’s important that you get the best ready mix for your specific job. That’s why we’ve created this Ready Mix Checklist to help you and your ready mix supplier create just what you need. Download your Ready Mix Checklist now.

The Importance of Concrete Mix Design

Why a good ready-mix concrete design is necessary

A good concrete mix design creates the foundation of a sound infrastructure.

Concrete mix design involves a process of preparation in which a mix of ingredients creates the required strength and durability for the concrete structure. Because every ingredient in the mix consists of different properties, it’s not an easy task to create a great concrete mix. It is imperative that all ingredients be tested to determine their physical properties and the bearing capacity of the project location.

The ingredients to be tested: water, fine aggregate (sand), coarse aggregate, cement, chemicals, reinforcement, and soil.

The values of the physical properties obtained after testing will be used as the basis for all concrete mix design considerations. This will ensure the structure will be sound and prevent failure of the mix. It is important to note that the ingredients for the mix might vary from one project location to another, so the physical properties must be tested for the requirements specified for each location.

Types of concrete mix

The two types of concrete mix are normal performance concrete and high-performance concrete, and they’re characterized by their compressive strength:

Normal Performance Concrete

A normal performance concrete mix has a performance strength ranging between 20 and 40 MPa. It is the more used mix of the two. Normal performance concrete has good workability if all of the mix ingredients are in accurate proportions. When freshly mixed, the concrete must be plastic or semi-fluid so that it can be molded.

High-Performance Concrete

A high-performance concrete mix has a performance strength above 40 MPa. The main purpose of using high-performance concrete is to reduce the weight, creep or permeability issues, and to improve the durability of the structure. Like the normal performance concrete mix, this mix must be plastic or semi-fluid when freshly mixed so that it can be molded.

Because high-performance concrete has a high cement content, it is often sticky and hard to be handled and placed. However, this does not cause the cement to bleed, an issue that normal performance concrete might run into.

Factors affecting concrete mix design

Strength and durability of the concrete mix design are dependent upon the following factors:

Grade designation: Concrete’s strength is measured in N/mm2 when subject to test after curing in any curing medium. The choice of concrete grade depends on its usage.

Choice of cement: Cement choice varies depending on usage. The cement should be tested for performance required by their usage before being tested in the design mix.

Choice of aggregate size: Aggregates needed for each mix is dependent upon the physical properties needed for the design. All aggregates must be quality sized before use.

Type of water: Any water used for concrete mix design should be tested before use to ensure it is within the range of water required for concrete. Most all consumable water is good for concrete work, but should still be tested.

Water to cement ratio: The ratio of water to cement should be tested for consistency, initial and final setting, soundness of the cement, workability, slump of the concrete and compacting factor.

Workability: This is the measure of ease of mixing concrete without segregation or bleeding. It mostly depends on the designed slump of the concrete.

Durability: This is the measure of the required strength (N/mm2) of any concrete grade after 28 days of curing. Durability should be control tested on site.

A quality concrete mix design is crucial for successful construction. At Concrete Supply Co., we sleep better at night knowing our end-to-end ready mix concrete solution meets the highest quality performance in concrete, and our integrity in doing so is unparalleled.

We offer a guide to help you find your perfect read mix. If durability and quality are what you’re looking for in a concrete mix, take a look at our guide and we’ll be sure to help you create the best mix for your project.