August 14, 2018

FAQ

What is the difference  between cement and concrete?

Cement and concrete are not the same thing, however, concrete does have cement as an ingredient.

Basically, concrete is made of cement, water, sand, and stone. Cement is a very fine powder made from limestone, sand, clay, and iron ore. In the correct proportions these ingredients are crushed and super-heated in a kiln to form “clinker”. The clinker is crushed again with the precise amount of gypsum and other ingredients.  The result is a fine powder known as cement. Concrete’s strength comes from the reaction between water and the chemical compounds in cement referred to as hydration. The aggregates in concrete (sand and stone both coarse and fine) are for volume only and are not considered active ingredients in the hydration process.

What is “Ready-Mixed” concrete?

Commercial Concrete delivers what is known as Ready-Mixed Concrete. When you place a concrete order, our specialists match your requirements with a specific mix design from our database. The mix ingredients are then sent to batch panels that load all of the raw materials into a drum which mixes the concrete. When the concrete truck arrives at the job site, the product is properly mixed and ready to pour. Each load is custom made to suit the application according to a specific mix design.  The customize mix design is put together just moments before the truck leaves for the job site. The batching of the raw materials in their specific quantities is computerized to guarantee accurate combinations and ensure reproducible mixes.

What is concrete used for?

Concrete is considered to be one of the most versatile building materials used in today’s construction.  Concrete is used in place of large steel girders and steel decking.  Reinforced concrete is used to make building columns and decks in high rises. Concrete is an economical building solution that is increasingly used in today’s construction.

Concrete is extremely versatile and is widely available and can be used in a variety of applications.  Concrete is commonly used in large building construction as well as in residential applications for driveways, house foundations, walls and much more.

Concrete is also used for paving, curb and gutter applications. “Precast concrete” is also used to make pre-made molds.  Molds are filled with concrete to produce a host of projects such as drainage piping or underground vaults. Tilt-up concrete construction is a building process mainly used in large warehouses with a large flat floor and semi-identical wall sections. Construction crews first pour a large flat floor then spray a non-stick film onto the floor. The wall sections are actually formed on top of the floors and then “tilted up” into place using a crane.

How is the strength of concrete measured?

The reaction between water and cement gives concrete its strength. The important water-to-cement ratio is responsible for the strength of the finished product. Concrete strength is usually measured by its compressive and flexural strength in Pounds per Square Inch (PSI). When you order a “Bag” mix you’re really ordering a specific quantity of cement per cubic yard of concrete. Using some conversion factors you can translate between the two.

It takes time for concrete to achieve its full strength. They say that the innermost concrete poured in the Hoover Dam is still hardening to this day! Often concrete is measured for strength at intervals of 7 days, 14 days, 28 days, and sometimes 56 days. We assume that the 28 day strength test will be an accurate measurement of the final strength of the product.

Your account representative can help you determine what strength of concrete you need. As you can imagine, cement is a costly material in the production of concrete. We tailor specific mixes to specific applications so that you can successfully accomplish the goals of your project in an economical way.

Why would you add ice or hot water to your concrete?

Weather conditions are often the enemy of concrete. Extremely hot dry weather causes concrete to set up very quickly, making it difficult to place and finish. Extremely cold weather can cause the top layer of concrete to freeze and flake off, often ruining hours of hard work and thousands of dollars worth of material. Rain can make concrete difficult to finish as the rain washes away the smooth creamy layer that finishing trowels bring to the surface, exposing the aggregate. That’s a lot to worry about. Thankfully, extra products can help.

Ice: During the summer months you can also substitute ice for a percentage of water in the mix in order to lower the core temperature of the concrete and slow the hydration rate. This helps counteract the effects of the air temperature and the heat contained in the raw materials. Ask your account representative about adding ice to your mix.

Hot Water: During the winter months we substitute regular water with heated water to increase the core temperature of the concrete to prevent freezing and allow more time for the hydration process to take place.

What is air entrained concrete?

Air Entrained Concrete: Concrete inherently contains entrapped air of less than 3% by volume as a result of the mixing process. Air Entraining Admixtures are used to entrain air contents of 4-8% by volume of concrete. Entrained air is necessary to protect concrete that is exposed to freeze/thaw cycles in a saturated state. These microscopic entrained air bubbles capture water and allow it to freeze and thaw without deteriorating the concrete.

What other ‘extra products’ can help me?

Retarder: Retarder is used to decrease the hydration rate of cement, thus giving you or your contractor more time to place and finish our products before the concrete begins to set. Retarder can be well worth your additional investment. It provides an added measure of workability and reduces the rate of heat increase produced by the hydration process. Consider adding retarder on hot, dry days to slow the set rate, allowing for a better finish. Also consider adding retarder if you need more than 30 minutes to unload the truck (i.e. if you’re going to be using buckets or wheelbarrows to transport the concrete from the truck to your work area). By adding retarder to your mix you can expect to retard the set time by 1.5 hours to 8 hours depending on the dosage that you order. You can use retarder for just about any concrete application.

Water Reducers: Water reducers are often used to increase the workability and the strength of concrete. It makes concrete “wetter” without adding water. If you’re pouring plain concrete and find that it’s difficult to place or pump, you may be tempted to ask the driver to add additional water to the mix. Beware that by adding water you could be reducing the compressive strength of the finished product. If, however, you choose to add a water reducer, you can expect a more workable product with the benefit of needing less water to make it “wet”. The result is a high-strength mix that can be pumped at a 4″-6″ slump. You can also achieve a strength gain over traditional concrete when poured at the same slump.

Your account rep can suggest an appropriate dosage if you’re interested in adding water reducer to your mix.

Accelerators: Accelerators are often used in cold weather to speed up the setting time of concrete. In cold weather it’s often helpful to add accelerators to speed up the cement hydration therefore increasing the initial set of the concrete. Always take great care when pouring concrete in cold temperatures. You’re account rep or salesperson can help you determine the appropriate amount of accelerator for your application.

Accelerators can also be used in high-early mixes, or mixes that require high strength in a short amount of time. Concrete contractors on high rise projects often use high-early mixes when pouring columns and decks to produce enough strength in 7 days to pour the next elevated deck and columns rather than waiting for 14 or 28 day compressive strength. This facilitates the rapid building schedules that general contractors often require.

What precautions should be taken when working with concrete?

Concrete itself is a relatively safe material with which to work, however, the delivery and placement of concrete can have some inherent dangers. You can mitigate most risk by taking a few simple precautions:

  1. Wear personal protective equipment including safety glasses, PVC gloves, rubber boots, a high visibility vest, a hard hat, and fall protection if necessary.
  2. Fresh concrete may irritate your skin – be sure to wear gloves and rubber boots. If you’re going to be finishing the concrete on your knees with a float, be sure to wear knee pads that are soft and waterproof. Consult a medical professional if you experience irritation in the eyes or prolonged skin irritation.
  3. Be sure that you have a location large enough for a mixer truck to navigate and park safely, out of the flow of traffic. Our mixer trucks are rear-discharge meaning that the driver will have to back his or her truck into position. A mixer is nearly 12’ high, 9’ wide, and 25’ long. Be sure that your driveway or job site can accommodate a truck of this size.
  4. Mixer trucks can weigh between 36,000lbs and 75,000lbs depending on the load. Be sure that your driveway or job site entrance can support the weight.
  5. Beware when placing concrete below grade, or ground level. Be sure that you provide appropriate escape inclines and adequate support to any loose dirt to prevent a cave-in.
  6. Be sure that you have a plan to effectively unload the concrete safely. If the truck cannot directly access the site of your pour you will likely have to use buckets, a wheelbarrow, buggies, or even a concrete pump. Be careful not to injure yourself by carrying loads that are too heavy.
  7. Be aware of your surroundings at all times, especially when working with large equipment including mixer trucks, pump trucks, etc. Stand clear when equipment is in motion and work safely near all equipment.
  8. Concrete is often poured in places that are by nature “unfinished”. Watch for dirt access roads, ruts, muddy conditions, hazardous inclines, or slippery surfaces.
  9. Plan for incidents and injuries. Make sure you know who to call if someone were injured on your job or at your home. Ask your contractor about your liability for an injury while at your home or jobsite. Also ask your contractor about their liability concerning any property damage that may take place during construction. The more you know, the more prepared you’ll be.

Do you deliver concrete to my area?

Commercial Concrete delivers concrete to everywhere from Manhattan to Montauk and everywhere in between.

Why should I order concrete from Commercial Concrete?

We know that business is all about value and we strive to make sure that our products and services add value to your project. From the first phone call to the final invoice we want your experience with us to be outstanding. That means accuracy in placing your order, honest and up front pricing, quality raw materials, on time delivery, and accurate billing.

We never cut costs or boost profits by cutting corners in any aspect of production, from raw materials to the finished product. We insist on quality materials to produce quality products that are industry-proven. Our focus is on outstanding customer service paired with a quality product at a competitive price point. We think you’ll be impressed!