Concrete & Cement Defined
Contrary to popular belief, concrete and cement are not the same thing; cement is actually just a component of concrete. Concrete is made up of three basic components: water, aggregate (rock, sand, or gravel) and Portland cement. Cement, usually in powder form, acts as a binding agent when mixed with water and aggregates. This combination, or concrete mix, will be poured and harden into the durable material with which we are all familiar.
Components of Concrete
There are three basic ingredients in the concrete mix:
1. Portland Cement
3. Aggregates (Rock and Sand)
Portland Cement - The cement and water form a paste that coats the aggregate and sand in the mix. The paste hardens and binds the aggregate and sand together.
Water - Water is needed to chemically react with the cement (hydration) and too provide workability with the concrete. The amount of water in the mix in pounds compared with the amount of cement is called the water/cement ratio. The lower the w/c ratio, the stronger the concrete (higher strength, less permeability).
Aggregates - Sand is the fine aggregate. Gravel or crushed stone is the coarse aggregate in most mixes.
Tips on Ordering Concrete
Ordering concrete is easy, even if you are a first time caller. Our dispatchers are trained to guide you through every step of the way. Here are a few important tips to remember to help in placing a successful order:
1) Give the day you are going to need the concrete.
2) Give the time you want the concrete.
3) Give the address you want the concrete delivered. Timely deliveries are the key to our business. We appreciate all the information that you can provide to guarantee excellent service.
4) Give a contact number where the concrete dispatcher can call you the day of the delivery.
5) Give the strength and size stone or mix design you are ordering.
6) Give the total number of yards needed for your project. If you do not know the concrete dispatcher will be more than happy to calculate it for you or a concrete calulator is provided on the previous webpage. A good rule of thumb is take your calculation and add 4% to 10% to the total to account for waste, spillage, over-excavation, settlement, spreading of forms, loss of entrained air or any other changes in volume. Concrete can be ordered in 1/2 yard increments.
7) If you have multiple concrete loads let the concrete dispatcher know the spacing you want on the trucks. For example, "I need the trucks 30 minutes apart."
8) Inform the concrete dispatcher on what you are pouring (Driveway, Garage, Sidewalk, Back Patio, Pool Collar, Curb, Basement Floor, etc.) and how you are going to unload the concrete mixer. (Truck can directly pour from chute, wheelbarrow, concrete pump, crane bucket, etc.)
Confirm your order the day before you want the concrete or even ninety minutes before your scheduled delivery time to insure proper accuracy.
How To Hire a Contractor
Desired Properties of Concrete
1) The concrete mix is workable. It can be placed and consolidated properly by yourself or your workmen.
2) Desired qualities of the hardened concrete are met: for example, resistance to freezing and thawing and deicing chemicals, watertightness (low permeability) , wear resistance, and strength. Know what you are trying to achieve with the concrete.
3) Economy. Since the quality depends mainly on the water to cement ratio, the water requirement should be minimized to reduce the cement requirement (and thus reduce the cost).
Take these steps to reduce the water and cement requirements:
use the stiffest mix possible.
use the largest size aggregate practical for the job.
use the optimum ratio of fine to coarse aggregate.
Discuss how to achieve your goals for the concrete with one of Atlantic Masonry Supply's concrete dispatchers.
Fibers can be added to the concrete mix in lieu of welded wire mesh.
The problem with welded wire mesh is that it often ends up on the ground from being stepped on as the concrete is being placed. (particularly if no support blocks are used). Another problem is that mesh does not prevent or minimize cracking-it simply holds cracks that have already occurred together.
If you could look into a section of concrete poured with fibers you would see millions of fibers distributed in all directions throughout the concrete mix. As micro cracks begin to appear due to shrinkage as water evaporates from the concrete (plastic shrinkage), the cracks intersect with the fibers which block their growth and provide higher tensile strength capacity at this crucial time.
Admixtures are materials other than cement, sand, aggregates, and water that are added to concrete immediately before or during mixing to modify the properties of hardened concrete or to ensure the quality of concrete during mixing, transporting, placing, and curing. Admixtures can be used to provide greater plasticity, workability and earlier levels of strength than from normal concrete.
Accelerating Admixture - Accelerators are added to concrete to reduce setting time of the concrete and to accelerate early strength. The amount of reduction in setting time varies depending on the amount of accelerator used.
Retarding Admixtures - Are often used in hot weather conditions to delay setting time. They are also used to delay set of more difficult jobs or for special finishing operations like exposing aggregate. Many retarders also act as a water reducer.
Air Entraining Admixtures - Must be used whenever concrete is exposed to freezing and thawing, and to deicing salts. Air entraining agents entrains microscopic air bubbles in the concrete: when the hardened concrete freezes, the frozen water inside the concrete expands into these air bubbles instead of damaging the concrete.
Air entrainment improves concrete workability
Air entrainment improves durability
Air entrainment produces a more workable mix
Water Reducing Admixtures - Reduces the amount of water needed in the concrete mix. The water cement ratio will be lower and the strength will be greater. Most low range water reducers reduce the water needed in the mix by 5%-10%. High range water reducers reduce the mix water needed by 12% to 30% but are very expensive and rarely used in residential work.
Super P - Super P stands for super plasticizers also known as high range water reducers. Its a chemical admixture added to the concrete to make the concrete extremely workable increasing the flowability of the concrete without reducing the concretes strength. The effects of super P are only temporary (15-60minutes) and is generally added on the job by the concrete mixer driver or quality control representative from the company. Super P can reduce the mix water needed by 12% to 30%.
Atlantic Masonry Supply runs a fleet of 3 Oshkosh S-Series Front Discharge Concrete Mixer Trucks. The front discharge system has several advantages over the rear discharge truck. The main advantage to the front discharge truck is that it can be driven directly into a pouring location. This allows quick and safe positioning by the driver. Since an extra worker is not needed to direct the driver, contractor costs and time on the job site are decreased. Another advantage of the front discharge mixer truck is that while in the cab, the driver can control the pour and have a clear view of chute position. This allows quicker chute positioning and subsequent truck movements during a longer pour. Safety is also improved since the driver does not leave the cab. Current front discharge mixer trucks are equipped with standard all-wheel drive and off-road tires. This permits the front discharge truck to have greater and easier access to difficult locations. Contractors benefit from this aspect because it reduces the need to build access roads to job sites.
Frequently Asked Questions
WHAT KIND OF MIX DO I NEED?
There are 2 basic mixes: 3/4" stone which is usually dumped out of the back of the truck and 3/8" stone which is usually pumped or you can get mixed stone which is a combination of both.
WHAT STRENGTH DO I NEED FOR MY PROJECT?
You will have to determine the strength of the concrete that you need. The minimum strength we deliver is 3000 psi, which is typical for non-load bearing items as patios, walkways, footings and wall grout. A typical driveway could be 3000 psi for passenger cars or 3500 psi for SUV’s, trucks or motor homes.
HOW MANY YARDS DO I NEED?
Take your measurements and then enter it in our volume calculator on the right hand side of this page. Some concrete will remain in the truck and/or pump so don’t forget to add a little extra to make sure you have enough. You can also give your dimensions to the concrete dispatcher and we will be more than happy to figure it out for you.
HOW DO I DECIDE IF I NEED A PUMP OR NOT?
You have 3 choices for getting the concrete from the concrete truck to your project:
1. Place it using the truck’s chutes, which extend about 12' from the front of the truck (you will need about 14' clearance and about 10' width for the truck)
2. Pump it using a concrete pump (we can arrange at separate cost)
3. Wheelbarrow: If there is not room for a ready-mix truck to get within 12' of your project, you will need to pump it or wheelbarrow it. If you decide to wheelbarrow, keep in mind that one yard of concrete weighs about 4,000 pounds and that you will probably incur some truck time.
WHAT CAN I DO TO PREVENT CRACKING?
Concrete shrinks during the hydration process and has a tendency to crack. This is called shrinkage cracking. The least expensive product for reducing plastic shrinkage cracking is FIBERMESH. Millions of tiny fibers are added at the time of batching. These fibers reduce plastic shrinkage cracking and improve durability, among other things. Go to www.fibermesh.com for more information.
DO YOU FORM AND FINISH THE CONCRETE?
No, we are a ready-mix supplier. You or your concrete contractor get the job ready. Our truck delivers the concrete and your workers do the rest. Give us a call and we will be happy to recommend a handful of concrete contractors that are reputable in your area.