FREQUENTLY ASKED QUESTIONS
WHAT IS AGGREGATE?
The short answer is stone, sand, and gravel. But that is just scratching the surface. It is the grains of sand that make up our roads and sidewalks. It is in the bricks and concrete blocks that make up the walls of our homes, schools, and workplaces. Aggregate also plays a lesser known yet vital role in our water purification process and can even be found in pharmaceuticals, toothpaste, make-up, paint and paper among other products we use on a daily basis.
HOW MUCH AGGREGATE DO WE USE EACH YEAR?
The average American uses ten tons of aggregate per year; 400 tons of aggregate on average is used for the construction of a new home and there are approximately 38,000 tons of aggregate in a mile of interstate.
WHERE IS AGGREGATE USED?
We use sand, stone and gravel to build things like roads, houses, schools, hospitals, playgrounds, baseball diamonds, subway tunnels, and bridge abutments, but beyond these obvious uses is a whole host of lesser known uses for aggregate. For example, did you know that glass, make-up, paint, toothpaste, household cleaners, pharmaceuticals, baby powder and even chewing gum are also made with some form of aggregate?
HOW DO WE CHOOSE WHERE TO PUT A QUARRY?
Because aggregates are a non-renewable resource, our industry continually struggles to find conveniently located sites that 1) have an abundant supply of aggregate, 2) are conveniently located to the location they will be used in, and 3) are unconstrained by the myriad of competing land uses that could render the deposit unusable. Our industry sometimes faces opposition when a pit or quarry permit is applied for. Everyone needs aggregate, but who wants a quarry or pit next door to them when they could have a park or even a new shopping center instead? The reality is that most opposition comes before a pit or quarry is licensed. Once operations begin, neighbors quickly realize that living next to a pit or quarry is quite pleasant.
WHAT HAPPENS TO A QUARRY ONCE THE AGGREGATES ARE EXTRACTED?
The fate of a pit or quarry is often known even before it is ever developed. In fact, a mandatory part of applying for a license to begin extraction is to have a proposed rehabilitation plan in place. There is, however, a public planning process that must be satisfied prior to a new land use being established "post pit". Just because a pit approval is sought it does not mean that the "after use" development is automatically approved.
Regardless of what the end use will be for a pit or quarry, the rehabilitation process will still begin the moment topsoil is removed to uncover the aggregate deposits below. The topsoil is removed and preserved along with all its seed sources, returning to the pit or quarry when mining is completed. In this way, our industry can ensure the sites are returned to their natural state or are improved upon by turning them into lakes, golf courses or even college campuses.
IS AN AGGREGATE QUARRY ENVIRONMENTALLY RESPONSIBLE?
READY MIX FAQ
WHAT IS CONCRETE?
Concrete is a material made primarily from cement, aggregates (rock and sand), and water. Concrete dates back more than 5,000 years and is the most widely used man-made product in the world.
WHAT IS THE DIFFERENCE BETWEEN CEMENT AND CONCRETE?
Although the terms cement and concrete often are used interchangeably, cement is actually an ingredient of concrete. Concrete is a mixture of aggregates and paste. Through a process called hydration, the cement and water harden and bind the aggregates into a solid mass of concrete. This hardening process continues for years meaning that concrete gets stronger as it gets older.
WHAT IS READY-MIX CONCRETE?
Ready-mix concrete is an unhardened, fluid form of concrete that is delivered in a concrete truck that agitates and mixes the concrete on the way to the job.
WHAT ARE THE MEASUREMENTS FOR A READY-MIX TRUCK?
Truck measurements can vary based on the location and the manufacturer. Below are the specifications for our trucks here at 711 Materials:
Length: 35 Feet
Width: 10 Feet
Height: 13 Feet
Weight: 66,000 Lbs. Fully Loaded
Chute Reach: 10 feet to 14 feet
HOW DO YOU MEASURE FOR CONCRETE?
Concrete is measured in cubic yards (areas 3’x 3’ x 3’). You can use our concrete calculator on the Resources page to measure how much concrete you will need. It’s incredibly important that you measure accurately and order enough concrete. It’s a good idea to order a little more than you think you’ll need.
For our concrete calculator click here………………..
WHAT IS SLUMP?
Slump measures the consistency of a batch of fresh concrete. It refers to the ease with which the concrete flows, thus indicating the workability of the concrete. Different types of jobs require different slump ratings. A typical concrete mix is normally designed with a 3” to 5” slump. Slump testing is used on-site to ensure uniform consistency between individual batches of concrete.
WHAT ARE THE TEMPERATURE REQUIREMENTS FOR PLACING CONCRETE?
Cold Weather – Normal concrete will not set or harden when the temperature is below 35F. When temperatures are cool, it is recommended to add hot water and/or set accelerators to increase the set times and allow for the concrete to finish at a more reasonable rate.
Hot Weather - High temperatures above 90 degrees can make concrete set faster than recommended, reducing the strength of the concrete. Strong winds and low humidity can also cause problems with plastic shrinkage and drying shrinkage potential. To avoid these problems, use of hydration stabilizing admixtures, and proper finishing techniques are crucial.
WHY DOES CONCRETE CRACK?
Concrete, like all other materials, will slightly change in volume when it dries out. In typical concrete this change amounts to about 500 millionths. Translated into dimensions-this is about 1/16 of an inch in 10 feet. The reason that contractors put joints in concrete pavements and floors is to allow the concrete to crack in a neat, straight line at the joint when the volume of the concrete changes due to shrinkage.
WHAT IS AIR-ENTRAINED CONCRETE?
Air-entrained concrete contains billions of microscopic air cells per cubic foot. These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes. Air-entrained concrete is produced through the introduction of air-entraining agents at the concrete batch plant. The amount of entrained air is usually between 4 percent and 7 percent of the volume of the concrete but may be varied as required by special conditions. It is best to use air-entrained concrete anytime your concrete will be exposed to freeze-thaw conditions. Please make sure to check ACI for proper placing techniques.
WHY DO CONCRETE SURFACES FLAKE AND SPALL?
<h5 class="font_5">Concrete slabs and surfaces that are exposed to freeze-thaw conditions are susceptible to spalling or scaling. When concrete is saturated with water and temperatures approach freezing, the water freezes and causes stress within the concrete. The use of air-entrained concrete, with a low water-to-cement ratio, can help minimize this happening. Please see ACI and ASTM standards for other options or more information on this subject.</h5>
WHAT IS PLASTIC SHRINKAGE CRACKING?
Plastic shrinkage cracks are caused by a rapid loss of water from the surface of the concrete before it has set. Conditions that can lead to this include winds in excess of 5 mph, low relative humidity and high ambient and/or concrete temperatures. Synthetic fiber reinforcement incorporated into your concrete can help minimize the possibility of plastic shrinkage cracking. Please see ACI or ASTM standards for other options to minimize cracking.
WHAT ARE CONCRETE FIBERS?
Concrete fibers can be added to the concrete mix in lieu of welded wire mesh or even rebar in certain applications. Concrete fibers create three-dimensional reinforcement throughout the concrete whereas welded WWM or rebar is placed on one plane. 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 form the concrete (plastic shrinkage), the cracks intersect with the fibers which block their growth and provide higher tensile strength capacity at this crucial time.
WHAT ARE ADMIXTURES?
Admixtures are used in concrete to enhance the durability, workability and strength characteristics in concrete mixes. The more commonly used admixtures include:
Water reducing admixtures—Water reducers, reduce 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, or superplasticizers, reduce the mix water needed by 12% to 30% but are very expensive and rarely used except for special placement needs.
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 (speak with 711 Dispatch and describe your application for options). Typically, only non-chloride accelerators are in use today.
Retarding admixtures—Also known as hydration stabilizers, retarders are often used in hot weather conditions to delay setting time. They are also used to delay set of more difficult jobs or when extended delivery times are required due to jobsite location.
IS CONCRETE RECYCLABLE?
Recycling actually occurs from beginning to end with concrete. Many industrial byproducts (like flyash or furnace slag), can be added to concrete mixes, which reduces the reliance on raw materials. When the lifespan of concrete comes to an end, it can be recycled and used in a variety of applications.