Frequently Asked Questions

At Knight’s, we’re dedicated to providing solutions to any of your construction needs. We pride ourselves on staying a step ahead and solving any potential issues in the process of our business. Check out the FAQs below to learn more about what others are asking and how we can help.

If your question still isn’t answered here, fill out the Ask Box at the bottom of the page.

Does Knight’s Redi-Mix finish concrete?

No, but we can provide you with contact information for a quality concrete contractor.

What is the minimum amount of concrete I can order?

Any concrete order of less than 5 cubic yards may have a minimum order charge. Contact Dispatch for more information and pricing.

How much time do I have to unload a truck?

We typically allow 5 to 6 minutes per cubic yard to unload, plus additional time to place the truck. Any time overages may result in additional charges.

How do I pay for my concrete order?

It is recommended that you set up an account with Knight’s Redi Mix. All non-account orders are COD. We accept cash and credit cards. COD orders must be paid in before batching.

What is your concrete service delivery area?

We serve the Berkeley, Dorchester, Charleston, and Colleton counties in the Lowcountry, and all of Richland, Lexington, Kershaw, and Fairfield Counties in the Midlands.

What is Plastic Shrinkage Cracking?

Plastic shrinkage cracking (PSC) are cracks which appear on the surface of fresh concrete while it is still in a plastic or non-hardened state. This type of cracking is probably the most common type of cracking. These cracks are typically parallel to each other approximately 1 to 3 feet apart, are shallow, and generally do not run the entire length of the slab. While this type of cracking may be unsightly, PSC rarely impacts the strength or durability of the concrete.

How do I Minimize Plastic Shrinkage Cracking?
In simple terms, plastic shrinkage cracking (PSC) occurs when the top surface layer of the concrete dries out before the lower portions of the plastic concrete. On an ideal concrete slab, the concrete hardens from the bottom to the top causing the moisture, or bleed water, to rise to the top surface of the concrete. PSC occurs when the rate of surface moisture evaporation exceeds the rate at which the bleed water can replace it. Weather conditions play a critical factor in PSC and you are more likely to have PSC on days with wind velocity above 5 mph, low humidity, and/or high temperatures.
How does hot weather impact concrete placement?
  • Increased water demand which may lead to higher water/cement ratios and lower strengths
  • Accelerated slump loss and loss of entrained air
  • Faster set time
  • Increase potential for plastic shrinkage cracking (see Plastic Shrinkage Cracking) and other types of cracking
  • Decreased strengths if concrete is exposed to continuous high temperatures without proper curing techniques
Why does concrete crack?

Concrete, by nature, shrinks as it hardens. When concrete is placed on supporting soil or around steel reinforcement, the concrete mass is prevented from shrinking. This restraint creates internal forces exceeding the strength of concrete. Cracks form to relieve these forces.

Does the presence of cracks indicate a structural problem?

In most instances, the answer is no. Very narrow “hairline” cracks are aesthetic in nature and do not indicate any structural problem. Cracks that have movement where one side of the crack moves relative to the opposite side should be investigated by a professional engineer.

Can I replace wire mesh with fibers?

The answer depends on the intended purpose of installing wire mesh. If control joint spacing exceeds 30 times the concrete thickness, then wire mesh should be used to hold random cracks together. If control joint spacing does not exceed 30 times the concrete thickness, wire mesh can be omitted, and fiber can be used to reduce surface cracking resulting from rapid evaporation (plastic shrinkage cracking) and improve fatigue strength.

Can jobsite addition of water increase cracks?

Concrete is designed and delivered by the Ready Mix Concrete Producer according to industry standards that define mixes to meet the intended performance. Adding water at the jobsite can decrease the strength and increase cracking in concrete. If a higher slump is required, consider using water reducing admixture or superplasticizer.

How much water can I add to an eight-yard load of concrete without causing problems?

No more than 2 gallons of water should be added per cubic yard of concrete. Concrete should be ordered based on strength and workability. Increased workability can be achieved by using admixtures.

What can be done to make concrete easier to place?

Chemical admixtures have been developed in recent years that make concrete user friendly.

How much concrete do I need?

Concrete is sold by the cubic yard. Calculate this volume by multiplying the area (ft) by the thickness (ft) then divide by 27. If math is not your favorite subject, contact a Knight’s Redi-Mix representative at (843) 821-7600.

I am building a patio in my fenced-in back yard. How can I get the concrete back there?

Consider these two options. Concrete pumps are used to place concrete in hard to reach places. There are also mechanical transport devices such as Georgia buggies that are used to deliver the concrete from the truck parked on the street to the desired location.

Are there any special requirements that I should know about the concrete truck making a delivery to my project?

Fully loaded concrete trucks are heavy and may cause damage to driveways designed for lighter vehicles. An area must be provided for the driver to wash out the truck’s chute.

The tile in our house will not stick to our concrete floor due to moisture. What causes this problem?

Many of the adhesives used today are more water-sensitive due to restrictions on the use of volatile organic emissions (VOX) products. Concrete slab moisture can originate from the following sources: 1. When the slab is below the ground water table or when it comes in contact with wet soil from rain, irrigation systems, or broken plumbing. 2. Fine-grained soils can draw water from considerable distances allowing the water to saturate the sub grade through capillary action and move through the slab. 3. Water vapor from damp soil can condense on the slab surface especially when the air on the concrete surface is cooler and at a lower humidity than the damp soil below the slab. 4. Placing floor covering materials before a slab has had time to dry to an acceptable level or after the slab had recently gotten wet from rain, etc.

What are joints?
Joints are pre-planned cracks to accommodate the expansion and shrinkage of concrete from changes in moisture and temperature.

Although irregular cracks are unsightly and difficult to maintain they generally do not affect the integrity of the concrete. Cracks in concrete can be Controlled and minimized by properly designed joints. There are three types of common joints:

  • Contraction joints
  • Isolation or expansion joints
  • Construction joints
What types of colored finishes are available?
There are four methods for coloring concrete.

  1. You can add color pigment to the entire slab. This increases the cost of the concrete, but the color will be evenly distributed throughout the slab and will reflect the color in any cracks that may occur. Using white Portland cement produces brighter, cleaner colors and the color should be mixed with the dry cement before adding to the concrete mix.
  2. The color pigment can be added to a top layer of concrete only. The base slab should have a rough texture to provide a better bond then a colored topping can be added as soon as the base slab is firm enough to hold the finisher’s weight. This method saves some money, but a good finisher is a must with this method.
  3. Dry-Shake colored materials can be added to the concrete after the concrete has been bull floated and excess moisture has evaporated. The material is shaken evenly by hand over the surface and then floated into the surface. The dry-shake material must be evenly applied or no uniformity in color and/or peeling could result. Most dry-shake compounds contain a curing compound that will help the concrete to cure properly.
  4. Existing slabs can be colored using stains and paints. Stains typically give a no uniform color but that can also be part of the appeal. Stained concrete pavements are very popular right now. Paints can wear away with heavy traffic and must be renewed periodically.
Submit a Question

10 + 11 =

Call Now Button