History has shown us that in times of tough market competition innovation and flexibility are paramount. Can your organization turn fast in the water or are you bogged down in imaginary or real limitations? How much time are you thinking instead of reacting to market changes?

Winners that emerge from any economic downtime are those that became lean and efficient. Nowadays we can use the terms lean, green, and tech savy to paraphrase key skills for modern concrete ready mix providers. Your concrete company must answer customer needs and not create a gas war competition environment that will bring all participants to the no profit zone.

The concrete ready mix companies that are doing the best are the companies that are thinking, reevaluating and doing what it takes to meet current market contions. Remember, these times may just turn out to be the focal points that inspire your concrete ready mix company to new methods, practices and services.

Mizzy and Chris Zdroj and their three children were the recipients of the new home as EFC Custom Homes of Bastrop and “Extreme Makeover: Home Edition” harnassed the power of more than 3,000 volunteers. Mizzy is an unpaid volunteer firefighter who battled the Bastrop wildfire while her own house burned. Her fellow firefighters nominated her for the home makeover.

The builder, EFC Custom Homes of Bastrop, selected Lauren Concrete for this precision timetabled build. “We are working under an amazing schedule and Lauren Concrete has the state of the art dispatching and technical systems to coordinate the pour with precise deliveries” said one worker on location at the site. “Lauren Concrete has built a reputation as the go to company when you need the finest materials and a disciplined team. That’s why they were selected from all the ready mix companies in Central Texas”.

There was an added surprise for the Bastrop community, Extreme Makeover: Home Edition” remodeled the Heart of the Pines Volunteer Fire Department building located next to the Zdroj home and other companies also donated firefighter uniforms and additional equipment.

I am in the late stages of an addition to my home which includes a master bath and covered patio. The slab was poured in late November 2010 all at the same time (bath slab and patio). We had a major storm roll thru the afternoon/evening the concrete was poured but the concrete did sit for 4-6 hours before it started raining. As the addition progressed, I started noticing cracks in the concrete. The tile guy found nine hairline cracks across the bath area alone. Last month I noticed a crack all the way across the patio, which is about 16′ x 30′. I refuse to believe that this is “normal” like the contractor says. I had a detached garage and driveway extension built summer of 2009 and that concrete doesn’t have any cracks at all…..even with the recent trucks driving over it for the current addition. I believe the concrete supplier didn’t mix the concrete properly. Is there any way to test a sample of the concrete or have it inspected by an expert? What are my options if I find out the concrete is substandard?

Some of the helpful replies:

It’s extremely common for concrete to crack. it’s far more uncommon for it NOT to crack. There are several reasons for cracks. The two most likely are:
1) The concrete was poured much too wet, leading to excessive shrinkage as it cured. Many times, contractors add a lot of water to the mix to make it easier to pour it out of the truck. When the concrete cures, it loses water and shrinks a bit. Too much added water leads to a high water to cement ratio and therefore a lot of cracking, and typically within a couple of days of the pour!
2) There were not enough crack control joints, or they were improperly installed. These are the joints that are either tooled in while the concrete is wet, or sawed in as soon as possible after the concrete sets up. They are designed to control random cracking. There are specific ways they need to be installed. Probably the least likely scenario is that the concrete was defective. It’s more typically contractor error. Did the same contractor pour both of the slabs you mentioned? I wrote an article about concrete cracks. It can be found at www.4greatconcrete.com under the artcles and publications link. It goes into much more detail as to other causes of cracking as well. Good luck.

Although you were not there when they actually filled the truck with the appropriate materials, once the truck comes to the job site, the contractor or the man in charge of the concrete usually takes a look at the concrete by pouring a little into the shute. So the driver of the concrete truck gives this blank look and looks at the contractor or the man in charge and sometimes the man in charge will have the driver add water so he can work the concrete easier. At that point the question would be, who is responcable for the mixture of the concrete? As it is not feasable to hire a state licensed testing company to be there during the pour on a small job, that would have been possibly the only way to protect yourself. So the options are tear it out or live with it, sorry to be blunt.

If concrete is of perfect mixture and of perfect placement and perfect subgrade(of course there is nothing perfect in concrete)over a period of time will crack every 15 feet. The control joints just try to get the crack to happen at the control joint. So the object is to make the control joints asthetically pleasing to the eye with the surrounding architecture. The more control joints the better chances you have of hiding the cracks. Climate – soil conditions – placement voids – where the rebar is inside the concrete and mix all will have a contributing factor in a crack.

Would such a process be effective or would I be wasting time and money?

Here’s our expert’s answer:

It won’t be miraculous buy it will be effective.
We have a waterbased stain that will color everything including your sneakers. Very potent.

Acid stain may not be as effective with different surfaces and patched areas.

This question can only be answered by the professionals associated with the project. Concrete cures at different rates depending on the constituent ingredients and the ambient conditions it is exposed to. Your contractor (concrete supplier) should know what sort of curing is required for the particular mix being used. Also, by following their recommendation, you maintain whatever warranty that might be associated with the work performed. If there is a problem that occurs later on, they can’t blame you for not curing it properly if you did it according to their instructions.

You can tackle this several ways. The professionals will drive grade stakes inside the forms at convenient intervals (less than the width of the screed board). The grade stakes will have the proper level marked on the stake, usually a nail in a wooden stake. You can place some concrete in the forms and using the grade stakes as a guide, begin screeding the concrete. As you get the proper grade on the concrete, you can pull the grade stakes. As you can tell, this requires a little experience to get it just right, but beginners can do it with less accuracy.
Another method is to get a probe, such as a stick or steel stake, mark it with the depth you want the concrete to be, then place the concrete in the forms. Screed the concrete and probe to ensure the proper depth. This is not as efficient as the first method, but it will get the job done with a little more effort. You can set construction joints (1×4’s, metal keyway forms, etc) inside the forms at intervals of 25-30 times the depth of the slab. You can use these as screed guides.

Finally, you can set screed guides inside the forms using 2×4’s and stakes so that the bottom of the 2×4’s are at the top of where you want the concrete to be. Nail ears on the end and top of your screed board so that when you set the screed board on the screed guides, the bottom of your screed board is even with the bottom of the screed guide, thus level with the top of where your concrete will be. Once you get your concrete down and screeded, you can pull these screed guides and fill in the stake holes and re-level by eye.

Reinforcement steel in flatwork is strictly for crack control. The best crack control is affected by putting the steel in the upper half of the slab. If your contractor can guarantee he will keep the wire mesh in the upper half of the concrete, that will do as well as rebar. Make sure he gives at least 3/4″ cover to whatever reinforcement he uses. The standard driveway depth is 4″, but that doesn’t mean that depth is right for you. It really depends on the soil conditions and the load you will be putting on the concrete. Thickened edges (beams) are highly recommended for the outsides of the driveway. This will enable the edges to take that occasional load on the edge or coming onto or off of the edge. Normal
Portland cement concrete likes to crack every 10-12′, so jointing in all directions no more than 10′, with the joints being a minimum of 1/4 the slab depth, should help the expansion/contraction problem. There are two types of joints: contraction and construction. Contraction joints are usually installed with a concrete saw after the concrete gets hard or a jointing tool while the concrete is still fresh. Construction joints are preinstalled dividers such as redwood strips, aluminum keyways, or other physical barriers. Either type of joint will allow for expansion/contraction, so if you don’t want redwood every 10′, you don’t have to have it. Make your joints as square as you can. Try to avoid rectangular jointing sections. Make sure the contractor orders concrete that has 4-6% entrained air, since you live in conditions that probably require salting of roads. The air will enhance the concrete’s freeze/ thaw durability and make it less susceptible to salt damage. I could spend at least 8 hours going over things to look out for and things to avoid. The main thing is sitting down with the contractor before you sign a contract, and tell him how you want the thing to look when he gets finished. Discuss whether visible cracks are acceptable or not. Discuss a warranty. Tell them what you want in the end, put it in your contract, then get out of his way and let him give you what you want. If he doesn’t give you what he says he would in the contract, you have legal standing for a remedy. Also, let him buy the concrete so
he can’t blame you for buying an inferior product that he couldn’t work with.

Candidates must have experience with Command Alcon software.

This is not an entry level position. Professional experience as a ready mix dispatcher is a prerequisite. The geographic location for this job is the Austin, Texas area.

How to apply:  please email resume and requests to: hr@concrete.com

*No phone calls, please – email correspondence only - send resume in PDF or doc format

By George W. Seegebrecht and Steven H. Gebler
Contributing Editors
www.concrete.Com

One widely used specialty concrete is known as “shotcrete.” The major difference between shotcrete and its close cousin, concrete, is the placement method. Concrete is discharged from a ready-mix truck, placed on the ground or in forms and then must be vibrated for compaction. By contrast, the shotcrete process, whether using wet or dry material feed, does not require forming or compaction thereby enhancing design creativity and application flexibility, often resulting in a savings of time or money

Shotcrete, was originally called “Gunite” when Carl Akeley designed a doubled chambered cement gun in 1910. His apparatus pneumatically applied a sand-cement mixture at a high velocity to the intended surface. Other trademarks were soon developed known as Guncrete, Pneucrete, Blastcrete, Blocrete, Jetcrete etc. all referring to pneumatically applied concrete. Today Gunite equates to dry-mix process shotcrete while the term “shotcrete” usually describes the wet-mix shotcrete process. At point of application, both are typically referred to as shotcrete.

Dry-mix process shotcrete, introduces and mixes the required water at the application nozzle as the dry cementitious materials (fly ash, slag, silica fume etc.) and aggregates are delivered through the “gun” The nozzleman controls mix consistency, adjusting water addition to suit the changing conditions of the work area. The dry-mix process also is well suited for sporadic application operations since the majority of the water only comes into contact with the cementitious materials as it leaves the nozzle.The wet-mix process utilizes concrete delivered to the job that is thoroughly mixed excluding of any required accelerators. The ingredients are generally delivered in ready-mix trucks as with normal concrete. Accelerators or other admixtures may still be metered into the slurry at the nozzle along with air under pressure to increase the velocity of the material and improve control of the application or “shooting” process.

The impact velocity of properly applied shotcrete instantly compacts the material, yielding an “in-place” mix that is richer in cement and higher in strength than the same mixture prior to placement. Typically, a fine aggregate dry-mix shotcrete mix delivered in a 1:3 cement to aggregate proportion upon entering the application gun results in a 1:2 cement to aggregate ratio when in place. What appears to be a waste of materials and a dust nuisance known in the trade as “rebound” and overspray, actually results in dense, high-strength shotcrete as a portion of the aggregate ricochets off the receiving surface and away from the placement location. The loss through rebound will vary depending upon the dryness of the mix, the shooting distance from the surface, wind conditions, etc. The intended thickness is generally overshot, trimmed back to the design thickness and finished to the desired surface texture and appearance.

While the dry mix process sounds quick and economical, it requires precautions to ensure application quality. The nozzleman’s workmanship and experience are critical, since the nozzleman controls the critical water-to-mix ratio going into application equipment. With the wet-mix process, the nozzleman has no control over the consistency of the mix delivered to the job site, but can control the velocity of the materials and the addition of accelerators as the mix leaves the nozzle.

Just as in concrete mix designs, the water-to-cementitious materials ratio remains the single most important parameter influencing the compressive strength, shrinkage and overall durability of the final product. Application technique is also crucial and less forgiving than ordinary ready-mix. Good “shooting” technique can mean the difference between a dense high-strength material or one that looks good on the finished surface but actually has underlying sand pockets, voids and poorly encased reinforcing steel. Poor application technique increases the probability of cracking and its negative ramifications.The shotcrete process is more versatile than conventional concrete placement. If the shooting surface is sound, clean and accessible, shotcrete can be applied in very difficult or complex shapes or sections where conventional concrete formwork would prove difficult or impossible as well as cost prohibitive. Shotcrete is especially applicable for unique shapes desired in complex shapes, swimming pools and other unique features of aquatic parks. It can also be an excellent overlay and repair material for existing structures because of its potential to achieve good bond strength and low permeability.

The nuances and differences between concrete and shotcrete are too numerous to cover in a short article. Selecting a concrete placement method, whether it be conventional concrete, wet-mix or dry-mix process shotcrete, can be a challenging task, since there are positive aspects of each for almost every application. While it is true that one approach may be more applicable, adaptable or economical than another, the final concrete placement selection for the project should be based on project design, material performance criteria and overall budget.

By Kenneth Wayne Meyer
Contributing Editor
www.concrete.com

As it hardens, the cement and water begin to shrink, and the stresses created by this shrinking cannot be overcome by the small amount of strength developed by the young concrete. If you place the concrete on a windy day, the top may start to harden before the bottom, which will cause the concrete to shrink unevenly (plastic shrinkage cracks.) Also, if the ground underneath the concrete is not level, there will be an unequal dragging force while the concrete shrinks, also causing stresses the new concrete cannot withstand. So, how do you get concrete with no VISIBLE cracks in it? By following a few simple steps before and after you place the concrete, you will have a very nice looking structure that will require very little maintenance, and give you years of enjoyment.

Before you place the concrete, make sure your subgrade (ground beneath the concrete) is thoroughly compacted and level. The absolute best thing to do is get a garden tiller, till the soil to a depth of 6 inches, then rent a hand operated compactor and compact the soil vigorously. This will help ensure there are no soft spots. You can apply a layer of cushion sand if you want. This will help achieve a totally level surface and allow a consistent friction to the shrinking concrete. Four inches of washed sand ought to be plenty for the cushion. If you use a wire mesh for reinforcement, use panels and not rolls. The rolled wire mesh is extremely difficult to keep in the top half of the concrete, where it HAS to be in order to do its job. You can also use reinforcement bars (rebar) tied together with steel wire, but spacing and size requirements vary based on load and soil conditions, so it is hard to recommend a standard set up for that. If you do use rebar, it is essential that you keep it in the top half of the concrete. You can use stones, broken brick or you can buy plastic chairs that the steel will sit on to keep it in the proper position when you place the concrete. You can also have the ready mix concrete company supply fibers to the mix. These fibers are usually nylon or polypropylene. They help keep the cracking of the concrete on a micro level instead of a macro level (where you can see the cracks with your naked eye.) Steel reinforcement also helps keep cracking in check, but if cracking does occur, the steel, when properly placed in the concrete, will hold the concrete together, whereas fibers will not do that.

Okay, you’ve got your subgrade ready, you have placed a plastic vapor barrier on the subgrade for slabs that will support dwellings, your steel is sitting nicely on your plastic chairs in the proper position, and you now have 14 of your closest friends on their way over to help you place the concrete you have coming. When the concrete arrives, if you don’t have a vapor barrier, wet the subgrade without puddling the water so that the water in the concrete will not be absorbed by the dry subgrade, thus causing uneven drying and the dreaded plastic shrinkage cracks. Once the concrete is placed, make sure to protect it from high winds and direct sunlight so the concrete will dry evenly from top to bottom. You are now ready to perform the most important step in preventing noticeable cracking. Contraction joints are the secret to no cracking! By placing contraction joints that are at least 1/4th the depth of the concrete and on intervals of 25 to 30 times the depth of the concrete (usually easiest with a jointing trowel or tool while the concrete is still fresh), you will almost ensure there will be no visible cracking in your concrete. If your slab is 4 inches thick, the joints must be at least 1 inch deep and placed every 100 to 120 inches. If you cannot use a jointing tool to put the joints in, you can hire a concrete sawing contractor to do this for you. Make sure he cuts the joints a minimum of 1/4th the slab depth. This jointing method helps the concrete crack at the weakest point. This is why it is so important for the joints to be deep enough. Variations in subgrade levels could cause greater stress in the concrete in an area where the joint isn’t deep enough, and the concrete will crack outside the joint. Once your joints are in place, and the concrete has cured for about two weeks, you are ready to seal the joints. This will prevent water from migrating into the subgrade and expanding and contracting, or getting into the joints and freezing, causing the water to expand and breaking out the concrete around the joints. You now have a concrete structure that will serve you well.