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slug: what-is-the-role-of-quality-control


The importance of quality can never be overlooked. It is crucial that every precast structure be able to perform its function successfully. To ensure that this takes place, the development of the product will need to be monitored and inspected. To accomplish this, a certified Quality Control Technician or “QC” will need to conduct inspections throughout the entirety of the structure’s development. In a future blog, we will introduce you to our NPCA and ACI certified Quality Control inspectors. For now, let’s discuss the role of QC and the steps that they take to ensure that each product is produced to meet or exceed customer needs.


Before production can begin, it is important that the correct materials are selected for the structure. The aggregates and materials that go into the concrete such as sand and rock will be inspected upon arrival and before a batch mix is created. It is also important to know if any moisture is within the aggregates, this can impact the consistency of the concrete. Additives may also be necessary and useful when creating the proper batch mix. Additives can help the concrete’s flowability along will helping the concrete’s curing and strength.

When inspecting materials, the cement should first comply with ASTM C150 or “Standard Specification for Portland Cement” and should conform to Type I/II Blended. There should be moderate hydration and moderate resistance to sulfates. The materials will also be certified through a mill test report for each shipment or batch of cements. Type F Fly Ash will be used and should comply with ASTM C618. Admixtures should also comply with ASTM C494 and ASTM C1017. Aggregates including rock and sand should also conform to the requirements of ASTM C33, or the “Standard Specification for Concrete Aggregates.” Additionally, the aggregates will be evaluated, and documentation will be kept on file at the plant for potential harmful expansion from alkali reactivity. 




Building the rebar cage is the first phase of constructing any precast structure. It provides the strength and integrity for the structure. Before construction of the product can begin, the drawings for the structure must first be approved. Details for the rebar will also be supplied regarding appropriate sizing and spacing for the structure. Once the drawings have been verified, the first day of construction will be scheduled. The rebar cage will be constructed one day prior to the structure being poured. The measurements of the rebar cage will be checked throughout the entirety of its construction by the rebar crew. Once the construction of the cage is complete, QC will check the dimensions of the structure to ensure that they match the drawings of the product.




The QC team will check and measure spacing between the rebar, along with measuring the height and width of the rebar cage to ensure that all measurements are correct. Once this step is complete, the pre-pour set up and pre-pour check can take place.



When the pre-pour set up is ready, QC will then check the set up before the structure is poured. They will check all dimensions of the mold including walls, terminators, openings, joints, and floor and top levelness. QC will also communicate with the Batch Plant Operator to verify the appropriate mix design for the structure. 



Once the pre-pour set up and QC checks are complete, the rebar cage can be put in place with the mold. The structure is now ready to be poured. 



When the batch mix for the structure has been prepared, QC will take samples from the concrete batch and conduct testing. The main purpose of taking samples is to learn the strength that the structure will have along with the consistency of the concrete. NCC or normal cement concrete and SCC or self-consolidating concrete are commonly used in the precast industry. The main difference between the two, is that SCC allows for increased consolidation, better distribution to congested areas, and an improved overall finish for the structure. QC will conduct “spread tests” which assess how easily the concrete flows. To conduct this test, the concrete will be poured into a cone. The cone will then be lifted, allowing the concrete to expand. Once it has expanded, QC will measure the diameter of the spread. The spread should measure between 22-28 inches. 




A certified quality control technician will also take the ambient temperature, followed by taking the temperature of the concrete.  



QC will also perform unit measure and volumetric testing. These tests work together to measure the weight of one cubic foot of the concrete and ensure that the batch is consistent with the mix design. The unit measure test consists of pouring the concrete into a unit weight bucket, and then it is malleted to ensure that the concrete is evenly distributed in the bucket. 

Next, the top will be striked off to remove any excess concrete and the bucket will be placed on the scale. The unit weight is determined by subtracting the weight of the empty bucket from the weight of the concrete and bucket together. After this, the volumetric test can be calculated by taking the unit weight measurement and dividing it by the volume of the empty bucket. This will give you the weight of the concrete per cubic foot. For example, our concrete typically weighs around 150 lbs per cubic foot. 



Measuring entrained air is also an important function of QC. Without air, the concrete does not have room to expand when exposed to freezing temperatures and could potentially put the structure at risk for cracking. 

An air entrainment meter can be used to take this measurement.  



Structures can have different pounds per square inch (PSI) level requirements. To know the strength of the product, samples will be taken of the concrete to test its strength. Testing is conducted after the first day, on the 7th day, 14th, and finally on the 28th day when the concrete has reached its full strength. 

The concrete cylinder will be placed in a concrete compression machine. The machine will compress down on the cylinder until it pops and measure the PSI that was needed to break the cylinder. This information is recorded by QC and will be supplied to the customer so that they know the strength of their product. 




Before stripping a structure, QC will check the PSI level to ensure that it is strong enough to remove from the mold. It is important that the surface is smooth and flat to ensure an accurate reading. 

Shown here is a Schmidt hammer measuring the PSI level of this pull box.

When performing this test, the PSI levels should be measured near the location of the anchors, since these areas will encounter the most tension when being lifted from the mold. 

When the product is stripped from the mold, QC will conduct a post-pour quality check. The QC team will verify that the dimensions of the structure are correct by measuring and checking all walls, openings, terminators, joints, and floor and top levelness. They will also inspect for any cracking, chipping, or spalls. If any of these are present, QC will order repairs for the structure. 

If all dimensions of the structure are correct and no repairs are needed, QC will sign off on the structure and a shipping date will then be determined. 



When transportation arrives, the product will be verified and signed off by the loading person and QC. Final checks will be conducted by QC to ensure that the structure drawings and line items match. They will also check again to ensure that no repairs are needed for the structure.

Once final checks are made by QC, the transportation driver will strategically secure the products and deliver them to the jobsite.



Consistently producing quality products for customers should always be a priority. Customer’s value high quality standards and they recognize those who make efforts to meet and their needs. Checking and conducting thorough testing for each individual product enables the precaster to ensure that the product will meet and exceed customer expectations. This, however, can only be accomplished with a knowledgeable and highly detail-oriented QC team. 



Stay tuned for our next article.

We hope this article was helpful. Please send in your questions to and we would be happy to help answer them.

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slug: tips-for-preparing-subgrade-and-installation-of-precast-concrete-products

Image sourced from ADE Consulting Group

The strength and integrity of a structure is important. Some will argue that the foundation that supports the structure is even more important. Let’s dig deeper into everything about the subgrade.


First off, what is the subgrade? The subgrade is what lies below the grade or ground level, providing a strong foundation for the structure. The subgrade can consist of different materials and can be of different depths. It is usually comprised of rock, sand, cement, or limestone. The depths of a subgrade can range depending on the contents of the soil and the size of the structure. For example, a smaller structure may only require a depth of a 6-inch subgrade whereas a larger structure may require a deeper subgrade that is closer to 20-30 feet. Larger structures may also require several different layers within the subgrade. These layers can consist of rock, sand, stabilized sand, cement, lime cement, limestone, and manufactured aggregates. Before the subgrade is prepared, there are a few steps that must first take place. The Engineer of Record does not only design the precast structure, but they will also create plans for the subgrade. When preparations for the subgrade are ready to begin, the customer will first contact a geotech company to conduct soil testing for the location of the structure. The Engineer of Record will give the plans for the structure to the Soil Engineer before they begin testing the soil. The testing will provide information about what properties the soil contains. Soil can be comprised of sand, clay, or rock. To conduct soil testing, the soil engineer will core the ground. The Geotech Engineer will make the decision on how far down to drill along with how many different places coring should take place. How deep to drill is also dependent on the structure’s size, weight, and the function that it will serve. Once the coring is complete and the soil sample has been tested, a report will be created and provided to the customer. The customer will then share the report with the Engineer of Record, and the Engineer of Record will now move forward with creating the plans for the subgrade. 



Trackhoes are commonly used to excavate the ground for a subgrade. 


The excavated ground will then be loaded into the back of a truck. If the dirt is contaminated, it will be disposed of. If it is clean and free of contaminates, it can be used in a variety of ways. If the job site has no use for the dirt, it can also be taken to other organizations such as schools, farms, or parks for landscaping or other projects that may be useful. If there is no need for the dirt, it will be transported to a landfill for disposal. 


When the subgrade is at the correct depth and all appropriate subgrade materials have been added, the subgrade will be compacted using a compactor machine that rolls and compacts the ground. It is critical that the subgrade is evenly compacted providing the ultimate strength for the structure. 

Imaged sourced from NMC CAT

A Motor Grader is another type of machinery that can also be used to flatten and compact grading. 

Image sourced from Water Pros

Water trucks and tanker trucks may also be used to deliver water and other materials that will assist with subgrade compaction. 

Reclamation machine. Image sourced from ASPHALTPRO

Reclaiming machines are also used to penetrate and mix the base with different pavement layers to create a level subgrade for the structure to sit. 




Shoring is a type of excavation that is done by installing large steel plates with steel I beams in between. It is designed to hold the earth and prevent the ground from caving in. Shoring plans must always be created by an engineer because it is a lengthy and technical process. There is also more risk involved. The shoring must also be removed once the precast structure goes in place. This form of excavation can be more extensive and can be a greater expense. 

Another form of excavation is a step back excavation, also known as stepping or benching. The ground is excavated to create horizontal steps at an incline that lead out of the excavation site. This type of excavation is also designed to prevent any caving in of the ground. One thing to note is that stepping puts you further from the center of the excavation, necessitating larger cranes. The location and size of the job site should also be considered when using step back excavation. This type of excavation can sometimes require significant space. This form of excavation usually involves fewer safety risks and has lower costs when compared to shoring.




Weather, particularly rain is always a factor that must be considered when excavating. If it rains while the ground is excavated, water may need to be pumped out until the subgrade is dry. Dewatering pipes or well-points can also be installed to facilitate drainage from the excavation site. 


It is important to ensure that the subgrade has been compacted correctly and is strong enough to hold the structure. Using a Dynamic Cone Penetrometer is a useful way to measure and check the compaction level of the subgrade.

Image sourced from ADE Consulting Group


Once the subgrade is compacted and inspected, the structure can be set into place. When this occurs, backfilling with the appropriate contents that have been approved by the Soil Engineer can begin. Backfilling material can consist of sand, rock, limestone, cement, and flowable concrete. This stabilizes the soil and provides it with more strength. 


The subgrade is a critical component of a precast structure’s longevity and performance. Following the correct protocol will ensure that the subgrade has been properly prepared for the structure. Here are a few steps to remember when developing a subgrade:

  • The Soil Engineer should test and identify soil properties which will determine the best components needed for the subgrade along with the correct backfill materials
  • The Engineer of Record should design an appropriate subgrade for the structure
  • Backhoes, trucks, compacting machines, and cranes with adequate reach will be needed 
  • Choosing which form of excavation to implement should always be specific to the job and should always account for the safety of all who are involved
  • Weather should always be considered, and the subgrade should be inspected after rain occurs before offloading the structure into place
  • An even compaction is key to giving the subgrade ultimate strength 



Stay tuned for our next article.

We hope this article was helpful. Please send in your questions to and we would be happy to help answer them.

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slug: understanding-chips-and-cracked-precast


There are occasions when cracks, chips, or spalls occur in concrete. When these forms of damage occur to a structure, it is important to understand the severity of the damage so you can use proper procedures to repair the concrete. In this article, we talk about the differences in these defects, what some of the common causes are, and what to look for when assessing how to repair a precast concrete structure.


Chipping is often the result of impact on the concrete, and they typically occur on the edges or corners of a structure. Chips are considered to be smaller areas of breakage on a concrete structure that can be as deep as 1 inch and as wide as 8 inches. Chips are usually seen as a cosmetic issue and normally do not impact the structural integrity of the structure. During the precast manufacturing process, chips can occur when structures are removed roughly from their molds or are improperly handled or stored.  On the jobsite, chips typically occur from improper handling of the product such wrapping chains around the structure and dragging it or unintentional collisions with other structures during the installation process. 



Spalls are similar to chips but typically occur on the edge of a concrete surface.  As is the case with chips, spalls are typically cosmetic in nature, but can range in size from small to large areas of the concrete edge. Like chips, they usually occur from impact or pressure applied to the edge of a concrete surface. Spalls that expose structural reinforcement are considered more severe and repairing these structures correctly is critical for the long-term life of the product. The most common cause of spalled edges occurs during handling and storage. Dunnage is typically used to support precast structures and allow access for forklift access underneath. Imperfections along the edges of the concrete surface can lead to a “point load” effect when the concrete is placed on dunnage or when forks are picking up the structure. This pressure concentrated in a small area along the edge of the surface can easily lead to a spalled edge. A great way to reduce the chances of spalling in these situations, is by creating a rounded or chamfered edge where the forks and dunnage will be supporting the structure.



Cracks can vary in size and depth and require more experience to evaluate. Concrete is inherently weak in tension and is designed with the expectation of it cracking up to the point where the steel reinforcement is located. Cracks can range from being minor and not require any treatment at all, to catastrophic and requiring major repairs to maintain the structural integrity of a product.

One type of minor cracking is surface cracks often found on the top surface of concrete structures. They are usually small in size, run across an unformed surface of a structure, and typically occur when the curing process is poor. Sometimes these cracks are called temperature or shrinkage cracks. These cracks occur when the surface dries quickly due to heat or wind and no controls are used to cure the surface at a slower rate maintaining moisture while the cement hydrates. These types of cracks may also present themselves if there is a high water to cement ratio in concrete mix design.

Another type of crack is called a re-entrant corner crack. These are very common and are due to stress on the corners of a structure. This usually occurs with structures that have squared off edges and the cracks will normally present themselves once the structure has cured. One way to minimize this problem is to create structures with rounded edges instead of squared off edges. Rounder edges provide more strength to the structure and can greatly help to reduce these types of cracks.

More severe cracking can occur on structures not properly handled or stored.  For prefabricated concrete structures, they should rest on level surfaces and on dunnage that has been properly placed based on the design of the structure. Concrete is heavy and instances with the weight not properly distributed across the dunnage can lead to excessive stress on the structure. If it has not been designed for those stresses, there is a potential for it to develop stress cracks. Storage of larger precast sections should be evaluated and designed by an engineer.



Before a structure is repaired, it is important to understand the cause of the damage and what the final use of the product will be. For any structures with major damage, an engineer should assess the damage and evaluate the structural integrity before moving forward with any repair. This ensures that the correct actions will be taken to properly repair the structure. In addition, industry best practice is to prepare a damage assessment report to dig into root causes in order to learn and prevent damage of future structures. 



One of the most common ways for precast products to get damaged is due to improper handling. The product should always be carefully lifted and stripped from its casting mold after reaching the design stripping compressive strength. Normally, precast structures are not at full 28 day design strength when being demolded, but there should be a stripping strength designated and the concrete should be tested to ensure it is as this designated stripping strength. Molds should also be checked to ensure that they are not causing any damage to the structure and working properly. If molds are not properly coated with a form release agent, it may create problems during the stripping process and allow binding up when the product is being removed. 



“Patching” is usually the term that is used when performing cosmetic repairs to concrete structures. Patch mixtures can be cement based or have additional mineral additives added to the mix. They can also be comprised of an epoxy mortar, epoxy cement, or a polymer mixture. When repairing a damaged structure, it is first important to understand the severity of the damage to the structure. Qualified and competent personnel should assess the damage and if necessary, a qualified engineer should be involved for any potential structural damage. 



In handling cosmetic repairs, the surface of the structure should first be prepared properly. Prepping the surface before the application of the repair material is one of the most important steps. The surface should be clean and free of any debris. Weather conditions should also be taken into consideration, as colder temperature will slow the patch material from curing. 

Once the surface the has been prepped and the patch mixture is ready, water or a bonding agent may be applied to the site with a brush. This adds moisture to the area. Once this takes place, a trowel can be used to apply the patch mixture. It is important that the mixture is applied evenly across the surface of the structure. 

Once the mixture has been evenly distributed, it can be smoothed over with sweeping motions.

Once the patch mixture has been evenly distributed, a brush will be used to smooth over the surface. 




It is important that when cracks, spalls, or chips damage a structure, the severity of the damage is assessed. Repairs can be costly, especially with structures that receive significant damage. Structures that receive extensive structural damage may even be required to be replaced. It is critical that the product is properly inspected when damage does occur to ensure that with repairs, it will still be structurally sound. It is also important to understand what the cause of the damage was, so that changes and preventative actions can take place for future structures. Understanding the extent and cause of the damage along with proper surface preparations, a compatible patch mix, and proper application are key to a successful repair. 



Stay tuned for our next article.

We hope this article was helpful. Please send in your questions to and we would be happy to help answer them.

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slug: new-locke-hq-finalist-2018-landmark-awards-houston-business-journal

Our brand new headquarters has already received some accolades! Designed by Synchro, our design-build partners through concept and construction, the new Locke HQ has become a finalist for the 2018 Landmark Awards by the Houston Business Journal. Our facility was considered one of the top new industrial real estate projects in Houston.

Check out the finalists and stay tuned for the results!

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slug: new-locke-facility-broken-ground-houston

We’re excited to announce that our all-new facility has broken ground.  We are working with the architecture and building firm Synchro based in Houston to design/build our new, industry-leading facility.

After several years of continued growth and demand for engineered precast concrete structures and metalwork, we have been forced to invest in more capacity.  That capacity looks like over 55,000 sq ft of new, state of the art design and manufacturing facilities. A custom-designed concrete batching system by Mixer Systems, Inc. will produce freshly batched concrete delivered with new OMi variable frequency drive overhead bridge cranes. Staged along four production runways will be dozens of custom-designed concrete mold systems developed by our fabricators and engineering team giving us the flexibility and efficiencies to produce concrete structures at the lowest costs.

In short, we’re building a world-class facility with the best equipment to match the talents of the people working at Locke Solutions.

It goes without saying, but we will also be displaying our own capabilities during the construction process of this building providing precast and metal fabricated elements throughout the facility.  To name a few items, we are manufacturing all of the components for the storm sewer system including maintaining a high-quality level of stormwater discharge from the property.

Other elements include a sand/oil interceptor with a sample well catch basin to further improve the water quality draining from our facility.

We have been fortunate to receive the support from contractors and engineering firms trusting us with their projects, and we will keep working towards maintaining that level of service and turnaround time they have grown accustomed to seeing from us.

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slug: surface-water-treatment-plant-sjra-packed-full-locke-products

Locke Solutions was just getting started around the time this Surface Water Facility was being designed, so when we were introduced to provide some small communication vaults, there were several questions about who exactly we were.

It didn’t take long for our LOCKE stickers to start showing up all over that job site though. Over the course of 4 years, we have provided product to 8 different contractors/wholesalers including directly to SJRA. We started with dozens of communication and electrical manholes to protect the “nerve system” of controls traveling between each of the different facilities on site.

We were then called to provide more than 500 sections of precast concrete trench sections used for housing the numerous chemical lines running between facilities.

During the production of the trench sections, we were then given the opportunity to take a look at 2 large water meter vaults designed as pour-in-place concrete structures due to the enormous sizes.

The larger of these vaults measured 42’ in length, 13’ in width, 10’ in height, and weighed a little over 215K lbs.

Even though it’s all buried underground, we’re proud to have the Locke name all over this incredible water treatment facility in Conroe, TX.