concrete / ready-mix
Concrete producers can leverage advanced concrete admixtures, predictive analytics tools, and more to improve efficiency, from materials management to batching to concrete delivery. The following articles are filled with tips and techniques for concrete production, from the selection of materials through the successful delivery of each concrete batch.
It isn’t often that you can equate coal-related products with energy efficiency, but when it comes to fly ash, it actually does help. This fine powder byproduct of coal plants is often used to replace natural materials in the production of concrete. Using fly ash reduces CO2 emissions. In fact, for every ton of cement replaced with fly ash, nearly one ton of CO2 is kept from entering the atmosphere.
Its primary benefits come from its durability and workability though. Replacing a certain percentage of Portland cement with fly ash imparts workability, allowing the concrete to be placed and finished more easily. Fly ash also reduces the internal porosity of the hydrated concrete improving its durability. In this way, ready mix producers can differentiate themselves by offering contractors a product that is both durable and workable.
If you’re like most concrete producers, you’re already well versed in the benefits of pozzolans, including fly ash and ground-granulated blast-furnace slag, for improving the durability and strength and reducing the permeability of concrete. Pozzolans like fly ash also reduce the cost of producing concrete. Notably, using pozzolans also allows you to produce concrete with less cement, reducing your carbon footprint.
However, concrete producers today have many questions about using traditional pozzolans that are byproducts of other industries.
- Will we face a shortage of fly ash as regions shift away from coal-fired power plants?
- Will the quality of the fly ash change as environmental regulations shift?
- Will I need to choose a different type of pozzolan? How expensive will it be?
These are all unknowns at this point… more
Small variations in the coarse or fine aggregates in the concrete mix can have a dramatic effect on the concrete’s overall performance. The size, shape, absorption and texture of aggregates will impact the strength, durability and workability of the concrete.
High quality aggregates are increasingly difficult to find. The scarcity of quality aggregates is leading to the increased use of lower quality aggregates. For example, many fine aggregates contain high levels of swellable clays. These clays may absorb water and chemicals, which can lead to poor workability, lower strength, and increased shrinkage and cracking.
With the use of lower quality aggregates on the rise, many contractors are relying on their ready-mix concrete producers to use concrete admixtures that minimize the impact of using poor quality aggregates. For example, clay mitigating, water reducing admixtures help to mitigate the detrimental impact of swellable clays, resulting in higher-quality concrete… more
There’s been a lot of talk about the benefits of high flow concrete, but how do you know when to use it and when is conventional concrete sufficient?
Many factors need to be considered with choosing a specific concrete category. First, consider where the concrete will be used. For example, control flow concrete is ideal for most slab on grade and formed concrete applications, while self-consolidating concrete is advantageous for use in highly reinforced and very difficult to cast applications… more
Concrete is typically easier to place and finish with slumps greater than those either specified, designed, or both. While specifications for large commercial projects often limit how much water can be added to the concrete mix, there are often no slump limits or controls over the amount of water added for small commercial and residential projects.
Many times, three or more gallons of water per cubic yard is added to the concrete to improve workability, with the intent of making it easier to place and finish. However, the addition of this much water causes any number of problems, including segregation, reduced strength and durability, and increased shrinkage and cracking.
Some ready-mix concrete producers use mid- or high-range water reducers to the mix to help mitigate these risks. Although this is an improvement, these mixes may still result in some form of segregation if the slump is excessive. Increased segregation causes headaches for contractors because it makes the concrete more difficult to pump and finish… more
Air entraining agents are concrete admixtures that entrain air in concrete when a structure will be exposed to moisture, freeze thaw cycles and deicing chemicals. When temperatures drop below freezing, water in concrete begins to freeze and the powerful expansive forces of freezing water can damage the concrete.
Air entraining agents entrain air by generating millions of stable, microscopic air voids in concrete. These uniformly dispersed air voids provide relief from the expansive freezing water, thereby preventing freeze thaw deterioration… more
Ready mix concrete producers can optimize fleet processes and avoid overdesign with the VERIFI® in-transit concrete management system, which can be installed on every ready-mix truck. The producer can tighten controls on the entire delivery process, continually managing slump between plant and jobsite.
Furthermore, when producers work within a performance-based specification, they can collect and analyze the in-transit concrete management system’s data for optimizing a given mix design to meet certain performance requirements. The reason? Visibility into the concrete mix as it’s transported from plant to jobsite, via this cloud-connected system… more
Sophisticated internet-connected sensors can provide concrete producers with real-time monitoring data across their entire fleet of trucks. This data is accessible on phones, tablets, laptops, and desktops. This means that wherever you are, you'll know that your concrete is arriving ready to pour at the right slump and water content… more
Concrete placement, curing and setting
Building exterior walls is usually a time-consuming process, but with tilt-up construction, walls can be created more quickly. That’s why tilt-up construction is one of the fastest growing construction methods in the US, with at least 10,000 buildings constructed each year. Many warehouses, including Amazon’s, were built using this process.
Economics is driving the move towards tilt-up construction. This building method can speed up construction, lower capital investment — and lower labor costs since it requires fewer skilled workers. Without vertical forming, fewer workers are needed, especially while placing the concrete. This is a big deal, particularly in urban areas where contractors are having a tough time finding skilled labor… more
Top down construction is increasingly popular due to its productivity benefits. This concrete construction method allows for above ground construction work to be carried out at the same time as excavation of the basement, resulting in significant time savings. Commonly used in urban areas, top down construction is often used for high rise buildings with deep basements and for underground structures such as car parks and transit systems.
There are typically space constraints in top down construction, particularly when pouring foundations underground. In these confined spaces, it’s next to impossible for workers or large machines to easily access concreting areas to vibrate concrete or move it around safely. The concrete needs to flow easily… more
As buildings soar higher and higher, it’s fascinating to see new technologies emerging to meet this demand. Here are three trends to keep an eye on if you’re designing or planning a new high-rise building.
Steel/concrete core wall system. This system uses two steel plates that are connected by steel spacing ties, with the cavity then filled with high strength concrete. This system eliminates the need for rebar and formwork. The core and perimeter steel can be built at the same time, because there’s no need to wait for the concrete to cure. Reports show that this type of steel/concrete construction can save time and money compared to traditional construction. In one high rise, the hybrid steel/concrete wall building took 377 working days, compared to the concrete core building, which took 474 working days… more
The global precast construction market is projected to reach $185 billion by 2022, spurred by increased construction spending and increased urbanization. According to a recent study by Allied Market Research, the demand for greater energy efficiency and faster construction is driving an increase in the use of precast concrete systems.
Precast concrete is often used to create structural systems (columns, beams, floors, girders, etc.), underground and utility systems (pipe, manholes, septic tanks, etc.), and building enclosure systems, such as insulated wall panels. Since precast concrete is cast in a controlled environment, it is easier to control the mix, placement and curing. As the precast concrete market grows, we’re seeing precasters adopt concrete construction innovations to achieve further efficiency gains… more
Many structural elements, such as shear walls and transfer girders, require large amounts of concrete. Traditionally, jobs were considered mass pours if the cross-sectional dimension of the concrete element was three feet across or more.
For these massive jobs, there is a concern both about the maximum temperature produced during concrete production and maximum temperature shifts that can occur before the concrete finishes curing. During the cement hydration process, the interior temperature of the concrete rises, while the outer concrete may be cooling. If the external and internal temperatures of the concrete differ too much, the concrete element will crack… more
Concrete linings are a fundamental part of ensuring the structural integrity of tunnels, but pumping and placing the concrete for these jobs is a cumbersome process. Numerous challenges can arise. For example:
- Access within the tunnel is very limited, so concrete with very good flow is critical.
- Conventional concrete is not ideal for this application since it does not flow well and it can cause an obstruction in the pump, resulting in costly delays.
Some contractors have tackled these challenges by using self-consolidating concrete, due to its high flow and workability. However, there can be some difficulties involved with using this type of concrete… more
Delivering, handling, placing, finishing and curing concrete can be difficult during the hot summer months. While producers work hard to keep concrete temperatures down and use concrete admixtures to minimize slump loss, there are still many things that can go wrong if precautions are not taken during hot weather.
The American Concrete Institute (ACI) states that conditions such as high ambient temperature, high concrete temperature, low relative humidity and high wind speed tend to impair the quality of freshly mixed or hardened concrete by accelerating the rate of moisture loss and rate of cement hydration, or otherwise causing detrimental results. For example, the combination of heat, wind and low humidity can cause water to evaporate too quickly from the surface of the concrete, leading to unattractive plastic shrinkage cracks. Fortunately, there are measures you can take to protect against these problems… more
- Functional Admixtures
- In-Transit Concrete Management
- Ready Mix/Precast
- Water Reducers