Available Admixtures
Admixtures for Concrete
Liquid and powdered admixtures for concrete are out in front, providing for concrete’s role as the unequalled leader in utility and desirability as the most versatile building material in the world.
Admixtures have enabled:
- Exterior concrete placements, allowing it to remain durable in environments where it will be subject to cyclic freezing and thawing while saturated with water
- Concrete to be placed underwater, even in flowing water
- Concrete to resist various chemical attacks
- Ultra-high compressive strengths, elevating load-carrying capacities for high-rises, bridges, and more
- Concrete set-times that permit contractors to maintain work schedules and profitability
- Reinforcing steel embedded in concrete to resist the destructive effects of corrosion
- More complete utilization of cement in concrete, which is the most expensive ingredient
- Increased concrete toughness and abrasion resistance
- And much more…
^ top
Accelerating Admixtures (Chloride & Non-chloride formulations)
The transformation of cement powder plus water to a hard, dense material resembling rock is through a chemical process commonly referred to as “hydration”. The rate at which hydration or hardening occurs can be influenced by many factors. Here we will discuss the factor of temperature.
How cooler temperature affects concrete set time
Warmer air or warmer surrounding surfaces make hydration occur more rapidly. Slower hydration occurs when surrounding temperatures are cooler. These variables affect concrete hardening time and rate of strength gain.
There are times when we cannot place concrete in temperatures which facilitate hydration taking place at a rate which will satisfy the need of the contractor to have concrete harden and gain strength in the required length of time. In such cases we can manipulate the rate of hardening and of strength gain chemically. Accelerating admixtures for concrete chemically hasten the rate of hydration. The amount and type of accelerating admixture used with a particular brand of cement affects the rate of hydration just as warmer and warmer temperatures affect that rate more and more.
Here is a rule of thumb that is commonly used to estimate how temperature will affect the rate of set of a given concrete. Let’s say that at 70 degrees, a given concrete gets hard in 6 hours. The rule of thumb states that with every 10 degree temperature decrease, the hardening time lengthens by one-third.
Temperature Hardening time70..............6 hours
60..............8 hours
50..............10.6 hours
40..............14.2 hours
Fortunately, accelerating admixtures affect the rates of hydration in concrete and can overcome the affect that colder temperatures have on concrete set time and strength gain. They can be used to make concrete placed in cool or cold weather set as if it were placed on a much warmer day.
Safely, economically, accelerate concrete set times and early strength gain through the use of BASF’s Master Builders Pozzutec 20+ non-chloride, non-corrosive admixture. Pozzutec 20+ is unequalled in reputation and proven performance in the market as the best, most cost-effective, consistent-performing, chloride-free, corrosion-free accelerator available.
Master Builders - Pozzutec 20+
When neither the corrosion of embedded metal in concrete nor the discoloration of finished slabs is a concern, and when specifications allow for its use, liquid calcium chloride is available for use at rates up to 2% by weight of cementitious material.
^ top
Air-entraining Admixtures
Cyclic freezing and thawing of concrete that has been saturated with water prior to freezing is a force so destructive that it can lead to the disintegration of hardened concrete. When water inhabiting the microscopic pores and voids in concrete freezes, it expands nine percent in volume as it turns to ice. This expansive force is equivalent to about 30,000 psi of outward pressure. As the cycles of freezing and thawing continue, the cracks and fissures created by the outward pressure multiply, allowing further intrusion or water, further multiplying the destructive effect.
In the 1930’s, a company called Master Builders developed a commercially available air-entraining agent for ready mixed concrete, so enabling quality concrete, well-placed and properly cured, to be cast outdoors and to resist the destructive forces of cyclic freezing and thawing. Today, County Materials utilizes the newest generation of air entraining admixtures from the Master Builders product line. Together with carefully selected concrete-making ingredients, coupled with concrete contractor skill and know-how, highly durable, freeze-thaw resistant concrete is a reality.
Air entraining agents are liquid chemical admixtures that are precision-batched into concrete at the ready mix plant. They disperse through the mix and result in microscopic voids---bubbles--which when the concrete hardens, leave a cast of that bubble; a hollow sphere. The bubbles are very small and very closely spaced. Thousands of these hollow spheres may inhabit each cubic inch of concrete. When the water-saturated concrete is exposed to sub-freezing temperatures for sufficient time for ice to form, the water is forced into these spheres by the growing pressure. In these thousands of spheres, the expansive force is relieved, instead of transferring the expansive force into the surrounding hardened concrete. Later, as the temperature increases, the ice melts, the pressures force the water back into the surrounding pore spaces, and the cycle of freezing and thawing has been completed with no damage to the surrounding concrete.
Master Builders - Air-Entraining Admixtures
^ top
Silica fume mineral Admixture
Silica fume is derived from processes involved in producing silicon metal. It is an ultra-fine powder which, when mixed into concrete produces special performance attributes, improving hardened concrete in two primary ways.
First, silica fume, fine as it is—finer than cigarette smoke—physically fills the voids between cement particles, increasing concrete density. Second, silica fume is a pozzolan—a type of mineral that reacts chemically within concrete to increase the “glue”—the calcium silicate hydrate gel—improving the strength and reducing the permeability of concrete. An extremely strong, durable concrete is the result.
The reduced permeability of concrete produced with silica fume greatly limits the ingress into hardened concrete of water, chlorides, sulfates, and aggressive chemicals known for promoting reinforcing steel corrosion and other types of distress in concrete. This makes silica fume mineral admixture the ideal product for use in parking garages, bridge decks, marine structures, and any construction that requires the protection provided by essentially impermeable concrete.
BASF Master Builders - Silica Fume
Silica Fume Association
^ top
Superplasticizers
County Materials has a long, successful history in intelligently, beneficially supplying the highest-performing superplasticizing admixtures in the markets we serve. From uses in our prestress concrete bridge girders, our precast concrete underground tunnel segments, in the ready mix concrete we supply for towering office buildings or for residential concrete foundation walls, we have the right superplasticizing admixture to meet the need.
Our technology partner in chemical admixtures, BASF, building on their unique understanding of concrete materials and polymer synthesis, has created a customized approach to developing admixture technology that has never before been seen in the construction industry.
The result is the new Glenium 7000 series of high-range water-reducing admixtures. Based on the next generation polycarboxylate technology, this revolutionary series of admixtures combines state-of-the-art molecular engineering with a precise understanding of our regional cements to provide specific and exceptional value to the concrete construction process.
Marry these chemical assets with County Materials’ sustained competency in aggregate extraction and control, our discerning materials selection and expertise in quality control and the result is a high performing series of flowable and self-compacting concrete mixtures that can be tailored to meet most any need.
BASF Master Builders Glenium High-Range Water-Reducing
4x4 Concrete System
Early Strength
^ top
Water Reducers
Water-reducing admixtures for concrete represent a most important family of products which have enabled concrete to meet the demands placed on a growing, changing market. County Materials incorporates mid range reducers in all of our concrete mixes. These can be oredered at different dosages depending on your needs. In the family of admixtures called “water-reducers”, we have products which enable concrete to be placed at a given slump with less water than the same concrete without the admixture. Reduced water means greater strength, improved durability and reduced cracking, all while maximizing cement efficiency, and more.
Water-reducers are available in formulations designed to accelerate hardening and strength gain, to extend the length of time it takes concrete to harden, and in formulations that are designed to be neutral as to concretes rate of hardening, but which increase ultimate strength.
Attributes that all of our water-reducers contribute to our concrete are:
- Superior workability, pumpability, and finishability
- Compressive and flexural strength increases
- Reduced water required for a given degree of workability
Earlier, in the section on accelerators, we discussed the effect that cold weather has on concrete’s rate of hardening. Let’s examine that topic with regard to hot weather.
Let’s say we have a concrete mixture that gets hard in 6 hours at 70 degrees. The rule of thumb we put forth was that with each 10 degree temperature change, the time to hardening changes by one-third:
Temperature Hardening Time
70..............6 hours
80..............4 hours
90..............2.65 hours
100..............1.75 hours
Regrettably, what may happen in the event of a delay in concrete placement during hot weather is that jobsite water may have to be added to maintain/regain placeability and workability. Negative potentials derive from jobsite water additions. When jobsite water is added the air-entrainment level is altered, compressive strength is decreased, shrinkage cracking is increased and concrete color is altered. To reduce the risk of water being added at the jobsite to maintain the required placeability and workability, a retarding water-reducer may be requested to be batched into the concrete at the ready mix plant.
Water-reducing retarders are not necessarily added for the purpose of slowing the set time—yet they can serve that purpose---but more importantly, they can be added solely to delay the rate of slump loss, thereby preserving the consistency of the as-batched concrete; doing so without adding potentially harmful jobsite water.
-
BASF Mid Range Water Reducer product links:
- PolyHeed 997
- 1725
- PolyHeed 1020
About our technology partner for admixtures
The Admixtures Systems business of BASF Construction Chemicals was founded in Cleveland, Ohio in 1909 as Master Builders, Inc. by chemist S. W. Flesheim. A visionary and pioneer in the construction market, Mr. Flesheim sought to bring innovative solutions to the industry. His first product was a cement/iron floor topping mix broadcast on top of freshly placed concrete to replace wood block systems used in factories at the time, dramatically improving wear resistance and appearance. Later, the company invented non-shrink grouts used to secure massive machinery and as foundations for large structures.
Early in the 20th century, the company was one of the first to supply water-reducing and air-entraining admixtures and to provide waterproofing for concrete mortars. These products and many others were used on such well-known construction projects as the Field Museum in Chicago, Hoover Dam, Panama Canal and the Sears Tower.
For nearly a century, the company has continued to push the limits of chemistry and convention to develop and introduce products that improve concrete in any application. Today, the Admixture Systems business remains a leading innovator in the development, manufacturing and marketing of chemical admixtures and silica fume for concrete used in the ready mix, precast, paving, manufactured concrete products and underground construction markets. They offer the widest range of concrete admixtures available from a single source, used to improve the plastic properties of concrete such as placing, pumping, finishing and appearance. Their respected Master Builders brand products improve hardened, engineering properties of concrete. They ensure high strength and durability, inhibit corrosion of steel embedded in concrete, reduce permeability, improve resistance to chemical attack, allow effective placement of concrete in extreme weather conditions, and even enable concrete to be placed underwater.
The Admixture Systems business operates as part of BASF – the world’s leading chemical company with customers in more than 170 countries, over 150 production sites worldwide and 95,000 employees. BASF is headquartered in Ludwigschafen, Germany, where it operates the world’s largest integrated chemical complex.
County Materials is proud to have BASF Construction Chemicals as our technology partner for concrete admixtures.
^ top