13M tons

of CO2 approx. saved last year (water reducers and accelerators)*

 

Address the Role of Water-Reducing Concrete Admixtures

Water reducers and superplasticizers are the most popular type of admixtures. They disperse the cement particles more evenly, leading to an increase in the flowability of the concrete and an improvement in its workability during placement. With these qualities, less water is needed, resulting in concrete with a lower porosity and therefore a higher load-carrying capacity per unit of cement used. For a given strength requirement, less cement is needed, reducing the carbon footprint of the concrete. Modern superplasticizers can enable water reductions of up to 40% and binder (cement) substitutions of up to 50%, without strength loss.

Discover concrete admixtures, fibers, and technologies to support your sustainability efforts.

*Reflects GCP internal estimates

 

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Concrete admixtures.

Chemicals are typically added at 0.01% - 0.3% by weight of cement to allow cement and concrete producers to reduce energy, water and carbon-intensive materials usage. Savings can be up to 30% for each category. This amount is equivalent to adding: ½ - 1 gallon (~2-4 liter) to a volume of concrete the size of a home refrigerator (1 m3) or 1 part additive/admixture in 250 - 500 parts of concrete.

GCP Complete Range of water-reducing admixtures

1.    ADVA® Superplasticizers:
a.    Release water that would otherwise be trapped within cement grain flocs, increasing the workability of the concrete without the need for additional water.
b.    Increase workability without additional water.
c.    Increase concrete strength by reducing the water/cement ratio.
d.    Maintain strength while reducing water and cement content.

2.    MIRA® Water Reducers:
a.    Enable easier finishing of concrete mixes. The finishing can be completed with fewer passes of the trowel machine.
b.    Provide optimum water reduction, compressive strength, and set times and improved finish when used in leaner mixes or mixes containing high pozzolan contents.

3.    ZYLA® Water Reducers:
a.    Work synergistically with other polycarboxylic-based mid- and high-range water reducer, enabling further reduction of cement in the concrete mix.
b.    Promote more complete hydration of Portland cement.

4.    CONCERA® Control-flow Concrete:
a.    CONCERA® admixtures allow for the creation of control flow concrete - a segregation-resistant concrete that is easy to place and finish. Its excellent passing and flowing ability significantly reduces labor costs and equipment wear and tear. Control flow concrete can be used for elevated decks, grade beams, foundation mats, pilings, walls, columns, and floors. [ Embed CONCERA video.]

Case Study. Using superplasticizers in SCM mixes

Superplasticizers can be used to reduce water in a mix, thereby lowering the effective water-to-cement (w/c) ratio. Abrams’ law will permit the replacement of cement with supplementary cementitious materials, such as fly ash, while maintaining equivalent strengths. For example, a reference concrete with 350 kg/m3 (590 lb/yd3) of cement and 200 kg/m3 (337 lb/yd3) of water (0.57 w-to-cement ratio) can be treated with a superplasticizer. The water content of the concrete can be reduced to 160 kg/m3 (270 lb/yd3), for a 20% water reduction.

That water reduction allows 70 kg/m3 (118 lb/yd3) of cement to be removed and replaced with 84 kg/m3 (142 lb/yd3) of fly ash, creating a w/c ratio of 0.445. Some sand can also be added to the mix to maintain equivalent yield.

Even without factoring in the supply chain and resilience benefits resulting from easier placement and longer structure lifespan, the sum of these changes results in concrete with a 19% reduction in CO2 emissions. Given that reducing the amount of water required to produce building materials is also a key sustainability goal, this process represents a significant opportunity for builders to make meaningful improvements in this direction.

Admixtures to enhance concrete quality and performance

DARASET®, POLARSET® Accelerators catalyze the hydration of cement, speeding up set times.

This allows greater integration of supplementary cementitious materials, such as slag or fly ash, by offsetting the negative effect supplementary cementitious materials have on early strength development. 

Accelerate cement hydration, resulting in shortened setting times and increased early compressive and flexural strengths.

Enable greater use of supplementary cementitious materials (SCMs), such as natural pozzolans, slag, or fly ash while maintaining set and early strength properties.

For every tonne of clinker that is replaced by slag or fly ash, embedded CO2 decreases by 0.60-0.90 ton.

Case Study. Using superplasticizers and set accelerators in SCM mixes

Following similar methods as the one used above, we can also illustrate how combining the use of superplasticizers with set accelerators can even further reduce the CO2 emissions of concrete while partially overcoming the lower early strengths that have been associated with higher levels of cement replacement. Using a similar dose of superplasticizer, we can reduce the water content of the mix to 169 kg/m3 (285 lb/yd3) and the cement content to 175 kg/m3 (295 lb/yd3). The cement removed is then replaced with 210 kg/m3 (354 lb/yd3) of fly ash, resulting in a w/c ratio of 0.44.

However, this time we’re using a set accelerator to partially overcome the lower early strengths associated with this high cement replacement level. (Later-age strength is typically not an issue for fly ash mixes.) Together, the changes result in concrete with a 34% reduction in CO2 emissions. If allowance for slower strength development were possible, thus allowing less accelerator use, the CO2 emissions would be even further reduced.

AIRALON®, DAREX®, DARAVAIR® Air entraining agents

AIRALON®, DAREX®, DARAVAIR® Air entraining agents, which are required by building codes in many freeze-thaw regions, trap small air bubbles in the concrete to provide pressure relief when water within the capillary pores expands during freezing, extending the service life of the concrete. These air bubbles also have a lubricating effect, improving the workability of the concrete, which can lead to an additional 2-5% reduction in water content. For mortar applications, which comprise about a third of global cement use, air entrainment can allow a reduction in cement content without loss of workability. In developing markets, where mortar applications are common, this can significantly reduce the carbon footprint of the industry.

Case Study. Using air entraining agents

Air entraining agents (AEAs) are surface-active agents that function by stabilizing small air bubbles in the concrete. This provides for pressure relief when entrained water expands during freezing. For this reason, AEAs are required by building codes in many freeze-thaw susceptible regions in the world.

Air entraining agents are also useful in imparting workability to low-strength lean concretes. Due to the low paste volume in these concretes, aggregate-aggregate friction is a major obstacle to workability and slump development. When air entrainment is increased a few percentage points, the desired workability can be achieved with slight reductions in cement and water contents, resulting in modest (~3%) reductions in CO2 emissions. However, when factors such as improved durability (as a result of reduced bleeding and better compaction) are accounted for, the environmental impact over the concrete lifecycle can be considerable.