Admixtures – State of the IndustryJoseph A. Daczko, FACI

67th Annual Concrete ConferenceUniversity of MinnesotaDecember, 2017

Outline

Admixtures for Concrete Definition Types

The multi-faceted demands placed on a concrete mixture

How do admixtures help satisfy the demands placed on concrete? Primary value recipients Others

State of the Industry

New Opportunities

Admixtures for Concrete

Admixture Definition: a material other than water, aggregates, cementitious materials,

and fiber reinforcement, used as an ingredient of a cementitious mixture to modify its freshly mixed, setting, or hardened properties and that is added to the batch before or during its mixing.- ACI Concrete Terminology.

ASTM C 494 – Lists 7 basic Types Type A – Water-reducing Type B - Retarding Type C - Accelerating Type D – Water-reducing & retarding Type E – Water-reducing & accelerating Type F – Water-reducing, high range Type G – Water-reducing, high range & retarding Type S – Specific Performance

It’s not about the admixture…..it’s about concrete performance!

WHAT DO YOU WANT FROM ME?

HAS IT SET YET??

TOO EXPENSIVE

LOW HEAT!!

WATER TIGHT

I CAN’T FINISH THIS

WRONG COLOR

AIR’S TOO HIGHAIR’S TOO LOW

MODULUS OF WHAT?

Satisfying Everyone

The performance targets of concrete mixtures depend on who you are talking to.

Owner How long will it last? When can I open? Architect How does it look? Engineer Is it strong enough? Stiff enough? Contractor Can I finish it? How does it set? Concrete Producer Can I make it economically and efficiently?

Admixtures are intended to help facilitate the balancing of these multifaceted demands

How Admixtures Facilitate Balancing Performance Demands

Low slump SCCFlowing ConcreteModerate slump

Conc

rete

Str

engt

h

W/CM Ratio

BUT(-) (-)(-)(-)(-)

Who Benefits from Certain Admixtures?

Set Controlling Admixtures

Type B (D) – Retarding & Type C (E) - Accelerating

Primary – Concrete Contractor?What happens when one member of

the chain rather than multiple members is the primary recipient?

Who Benefits from These Admixtures?

Underwater anti-washout admixture Corrosion Inhibiting admixture

Workability retaining admixture Viscosity modifying admixture

Increasing Viscosity

State of the Industry - Concrete 2029

VISION– Where do we want to be in 2029 as an Industry? Cross functional industry collaboration -

New Opportunities – What do we see?

Volume Stability

Constructabiity

Sustainability

High Rise Construction & Constructability

Cement Hydration Process

Hydration+ Water

The crystallization of CSH occurs close to the surface or onto the surface itself creating a layer which slows down the diffusion of products and reactants(topochemical reaction)

Cement Hydration Process

Suspended CSH seeds

Why wait for the crystallization of the nuclei to be formed if we can add them?

14

Master X-SeedEnhancement in Compressive Strength (NOT set acceleration)

(Nominal cementitious materials content of 611 lb/yd3 [362 kg/m3] with 20 percent fly ash, w/cm of 0.47

Volume Stability –Drying Shrinkage in Concrete - Cracking

Drying shrinkage cracking: when concrete is restrained, cracking that occurs after hardening due to shrinkage (volume change) caused by concrete mixture water, that is NOT consumed during hydration, leaving the system.

But – How much and how fast?

What do we consider?

Materials

Mixtures proportions

Curing

Admixtures

Fibers

Initial crack width, 𝒘𝒘𝒊𝒊

Time to cracking, 𝐭𝐭

Increase in crack width

after initiation,

∆𝒕𝒕

The relative performance measure is used to compare the effectiveness of the treatments

∆𝑤𝑤𝑝𝑝a

Example: Crack Timing and Width

Restrained Slab Test Results• Reference• Macro Fibers• Shrinkage reducing admixture (SRA)• Crack reducing admixture (CRA) • SRA + Macro Fibers• CRA + Macro Fibers

Extending Joint Spacing

Made possible by synergy of;

Material research

Design considerations

Base preparation

Construction practices

Concrete proportioning

Fiber and admixture technology

This is happening today across N America

Conclusions

The importance of chemical admixtures is that they enhance concrete performance in a variety of ways

The beneficiaries of those enhancements also vary – producer, contractor, engineer, architect, owner

There are cross functional movements within our industry (concrete 2029, this conference etc.) that improve our communication and help us to grow the industry

Chemical admixtures are a critical to achieving targeted concrete performance from fresh to long term durability properties

20Footnote Text12/14/2017