This document discusses the use of calcium nitrate as an additive for concrete, especially for cold weather concreting. It explains that calcium nitrate acts as a setting accelerator that allows concrete to set earlier and generate heat, which helps prevent freezing. Recommended dosages vary depending on the purpose and cement type, but calcium nitrate can reduce setting times, enhance strength, and inhibit corrosion. The document also reviews products containing calcium nitrate and the research conducted to support its use in high quality concrete production.

1. Concrete and Calcium Nitrate
An Introduction to Improved Cold Weather Concreting
Dr.-Ing. Wolfram Franke
Yara Industrial
Application Development
Yara Technology Center
Wolfram.Franke@yara.com
www.yara.com

2. Topics
I. Calcium nitrate as a setting accelerator
II. Calcium nitrate and cold weather concreting
III. HESQ: Product and Application development for high
quality concrete production
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3. I. Calcium nitrate as a setting accelerator
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4. Why Calcium Nitrate?
 General demand for non-corrosive
accelerator
– Setting Accelerators are required
to improve performance and
productivity
– Chloride-based accelerators
cause severe corrosion damage
 Yara* performs systematic
research on possible industrial
applications for calcium nitrate
– In 1992 Norsk Hydro approached
SINTEF, Trondheim/Norway, to
start in-depth research of
possible concreting applications
* formerly Norsk Hydro
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5. What brought the breakthrough ?
 A unique project involving CN was the construction of the “Troll” oil/gas
platform in the North Sea (construction 1991-1994)
 Slip formation led to the need for a plasticizer - Productivity went down:
– A non-corrosive accelerator was needed
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Troll: the largest movable structure on Earth

6. What does Calcium Nitrate do ?
 Calcium Nitrate (CN) as a molecule
– Setting: Calcium speeds up the early hydration stage
– Strength enhancement and Corrosion inhibition: Calcium reduces porosity
– Corrosion Inhibition: Nitrate oxidizes dissolved rebar iron and forms a
protective layer around rebar, comparable to the effect of Nitrite
 CN benefits over comparable alternatives
– CN does not corrode reinforcement, unlike Calcium Chloride
– CN does not provoke alkali aggregate reactions, unlike Sodium Nitrate or
Sodium Nitrite
– CN is environmental friendly, unlike Calcium Nitrite
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7. Calcium Nitrate as a setting accelerator
 CN is a setting accelerator
– Start of setting is shifted forward
in time
– The reactions intensity within
setting is not affected (no
hardening accelerator)
 Efficiency depends strongly on
type of cement
– CEM I 52.5, CEM II-V, CEM II-L
benefit over full temperature range
– CEM I 42.5 benefits on low
temperatures only
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© H. Justnes
60
55
50
45
40
35
30
25
20
15
Temperature development
(cement paste, w/ c = 0 .4 5, 2 0 deg C)
0 3 6 9 12 15 18 21 24
temperature in deg C
time of experiment in h
CEM II A-V 42.5 R
CEM II A-V 42.5 R
+ 1CN
CEM I 52.5 N
"white"
CEM I 52.5 N
"white" + 1CN

8. II. Calcium nitrate and cold weather
concreting
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9. How does cold weather concreting work ?
 Purpose of an “antifreeze” agent
are:
– Prevent temperature decrease
below 5 °C within setting period
– Prevent freezing of water needed
for hydration until a certain
concrete strength is reached
– Prevent freezing the first day
 Calcium Nitrate
– Reduces setting time, produces
heat earlier and thereby provides
the necessary temperatures for
hydration
– does not reduce the freezing
point of the mixing water
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2 hours earlier
7 hours earlier
Justnes and Nygaard (1993)

10. Best practice in compliance with ACI_306R-88
Wrong Right Cover film
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T
5 deg C
0 deg C
Concrete
Insulation Mould
Cover film
Frostfree ground or ”permafrost”
T
Concrete
Mould
Temporarily frozen ground
5 deg C
0 deg C

11. Antifreeze:
Keys are water control and set acceleration
 The concrete hydration of surface close areas is
crucial as the reinforcement is often placed here
 For the concrete hydration the availability of water is
essential. The two ways to prevent its freezing are
– Keep water warm (for instance by hydration heat, as a
result of a set accelerator like NitCal) – dynamic solution at
light frost
– Increase salt concentration of water to prevent freezing –
static solution for deep frost
 The way to increase salt concentration is the reduction
of water, as the amount of salt added by admixtures is
limited
 The combined use of NitCal and a strong water
reducing agent is recommended to obtain w/c ratio as
low as 0,3 and thus minimize excess water.
 When doing so, only minor ice formation is expected,
and concrete can hydrate at even -15°C
 Attention:
– In this manner produced concrete develops compressive
strength very slowly
– Final compressive strength might be reduced
– Use of insulation is mandatory to support hydration
– Use of hardening accelerator like Thiocyanate/Rhodanide
or Aluminum Nitrate is recommended for concreting jobs
below -10°C
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12. III.HESQ: Product and Application
development for high quality
concrete production
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13. How to get Calcium Nitrate ?
 CN as water-free molecule is
difficult to obtain and handle
– Strong oxidizer with challenging
REACH classification
– Not available on the market
 CN needs are provided as
specialized products with improved
handling and storage properties
– Liquids:
• CN solutions with different
concentrations
– Solids:
• Calcium-Ammonium-Nitrate
(free flowing granule)
• Calcium-Potassium-Nitrate
(free flowing granule)
• CN tetra hydrate
(wet powder)
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?
??
Composition of CN products
0 % 20 % 40 % 60 % 8 0 % 100 %
CN 4 5% old
CN 4 5% new
CN 50% old
CN 50% new
NitCal
NitCal/K
CN Tetrahydrate
Ca(NO3)2 NH4NO3 or KNO3
Crystal Water Free Water

14. Market Support, Research and Development to
ensure high quality concrete production
 Market support
 Coordination of external R&D
 Customer communication
 Workshops and technical meetings on NitCal
 Concept development
 Screening tests, pre-testing
 (ISO certified production)
 Certified testing
 Expertise
 Market Support
 Special projects on Lignosulphonate and NitCal
 Durability testing
 Corrosion Inhibition, Models, Simulation
University of
California
UCLA
W.Franke 5/09/2014 Page 14

15. Which dosages are recommended ?
 The recommended CN dosages depend strongly on
– Cement type used, the “antifreeze” feature in particular demands prior testing
– Purpose of dosage
 CN dosages refer to CN active contents
– important when blends, hydrates and solutions are used!
Corrosion Inhibitor
(increasing duration to corrosion start by 20%)
Strength enhancement
(additional 10% of compressive strength)
Antifreeze
(reduce setting time by up to 3h at +5°C)
Counteraction of Plasticiser
(reduce setting time by 4h at +20°C)
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0 1 2 3 4 5
Setting Accelerator
(reduce setting time up to 50%)
characteristic up to dosage as % of cement weight
(Given recommendations need to be proven in pre-tests with the local cement)

16. Thank you for your attention!
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Yara Porsgrunn Plant

17. Important notice
• Yara disclaims all responsibility and liability for any expenses, losses,
damages and costs incurred as a result of relying on or using the
information contained in this document. Yara reserves the right to adjust and
revise this document at any time.
• Any forward-looking statement made by Yara in this document is based only
on information currently available to Yara and speaks only as of the date on
which it is made. Yara undertakes no obligation to publicly update any
forward-looking statement.
• No rights, including, but not limited to, intellectual property rights, in respect
of this document are granted to any recipient unless specifically stated.
• ©Yara International ASA. All rights reserved.
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