1. WG on Composite Cements: Austin Meeting 2017
Austin, January 2017, Heiko Plack

2. Proposed Agenda
Update WG roster/member list
Status of Annex B „Composite Well Cements“
Way forward discussion
Miscellaneous

3. WG Members (Current Emailing List)
Informative:
John Buflod, API
Deryck Williams, Chevron
Members (interested parties?):
Dan Mueller, ConocoPhillips
Bernard Fraboulet
André Garnier, Total
Jerry Calvert
James Reid, Oxy
Glen Benge
Gunnar De Bruijn, SLB
David Stiles, ExxoMobil
Erick Cunningham, BP
Bill Ulrich, HolcimLafarge
Rick Lukay, OFITE
Joe Shine, SaudiAramco
Tom Griffin
Scott.Saville, Ametek
Luis Padilla, Chevron
Felipe Padilla, Baker Hughes
Scott Podhaisky, LafargeHolcim
Simon James, SLB
Anand Krishnan, Cemex
Grégory Galdiolo, Curistec
Antonio Bottiglieri, Baker Hughes

4. Status of Annex B „Composite Well Cements“
May 2016: Ballott closed and passed
June 2016: Summer Meeting in DC
all comments addressed
decision to „pre-publish“ the Annex as an amendment to current API Spec 10A
July 2016: submission of final draft to API including all changes,
corrections and amendments as addressed by the WG
October 2016: observation that API Spec 10A is still also an ISO
document, thus pre-publishing the Composite Annex is not possible for legal reasons
decision to add the approved Annex directly to the next (25th) edition of Spec 10A and get it out ASAP.

5. Way forward discussion
… can be an open kick-off discussion
on how to further develop our “virgin” composite section of API Spec 10A,
also considering the addition of other composite materials, e.g. limestone, …
and possible ways to investigate/determine their suitability.
Optional: Short Presentation:
“Effect of limestone addition to construction cement and concrete – a generic summary and first appraisal on suitability for composite OWCs”

6. Austin, January 2017, Heiko Plack
WG on Composite Cements: “Effects of limestone addition to construction cement and concrete – a generic summary and first appraisal on suitability for composite OWCs”
Austin, January 2017, Heiko Plack

7. What Is Limestone?
A sedimentary rock consisting predominantly of calcium carbonate, varieties of which are formed from the skeletons of marine microorganisms and coral: used as a building material and in the manufacture of lime and cement.
Three types of calcium carbonate-containing rock are mined and used by industry: limestone, chalk and dolomite.
Depending on the composition (origin) and use there are different qualities of limestone.
All have impurities such as clay but some rocks are over 97% pure calcium carbonate.

8. What Is Limestone? In the following discussion of:
Quality requirements (EN 197-1) and performance effects of limestone as a composite material for construction cements and concrete.

9. What is Portland-Limestone Cement (PLC)? - I -
Either a blend of Portland cement with separately ground limestone powder or (more common) … an interground product obtained by adding crushed and dried limestone to the finish mill, along with clinker and gypsum. Common PLCs contain between 5% and 15% limestone. Note: Most ordinary portland cement (e.g. ASTM Type I/II) also contain up to 5% limestone, … as permitted by most of the applicable construction cement standards.

10. What is Portland-Limestone Cement (PLC)? - II -
In almost all cases, the limestone used in PLC is the same limestone used as a raw material for cement production at that plant.

11. EN 197-1:2011

12. EN 197-1:2011 – Limestome Requirements/Classification

13. Summary Limestone Requirements/Classification
Calcium carbonate content: = minimum 75 wt-%
Clay content, by methylene blue test: = maximum 1,20 g/100g
- Effects of clay: discussed later …
high clay contents can also be detected by measuring (inner) specific surface area by BET (adsorption of nitrogen),
higher BET = higher clay content = rather negative
Total organic carbon (from remaining geogenic material) =
LL quality = maximum 0,20 wt-%
L quality = maximum 0,50 wt-%
Note: higher TOC of limestone is believed to lessen freeze-thaw resistance of concrete
= not applicable to OWC!

14. (Preliminary) Conclusion - I -
For portland-limestone construction cements and concrete, - the main quality criteria for limestone as cement component is … - a high calcium carbonate content (purity) vs. an as low as possible clay (Montmorillonite) content.

15. (Preliminary) Conclusion - II -
Preliminary assumptions for Composite OWC: Addition of limestone, mainly by intergrinding and with less than 20 wt-.-% may lead to improved performance of OWCs (e.g. rheology, early strength, slurry yield) Only use of selected quality limestone? - high calcium carbonate content, - low clay content (additive response, mix water requirement, …) Limestone powder is inert at basic pH values but prone to acidic attack at pH < 7, e.g. from carbonic acid (dissolved CO2)

16. WG on Composite Cements: Backup
Austin, January 2017, Heiko Plack

17. Limestone Addition - Chemical Resistance
Limestone is an inert material, not or slowly reacting chemically … … in a basic pH environment, like present in capillary pores of hydrated cement. However … like portland cement, limestone powder is prone to chemical degradation … … in an acidic environment with low pH, i.e. when exposed to carbonatic acid (dissolved CO2) Note: Limestone addition lessens the resistance of a cement matrix to chloride migration, … … however, pure Grade HSR cements are even worse.

18. Limestone Addition - Strength Effects - I -
Qestion: do we really need the high final strength potential of pure portland API OWC? Because of being inert, limestone does chemically not or little contribute to cement strength. - literally „diluting“ the strength potential of OPCs

19. Limestone Addition - Strength Effects - 2 -
However,
when intergrinding limestone (usually <20wt-% content) it can improve early strength of PLCs:
- limestone is easier to grind than portland cement clinker
- limestone accumulates in the fine and finest particle size fractions
- thereby flattening the PSD and improving the packing of solids
also:
finest limestone particles can act as a core/nucleus for quicker growth of hydrating cement particles around the limestone particles

20. Limestone Addition - Rheology And Yield Effects - I -
Because of flattening the PSD respectively optimized grain size distribution, common PLCs with <20% interground limestone often show a better „workability“ in concrete. Prove whether this also applies to OWC slurries! However … The higher fineness of added limestone usually also requires a certain increase of mix water content, this leading to - lowering slurry density - higher yield of PLCs - stabilization of slurry (low free fluid) Note: Limestone with higher clay contents negatively affect rheology too, because of higher specific area and increased physical absorption of mix water

21. Limestone Addition - Rheology And Yield Effects - II -
Summary rheology effects of limestone addition: Smaller addition (<15 wt.-%) and intergrinding … can lead to … … improved rheology and likewise stabilized slurries … due to improved grain size distribution and solid packing Addition of higher amount of limestone (>10 wt.-%) by blending … usually lead to … … less good rheology or at least a much higher mixwater requirement. Most negative: high clay (Montmorillonit) content in limestone

22. Limestone Addition - Compatibility/Response to Chemicals (… In Concrete)
Clay contaminations in limestone often lead to increased consumption of dispersant, especially when using Polycarboxylates (PCE).
PCEs are „built in“ the inner chemcial structure of Montmorillonit clays and thus are not available anymore for dispersing the cement paste.
Source: Prof. Dr. Johan Plank, Technical University Munich, Beton
Similar effects on common OWC field additives?
- subject to confimation/prove
- Per se exclusion of high clay (Montmorillonit) containing limestone from production of Composite OWC?