Login
Login

superplasticizer

{{Short description|High strength concrete additive}}

Superplasticizers (SPs), also known as high range water reducers, are additives used for making high strength concrete or to place self-compacting concrete. Plasticizers are chemical compounds enabling the production of concrete with approximately 15% less water content. Superplasticizers allow reduction in water content by 30% or more. These additives are employed at the level of a few weight percent. Plasticizers and superplasticizers also retard the setting and hardening of concrete.{{cite book |isbn=978-0-7277-3611-6|doi=10.1680/pc.36116.185 |chapter=Admixtures and Special Cements |title=Portland cement, Third edition |author=Gerry Bye, Paul Livesey, Leslie Struble |year=2011 |doi-broken-date=1 November 2024}}

According to their dispersing functionality and action mode, one distinguishes two classes of superplasticizers:

  1. Ionic interactions (electrostatic repulsion): lignosulfonates (first generation of ancient water reducers), sulfonated synthetic polymers (naphthalene, or melamine, formaldehyde condensates) (second generation), and;
  2. Steric effects: Polycarboxylates-ether (PCE) synthetic polymers bearing lateral chains (third generation).{{cite journal |last1=Lu |first1=Bing |last2=Weng |first2=Yiwei |last3=Li |first3=Mingyang |last4=Qian |first4=Ye |last5=Leong |first5=Kah Fai |last6=Tan |first6=Ming Jen |last7=Qian |first7=Shunzhi |title=A systematical review of 3D printable cementitious materials |journal=Construction and Building Materials |date=May 2019 |volume=207 |pages=477–490 |doi=10.1016/j.conbuildmat.2019.02.144|hdl=10356/142503 |s2cid=139995838 |hdl-access=free }}

Superplasticizers are used when well-dispersed cement particle suspensions are required to improve the flow characteristics (rheology) of concrete. Their addition allows to decrease the water-to-cement ratio of concrete or mortar without negatively affecting the workability of the mixture. It enables the production of self-consolidating concrete and high-performance concrete. The water–cement ratio is the main factor determining the concrete strength and its durability. Superplasticizers greatly improve the fluidity and the rheology of fresh concrete. The concrete strength increases when the water-to-cement ratio decreases because avoiding to add water in excess only for maintaining a better workability of fresh concrete results in a lower porosity of the hardened concrete, and so to a better resistance to compression.{{cite journal |title=Design and function of novel superplasticizers for more durable high-performance concrete (Superplast project) |author1=Houst, Yves F. |author2=Bowen, Paul |author3=Perche, Francois |author4=Kauppi, Annika |author5=Borget, Pascal |author6=Galmiche, Laurent |author7=Le Meins, Jean-Francois |author8=Lafuma, Francoise |author9=Flatt, Robert J. |author10=Schober, Irene |display-authors=etal |journal=Cement and Concrete Research |year=2008 |volume=38 |issue=10 |pages=1197–1209 |doi=10.1016/j.cemconres.2008.04.007}}

The addition of SP in the truck during transit is a fairly modern development within the industry. Admixtures added in transit through automated slump management system,{{Cite web |url=http://verificoncrete.com/what-is-verifi/admixtures/ |title = In-transit concrete management system | GCP Applied Technologies}} allow to maintain fresh concrete slump until discharge without reducing concrete quality.

Working mechanism

File:PEG-aminoDisphosphonic.png-terminated polyethers are effective superplasticizers.]]

Traditional plasticizers are lignosulfonates as their sodium salts.{{cite book|chapter=Superplasticizers and the rheology of concrete|author=R. Flatt, I. Schober|title=Understanding the Rheology of Concrete|year=2012|isbn=978-0-85709-028-7|publisher=Woodhead|editor=Nicolas Roussel}} Superplasticizers are synthetic polymers. Compounds used as superplasticizers include (1) sulfonated naphthalene formaldehyde condensate, sulfonated melamine formaldehyde condensate, acetone formaldehyde condensate and (2) polycarboxylates ethers. Cross-linked melamine- or naphthalene-sulfonates, referred to as PMS (polymelamine sulfonate) and PNS (polynaphthalene sulfonate), respectively, are illustrative. They are prepared by cross-linking of the sulfonated monomers using formaldehyde or by sulfonating the corresponding crosslinked polymer.{{cite journal|title=A review of cement-superplasticizer interactions and their models|author1=Mollah, M. Y. A. |author2=Adams, W. J. |author3=Schennach, R. |author4=Cocke, D. L. |journal=Advances in Cement Research|year=2000|volume=12|issue= 4|pages=153–161|doi= 10.1680/adcr.2000.12.4.153}}

File:Suspension PCE.jpg superplasticizer stabilizing a colloidal suspension through steric interactions thanks to its lateral chains. Note: the PCE molecules are adsorbed onto positively-charged cement particles (tricalcium aluminate ({{chem2|C3A}}) mineral phase).]]

The polymers used as plasticizers exhibit surfactant properties. They are often ionomers bearing negatively charged groups (sulfonates, carboxylates, or phosphonates...). They function as dispersants to minimize particles segregation in fresh concrete (separation of the cement slurry and water from the coarse and fine aggregates such as gravels and sand respectively). The negatively charged polymer backbone adsorbs onto the positively charged colloidal particles of unreacted cement, especially onto the tricalcium aluminate ({{chem2|C3A}}) mineral phase of cement.

Melaminesulfonate (PMS) and naphthalenesulfonate (PNS) mainly act by electrostatic interactions with cement particles favoring their electrostatic repulsion while polycarboxylate-ether (PCE) superplasticizers sorb and coat large agglomerates of cement particles, and thanks to their lateral chains, sterically favor the dispersion of large cement agglomerates into smaller ones.{{cite journal | last1 = Collepardi | first1 = M. | title = Admixtures used to enhance placing characteristics of concrete | journal = Cement and Concrete Composites | date = January 1998 | volume = 20 | issue = 2–3 | pages = 103–112 | issn = 0958-9465 | doi = 10.1016/S0958-9465(98)00071-7 | pmid = | url = https://www.sciencedirect.com/science/article/abs/pii/S0958946598000717| url-access = subscription }}

However, as their working mechanisms are not fully understood, cement-superplasticizer incompatibilities can be observed in certain cases.Ramachandran, V.S. (1995) [https://books.google.com/books?id=TnWS5nfiYm0C&pg=PA121 Concrete Admixtures Handbook – Properties, Science, and Technology], 2nd Edition, William Andrew Publishing, {{ISBN|0-8155-1373-9}} p. 121

Common superplasticizer types

File:Naphthsulfonate+CH2O.png/formaldehyde polymer used as a superplasticizer.]]

  • Sulfonated Naphthalene Formaldehyde
  • Polycarboxylate Superplasticizer (PCE), also called water reducer, is an additive used in concrete and mortars. It improves the flowability without increasing the water content. This allows for high-strength, high-performance concrete and mortar with lower water-to-cement ratios. SCE accelerate the early strengthening of concrete or mortar.{{cite book |doi=10.1002/14356007.w07_w01 |chapter=Construction Chemistry |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2021 |last1=Blask |first1=Oliver |last2=John |first2=Elisabeth |last3=Stephan |first3=Dietmar |pages=1–80 |isbn=978-3-527-30385-4 }}{{Cite web |url=https://landuchem.com/novastar-specialty-additives/polycarboxylate-superplasticizer-pce-powder-and-flake/ |title= Polycarboxylate Superplasticizer PCE Powder and Flake}}

See also

References

{{Reflist}}

Further reading

{{Refbegin}}

  • {{cite book | last1 = Dodson | first1 = V.H. | date = 29 June 2013 | title = Concrete Admixtures | publisher = Springer Science & Business Media | pages = | isbn = 978-1-4757-4843-7 | url = https://books.google.com/books?id=9NEFCAAAQBAJ&pg=PR11}}

{{Refend}}

External links

  • {{Cite book | first1 = Pierre-Claude | last1 = Aïtcin | first2 = Robert J. | last2 = Flatt | date = 12 November 2015 | title = Science and Technology of Concrete Admixtures | publisher = Woodhead Publishing | pages = | isbn = 978-0-08-100696-2 | url = https://books.google.com/books?id=rtlxCQAAQBAJ&pg=PP1}}

Category:Cement

Category:Concrete

Category:Chemistry

Category:Colloidal chemistry

Category:Heterogeneous chemical mixtures

Category:Concrete admixtures