From a view of alkali solution: alkali concentration to determine hydration process of alkali activating metakaolin

State key laboratory of high performance civil engineering materials, Jiangsu Research Institute of Building Science, Nanjing, China

MU Song , JIANG Qian , LIU J. Zhong and SHI Liang

1st International Conference on Calcined Clays for Sustainable Concrete, 23 to 25 June, 2015, EPFL, Lausanne

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 2/24

Brief introduction on JSRIBS

Jiangsu Research Institute of Building Science CO., LTD （JSRIBS）wasestablished in 1958, which is composed of 11 sub-companies and 7 R&Dcenters in the field of construction materials and technology

State key laboratory of high performance civil engineering materials isestablished from SOBUTE R&D center which is mainly specialized in thechemical admixtures for concrete, high-tech for innovative concrete, etc

SOBUTE brand is China Famous Trade Mark

2014 year

sales is

500 millions Euros

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 3/24

Intelligence and contributions

Group leaderProf. Miao Changwen

Member of the Chinese Academy of Engineering

President of RILEM China division

Full-time professor of Southeast Uni.

Research staff：100 staffs with differentbackgrounds of cementitiousmaterials, organic chemistry ，

structural engineering, etc.

Three gorges dam Hanzhou Bay bridge

Contributions

the Chinese national project

the longest bridge across the sea in the world

Nuclear power plant Beijing-Shanghai high speed railway

the longest railway of high speed train in the world

Strict requirements forConcrete property

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 4/24

Outline Motivation

Experiments

Results Penetration resistance and setting time

Hydration heat

Compressive strength

SEM

Conclusions

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 5

Motivation

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 6/24

New binder materials are need to create better world

CO2 emission greenhouse effect

Miner exploitationnature destruction

Energy consumptionsustainable issue

Low carbon, low cost and good performance

Is the solution for development of

next generation of cementious binder Xingyi cityGUI ZHOU

China

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 7/24

Possible solutions for new binder

Dissolution Polycondensationaluminuosilicate materials

Geopolymer system

LC3 system

Cement clinker

Calcined clay

Gypsum

CaCO3+C3AH6+5H2O= C4ACH11

limestone

Structural material

Functional material

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 8/24

Utilizing metakaolin-based geopolymer to prepare inorganccoating to protect concrete under severe condition

Quick hardening and early strength

Low permeability

Environment-friendly materials with a low cost

Good adhesion strength

Excellent aging resistant performance

Inorganic polymer coating

(IPC)

Pore refinement

Interfacial microstructure

Chemical Bonds:P=O（585 KJ/mol)＞Si-O(459 KJ/mol)＞P-O(360 KJ/mol)＞C-C(346 KJ/mol）

No emission of VOCandusing waste materials

Geopolymeriazation

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Our progress on metakaolin-based geopolymer development

Geopolymer coating in the laboratory level

10% H2SO4 for 7 days

Chloride migration of concrete applied

by the coatingat age of 7days

Cracking resistance Adhesive strength Corrosion resistance

Coating for Concrete sewage Coating for waste water disposal

Possible application fields

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 10/24

Our progress on metakaolin-based geopolymer development

Liquid sealer in the industrial level

Capillary suction1 KPa

water penetration

Ningbo Bridge girder-chloride transport

AnJiang Tunnel for highway-sulfate attack Customer

Industrialapplications

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Alkali solution is one key component for geopolymer synthesis

Reaction mechanismDuxson P, Fernandez-Jimenez A, Provis JL, et al. Geopolymertechnology: the current state of the art. Journal of Materials Science.2007;42(9):2917-33.

Step 1

Step 2

Step 3

Step 4

Step 5

Alkali dissolves aluminosilicateparticles into aluminate and silicate ions

Alkali metal ions balance the charge ofgeopolymer systerm

From Duxsonet al

From Davidovits et al

What’s effect of high concentration of alkali solution on metakaolin-

based geopolymer at room temperature ?

Without calcium ions

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Experiments

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Materials

Metakaolin:

pink appearance was presented after calcination at 800 to1000 oC

total content of SiO2 and Al2O3 accounts for about 94 %

90 percentages of metakaolin has a particle size below 5.43μm, and the average particle size is 1.73 μm.

SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 Loss

60.85 34.51 0.95 0.5 0.39 0.19 0.34 1.82 0.88

Chemical composition of metakaolin /wt%

Particle size distribution of metakaolin

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 14/24

Materials

Sodium silicate: liquid, ratio of SiO2/Na2O is 2, 42.5% solid.content

Sodium hydroxide: liquid, sodium silicate， 12.5 mol/L，15mol/L and 20 mol/L

Solutions were stored for a minimum of 24 hours prior to use toallow homogenization.

Geopolymer mixture

Sample Metakaolin (g)

Modulus of water glass

Sodium silicate (g)

Concentration of sodium hydroxide

(mol/L)

Sodium hydroxide (g)

Water/Solid

Final modulus of water glass

C12.5 1000 2 902 12.5 722 1

0.82±0.02C15 1000 2 958 15.0 719 1

C20 1000 2 1068 20.0 694 1

Alkali solution

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 15/24

Test methods

Penetration test：

setting time can be determined as the time ofresistance reached at 0.5 Mpa

Average of two repeated tests were taken forthe value of resistance and setting time.

20 ± 2 oCRH 65%

Hydration heat：TAM AIR，paste was mixed by manual, andthen within 5 minutes the sample ampoules were filled with10 g paste

SEM: Quanta 250 from FEI, USA

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Results

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Penetration test

Increased alkali concentration decreased the time to reach the 0.5 MPa of penetration resistance;

As the concentration of alkali solution increased from 12.5 mol/L to 20 mol/L, the setting time decreased from 46 minutes to 33 minutes.

High concentration of NaOH accelerated geopolymerization

large amout of silicate and aluminate ions can be dissolved from metakaolin into the solution

Phair JW, Van Deventer JSJ. Minerals Engineering. 2001;14(3):289-304.

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 18/24

Hydration heat

With increasing concentration of alkali solution, exothermic rate of alkali-activated metakaolinsignificantly increased;

the maximum exothermic rate of20 mol/L of alkali solution wasabout five times than 12.5 mol/Lof alkali solution.

High concentration of NaOHresulted into a high rate ofexothermic reaction in a shortperiod

0 100 200 300 400 5000.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

Hea

t flo

w (w

/g)

Time (min)

C12.5 C15 C20 PII52.5(0.3)

Effect of NaOH concentration

Metakaolin-based geopolymershown a earlier age ofexothermic reaction thanPortland cemment;

12.5 mol/L of alkali solution hada significantly lower exothermicrate than Portland cement

By comparison with Portland cement

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Compressive strength

With the increased concentration of NaOH,compressive strength exhibited adecreased trend and then recovered undera role of the high concentration in theentire age of 60 days

Decreased strength at late age has beenobserved for alkali-activated metakaolin

Over high concentration of alkali substance decreased the strength of geopolymer

Chindaprasirt P, Chareerat T, Sirivivatnanon V.Cem Concr Compos. 2007;29(3):224-9.

FA

MK

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Microstructure

C12.5（7d）×5000 C12.5（28d）×10000

C15（28d）×20000 C20（28d）×30000

Unreacted particles of sodiumhydroxide have been found atage of 7 days

Geopolymer products transformedfrom amorphous phase intocrystalline phase with a shape ofpetals

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Microstructure

Atomic ratio

C12.5（28d） C15（28d） C20（28d）

A B A B A B

Si/Al 1.45 1.40 1.51 1.27 0.93 1.14

Si/Na 1.89 1.35 3.78 1.71 0.48 0.81

Element analysis by EDAX

C12.5（28d）×10000 C15（28d）×20000

C20（28d）×30000

Atomic ratio of Si/Al decreased graduallyfrom about 1.4 to 1.0

Atomic ratio of Si/Na significantlydecreased by about 40 %

Higher concentration of alkali solution decreased the ratio of Si/Al

and Si/Na so as to deteriorate the mechanic property.

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 22

Conclusions

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 23

Proper concentration of alkali solution can be helpful forpolycondensation process, but the over high concentrationdeteriorated the microstructure and decreased the strength;

Optimized concentration of NaOH was 12.5 mol/L formetakaolin-based geopolymer.

江苏省建筑科学研究院有限公司 Jiangsu Research Institute of Building Science 24

Thanks for your attention !

Acknowledgements

Thanks for the financial support from the China Postdoctoral Science Foundation (Grant No.: 2013M531296) and the Postdoctoral Science

Foundation of Jiangsu Province, China (Grant No.: 1301160C)

MU SongEmail: musong@cnjsjk.cn