E_2_BTouil

DURABLE STRUCTURESLNEC Lisbon 31 May - 1June 2012

EFFECT OF POZZOLAN ON LOCALS CONCRETE SUSTAINABILITY.

Mr B. TOUIL 1, Pr F. GHOMARI 1 , Dr BEZZAR 1 , Pr A. KHELIDJ 2 and Dr STEPHANIE 2

1 University of Tlemcen (ALGERIA)2 University of Nantes (FRENCH)


Contents

1. Introduction

2. Objectives

3. Materials and procedure

4. Results and discussion

5. Conclusion

ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC Lisbon Portugal 31 May - 1 June 2012

LNEC

ICD

S12


Inside view Column erodedWater tank: Ghazaouet (coastle city)

Overview

Bridge close the sea : Oran (coastal city)Beams cracked

Consequences : Complex and expensive repairs 3/20

Overview Column degraded

Materials, Procedure Results ConclusionsObjectivesIntroduction

Observations : Number of structures are damaged


Durability of structures in agressive environment

saltair

rust

Reduction of PH

The steel bar

Conditions for corrosion and mechanism

Reinforced Concrete Deterioration

Concrete healthyConcrete contaminated with carbonic or chloride

OXIDATIONFe ---> Fe ++ + 2e -

REDUCTIONO2+ 2H2 O + 4e ----> 4OH-

2Fe (OH)3 Fe2O3.H2O + 2H2O

4/20

Materials, Procedure Results ConclusionsObjectivesIntroduction Problematic :


LNEC

ICD

S12


5/20

- Natural material which does not require great energy in itsextraction and use (only grinding)

- Reduce the overall cost of the concrete with the valorizationof an economical natural materials (natural pozzolan).

-Reducing the ecological impact (substitution of part of cement).

Powder 80 m


Natural pozzolan :

Unrefined material

But what about the sustainability ?


6/20


Objectives: Influence of POZZOLAN on the performanceof concrete.

Basic Proprieties

Durability

Workability

Material: microstructural characterization(physico-chemical properties) .

Structure : Overall Characterization (notion de dure de vie ou de service).

Compressive strength

- improving the performance of concrete by using the basic approachPerformance (Indicators of sustainability)

- To ensure reliability of structures


LNEC

ICD

S12


7/20

Materials : Cement CPJ-CEMII/A 42,5 (85% clinker et 12% pozzolan) (Bni Saf) Aggregates (Career ENG of Sidi Abdelli):o Sand 0/4o Class of aggregates 4/8, 8/16 and 16/25 (G/S) optimised = 1,68. Natural Pozzolan "P" (carrer of Bouhmidi Bni saf)

(used after crushing and sieving 80 ).

Mixtures :For the comparative approach, the concretes to qualify withadded pozzolanic are referenced CPZ (5%, 10% and 15%replacement of cement mass)and compared to control concrete BO which is derived fromthe optimized formulation research of Boukli and al. (April 2009).



Concretes studied

Mix ingredients(Kg/m3) OC CPZ5 CPZ10 CPZ15

Aggregate 16/25 533 533 533 533

Aggregate 8/16 432 432 432 432

Aggregate 4/8 144 144 144 144

Sand 0/4 660 660 660 660

Cement CEM II/A 42.5 350 332.5 315 297.5

Pozzolan (Bni saf) - 17.5 35 52.5

Water 192.5 192.5 192.5 192.5

W/L 0.55 0.55 0.55 0.55

8/20

k : Factor taking the activity of the addition is equal to zero.(table NA.3 of coefficient k, norm NF EN 206-1)



LNEC

ICD

S12


Cutting discs Lateral sealing (2 coats epoxy resin) Rectification (planes faces and parallel)

Prparation of samples : according AFREM

Disc of concrete

9/20



Saturation of the samples according to the modified procedure AFPC-AFREM, evaluation of the open porosity

Realization of vacuum dry samples for 24 hSaturation at half height of samples for 24 h Total saturation of the samples in a solution for 24 h.

10/20

Desiccator + vacuum pump



LNEC

ICD

S12


Permeability test

11/20

With :

Q: Gas flow

A: sample section area

L: thickness

: the dynamic viscosity of gasP1 and P2: absolute pressure at the gas entrance and outlet

Test realized after 28 days, drying at85 C, and stabilization of the mass.

Pressure used : 3 , 2.5 , 2 , 1.5 et 1 barsof nitrogen gas.

CEMBUREAU permeameter



Steady state : application of Nernst-Plankequation

Bton satur

Application of electric field > 12 V

(Andrade, & 1993)

Transport des ions chlorure

Evaluation of diffusion coefficient of ions Cl-

Migration Cell 12/20

Principle of migration test



LNEC

ICD

S12


TGA : Content of portlandite Ca (OH)2

The TGA were made on powders (50 mg) obtained after crushing and sieving the concrete (less than 80m). the loss mass recorded between 400 et 600 C, allowed us to evaluate content of Ca(OH)2. 13/20



Comparaison between the porosity of concretes after 28 days

Concretes OC CPZ 5 CPZ10 CPZ 15

Compressive strength at 28 days(Mpa)

34,10 38,0 40.20 39,5

Dry bulk density (kg/m3) 2237 2237 2383 2490

Porosity accessible to water (%) 16,08 13,06 13,79 13,77

Durability class(AFGC, 2004)

Very low Average Average Average

Open porosity :

14/20

The open porosity of concrete is influenced by the composition of concrete.



LNEC

ICD

S12


Permeability test : Effect of pozzolan on permeabilities

15/20

KV = 1.6 10-16 m

The CPZ have permeabilities low compared to OC. This behavioris related to the pozzolanic reaction.It is also due to the densification of porous media.

y = 0,0626x + 0,5499R = 0,9875

0,0

0,2

0,4

0,6

0,8

1,0

1,2

0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0

Ka

( 1

0-16

m)

1/Pm( 10-6 MPa-1)

CPZ10

KV = 5.5 10-17 m

y = 0,067x + 0,3863R = 0,9962

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0

Ka

(10-

16m

)

1/Pm (10-6 MPa-1)

CPZ15

KV = 3.9 10-17 m

y = 0,092x + 0,6204R = 0,9987

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

0 2 4 6 8

Ka

(10-

16m

2 )

1/Pm (10-6 Mpa-1)

CPZ5

KV = 6.2 10-17 m



Effect of pozzolan on chlorides diffusion Coefficient of diffusion of chlorides:

16/20

The reactivity of the pozzolan reinforces the effects ofhydration (decrease of pores) and prevents the penetration ofchlorides.

0

0,5

1

1,5

2

2,5

3

3,5

0 100 200 300 400

Chl

orid

e co

ncen

trat

ion

(g/l)

Time (h)

CPZ5 Dmig = 3,96 e-12

CPZ15 Dmig = 3.75 e-12

CPZ10 Dmig = 3,57 e-12

OC Dmig = 5,13 e-12



LNEC

ICD

S12


Effect of pozzolan on concrete tested Content of portlandite Ca (OH)2 :

17/20

The partial replacement of cement by pozzolan causes a decrease in portlandite of concrete .


Concrete OC CPZ 5 CPZ 10 CPZ 15

Content of Ca(OH)2 (mg/g of concrete) 3,29 2,45 1,48 1,24


Conclusions The substitution of part of cement by natural pozzolan even in smallproportions 5, 10 and 15%, has an impact on porosity of ordinaryconcrete and largely determines the transport mechanisms in concrete.In terms of sustainability, it is systematically confirmed by recording areduction of permeability coefficient and coefficient of diffusion whenpasses from ordinary concrete OC to a pozzolanic concrete CPZ.

In the long term these properties increases significantly, in terms ofkinetics on the pozzolanic activity with time.

In the concretes containing pozzolan (CPZ), the quantity of Ca(OH)2was lower, due to the dilution of cement and to the pozzolanic reaction.However, this does not necessarily mean that the potential durability alsodecreases. It depends on the permeability or diffusion coefficients, majorindicators of sustainability.

18/20



LNEC

ICD

S12


Thank you for your attention

19/20


LNEC

ICD

S12

Documents

E_2_BTouil