1st international conference on concrete sustainability DUBAI, December 13-14, 2010 A SUSTAINABLE CONCRETE WITH NATURAL POZZOLAN NATURAL POZZOLAN KHARCHI Fattoum Professor, Research Director Houari Boumediene University (USTHB) Civil Engineering Faculty, Built Environment Res.Lab.(LBE) BP 32 Bab Ezzouar, 16111Alger, Algeria E-mail: kharchifcong@yahoo.fr g@y Tel & Fax: +213 24 72 24, +213 21 24 79 14 Mobile: +213 555 41 60 43-Website: www.lbe.usthb.dz 2010 International Concrete Sustainability Conference, Dubai, UAE 1
Deterioration of the concrete Physical Chimical Structural loading Thermal shock Swelling Shrinkage Carbonation Abrasion Alk li Alkali - aggregate t Leaching … Ions chlorine Attack sulfatic Attack ... Expansion, Cracking, Alteration 2010 International Concrete Sustainability Conference, Dubai, UAE 2
Solutions: Supplementary cement Solutions: Supplementary cement materials: SF materials: SF FAsh materials: SF, materials: SF, FAsh FAsh FAsh ….. ….. Algeria: exist: laitier Algeria: exist: laitier (washes of (washes of siderurgique industry) and natural siderurgique industry) and natural g q g q y) y) pozzolan, pozzolan, 2010 International Concrete Sustainability Conference, Dubai, UAE 3
Effect of natural pozzolan on concrete Effect of natural pozzolan on concrete resistance to sulfate attacks resistance to sulfate attacks resistance to sulfate attacks. resistance to sulfate attacks. Pozzolan is from the region of BENI SAF Pozzolan is from the region of BENI SAF in the west of Algeria. in the west of Algeria. g The conference is organized in two parts The conference is organized in two parts 1- - Attacks mechanisms + effects on durability in Attacks mechanisms + effects on durability in general. general. 2- - Experimental program and results Experimental program and results 2010 International Concrete Sustainability Conference, Dubai, UAE 4
Sulfate attack is a chemical aggression. Sulfate attack is a chemical aggression. Water presence Water presence Water presence Water presence Permeability concrete Permeability concrete Sulfate ions SO Sulfate ions SO 4 is associated to different Sulfate ions SO is associated to different Sulfate ions SO is associated to different is associated to different cations cations depending of environment (soil, depending of environment (soil, sea water…etc) sea water…etc) ) 2010 International Concrete Sustainability Conference, Dubai, UAE 5
� SOILS SOILS gypsum ( gypsum (sulphate sulphate de calcium). de calcium). gypsum not very soluble in water gypsum not very soluble in water -------- -------- slow attack slow attack � SEA WATER SEA, UNDERGROUND WATER SEA WATER SEA, UNDERGROUND WATER Sulfates de magnesium Sulfates de magnesium (MgSO4) (MgSO4) � ----------- ----------- the most the most agressive the most the most agressive agressive because very soluble in agressive because very soluble in because very soluble in because very soluble in water , also (K2SO4 water , also (K2SO4 - - Na2SO4). Na2SO4). � AGRICULTURAL SOILS AGRICULTURAL SOILS ammonium sulfates ammonium sulfates (NH4)2SO4 (NH4)2SO4 also K2SO4, MgSO4) also K2SO4, MgSO4) � CANALISATIONS CANALISATIONS: H CANALISATIONS CANALISATIONS : H 2 H S ( 2 S (gas) react with aerial bacteria and S ( S (gas) react with aerial bacteria and ) ) t t ith ith i l b i l b t t i i d d product sulphates ion SO 4 product sulphates ion SO 4 2010 International Concrete Sustainability Conference, Dubai, UAE 6
sulphates attacks External Internal Gypseous or sulfurous Granulats soils Addition of gypsum to clinker gyp Under ground water and sea water g Hydration reaction energy in massive Industrial pollution concrete Bacteriological transformation Destructive expansion Destructive expansion 2010 International Concrete Sustainability Conference, Dubai, UAE 7
sulfates Attack Characteristics of the concrete Environement Process of assessment of the aggression P f t f th i Transfer of the ions sulphate Chemical reactions between the controlled by the permeability and t ll d b th bilit d components of the cement and the t f th t d th 2 - ions diffusity of the material. SO 4 Expansion phenomenon Expansion phenomenon Apparition of new crystalline phases Apparition of new crystalline phases 2010 International Concrete Sustainability Conference, Dubai, UAE 8
Schematic presentation of the attack to the sulphates Pores, capillary High E/ C, mauvaise cure Water Microcracking (structural loading,heat and cold, drying and EAS watering cycles ) High Sulphate Permeability Environement External External AES : External Attack Sulphate 2010 International Concrete Sustainability Conference, Dubai, UAE 9
Chemical interactions I) Secondary gypsum formation Ionic substitution between the portlandite and the sulphates case of the sulphate of Na 2 SO 4 sodium Ca (OH) 2 + Na 2 SO 4 + 2H 2 O CaSO 4 .2H 2 O + 2NaOH ( Secondary gypsum , expansion) II) Secondary ettringite formation II) S d tt i it f ti Starting from the residual anhydrous C3A C 3 A + 3CaSO 4 .2H 2 O + 26H 2 O C 3 A.3CaSO 4 .32H 2 O (Ettringite, expansion) from hydrated aluminates (Monosulfoaluminates) C 3 A.Ca (OH) 2 .xH 2 O + 2Ca(OH) 2 + 3SO 4 + 11H 2 O C 3 A.3CaSO 4 .32H 2 O (Ettringite expansion) (Ettringite, expansion) 2010 International Concrete Sustainability Conference, Dubai, UAE 10
Case of the magnesium sulphate MgSO 4 1 Formation of expansive product 1.Formation of expansive product weak solubility ) Ca (OH) 2 + MgSO 4 CaSO 4 + Mg(OH) 2 (Brucite, C 3 A + 3CaSO 4 .2H 2 O + 26H 2 O C 3 A.3CaSO 4 .32H 2 O ( Ettringite , expansion ) C A + 3CaSO 2H O + 26H O C A 3CaSO 32H O ( Ettringite expansion ) Substitution of the Ca2+s ions by the Mg2+s ions in the C-S-H C S H + MgSO C-S-H + MgSO 4 CaSO CaSO 4 .2H 2 O + (C , M)-S-H ( weakly cohesive ) 2H O + (C M) S H ( weakly cohesive ) Consequences are an expansion et cracking due to secondary ettringite and a resistance loss due to the consumption of CSH. The silicate of hydrated magnesium (Mg-S-H) formed doesn't have any binding properties, and therefore the hydrated becomes soft and disjointed 2010 International Concrete Sustainability Conference, Dubai, UAE 11
Primary Primary ettringite ettringite = formed in = formed in begining begining cement hydration . cement hydration . Not Not nocive nocive but indispensable to regulate but indispensable to regulate cement p p g g cement prise prise. p . Secondary ettringite Secondary ettringite =Expansive, =Expansive, - molar volume is to 3 à 8 higher than primary ettringite molar volume is to 3 à 8 higher than primary ettringite molar volume is to 3 à 8 higher than primary ettringite molar volume is to 3 à 8 higher than primary ettringite molar volume. molar volume. - crystallize in hard concrete crystallize in hard concrete 2010 International Concrete Sustainability Conference, Dubai, UAE 12
Experimental p programm 2010 International Concrete Sustainability Conference, Dubai, UAE 13
The study was conducted on three types The study was conducted on three types The study was conducted on three types The study was conducted on three types of concrete: an ordinary concrete BO BO , a of concrete: an ordinary concrete , a high performance concretes BHP high performance concretes g g p p BHP (with ( (with superplastizer superplastizer) and a concrete with ) and a concrete with pozzolan BHPZ pozzolan BHPZ . Following parameters . Following parameters were studied: were studied: t di d t di d Expansion, shrinkage, chloride Expansion, shrinkage, chloride penetration and strength of concrete penetration and strength of concrete penetration and strength, of concrete penetration and strength, of concrete specimens immersed in the solution specimens immersed in the solution containing 5% NH4SO4 ammonium containing 5% NH4SO4 ammonium g sulphate sulphate. . 2010 International Concrete Sustainability Conference, Dubai, UAE 14
MATERI ALS Cem ent : CEMI I / A 4 2 .5 Surface spécifique ….3400-3650 cm 2 /g minéralogy minéralogy Chem ical com position Composition Al 2 O Na 2 C 4 A CaO SiO 2 FeO 3 MgO RI SO 3 PAF K 2 O CaOl C 3 S ßC 2 S C 3 A O F 3 24.3 59.8 16.9 11.6 60.88 5.56 3.83 1.08 3.30 0.27 2.37 0.23 0.48 0.71 6.56 5 5 3 3 4 4 4 4 Tab1 : Chem ical and m inéralogy com position of the cem ent Sa d Sand : Rolled siliceous sand of 3,5 mm maximum aggregate size. o ed s ceous sa d o 3,5 a u agg egate s e Density = 2, 60 Aggregates : class 3 / 8 and 8 / 1 6 of silico-chaky origin ( carrer) Aggregates : class 3 / 8 and 8 / 1 6 of silico chaky origin ( carrer) Density = 2, 50 2010 International Concrete Sustainability Conference, Dubai, UAE 15
I .4 ) Natural pozzolan of volcanic origin. � Density = 2, 65 � Specific surface = 9500 cm 2 /g L’indice d’activité de la pouzzolane utilisée a été déterminé selon la norme EN 450 � i = Rc (MZ25) / Rc (MZ0) = 0.82 la pouzzolane étudiée est donc réactive Elém ent Fe 2 O SiO 2 Al 2 O 3 CaO MgO SO 3 K 2 O Na 2 O P.A.F R.I s 3 % 44,95 16,91 9,47 14,59 3,76 0,20 1,35 1,34 4,30 0,56 Tab2 : Chem ical com position of the pozzolan 2010 International Concrete Sustainability Conference, Dubai, UAE 16
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