Permeability properties of fine recycled aggregate concrete Luís Evangelista 1,3 , Jorge de Brito 1,4 1 University of Stavanger, Norway 2 Instituto Superior Técnico, Portugal 3 CERIS – ICIST, Instituto Superior Técnico, Portigal
TABLE OF CONTENTS 1. INTRODUCTION 2. STATE-OF-THE-ART 2. EXPERIMENTAL PROGRAM 3. POROSITY OF FRAC 3.1. Water absorption by immersion 3.2. Capillary water absorption 3.3. Carbonation 3.4. Chloride penetration resistance 3.5. Electrical resistivity 4. CONCLUDING REMARKS
I NTRODUCTION World population growth and mass exodus to urban areas keeps the construction industry ever increasing. It is estimated that 10 billion of m 3 of concreet EUA: 130 Mt/y EU: 380 - 850 Mt/y are produced each year. China: 325 - 345 Mt/y The natural aggregates consumption is between 17 By the year 2020, 70% of CDW roduced and 37 x10 3 Mt/year in EU has to be reintroduced in the industrial cycle.
I NTRODUCTION One way of solving both problems is by using recycled aggregates in concrete production. Currently, the trend is AFR CRA FRA have very high water absorption and high levels of contaminant particles. Research objective To evaluate the performance of FRAC made with different replacement ratios, so that the existing trend may change in the near future
S TATE - OF - THE - ART Initial studies on FRAC showed that the environmental • benefits were outweighted by the poorest performance. As a result, the existing standards ban or strongly limit • the use of FRA in concrete production From the beginning of the XXI century, new studies seem to contradict the • common knowledge that the use of FRA is very harmful to concrete performance, if FRA are treated as they should. Durability wise, FRAC show considerably poorer behavior than conventional • concrete. Some previous results showed performance losses above 100%, due to the higher porosity of FRA.
E XPERIMENTAL PROGRAM CEM I 42.5R cement, 2 natural CNA and 2 FNA were used. • The FRA used were produced in laboratory, in • order to control all properties. The effective water / cement ratio has been • corrected in order to include water to be absorbed by the FRA. 10, 30, 50 and 100% replacement ratios (%V) • were used. D URABILITY TESTS (5 TESTS ) 1. Immersion (28 and 120 d) 2. Capillarity (28 and 120 d) 3. Carbonation (28 and 120 d) 4. Chloride penetration (28 and 120 d) 5. Electrical resistivity (28 and 120 d)
P OROSITY OF FRAC Water bsorption by immersion 18.00 18.00 Water absorption by immersion • Absorção de água por imersão - A im Absorção de água por imersão - A im 17.00 17.00 presented a linear increase with the 16.00 16.00 replacement ratio. There was an 15.00 15.00 increase of about 20% compared to the (%) (%) 28 dias 28 dias 14.00 14.00 120 dias 120 dias reference concrete, regardless of the 13.00 13.00 test age. 12.00 12.00 11.00 11.00 10.00 10.00 The higher porosity and the higher w/c • 0 0 20 20 40 40 60 60 80 80 100 100 Taxa de substituição - (%) Taxa de substituição - (%) ratio are the main causes for this. 7.0 7.0 BR - 28d BR - 28d B10R - 28d B10R - 28d Capilarity B30R - 28d B30R - 28d B50R - 28d B50R - 28d Absorção capilar (kg/m 2 ) Absorção capilar (kg/m 2 ) 6.0 6.0 B100R - 28d B100R - 28d 5.0 5.0 Capillary water absorption increases • 4.0 4.0 significantly with the replacement ratio. 3.0 3.0 2.0 2.0 The sorptivity coefficients increase 185% • 1.0 1.0 for 100% replacement ratio. Up to 50%, 0.0 0.0 FRAC can still be considered of high 0 0 24 24 48 48 72 72 Tempo - t (horas) Tempo - t (horas) quality.
P OROSITY OF FRAC Carbonation 25.0 25.0 Carbobation depth increase with the BR BR • Prof. de carbonatação - d (mm) Prof. de carbonatação - d (mm) B10R B10R replacement ratio, for any given age. 20.0 20.0 B30R B30R B50R B50R B100R B100R 15.0 15.0 Carbonation coefficient increases about • 10.0 10.0 60% for C100R, compared to the reference concrete. 5.0 5.0 0.0 0.0 0 0 28 28 56 56 84 84 112 112 140 140 168 168 196 196 Tempo - t (dias) Tempo - t (dias) Chloride penetration 30 30 30 30 Coeficiente de difusão de cloretos - Coeficiente de difusão de cloretos - Coeficiente de difusão de cloretos - Coeficiente de difusão de cloretos - Chloride penetration increases linearly • D nssm = 1.0676.S + 9.2007 D nssm = 1.0676.S + 9.2007 25 25 R² = 0.8677 R² = 0.8677 with the repacement ratio, with a 25 25 D nssm ( x 10 -12 m 2 /s) D nssm ( x 10 -12 m 2 /s) D nssm (x10 -12 m 2 /s) D nssm (x10 -12 m 2 /s) 20 20 maximum gain of 60%, for C100R. 20 20 15 15 28 dias 28 dias 10 10 There is also a good correlation between 120 dias 120 dias • 15 15 the chloride coefficient and the 5 5 capillary water absorption, as well as 10 10 0 0 5 5 0 0 20 20 10 10 40 40 60 60 15 15 80 80 100 100 20 20 with the porosuity measured through Coeficiente de absorção capilar - S ( x 10 -2 mm/min 0.5 ) Coeficiente de absorção capilar - S ( x 10 -2 mm/min 0.5 ) Taxa de substituição - r (%) Taxa de substituição - r (%) MIP .
Apresentação de resultados P OROSITY OF FRAC Electrical resistivity 80 80 Resistividade eléctrica - m ( .m) Resistividade eléctrica - m ( .m) 75 75 The Electrical resistivity of concrete is • 28 dias 28 dias 70 70 reduced with the presence of FRA, up to 120 dias 120 dias 65 65 a maximum variation of 24% 60 60 55 55 These results are directly inflenced by 50 50 • 45 45 the higher w/c ratio, and the higher 40 40 porosity of the aggregates. 0 0 20 20 40 40 60 60 80 80 100 100 Taxa de substituição - r (%) Taxa de substituição - r (%) It is possible os establish a good • 30 30 Coeficiente de difusão de cloretos - Coeficiente de difusão de cloretos - correlation model between the 28 Dias 28 Dias 25 25 120 dias 120 dias electrical resistivity of FRAC and their D nssm (x10 -12 m 2 /s) D nssm (x10 -12 m 2 /s) Regressão Regressão chloride penetration resistance, 20 20 allowing to determine the corrosion potencial faster. 15 15 �1,917 �1,917 D nssm � 51009. ρ � D nssm � 51009. ρ � 10 10 40 40 45 45 50 50 55 55 60 60 65 65 70 70 75 75 80 80 Resistividade eléctrica - m ( .m) Resistividade eléctrica - m ( .m)
C ONCLUDING REMARKS C10R C30R C50R C100R = = Immersion Capillarity Carbonatação Chloride penetration = = resistance = = Electrical resistivity = = = Betão armado (F máx ) “=“ ≤ 10% “---” > 60% 10%< “-” ≤ 30% 30% < “--” ≤ 60%
C ONCLUDING REMARKS B10R B30R B50R B100R = = - - Immersion - Capillarity Carbonatação Chloride penetration = = - resistance = = - - Electrical resistivity = = = - Betão armado (F máx ) “=“ ≤ 10% “---” > 60% 10%< “-” ≤ 30% 30% < “--” ≤ 60%
C ONCLUDING REMARKS B10R B30R B50R B100R = = - - Immersion - -- Capillarity -- -- -- -- Carbonatação Chloride penetration = = - -- resistance = = - - Electrical resistivity = = = - Betão armado (F máx ) “=“ ≤ 10% “---” > 60% 10%< “-” ≤ 30% 30% < “--” ≤ 60%
C ONCLUDING REMARKS B10R B30R B50R B100R = = - - Immersion - -- --- --- Capillarity + -- -- -- -- Carbonatação Chloride penetration = = - -- resistance = = - - Electrical resistivity = = = - Betão armado (F máx ) “=“ ≤ 10% “---” > 60% 10%< “-” ≤ 30% 30% < “--” ≤ 60%
C ONCLUDING REMARKS The permeability properties for FRAC are clearly influenced by the presence and quantity of FRA. This is in direct relation with the inclusion of materials that are more porous and allow the transport of fluids through them. - Water absorption by capillarity is influenced by the presence of FRA and by the water/cement ratio; the age does not seem to affect the performance beyond 28 days; - Capillary absorption is follows the same trend, even though the age effects are noticeable; - Carbonation resistance has a major decrease with the presence of FRA; - Chloride penetration presents a good correlation with capillary absorption; - Electrical resistivity can be established based on the chloride diffusion.
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