Compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete incorporating class-F fly ash

Abstract

The effects of fly ash on the compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete were investigated. Two series of concrete mixtures were prepared. The concrete mixtures in series I had a water-to-binder ratio and a cement content of 0.55 and 410 kg/m³, respectively. The concrete mixtures in series II had a water-to-binder ratio and a cement content of 0.45 and 400 kg/m³ respectively. Recycled aggregate was used as 20%, 50%, and 100% replacements of natural coarse aggregate in the concrete mixtures in both series. In addition, fly ash was used as 0%, 25% and 35% by weight replacements of cement. The results show that the compressive strengths of the concrete decreased as the recycled aggregate and the fly ash contents increased. The total porosity and average porosity diameter of the concrete increased as the recycled aggregate content increased. Furthermore, an increase in the recycled aggregate content decreased the resistance to chloride ion penetration. Nevertheless, the replacement of cement by 25% fly ash improved the resistance to chloride ion penetration and pore diameters and reduced the total porosity of the recycled aggregate concrete.

Keywords

durability properties / recycled aggregate concrete / fly ash

References

[1] Poon CS, Azhar Salman. An Investigation on the Scope and AppliCations of Recycled Aggregates in the Hong Kong Construction Industry[J]. One day Annual Seminar on Environmentally Friendly Structures, 2001, 5: 45-54.

[2] Collins RJ. Dhir RK, Henderson NA, Limbachiya MC. Recycled Aggregates-application and Control Issues [C]. Proceeding of the International Conference on the Use of Recycled Concrete Aggregates, 1998 UK: Thomas Telford. 169-175.

[3] Poon CS, Kou SC, Lam L. Use of Recycled Aggregates in Moulded Concrete Bricks and Blocks[J]. Construction and Building Materials, 2002, 16: 281-289.

[4] Wainweight PJ, Trevorrow A, Yu Y, Wang Y. Lauritzen EK. Modifying the Performance of Concrete Made with Coarse and Fine Recycled Concrete Aggregates[M]. Guidelines for Demolition and Reuse of Concrete and Masonry, 1993 Denmark: E & FN SPON. 319-330.

[5] Topcu IB, Sengel S. Properties of Concretes Produced with Waste Concrete Aggregate[J]. Cement and Concrete Research, 2004, 34: 1307-1312.

[6] Xiao JZ, Li JB, Zhang Ch. Mechanical Properties of Recycled Aggregate Concrete under Uniaxial Loading[J]. Cement and Concrete Research, 2005, 35: 1187-1194.

[7] Dhir RK, Limbachiya MC, Leelawat T. Suitability of Recycled Concrete Aggregate for Use BS 5328 Designated Mixes [J]. Proc. Instn Civ. Engrs & Bldgs, 1999, 134(8): 257-274.

[8] Uchikawa H, Hanehara S. Dhr RK, Dyer TD. Recycling of Concrete Waste. Concrete for Environment Enhancement and Protection, 1996 London: E&FN SPON. 163-172.

[9] Gomez-Soberon JM V. Porosity of Recycled Concrete with Substitution of Recycled Concrete Aggregates an Experimental Study[J]. Cement and Concrete Research, 2002, 32: 1301-1311.

[10] Mueller A, Winkler A. Dhir KR, Henderson NA, Limbachiya MC. Characteristics of Processed Concrete Rubble. Uses of Recycled Concrete Aggregate. Sustainable Construction, 1998 London: Tomas Telford. 1109-1119.

[11] Wainwright PJ, Cabrera JG. Goumans J J K M, Van Der Sloot H A, Aalbers T G. Use of Demolition Concrete to Produce Durable Structural Concrete. Environmental Aspects of Construction with Waste Materials, 1994 The Netherlands: Elsevier. 553-562.

[12] Zhang B. Relationship between Pore Structure and Mechanical Properties of Ordinary Concrete Under Bending Fatigue[J]. Cement and Concrete Research, 1998, 28(5): 699-711.

[13] British Standard Institute, BS 812: Part 103. 1.Methods for Determination of Particle Size Distribution[S], 1985

[14] BS 1881 Part 116.Testing Concrete Part 116: Method for Determination of Compressive Strength of Concrete Cubes[S]. British Standards Institution, 1983

[15] BS 7591 Part 1.Method of Evaluation by Mercury Porosimetry [S]. British Standards Institution, 1992

[16] Leng F, Feng N, Lu X. An Experimental Study on the Properties of Resistance to Diffusion of Chloride Ions of Fly Ash and Blast Furnace Slag Concrete[J]. Cement and Concrete Research, 2000, 30(6): 989-992.

[17] Mindess S, Young JF and Darwin D.Concrete[M]. 2nd edition, Prentice Hall, 2003