Usability s Perspectives of Recycled Aggregate Concretes (RAC) for Structural Applications

Transcription

1 Usability s Perspectives of Recycled Aggregate Concretes (RAC) for Structural Applications MARIO BASSAN, FULL PROFESSOR MARCO QUATTRONE, ENG. PHD CANDIDATE VITTORIO BASILICO, DR. ENG. Wascon 2009 Lyon 3-5 June

2 TABLE OF CONTENTS 1. OVERVIEW REGARDING C&D WASTE IN ITALY 2. FRAME OF NORMATIVE REFERENCE 3. MAKING OF RECYCLED AGGREGATES 4. TESTING ON SPECIMENS 5. TESTING ON FULL SCALE STRUCTURAL ELEMENTS 6. CONCLUSIONS 2

3 Quantitative Data OVERVIEW REGARDING C&D WASTE IN ITALY C&D Wastes produced between1999 and 2002 [Eurostat] C&DW recycling in Italy. Recycling rate = 10% [ANPAR] Qualitative Data The differences depend on different factors as climate, availability of raw materials, consolidated construction techniques etc. Typological classification of C&DW - percentages [ANPAR, 2007] 3

4 D. Lgs. n 152/2006 Environmental Code D. M. n 203/ Decree 30% D.M Construction Rules UNI EN Concrete - Specification, performance, production and conformity UNI EN Aggregates for concrete UNI 8520:2005 Aggregates for concrete - Additional provisions for the application of EN UNI EN FRAME OF NORMATIVE REFERENCE Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction Italian Construction Rules. Recycled aggregates in concrete. Source of recycling material Class of Concrete Rate of use Demolition of building (debris) = C8/10 Up to 100% Demolition of concrete or reinforced concrete Reuse in certified precast concrete industries any class of concrete Reuse in certified precast concrete industries class of concrete > C45/55 C30/37 Up to 30% C20/25 Up to 60% C45/55 Up to 15% Same class of original concrete Up to 5% 4

5 MAKING OF THE RECYCLED AGGREGATE Production waste Sorting by vibrating screen Heaps of recycled aggregates Crushing by grab Primary Crushing by jaw crusher Fraction used to make the concrete 5

6 CHARACTERIZATION OF THE RECYCLED AGGREGATE Table. Classification of recycled aggregate s fraction Precast Plant Description Fraction Generale Prefabbricati Prestressed Beam San Salvo CH R ck =55 Mpa A Generale Prefabbricati Column San Salvo -CH R ck =50 Mpa B Generale Prefabbricati Hollow core slab (Spiroll) San Salvo -CH R ck =55 Mpa C Precompressi Centro Nord - Cerano(NO) Crushed concrete D Generale Prefabbricati Bettona(PG) Crushed concrete E RDB -Monticelli (PC) Hollow core slab F RDB -Montepulciano (SI) Column R ck =50 MPa G RDB - Montepulciano (SI) Hollow core slab R ck =55 MPa H RDB - Montepulciano (SI) Prestressed elements R ck =55 MPa I Table. Physical properties of the recycled aggregate Fraction Relative Humidity (%) Water Absorption (%) Density (g/cm 3 ) Dry Density (g/cm 3 ) A 5,92 8,34 2,50 2,31 B 6,21 9,21 2,38 2,16 C 4,25 7,70 2,47 2,25 D 2,84 5,56 2,58 2,34 E 3,35 7,26 2,47 2,24 F 3,17 7,63 2,48 2,22 G 3,82 7,86 2,37 2,18 H 3,57 8,34 2,41 2,21 I 6,50 9,97 2,32 2,07 Granulometry distribution of the fractions listed in the table 6

7 CHARACTERIZATION OF THE RECYCLED AGGREGATE Water absorption for natural aggregates and recycled ones Variation of the granulometry after different mixing times 7

8 Group I - Making the specimens TESTING ON SPECIMENS Group II - Making the specimens 4 groups with 6 cubic specimens for every group 4 groups with 5 cubic specimens and 6 cylindrical specimens for every group Specimens after the casting Specimens after the casting Mix design of the concretes quantities for 1 m 3 of mix 8

9 Group I - Results TESTING ON SPECIMENS Compression strength - sharp remarks Compression strength (mean value) and slump Compression strength Linear fit of mean value Compression strength max, mean and min values 9

10 Group I - Statistical analysis TESTING ON SPECIMENS Summary for R100 W/C 0,45 Summary for R100 W/C 0,50 Summary for R100 W/C 0,55 Summary for R100 W/C 0,60 10

11 Group II - Results TESTING ON SPECIMENS Compression strength - sharp remarks Compression strength (mean value) and slump Compression strength Polynomial fit of mean value Compression strength max, mean and min values 11

12 Group II - Statistical analysis TESTING ON SPECIMENS Summary for R100 W/C 0,45 Summary for R100 W/C 0,50 Summary for R100 W/C 0,55 Summary for R100 W/C 0,60 12

13 Group II - E modulus results TESTING ON SPECIMENS Cylindrical specimen during the test Elastic Modulus vs W/C ratio Group R100 Experimental quantities Calculated quantities W/C Ratio f cm [MPa] E cm [MPa] E cm [MPa] Δ% 0,50 49, ,77 Cylindrical specimen after the test 0,55 48, ,38 0,60 38, ,25 13

14 MAKING OF FULL SCALE STRUCTURAL ELEMENTS Production of the hollow core slabs Ordinary concrete slabs RAC s slabs with 20% of recycled aggregate (on the left) and with 30% (on the right) 14

15 TESTING ON FULL SCALE STRUCTURAL ELEMENTS Equipment to vibrate the specimens Specimens made during the casting of slabs Mix design of the concretes quantities for 1 m 3 of mix Compression strength of the used concretes 15

16 TESTING ON FULL SCALE STRUCTURAL ELEMENTS Static scheme for the bending test UNI EN Precast concrete products - Hollow core slabs Cross section Diagram of the bending moment Diagram of the shear Hollow core slab on the bench 16

17 TESTING ON FULL SCALE STRUCTURAL ELEMENTS Hollow core slab during the bending test Cracking of the slabs Appearance of the first crack (on the top) Crack at the breaking (on the bottom) 17

18 TESTING ON FULL SCALE STRUCTURAL ELEMENTS - RESULTS Breaking load for bending Load vs displacement at midpoint Breaking load - mean values Load vs displacement at midpoint mean values 18

19 TESTING ON FULL SCALE STRUCTURAL ELEMENTS Static scheme for the shear test UNI EN Precast concrete products - Hollow core slabs Load s application point equals to 2,5 h cross section Diagram of the shear Diagram of the bending moment Slab during the shear test 19

20 TESTING ON FULL SCALE STRUCTURAL ELEMENTS - RESULTS Shear test s modality Breaking load for shear sharp remarks Breaking load for shear mean value Variation in % for breaking load for shear 20

21 CONCLUSIONS To achieve a good RAC is necessary a good quality recycled aggregate; the quality is linked to the homogeneity of the debris Passed the 30% mark of coarse recycled aggregate substitution, the behaviour of RAC and ordinary concrete, at fresh and hard state, starts to be different The E modulus variations, experimentally determined for RAC with 100% of coarse recycled aggregates, are aligned with literature s data and with the recommendations of many Countries The use of 100% of recycled aggregates from precast production waste allows to make high-strength recycled aggregate concrete This kind of RACs can be used for the ordinary applications Regarding the structural elements, it possible to state that no differences in behaviour between ordinary and recycled concrete have been noticed 21

22 ACKNOWLEDGMENTS The financial support of ASSOBETON (Italian Association of Concrete Industries) through Project Ulisse. The technical support of Precompressi Centro Nord (Gruppo Centro Nord SpA) and RDB SpA. 22