Lightweight Self-Compacting Concrete (L-SCC): Systematic approach and case study

Transcription

1 Lightweight Self-Compacting Concrete (L-SCC): Systematic approach and case study 5th International RILEM Symposium on Self-Compacting Concrete (SCC2007) 3-5 september 2007, Ghent Cauberg Niki, BBRI Kestemont Xavier, Argex

2 Why lightweight SCC? Reduction in dead load Transport weight Objectives research Mix design method for precast plants Flexibility: basic materials compressive strength and density Density classes (D-class) Requested compressive strength class (LC-class) D 1.6 LC 25/28 (1400 < oven-dry density < 1600 kg/m³) LC 30/33 LC 35/38 D 1.8 LC 30/33 (1600 < oven dry density < 1800 kg/m³) LC 35/38 LC 40/44 D 2.0 LC 45/50 (1800 < oven dry density < 2000 kg/m³) LC 50/55 2/10

3 Approach (Brouwers) Mix Design & Materials Chinese Method Modified Andersen and Andreassen gradings No fixed ratios paste/sand/gravel Sand = 40% Compressive strength Cement SCC = 100% = Mortar Powder =50% + Aggr. Gravel Water/Adm Air PSD [%] Filler Water/Adm Mix type D1.6 Modified A&A Fuller Water demand, larger relative flow Particle size [µm] 3/10

4 Approach (Brouwers) Mix Design & Materials No fixed ratios paste/sand/gravel Less cement/filler, more (fine) sand Input PSD: optimal packing, robust mixtures, good rheology, more sand, cheaper PSD [%] CEM I 52.5 R Limestone filler Sand 0/2 Sand 0/5 Lightweight sand (Argex AR 0/4 650) Lightweight aggregate (Argex AM 4/8 650) Lightweight aggregate (Argex AM 4/8 750) Particle Size [µm] 4/10

5 Lightweight aggregates Mix Design & Materials expanded clay, porous, cellular structure 0/4 mm (650) and 4/8 mm (650 or 750) water absorption! -> prewetting % Waterabsorption [%] Water absorption after 5' [%] 10.0% 8.0% 6.0% 4.0% 2.0% Time [minutes] 0.0% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% Initial humidity of the Lightweight Aggregates, before testing [%] 5/10

6 Typical mix design 3 classes Mix Design & Materials Mixture design [kg/m³] LD 1.6 D 1.8 D 2.0 LC 30/33 LC 35/38 LC 45/50 Cement (CEM 1 (52.5 R LA) Limestone filler Sand 0/ Sand 0/ Lightweight aggr. 0/ Lightweight aggr. 4/ Lightweight aggr. 4/ Water SP VMA Theoretical density [kg/m³] W/C [-] W/P [-] SP and VMA dosage: stability of the mixture (water variations) inhibits floating of the lightweight aggregates («inverse segregation») surface finish 6/10

7 Typical test results 3 classes Characteristics fresh concrete LD 1.6 D 1.8 D 2.0 Slump flow [mm] T50 mm [s] Funnel time [s] J-Ring (slump flow) [mm] with blocking step (h1/h2) L-Box (ratio)* Air-ratio [%] Fresh density [kg/m³] Characteristics hardened concrete f_cm_cube 1d [N/mm³] f_cm_cube 7d [N/mm³] f_cm_cube 28d [N/mm³] f_ck_cube 28d [N/mm²] Resulting LC-class LC 30/33 LC 35/38 LC 45/50 Oven-dry density 28d [kg/m³] E-modulus [N/mm²] ~ Target value ~> Wide range ~ Eurocode 2 Shrinkage: 300 to 400 µm/m at 2 months, measurements ongoing 7/10

8 Theory -> empirical curves Upper limit Basic curve D 1.6 Lower limit PSD [%] D A&A 0.23 < q < 0.5 Particle size [µm] D21 D42 D43 D44 D45 D46 D47 D48 D49 D50 D51 D52 D56 D57 D58 D59 D60 D61 D62 A&A1 A&A2 A&A3 PSD [%] Particle size [mm] 8/10

9 Case study: first industrial tests Large-scale tests (precast plant) housing elements ( mm³) Mixture design [kg/m³] Cement 354 Limestone 225 W/C [-] 0.59 Characteristics fresh concrete Slump flow [mm] 675 Funnel time [s] 13 Fresh density [kg/m³] 2059 Characteristics hardened concrete f_cm_cube 28d [N/mm³] 51 Oven-dry density 28d [kg/m³] /10

10 Mix design method s Chinese method, modifications by Brouwers and empirical adaptations Including effect of PSD s Optimal packing, robust mixtures Resulting mixtures Slump flow , funnel time 5 25 s Density range, oven-dry: kg/m³ Compressive strenght: LC 20/22 LC 50/55 Implementation in precast plants: more industrial tests are planned Surface finish: some work to be done 10/10

11 Thank you very much for your attention! Questions?

12

13