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2016SummerShotcreteEMag

Goin’ Underground Table 2: Primary Shotcrete Mixture Design P1 Content Type Quantity, kg/m3 (lb/yd3) Ratio/dosage* Cement CEM I 52.5 N 420 (708) — Water — 173 (292) 0.41 Aggregate Limestone (0/4) 590 (995) — Aggregate Marine Sand (0/4) 590 (9950 — Aggregate Limestone (2/6) 505 (851) — Microsilica slurry EMSAC 500 S 52 (88) 12.38% Retarder Pantarhol 85 (VZ) 6 (10) 1.43% Superplasticizer Pantarhit T100CR (FM) 4.8 (8) 1.14% Accelerator Gecederal F 2000 HP Added at spray 5.50% (averaged) Steel fibers Steel HE 55/35 35 (59) — *Dosage in percentage (%) of cement weight basis lining section in the Eastbound Rail Tunnel – West (EBRT-W) pilot tunnel. EBRT-W Pilot Tunnel Primary Shotcrete Lining Section Five shotcrete panels were tested using a needle penetrometer and stud-driving as described in Table 1. Concurrently, thermal imaging was performed. Figure 4 shows real time strength (dashed lines) and temperature (dotted lines) histories. The strengths of up to 14.5 psi (1.0 MPa) were determined using the needle penetrometer while the rest were determined using standard- method green cartridge stud-driving using Hilti DX 450 SCT as described in its operating instructions (Hilti, 2009). It can be seen that the panels have achieved strengths of around 2180 psi (15.0 MPa) at the age of 12 hours and have approached the upper limit of the stud-driving test. Therefore, further mechanical testing was not useful. In the case of the temperature histories, a typical temperature variation pattern was observed with initial lowering of temperature, approaching 84°F (29°C), during the first hour after spraying and increasing thereafter, peaking at more than 88°F Shotcrete • Summer 2016 51


2016SummerShotcreteEMag
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