Sustainability Design Example 2:1.5 m High Retaining Wall

A 180 m long by 1.5 m high retaining wall was recently developed as a pilot appli­cation of RPC technology in the construction of a 90 m long monsoon drain for a housing development project in Ipoh, Malaysia (Fig. 5.7a). The design surcharge load is 10 kPa at service and 15 kPa at ultimate. For a conventional reinforced con­crete L-shaped wall, the wall will have a minimum of 150 mm thick footing and 100-150 mm thick stem (Fig. 5.7c). For the RPC solution, the L-shaped wall

Table 5.4 Material quantities and EIC for 40 m long road bridge

RPC

(m3)

Grade-60 OPC concrete (m3)

Grade-40 OPC concrete (m3)

Geopolymer

concrete

Steel

reinforcement

Conventional design (OPC concrete) Precast 40 m super-tee 0

173.26

0

0

53.17

girders

End crosshead (inc.

0

0

124.9

0

16.61

wing-wall, approach slab and diaphragm)

RC deck (total) — 1.5%

0

0

120

0

14.1

Reo.

RC Parapet — 1.0% Reo.

0

0

31.3

0

2.45

Sub-total

0.0

173.3

276.2

0.0

86.4

Mass of material used

0

407.2

649.1

0

86.4

(tonne)

Embodied energy (GJ)

0

468

627

0

2,046

CO2 (tonne)

0

84

112

0

188

GWP (tonne CO2 eq.)

0

171

250

0

379

Conventional design (Geopolymer concrete) Precast 40m super-tee 0 0

0

173.26

53.17

girders

End crosshead (inc.

0

0

0

124.9

16.61

wing-wall, approach slab and diaphragm)

RC deck (total) — 1.5%

0

0

0

120

14.1

Reo.

RC Parapet — 1.0% Reo.

0

0

0

31.3

2.45

Sub-total

0.0

0.0

0.0

449.5

86.4

Mass of material used

0

0

0

1056.3

86.4

(tonne)

Embodied energy (GJ)

0

0

0

602

2,046

CO2 (tonne)

0

0

0

143

188

GWP (tonne CO2 eq.)

0

0

0

143

379

RPC design

Precast 40m

108

0

0

0

17.1

DURA-U1750 girders

End crosshead (inc.

0

0

103

0

16.61

wing-wall, approach slab and diaphragm)

RC deck (total) — 1.5%

0

0

120

0

14.1

Reo.

RC Parapet — 1.0% Reo.

0

0

31.3

0

2.45

Sub-total

108.0

0.0

254.3

0.0

50.3

Mass of material used

257.9

0

597.6

0

55

(tonne)

Embodied energy (GJ)

835.0

0

577

0

1,304

CO2 (tonne)

115.5

0

103

0

120

GWP (tonne CO2 eq.)

274

0

230

0

220

Fig. 5.6 EIC comparison for 40 m span bridge

required only thin panels of 30-50 mm thick (Fig. 5.7d) and weighs just 260 kg/m, a factor of four times lighter than the conventional reinforced concrete solution. The RPC wall was proof loaded with back filled soil up to 1.5 m and with an addi­tional surcharge load of 25 kPa (Fig. 5.7e), 66% greater than the strength limit requirement and still it did not fail!

A comparison of the EIC results of the RPC retaining wall system against the conventional L-shaped retaining wall using Portland cement concrete and geopoly­mer concrete is given in Voo and Foster (2010) and presented in Fig. 5.8. In terms of material consumption, the RPC retaining wall consumes 76% less material than the conventional Portland cement concrete wall. In terms of the environmental indexes, the RPC wall requires less embodied energy and produces 48% less CO2 emissions. In terms of the 100-years GWP, the RPC solution provides a reduction of 35%.For the geopolymer concrete solution, again less virgin materials are consumed than for the Portland cement design, it has 25% lower embodied energy and 20% less CO2 gases are emitted. The geopolymer concrete solution has the least 100-year GWP in comparison with conventional Portland cement concrete and RPC solution.

Updated: 27 августа, 2015 — 8:47 дп