4.7.5 Non-dispersion Concrete in Water (NDC)

• Introduction

• Composites of NDC

• Properties of NDC

Introduction

• NDC is also called casting concrete in water.

• It is a new kind of concrete, cast in water and unlike ordinary concrete in which aggregate and cement paste will be separated if they react in water.

• Instrument sketch map of connecting conduct construction

Introduction

Fig.4.7.9 Instrument sketch map of connecting conduct construction

Composites of NDC

• The main materials are cement, sand and stone, and some other admixtures (water reducing admixture)

• Cement: its strength grade is 42.5MPa at least.• Aggregate• Coarse aggregate.• Preferably scree; Continous gradation• Fine aggregate Preferably medium sand from M

x-=2.6～ 3.1 of fine modulus

• (NDCA) NDCA is the key material in NDC, whose main composites are water soluble ion and material with high specific surface area, whose main functions are strengthening cohesion and packing ability

• Packing fine particles • Other admixtures• High efficiency water reducing, accelerator

Composites of NDC

Properties of fresh NDCGood anti-dispersionGood mobility and packing abilityCertain retardation ability

Properties of hardened NDCNDC strength

Its quality and mixture quantity will influence the strength of NDC

Properties of NDC

Properties of NDCInfluences on NDC compressive strength by C/W 、 NDCA are

shown in Fig.4.7.10 and Fig.4.7.11.

Fig.4.7.10 Influences on NDC compressive strength by C/W

Fig.4.7.11. Influences on NDC compressive strength by NDCA

NDC permeability and resistance to impact are shown in Tab.4.7.7

Properties of NDC

kinds of concretepermanent in

1.2MPa compression

Weight/g

ordinary concrete

Total permeable within 5min

20679

NDC with NNDC-2

Average permeable height of 12.7cm in 24h

60.0

Tab.4.7.7 NDC permeability and resistance to impact

Properties of NDC

• Frost resistance– NDC frost resistance is not as good as

ordinary concrete• Dry shrinkage and moisture expansion of NDC

Compared with ordinary concrete.– NDC has good performance in water

retentivity and bleeding.– Its dry shrinkage is larger than ordinary

concrete but moisture expansion is smaller.