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Home arrow Engineering arrow Creep Behaviour in Cracked Sections of Fibre Reinforced Concrete: Proceedings of the International RILEM Workshop FRC-CREEP 2016

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Concrete Reinforcements

Six different fibres and a welded wire mesh were used to reinforce the sprayed concrete elements. The fibre dosage was proposed by each supplier, in compliance with the mixes commonly used in concrete for underground support (see Table 2). The welded mesh is the one used by the French National Railway Company in operations to reinforce existing tunnels. The reinforcement characteristics of the Reinforced Sprayed Concretes (RSC) were as follows.

Application

The spraying was carried out by a single operator using a Meyco Potenza robot. The dosage of the activator (Sika AF53) was electronically controlled by the concrete flow rate and set at a single value of 7 % for all of the concrete test specimens.

Table 2 Reinforcements characteristics

RSC

Type of reinforcement

Fibre dosage (kg/m3) or welded mesh characteristics

E (GPa)

Tensile

strength (MPa)

BF01

Polymeric fibres

8

6

550

BF02

Steel fibres

30

210

1650

BF03

Polymeric fibres

7

12

580

BF04

Steel fibres

30

210

1345

BF05a

Polymeric fibres

7

4.8

470

BF06

Amorphous metallic fibres

25

130

1800

WWM

Welded wire mesh

ST 50, 30 x 10 cm2 mesh, 8 mm diameter

210

540

aThis is a prototype fibre, not on the market

Compressive strength at 1, 7 and 28 days

BB

BF01

BF02

BF03

BF04

BF05

BF06

WWM

Day 7 (MPa)

36.7

35.4

36.3

32.6

32

37.5

35.7

36.7

Day 28 (MPa)

44.1

45.8

49.2

47.2

45.1

47.5

48.8

44.1

Basic Characteristics

Concrete slump, fresh concrete densities, air contents and compressive strength (see Table 3) were measured. They were very similar for all the samples. Slump measurements varied from 180 to 230 mm. Density varied from 2.360 to 2.375 kg/m3 and the air content from 1.5 to 2.1 %. The consistency of the results confirmed that the production and application were properly controlled.

Compressive strengths were measured, according to the EN 12390-3 test method, on cores (diameter 64, 128 mm high) extracted from sprayed panels. Mean compressive strength at 28 days was 46.5 MPa.

 
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