Efficiency of polypropylene and metallic fibres on control of shrinkage and cracking of recycled aggregate mortars

doi:10.1016/S0950-0618(99)00047-1

Construction and Building Materials

Volume 13, Issue 8, 1 December 1999, Pages 439-447

https://doi.org/10.1016/S0950-0618(99)00047-1 Get rights and content

Abstract

The use of recycled aggregates in mortar and concrete induces a large shrinkage due to the capacity of these aggregates to absorb a great quantity of water. The influence of polypropylene and metallic fibres (Fibraflex) has been studied in different proportioning to reduce shrinkage and cracking. The efficiency of polypropylene and metallic fibres to reduce restrained shrinkage cracking is evaluated by using a ring mortar cast around a stiff steel ring. By using fibres, the crack width decreases significantly. Free shrinkage results are equally investigated. Finally, crack width in reinforced fibre mortars is calculated analytically by using the model of Grzybowski and Shah. Results are compared with experimental values. The study demonstrates that theoretical values of crack widths correspond reasonably to experimental values.

Introduction

Although they represent a small fraction of the production of aggregates, recycled demolition materials are used more and more. Current methods of recycled aggregate enhancement are minor applications, such as precast blocks, foundation concrete and usual concrete.

Many tests have been made to study the feasibility of recycled aggregate concrete and to show the phenomena linked to the use of this concrete. One of the main technological problems is to master cracking of green concrete. The cracking is mainly generated by restrained shrinkage. It appears when the tensile stress developed by shrinkage is greater than the tensile strength of concrete.

To reduce the phenomenon of shrinkage and the induced cracking, satisfactory results are obtained by adding fibres. Fibres used in this study are polypropylene and Fibraflex fibres. Tests have been carried out using narrow rings of mortar next to rigid steel rings. Results concerning the number of cracks and their width are compared to the values obtained by a theoretical model.

Section snippets

Recycled aggregates

Studied recycled sands are produced by RMN (Recyclage des Matériaux du Nord) who use percussion crushers. During the crushing of rubble, the cement cover remains attached to original aggregates. The recycled particles have an irregular form and are composed of old cement paste, which covers the natural aggregates. A great quantity of fine aggregates come from the crushing of cement paste. CCD camera gives a clear picture of the two constituents (Fig. 1). The large porosity (approx. 15%) arising

Mortar matrix

The matrix is normal mortar with a cement/sand ratio=1/3, in which the volume of fibres supplies a part of aggregates. The water/cement ratio is kept constant for all formulations. The mortar used is made from:

•
recycled sand (0–6 mm) manufactured by RMN;
•
cement CPA 55 CEM I; and
•
water (W/C=0.75).

Two types of fibres were used: polypropylene and metallic fibres. The polypropylene fibres were 10 mm long and 0.035 mm in diameter. Metallic fibres ‘Fibraflex’ are ribbons of cast iron having a length of

Free shrinkage

Free shrinkage tests are conducted on prismatic samples 40×40×160 mm³. The conditions of drying are 20°C and 50% relative humidity. Average curves of free shrinkage vs. time are presented in Fig. 2, Fig. 3.

First, a big difference between recycled sand mortar and natural sand mortar can be observed. The important drying shrinkage of recycled sand mortar is generated principally by the large porosity and the water absorption of recycled aggregates. These parameters have a significant influence on

Restrained shrinkage cracking

Shrinkage cracking is a major problem for concrete structures, especially for flat structures, such as highway pavement, slabs and walls. One method to reduce the adverse effects of cracking due to restrained shrinkage is to reinforce concrete with fibres.

The method of the mortar ring cast next to a steel ring is used to simulate restrained shrinkage cracking. A number of experimenters [9], [10], [11], [12] used the same method. Strains are measured by using strain gauges placed around the

Conclusion

Recycled aggregate mortars induced a large shrinkage to plain mortar as compared to natural sand mortar. To reduce the consequence of shrinkage, two types of fibre should be added: polypropylene and metallic iron cast fibres. The action of these fibres was evaluated:

•
metallic fibres reduce shrinkage by approximately 15%; and
•
tiny changes were observed with polypropylene fibres.

After 180 days, a gain of weight was noticeable on the experimental curves of shrinkage vs. the drying percentage. This

References (16)

P. Acker
Les retraits du béton: origine physiques, paramètres d’influence, analyse par type d’ouvrage et par modes de mise en œuvre
RILEM GMC
(1995)
Edgington J, Hannant DJ, Williams RIT. Steel fiber-reinforced concrete. GB Building Res EST. Current paper c.p. 69/74,...
El Hachem M. Etude de l’influence de la fibre de fonte sur le retrait et la fluage du béton. Thèse doctorat, Ecole...
Houari H. Contribution à l’étude du comportement du béton renforcé de fibres soumis à l’action des charges maintenues...
P.N. Balagaru et al.
Properties of fiber-reinforced concrete: workability, behavior under long term loading, and air-void characteristics
ACI Mater J
(1988)
P.S. Mangat et al.
A theory of the free shrinkage of steel fiber reinforced cement matrices
J Mater Sci
(1984)
V.H. Young et al.
Practical prediction model for shrinkage of steel fiber reinforced concrete
Mater Struct
(1991)
Verbeck GJ, Helmuth RH. Structures and physical properties of cement paste. Proceedings of the Fifth International...

There are more references available in the full text version of this article.

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Efficiency of polypropylene and metallic fibres on control of shrinkage and cracking of recycled aggregate mortars

Abstract

Introduction

Section snippets

Recycled aggregates

Mortar matrix

Free shrinkage

Restrained shrinkage cracking

Conclusion

Les retraits du béton: origine physiques, paramètres d’influence, analyse par type d’ouvrage et par modes de mise en œuvre

RILEM GMC

Properties of fiber-reinforced concrete: workability, behavior under long term loading, and air-void characteristics

ACI Mater J

A theory of the free shrinkage of steel fiber reinforced cement matrices

J Mater Sci

Practical prediction model for shrinkage of steel fiber reinforced concrete

Mater Struct