Crack control in screed using A142 steel fabric or mixed structural polypropylene fibres with regard to toughness and residual strength

Abstract

Purpose

To evaluate manufacturers' claims that structural polypropylene fibres provide satisfactory crack control reinforcement and compare the findings against steel fabric used as crack control in screeds where tensile forces are likely to occur.

Design/methodology/approach

The procedure used to provide load, deflection data, toughness indices and residual strength factors was compliant with ASTM C1018‐97 and in part ASTM C78‐02 to define first crack toughness and first crack strength.

Findings

A142 steel fabric reinforcement as used in screeds was more effective in producing toughness and residual strength when directly compared with the performance of structural polypropylene fibre reinforced concrete. Where polypropylene fibre reinforced concrete did have an advantage over the steel reinforced concrete was when I₂₀ was exceeded and the deflection and crack width was excessive. Steel fabric tended to fail and/or the screed material failed either prior to or in excess of I₂₀, whereas the fibre reinforced concrete held together albeit at a very much reduced load transfer when compared with steel fabric.

Practical implications

If the forces to be encountered through expansion or contraction are small, then, due to the small distances between the fibres redistributing the stress and minimising the cracks within the concrete matrix, polypropylene fibres may be suitable for crack control when directly compared with A142 fabric reinforcement. The use of fibres has benefits to the floor screed companies, using screed‐laying machines as the process avoids laying steel on which the screed machine will have to operate.

Originality/value

There is a general lack of research coverage examining crack control in screed floor finishing materials.

Citation

Richardson, A.E. and Fallow, C. (2006), "Crack control in screed using A142 steel fabric or mixed structural polypropylene fibres with regard to toughness and residual strength", Structural Survey, Vol. 24 No. 4, pp. 319-331. https://doi.org/10.1108/02630800610704454