Errors during casting 67
within a cage and cannot follow the settlement of the concrete. As a consequence, the concrete ‘slides’ off the reinforcement bars, leaving a crack
opening on top of it. Underneath the reinforcement bars, a void can be created. This phenomenon leads to mechanical problems due to the reduced
bond between the steel reinforcement and the concrete, as well as to durability problems due to accelerated ingress of aggressive substances with
almost immediate and open access to the reinforcement bars.
While bleeding on top surfaces are a regularly occurring and well-known
phenomenon, water movements can also occur between the concrete and
the formwork. This can lead to small stripes, also called ‘sand stripes’,
resulting from the upward water movement carrying small powder and
sand particles. The risk of sand stripes increases in the case of a too high
water content in the concrete and in the case of too long vibration.
references
Bartos P.J.M. and Cleland D.J. (Eds.) (1993) ‘Special Concrete: Workability and
Mixing’, London, E&FN Spon.
Chang P.-K. and Peng Y.-N. (2001) ‘Influence of mixing techniques on properties of
high performance concrete’, Cement and Concrete Research, 31, 87–95.
Chopin D., de Larrard F. and Cazacliu B. (2004) ‘Why do HPC and SCC require a
longer mixing time?’, Cement and Concrete Research, 34, 2237–2243.
De Schutter G., Bartos P., Domone P. and Gibbs J. (2008) ‘Self-Compacting
Concrete’, Whittles Publishing, Caithness, UK, CRC Press, Taylor & Francis
Group, Boca Raton, USA, ISBN 978-1904445-30-2, USA ISBN 9781-4200-6833-7, pp. 296.
De Schutter G., Audenaert K., Sichien J. and De Rouck J. (2001) ‘Experimental study
of the incorporation of LD-slag in massive concrete armour units for breakwaters’, 2nd Int. Conf. on Engineering Materials (Eds. Nagataki et al.), San Jose,
101–112.
Jézéquel P.-H. and Collin V. (2007) ‘Mixing of concrete or mortars: Dispersive
aspects’, Cement and Concrete Research, 37, 1321–1333.
Marinus J. (2011) ‘Pop-outs due to aggregates contaminated with free lime. Scientific
study of the risks’ (in Dutch and French), Beton, 209, January, 32–37.
Moerman B. (2010) ‘Contaminated concrete threatens construction sites’ (in Dutch),
De Standaard, 18 September 2010, 2.
RILEM TC 188-CSC (2006) ‘Casting of self-compacting concrete’, Final report
of RILEM Technical Committee 188-CSC, RILEM Report 35, RILEM
Publications sarl.
Taerwe L. (1996) ‘Concrete Technology’ (in Dutch), Lecture notes, Ghent University,
Belgium.
Taerwe L., Van Gysel A., De Schutter G. and Vyncke J. (1997) ‘Experimental determination of the steel fibre content in fresh and hardened concrete used for
concrete slabs on grade’, Proceedings of the Asia-Pacific Conference on Fibre
Reinforced Concrete, Singapore, August, 255–261.
within a cage and cannot follow the settlement of the concrete. As a consequence, the concrete ‘slides’ off the reinforcement bars, leaving a crack
opening on top of it. Underneath the reinforcement bars, a void can be created. This phenomenon leads to mechanical problems due to the reduced
bond between the steel reinforcement and the concrete, as well as to durability problems due to accelerated ingress of aggressive substances with
almost immediate and open access to the reinforcement bars.
While bleeding on top surfaces are a regularly occurring and well-known
phenomenon, water movements can also occur between the concrete and
the formwork. This can lead to small stripes, also called ‘sand stripes’,
resulting from the upward water movement carrying small powder and
sand particles. The risk of sand stripes increases in the case of a too high
water content in the concrete and in the case of too long vibration.
references
Bartos P.J.M. and Cleland D.J. (Eds.) (1993) ‘Special Concrete: Workability and
Mixing’, London, E&FN Spon.
Chang P.-K. and Peng Y.-N. (2001) ‘Influence of mixing techniques on properties of
high performance concrete’, Cement and Concrete Research, 31, 87–95.
Chopin D., de Larrard F. and Cazacliu B. (2004) ‘Why do HPC and SCC require a
longer mixing time?’, Cement and Concrete Research, 34, 2237–2243.
De Schutter G., Bartos P., Domone P. and Gibbs J. (2008) ‘Self-Compacting
Concrete’, Whittles Publishing, Caithness, UK, CRC Press, Taylor & Francis
Group, Boca Raton, USA, ISBN 978-1904445-30-2, USA ISBN 9781-4200-6833-7, pp. 296.
De Schutter G., Audenaert K., Sichien J. and De Rouck J. (2001) ‘Experimental study
of the incorporation of LD-slag in massive concrete armour units for breakwaters’, 2nd Int. Conf. on Engineering Materials (Eds. Nagataki et al.), San Jose,
101–112.
Jézéquel P.-H. and Collin V. (2007) ‘Mixing of concrete or mortars: Dispersive
aspects’, Cement and Concrete Research, 37, 1321–1333.
Marinus J. (2011) ‘Pop-outs due to aggregates contaminated with free lime. Scientific
study of the risks’ (in Dutch and French), Beton, 209, January, 32–37.
Moerman B. (2010) ‘Contaminated concrete threatens construction sites’ (in Dutch),
De Standaard, 18 September 2010, 2.
RILEM TC 188-CSC (2006) ‘Casting of self-compacting concrete’, Final report
of RILEM Technical Committee 188-CSC, RILEM Report 35, RILEM
Publications sarl.
Taerwe L. (1996) ‘Concrete Technology’ (in Dutch), Lecture notes, Ghent University,
Belgium.
Taerwe L., Van Gysel A., De Schutter G. and Vyncke J. (1997) ‘Experimental determination of the steel fibre content in fresh and hardened concrete used for
concrete slabs on grade’, Proceedings of the Asia-Pacific Conference on Fibre
Reinforced Concrete, Singapore, August, 255–261.