CRACK FORMATION RISK REDUCTION OF HPC/HSC BY SUITABLE CHOICE OF THE PLASTICIZER

CRACK FORMATION RISK REDUCTION OF HPC/HSC BY SUITABLE CHOICE OF THE PLASTICIZER

Paper in proceedings (conference paper)

Development of HPC/HSC is focused on properties improvement by porosity reduction. Low porosity means lower permeability and low permeability guarantee mechanical properties and better durability. At practical production of these types of concrete the aim of the mix designers is to lower W/C ratio, which could be primarily achieved by superplasticizers. Concrete with low W/C ratio - achieved by the use of super plasticizers - tend to early age cracking in higher rate. These cracks decrease final performance of the concrete – mechanical properties, durability etc. One of the reasons of the early age crack formation and subsequent decrease of concrete performance is due to thermal expansivity. Thermal expansivity of HPC/HSC is higher then of other types of concrete due to higher amount of binder (generally CEM I 42,5 R or 52,5R) with higher and faster hydration heat development. Reactive kinetics highly depends on additives. It is possible to remarkably influence the hydration kinetics and thus risk of early age cracking.

Development of HPC/HSC is focused on properties improvement by porosity reduction. Low porosity means lower permeability and low permeability guarantee mechanical properties and better durability. At practical production of these types of concrete the aim of the mix designers is to lower W/C ratio, which could be primarily achieved by superplasticizers. Concrete with low W/C ratio - achieved by the use of super plasticizers - tend to early age cracking in higher rate. These cracks decrease final performance of the concrete – mechanical properties, durability etc. One of the reasons of the early age crack formation and subsequent decrease of concrete performance is due to thermal expansivity. Thermal expansivity of HPC/HSC is higher then of other types of concrete due to higher amount of binder (generally CEM I 42,5 R or 52,5R) with higher and faster hydration heat development. Reactive kinetics highly depends on additives. It is possible to remarkably influence the hydration kinetics and thus risk of early age cracking.

COncrete, HPC, Hydration heat

ZACH, J., ŠŤASTNÍK, S.

01.01.2003

Sekurkon

Praha

80-86604-08-X

FC and HPC 2003

85

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