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The use of synthetic colloidal silica dispersions for making HPC and UHPC systems, preliminary comparison results between colloidal silica dispersions and silica fumes (SF)
A comparison of the mechanical properties (flexural and uniaxial compressive strenghts) between some mix formulations referred to the conventional reactive powder concrete systems (RPC) is done on this work. The comparison is done between mix formulations containing only silica fume (SF), (microsilica) at the optimal contents for the best mechanical properties and mix formulations containing only synthetic silica dispersion, or combination of silica dispersion with fly ash, SF, cristobalite or quartz powder. The results show that even though silica fume can be used at much higher percentages (20% to 30% referred to the cement content) with the mix formulations, adequate formulations containing only colloidal silica dispersions at much lower contents (1% to 7%), or silica dispersions combined with other pozzolanic additives can give the same results and even better ones. Hardened specimens of adequate formulations give mechanical properties that are well at the initial border of the zone of mechanical properties for UHPC systems (150 MPa to 165 MPa), actually without including any fibres or applying special setting or post-setting treatment (pressure, temperature programme) etc. Although the higher specific surface area of the silica dispersions increases the water demand and worsen somehow the workability, still adequate mixture proportioning may give fresh concretes having self flowing abilities in addition to the superior mechanical properties in the hardened state. The early strength development for some of the mixtures with silica dispersions is also generally faster and a little better than for those specimens casted only with SF. Additionally a microstructure investigation is done for the hardened specimens in order to see the similarities and differences between them. The use of adapted synthetic colloidal silica dispersions for cement systems, combined with other pozzolans, is very promising for HPC or UHPC applications.
The use of synthetic colloidal silica dispersions for making HPC and UHPC systems, preliminary comparison results between colloidal silica dispersions and silica fumes (SF)
A comparison of the mechanical properties (flexural and uniaxial compressive strenghts) between some mix formulations referred to the conventional reactive powder concrete systems (RPC) is done on this work. The comparison is done between mix formulations containing only silica fume (SF), (microsilica) at the optimal contents for the best mechanical properties and mix formulations containing only synthetic silica dispersion, or combination of silica dispersion with fly ash, SF, cristobalite or quartz powder. The results show that even though silica fume can be used at much higher percentages (20% to 30% referred to the cement content) with the mix formulations, adequate formulations containing only colloidal silica dispersions at much lower contents (1% to 7%), or silica dispersions combined with other pozzolanic additives can give the same results and even better ones. Hardened specimens of adequate formulations give mechanical properties that are well at the initial border of the zone of mechanical properties for UHPC systems (150 MPa to 165 MPa), actually without including any fibres or applying special setting or post-setting treatment (pressure, temperature programme) etc. Although the higher specific surface area of the silica dispersions increases the water demand and worsen somehow the workability, still adequate mixture proportioning may give fresh concretes having self flowing abilities in addition to the superior mechanical properties in the hardened state. The early strength development for some of the mixtures with silica dispersions is also generally faster and a little better than for those specimens casted only with SF. Additionally a microstructure investigation is done for the hardened specimens in order to see the similarities and differences between them. The use of adapted synthetic colloidal silica dispersions for cement systems, combined with other pozzolans, is very promising for HPC or UHPC applications.
The use of synthetic colloidal silica dispersions for making HPC and UHPC systems, preliminary comparison results between colloidal silica dispersions and silica fumes (SF)
Korpa, Arjan (author) / Trettin, Reinhard (author)
2004
10 Seiten, 18 Bilder, 4 Quellen
Conference paper
English
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