File Download
  Links for fulltext
     (May Require Subscription)
Supplementary

postgraduate thesis: Use of fillers to improve packing density and performance of concrete

TitleUse of fillers to improve packing density and performance of concrete
Authors
Advisors
Advisor(s):Kwan, AKHHo, JCM
Issue Date2012
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Chen, J. [陈嘉健]. (2012). Use of fillers to improve packing density and performance of concrete. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4819955
AbstractIt is generally very difficult to produce high-performance concrete having concurrently high strength, high durability, high workability and high dimensional stability. This is because low water content is required to achieve high strength and high durability, high water content and large paste volume are required to achieve high workability, and low cement content and small cement paste volume are required to achieve high dimensional stability. One way of overcoming such conflicts is to add fillers to increase the packing density of concrete so that the amounts of water and paste needed to fill voids could be reduced. In this study, the use of fillers to improve the packing density and performance of concrete is investigated by measuring the packing density and overall performance of cement paste and concrete mix samples with different types and amounts of fillers added. The packing density results revealed that finer fillers are more effective in improving the packing density for releasing more excess water (water in excess of that needed to fill voids) to lubricate the solid particles. Moreover, triple blending of two fillers of different fineness with cement can better increase the packing density than double blending of just one filler with cement. On the other hand, the workability, strength and dimensional stability results showed that the addition of condensed silica fume, fly ash microsphere or superfine cement could improve the overall workability-strength performance of cement paste through increasing the packing density of the cementitious materials, while the addition of condensed silica fume, fly ash or limestone fine coeuld improve the overall dimensional stability-strength performance of concrete through decreasing the cement content or cement paste volume. Hence, the incorporation of fillers to improve the packing density opens up the possibility of using ultra-low W/CM ratio and ultralow paste volume to produce an ultrahigh-performance concrete. However, despite increases in packing density and excess water, the addition of fillers does not always improve the workability. Generally, the addition of fillers would more significantly increase the workability at low W/CM ratio and less significantly increase or even decrease the workability at high W/CM ratio. In-depth analysis indicated that both the excess water and solid surface area have great effects on the rheology. In this regard, a parameter called water film thickness (WFT), which is defined as the average thickness of water films coating the solid particles and may be determined as the excess water to solid surface area ratio, is proven to be the key factor governing the rheology. Therefore, it should be the WFT rather than the packing density that should be maximized in the mix design of high-performance concrete. The addition of fillers would increase both the excess water and solid surface area. If the proportional increase in excess water is larger than the proportional increase in solid surface area, the WFT would increase, but if otherwise, the WFT would decrease. To increase the WFT, a filler that can significantly increase the packing density without excessively increasing the solid surface area is the best choice.
DegreeDoctor of Philosophy
SubjectHigh strength concrete.
Concrete - Additives.
Dept/ProgramCivil Engineering

 

DC FieldValueLanguage
dc.contributor.advisorKwan, AKH-
dc.contributor.advisorHo, JCM-
dc.contributor.authorChen, Jiajian.-
dc.contributor.author陈嘉健.-
dc.date.issued2012-
dc.identifier.citationChen, J. [陈嘉健]. (2012). Use of fillers to improve packing density and performance of concrete. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4819955-
dc.description.abstractIt is generally very difficult to produce high-performance concrete having concurrently high strength, high durability, high workability and high dimensional stability. This is because low water content is required to achieve high strength and high durability, high water content and large paste volume are required to achieve high workability, and low cement content and small cement paste volume are required to achieve high dimensional stability. One way of overcoming such conflicts is to add fillers to increase the packing density of concrete so that the amounts of water and paste needed to fill voids could be reduced. In this study, the use of fillers to improve the packing density and performance of concrete is investigated by measuring the packing density and overall performance of cement paste and concrete mix samples with different types and amounts of fillers added. The packing density results revealed that finer fillers are more effective in improving the packing density for releasing more excess water (water in excess of that needed to fill voids) to lubricate the solid particles. Moreover, triple blending of two fillers of different fineness with cement can better increase the packing density than double blending of just one filler with cement. On the other hand, the workability, strength and dimensional stability results showed that the addition of condensed silica fume, fly ash microsphere or superfine cement could improve the overall workability-strength performance of cement paste through increasing the packing density of the cementitious materials, while the addition of condensed silica fume, fly ash or limestone fine coeuld improve the overall dimensional stability-strength performance of concrete through decreasing the cement content or cement paste volume. Hence, the incorporation of fillers to improve the packing density opens up the possibility of using ultra-low W/CM ratio and ultralow paste volume to produce an ultrahigh-performance concrete. However, despite increases in packing density and excess water, the addition of fillers does not always improve the workability. Generally, the addition of fillers would more significantly increase the workability at low W/CM ratio and less significantly increase or even decrease the workability at high W/CM ratio. In-depth analysis indicated that both the excess water and solid surface area have great effects on the rheology. In this regard, a parameter called water film thickness (WFT), which is defined as the average thickness of water films coating the solid particles and may be determined as the excess water to solid surface area ratio, is proven to be the key factor governing the rheology. Therefore, it should be the WFT rather than the packing density that should be maximized in the mix design of high-performance concrete. The addition of fillers would increase both the excess water and solid surface area. If the proportional increase in excess water is larger than the proportional increase in solid surface area, the WFT would increase, but if otherwise, the WFT would decrease. To increase the WFT, a filler that can significantly increase the packing density without excessively increasing the solid surface area is the best choice.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.source.urihttp://hub.hku.hk/bib/B48199552-
dc.subject.lcshHigh strength concrete.-
dc.subject.lcshConcrete - Additives.-
dc.titleUse of fillers to improve packing density and performance of concrete-
dc.typePG_Thesis-
dc.identifier.hkulb4819955-
dc.description.thesisnameDoctor of Philosophy-
dc.description.thesislevelDoctoral-
dc.description.thesisdisciplineCivil Engineering-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.5353/th_b4819955-
dc.date.hkucongregation2012-

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats