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International Concrete Abstracts Portal

Showing 1-5 of 22 Abstracts search results

Document: 

SP261-11

Date: 

October 1, 2009

Author(s):

M. Sonebi, S. Stewart, and J. Condon

Publication:

Symposium Papers

Volume:

261

Abstract:

Self-consolidating concrete (SCC) is designed to exhibit high deformability and moderate viscosity to maintain homogeneity and adequate stability to fill the formwork, and encapsulate the reinforcement without any mechanical vibration. Any concrete should have high impermeability and low chloride diffusion to reduce the risk of corrosion and enhance service life. In this study, the effect of the replacement content of cement by supplementary cementing materials (SCM) and fillers. Limestone powder (LSP) replacement of 15% to 30%, ground granulated blastfurnace slag (GGBS) of 40% to 60%, and pulverized fly ash (PFA) of 20% to 35% are evaluated on the durability of SCC of grade C40/50. Fresh concrete properties and development of compressive strength were also evaluated. For the durability performance, all mixtures were tested at 28 days for the air permeability, water permeability, sorptivity, and chloride diffusion which were assessed by Autoclam, and Permit tests. The chloride migration coefficient was dependent on the type SCM and filler in use. The most durable SCC mixture, taking into consideration overall properties, was found to be the one containing 20% PFA, which showed low capillary water absorption, water and air permeation, and lower ionic diffusivity in comparison to the other mixtures. In general, SCC mixtures containing GGBS exhibited inferior performance regarding air and water permeability and sorptivity, but had satisfactory chloride resistance. SCC with 50% of GGBS demonstrates the lowest chloride diffusivity.

DOI:

10.14359/51663208


Document: 

SP261-10

Date: 

October 1, 2009

Author(s):

V. Corinaldesi and G. Moriconi

Publication:

Symposium Papers

Volume:

261

Abstract:

In this work, several self-compacting concretes were prepared by using three different types of fibers made of steel, poly-vinyl-alcohol (PVA), high toughness poly-propylene (PPHT), and two different types of mineral addition (limestone powder and powder from recycled concrete). The water-cement ratio (w/c) was in every case equal to 0.40. Fresh concrete behavior was evaluated by means of slump flow, V-funnel, and L-box tests while the hardened concrete behavior was evaluated by means of flexure and compression tests as well as free drying and restrained plastic shrinkage measurements. Excellent performances were generally detected, particularly for the selfcompacting concretes prepared with steel and PPHT fibers.

DOI:

10.14359/51663207


Document: 

SP261-15

Date: 

October 1, 2009

Author(s):

E.B. Lee, G.Y. Kim, K.M. Koo, and H.J. Lee

Publication:

Symposium Papers

Volume:

261

Abstract:

An analysis method for histories of hydration heat and autogenous shrinkage at early ages is suggested in this study. The early age properties and the relation between hydration heat and autogenous shrinkage of high-strength concrete were investigated. In the results, most autogenous shrinkage of high-strength concrete occurred in a few days after casting. The shape of autogenous shrinkage history corresponded well to the shape of hydration temperature history at early ages. There was a close relation between hydration heat and autogenous shrinkage at early ages, especially between hydration heating velocity (HHV) and autogenous shrinking velocity (ASV). And it is noted that HHV can affect the ultimate autogenous shrinkage.

DOI:

10.14359/51663212


Document: 

SP261-06

Date: 

October 1, 2009

Author(s):

D. Feys, G. De Schutter, and R. Verhoeven

Publication:

Symposium Papers

Volume:

261

Abstract:

Self-compacting concrete (SCC) is a very flowable cementitious material, which does not need external vibration during casting. On the other hand, somewhat surprisingly, pumping of self-compacting concrete requires higher pumping pressures than traditional concrete. This paradox can be fundamentally explained by studying the rheological properties of self-compacting concrete and linking them to pumping operations. This paper describes full-scale pumping tests on self-compacting concrete. The first part deals with the influence of the rheological properties of the concrete on the pumping process, showing that viscosity and shear thickening have a major importance. The second part discusses the influence of pumping on the rheological properties of the concrete, clearly showing a decrease in viscosity due to pumping. Structural breakdown and air content change the rheological properties of the SCC. If structural breakdown dominates the effects of the air content, the yield stress and plastic viscosity will decrease, and the SCC will show a larger tendency to segregate. If the effects of the air content dominate, the yield stress of the SCC will increase, possibly leading to improper filling of the formwork.

DOI:

10.14359/51663203


Document: 

SP261-17

Date: 

October 1, 2009

Author(s):

F. Tittarelli, S. Monosi, M.L. Ruello, and G. Moriconi

Publication:

Symposium Papers

Volume:

261

Abstract:

Used foundry sand (UFS) represents the highest amount of solid waste generated by foundries. At present, the general trend is disposal in landfills with two drawbacks: consumption of new raw materials and saturation of existing landfills. This material is classified non-hazardous and therefore its reuse is possible in several industrial sectors. In this study laboratory tests are presented regarding the reuse of waste foundry sand in mortar production by partly replacing the fine aggregate with UFS. The waste material was physically and chemically characterized and then it was added to mortars as fine aggregate replacement at dosage rates of 0%, 20%, and 30% sand by weight. At the dosage of 20%, an addition of previously washed UFS was also considered. The resulting washing water was used to manufacture cement pastes in order to investigate the effect of soluble UFS ions on the hydration kinetics of cement by thermogravimetric analysis. The obtained results showed that the addition of UFS decreases the compressive strength of mortars by about 30%, regardless of the addition rate, and has an accelerated setting effect on cement paste hydration. These undesirable effects are partially mitigated by using previously washed foundry sand.

DOI:

10.14359/51663214


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