ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 175 Abstracts search results

Document: 

SP-349_20

Date: 

April 22, 2021

Author(s):

Klaus-Juergen Huenger, David Kurth, Maria Brigzinsky

Publication:

Symposium Papers

Volume:

349

Abstract:

Alumino-silicate compounds (geopolymers) are important for alternative binders for mortars and concretes. Such systems normally have a solid (metakaolin, slag, ash) and a liquid (activator solution) component. A newly developed system here consists of a waste silicate material and an aluminate source, both with a very good solubility. Under the addition of water only, a structure formation process occurs to form an alumino-silicate network. The Si/Al ratio can be varied in wide ranges to produce binders with different properties.

It was very surprising that the mortar properties not only depend on the recipe, but also on the aggregate types. Different aggregate types (quartz, greywacke, rhyolite, diabas, basalt, granodiorite) were chosen to produce mortar bars. All components were intensively mixed dry or as a slurry. Already the sand component affects the workability, further the setting time, the strength development and, of course, the durability. The best results were obtained with quartz, the worst with diabase or basalt sands. Obviously, the chemical and mineralogical composition and therefore the soluble constituents of the sand under highly alkaline conditions affected the structure formation process of the alumino-silicate binder and therefore the mortar properties too. The observed effects have nothing to do with an Alkali-silica-reaction (ASR).


Document: 

SP-349_53

Date: 

April 22, 2021

Author(s):

Thomas, M.D.A., Smith, D. and Moffatt, E.G., Kasaniya, M.

Publication:

Symposium Papers

Volume:

349

Abstract:

This paper presents data on the durability of concrete produced using ground glass as a pozzolan. Various sources of glass were used including soda glass, E-glass and Pyrex glass. All the materials showed excellent pozzolanic activity when ground to pass 75-microns. The use of ground glass resulted in substantial reductions in permeability and chloride penetrability, and improved resistance to sulfate attack. Air-entrained concrete containing glass showed good freeze-thaw resistance. Low alkali E-glass and borosilicate glass were effective in preventing deleterious expansion due to alkali-silica reaction (ASR). Bottle glass, which contains substantial amounts of alkali, was not efficacious with regards to ASR. The inclusion of bottle glass results in very substantial increases to the pore solution alkalinity and this can result in substantial increases in expansion in concrete containing reactive aggregate and low-alkali cement. It is shown that the accelerated mortar bar test is not suitable for evaluating the impact of high-alkali materials on ASR as the alkalis contributed by the cementing materials are released when the mortar bars are masked by the conditions of the test (first immersed in hot water and then in hot NaOH solution).


Document: 

SP-349_25

Date: 

April 22, 2021

Author(s):

Klaus-Juergen Huenger and Mario Kositz

Publication:

Symposium Papers

Volume:

349

Abstract:

Supplementary cementing materials (SCM) have a great importance for preventing ASR in concrete structures worldwide. Different materials were used, e.g. fly ashes, silica fume or metakaolin. However, the results are often contradictory. What works with one aggregate does not necessarily work with another, or in other cases, the efficiency is not the same. Not all effects can be explained by fluctuations in the SCM composition.

Long-term investigations were carried out using three different aggregates. Concrete prisms were produced, and parallel aggregates were stored together with different SCM`s (different types and concentrations) in highly alkaline solutions with and without calcium hydroxide in the system. The reaction products, which precipitated as a result of the interactions between aggregate and SCM`s at different storage times, could be investigated by NMR and even XRD. The results were surprising because different aggregates formed different reaction products when using the same SCM. Such effects can only be explained by the release of different soluble minerals that are part of aggregates.

The conclusion is that obviously aggregates control the formation process of reaction products which are formed as a result of the interactions between SCM`s and aggregates. And these products are responsible for preventing ASR when using the SCM`s.


Document: 

SP-330-08

Date: 

September 26, 2018

Author(s):

Ivan Janotka, Pavel Martauz, and Michal Bacuvcik

Publication:

Symposium Papers

Volume:

330

Abstract:

Hybrid cement (H-CEMENT) is an innovative cement of the producer from Slovakia. H-CEMENT is suitable for the production of ready-mixed concrete of compressive strength classes up to C 30/37 (4350/5370 psi) along with shrinkage-reducing and alkali-aggregate reaction-mitigating properties. The results of 5-years of exposure of H-CEMENT mortar in an aggressive sulfate solution are compared with two reference cement mortars made either with CEM I or sulfate-resistant CEM I SR 0. Sulfate resistance of H-CEMENT was evaluated in the regularly-renewed aggressive 5% solution by none-destructive tests (dynamic modulus of elasticity and length changes), destructive tests (flexural and compressive strength), microstructure studies (XRD, TG-DTA and SEM), wet chemical analyses (mainly the estimation of SO3 content), and pore structure technique (MIP). The results give evidence of the same high sulfate resistance for H-CEMENT as that for CEM I SR 0 with C3A = 0.


Document: 

SP-330-05

Date: 

September 26, 2018

Author(s):

Chengning Wu and Junqing Xin

Publication:

Symposium Papers

Volume:

330

Abstract:

In order to improve compressive strength and the durability of concrete, such as, alkali-aggregate reaction resistance, chloride ion permeation resistance, carbonation resistance, and freezing and thawing resistance, a new type of combined cementitious materials was used to make the concrete. One part of the cementitious materials was high early strength Portland cement (similar to ASTM type III Portland cement), which had more than 63 mass% C3S and hydrated quickly to generate calcium hydroxide to accelerate pozzolanic reaction. Another part of the cementitious materials was fine blast furnace slag powders which had more than 6000 cm2/g Blaine specific surface area to get faster hydration with the calcium hydroxide. And other part of the cementitious materials was fly ash which had high specific surface area and low ignition loss to get faster pozzolanic reaction. According to the results of tests in this research, it is clear that the compressive strength of the concrete made with the combined cementitious materials is near that of the concrete made with the high early strength Portland cement only. However, the alkali-aggregate reaction in the concrete made with the combined cementitious materials is much lower than that of the concrete made with the high early Portland cement, and/or mixed with the fine blast furnace slag powders or fly ash respectively. It is also confirmed that chloride ion permeation resistance, carbonation resistance, and freezing and thawing resistance of the concrete made with the combined cementitious materials are improved considerably.


12345...>>

Results Per Page 




Please enter this 5 digit unlock code on the web page.