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Home > Publications > 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.
Showing 1-5 of 37 Abstracts search results
Document:
SP239-32
Date:
October 1, 2006
Author(s):
C. Maltese, C. Pistolesi, A. Bravo, F. Cella, T. Cerulli, and D. Salvioni
Publication:
Symposium Papers
Volume:
239
Abstract:
In this paper, the influence of different setting regulators on the performances of an inorganic acid based alkali-free accelerator was analysed. Setting time and compressive strength development were determined on clinker samples added with b-hemihydrate or anhydrite and admixed with the alkalifree accelerator. It was found that the lower is the setting regulator instantaneous dissolution rate, the shorter is the final set and the higher the compressive strength development (therefore the more efficient is the accelerator). In order to understand this phenomenon, physical (hydration temperature profile), chemical (TG and XRD), morphological (ESEM-FEG and specific surface area measurements) analyses were carried out on paste samples added with the accelerator.
DOI:
10.14359/18398
SP239-06
A. Bettencourt Ribeiro, A. Carrajola, and A. Goncalves
To analyze the performance of two shrinkage reducing admixtures (SRA), tests have been performed, in order to evaluate the influence of increasing dosages of the admixtures. Shrinkage, compressive strength and weight loss have been measured. The efficiency of the admixtures in controlling autogenous and drying shrinkage was evaluated using sealed and unsealed specimens. As the accepted mechanism of action of these products is the reduction on surface tension of the capillary liquid of concrete, surface tension of water solutions was also determined to compare the shrinkage reduction with the decrease of surface tension. Mixtures with four different dosages of each SRA were prepared. The results indicate that shrinkage reduction is not proportional to the decrease of surface tension. Secondary effects such as changes in the evaporation rate and in the compressive strength of specimens have to be considered. Results of sealed specimens are not fully consistent with the accepted main mechanism of action of these products.
10.14359/18372
SP239-21
K.C. Hsu, J.W. Chen, F.T. Jiang, and D.S. Hwung
Superplasticizer is one key component to greatly increase the workability of concrete. In this study, an amphoteric copolymer (PDA) was prepared and evaluated as concrete admixture. PDA was prepared froma-N, N-dimethyl-N-(3- bcarboxylate) acrylamino) propylammonium ethanate and acrylamide through free radical polymerization. The test results on cement pastes indicate that this polymer could uniformly disperse cement particles and enhance the fluidity of the system. Compared to a commercial sulfonated naphthalene formaldehyde condensates (NSF) superplasticizer, PDA requires less dosage to achieve good fluidity and provides better fluidity retention. Limited test data also show that PDA has better performance than NSF in terms of slump flow and flow retention of the resulting concrete.
10.14359/18387
SP239-19
B.O. Myrvold
The adsorption of sodium lignosulphonate onto cement was investigated. The cement has either been pre-hydrated or hydrated with the lignosulphonate present. The pre-hydrated cement particles grow with time, thus a larger surface is created and the plateaus in the adsorption isotherms increase. With lignosulphonate present there is hardly any growth of new surface. It is found that, a lignosulphonate that adsorbs strongly to the surface causes, less retardation than weakly adsorbed lignosulphonates. This can be explained by different interactions with the different minerals present.
10.14359/18385
SP239-08
T. Izumi, S. Dikty, and H. Yamamuro
A new polysaccharide derivative (NPD) is a thickener that has ionic functional groups and hydrophobic ones. This molecular structure generates unique properties [1], [2]. Generally current common thickeners like cellulose derivatives are much affected by variety and quantity of inorganic metallic ions dissolved from cement. The solubility of thickeners tends to decrease due to metallic ions. Therefore, under ion-exchanged water they add viscosity to water effectively, but the viscous property would be reduced with increase of metallic ions. On the other hand, NPD shows an opposite behaviour. As the concentration of inorganic salt such as NaCl increases, the viscosity of NPD aqueous solution rises significantly [1]. It is supposed that the formation of network structures generated by associating hydrophobic groups in the presence of metallic ions would cause excellent thickening ability. It is expected that NPD will be utilized as a thickener for self-compacting concrete and for anti-segregation in common concrete. Moreover, it is possible to make a so-called two in one product that owns both dispersability and viscous ability, because NPD is mixed with a superplasticizer easily without increasing solution viscosity.
10.14359/18374
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