| 1. |
- Westerholm, Mikael, et al.
(författare)
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Influence of fine aggregate characteristics on the rheological properties of mortars
- 2008
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Ingår i: Cement & Concrete Composites. - : Elsevier BV. - 0958-9465 .- 1873-393X. ; 30:4, s. 274-282
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents results from a laboratory study on the influence of crushed fine aggregate on the rheological properties, i.e., yield stress and plastic viscosity, of the mortar phase of concrete. The effect of grading, particle shape, etc. of the fine aggregates has been evaluated with the use of a viscometer suited for coarse particle suspensions. The evaluation has been done at different dosages of super-plasticizer and paste volumes by the use of an inert artificial "cement paste". The results show that the properties and amount of fine aggregate have a strong influence on the water demand and workability of the mortar, i.e., the rheology. The large amounts of fines often found in crushed fine aggregate primarily increases the yield stress of the mortar. The amount of fines also contributes to the plastic viscosity by increased interparticle friction. However, the results clearly show that the particle shape of the fine aggregate strongly contributes to the plastic viscosity. The influence of the properties of the fine aggregate is largely dependent on the paste volume of the mortar. Thus, by increasing the paste volume, negative effects of poorly graded and shaped aggregates can be eliminated or significantly reduced.
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| 2. |
- Westerholm, Mikael, et al.
(författare)
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Rheological properties of micromortars containing fines from manufactured aggregates
- 2006
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 40:6, s. 615-625
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns the influence of fines from manufactured aggregates on the rheological properties of the micromortar phase of concrete. Fines from nine different aggregates were included in the experimental work. The zeta potential of five of them was measured at different additions of superplasticizer in order to study the interaction between the surface of the fines and the superplasticizer. The rheological properties of the micromortars were studied at different volume concentrations of fines and at different concentrations in the paste phase, i.e., w/c ratios. Furthermore, the micromortars were studied at different dosages of a superplasticizer. The results show that the fines have different surface properties, i.e., zeta potential, and indicate that the superplasticizer only is adsorbed on some of them. The results from the rheological characterisation of the micromortars indicate that the higher water demand of concrete with manufactured aggregates partly can be traced to the properties of the micromortar phase of the concrete.
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| 3. |
- Westerholm, Mikael, et al.
(författare)
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Washing of aggregates : Influence on aggregate properties and mortar rheology
- 2006
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Ingår i: Nordic Concrete Research. - Oslo : The Nordic Concrete Federation. - 9788282080002 ; , s. 35-46
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Aggregates (0-2 mm) produced by blasting and cruching of bedrock often contains rough and flaky particles with free mica and other minerals in finer fractions. Consequently, concrete produced with this type of aggregate displays a higher water demand and lower workability than the corresponding concrete with glaciofluvial aggregate. In order to achieve the desired workability changes in the mix design and/or processing of the aggregate, e.g. sieving and washing, are required.In this paper, the effect of washing on the material properties, i.e., particle size distribution, specific surface area and sand equivalent value (SE-value), of aggregates from crushed bedrock has been studied. The effect of the washed aggregates on the water demand of mortars was also studied with rheological methods.The results show that the used washing procedure mainly removed particles below 125 µm with emphasis on particles smaller than 40 µm. Consequently, this resulted in a decrease in the specific surface area of the fine particles and, thus, a lower water demand of the mortar. This is verified in the mortar tests where the yield stress of mortars was significantly reduced when the washed aggregates were used.
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