Evaluation of Crushed Fine Materials

As natural resources of sand and fine material used in the concrete industry are becoming more scarce, crushed materials are being used to a greater extent. Shape and texture of machine crushed materials differ from aggregates naturally ground, layered and sorted under the course of millions of years. It is assumed that crushed aggregates are more angular and of less smooth texture than natural aggregates, which will affect the flow behaviour of a suspension containing crushed material. In the mix design process of cementitous suspensions, an adequate rheology of the micro mortar (all constituents in the concrete being able to pass a 0.125 mm sieve, including the cement) is crucial. In this paper, the shape of fine particles is linked to the micro mortar plastic viscosity of the filler suspension including cement. The plastic viscosity here serves as an important quality assessment of the filler, since the micro mortar workability features are vital for the final mix design quality of the concrete workability

Washing of aggregates : Influence on aggregate properties and mortar rheology

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. Godkänd; 2006; 20071121 (palle)</p

The use of by-products from metallurgical and mineral industries as filler in cement-based materials

This investigation has been made in order to make it possible to increase the use of by-products in cement-based materials. Use of by-products requires a screening procedure that will reliably determine their impact on concrete. A test procedure was developed. The most important properties were considered to be strength development, shrinkage, expansion and workability. The methods used were calorimetry, flow table tests, F-shape measurements, measurements of compressive and flexural strength and shrinkage/expansion measurements. Scanning electron microscopy was used to verify some results. Twelve byproducts were collected from Swedish metallurgical and mineral industries and classified according to the test procedure. The investigation showed that the test procedure clearly screened out the materials that can be used in the production of concrete from the unsuitable ones.Validerad; 2003; 20070112 (pafi

Washing of aggregates : Influence on aggregate properties and mortar rheology

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. Godkänd; 2006; 20071121 (palle)</p