An investigation into the use of manufactured sand as a 100% replacement for fine aggregate in concrete

Manufactured sand differs from natural sea and river dredged sand in its physical and mineralogical properties. These can be both beneficial and detrimental to the fresh and hardened properties of concrete. This paper presents the results of a laboratory study in which manufactured sand produced in an industry sized crushing plant was characterised with respect to its physical and mineralogical properties. The influence of these characteristics on concrete workability and strength, when manufactured sand completely replaced natural sand in concrete, was investigated and modelled using artificial neural networks (ANN). The results show that the manufactured sand concrete made in this study generally requires a higher water/cement (w/c) ratio for workability equal to that of natural sand concrete due to the higher angularity of the manufactured sand particles. Water reducing admixtures can be used to compensate for this if the manufactured sand does not contain clay particles. At the same w/c ratio, the compressive and flexural strength of manufactured sand concrete exceeds that of natural sand concrete. ANN proved a valuable and reliable method of predicting concrete strength and workability based on the properties of the fine aggregate (FA) and the concrete mix composition

Development of high shrinkage Polyethylene Terephthalate (PET) shape memory polymer tendons for concrete crack closure

YesThe shrinkage force exerted by restrained shape memory polymers can potentially be used to close cracks in structural concrete. This paper describes the physical processing and experimental work undertaken to develop high shrinkage die-drawn Polyethylene Terephthalate (PET) shape memory polymer tendons for use within a crack closure system. The extrusion and die-drawing procedure used to manufacture a series of PET tendon samples is described. The results from a set of restrained shrinkage tests, undertaken at differing activation temperatures, are also presented along with the mechanical properties of the most promising samples. The stress developed within the tendons is found to be related to the activation temperature, the cross-sectional area and to the draw rate used during manufacture. Comparisons with commercially-available PET strip samples used in previous research are made, demonstrating an increase in restrained shrinkage stress by a factor of two for manufactured PET filament samples.Thanks must go to the EPSRC for their funding of the Materials for Life (M4L) project (EP/K026631/1) and to Costain Group PLC. for their industrial sponsorship of the project and author

Structural and geo-environmental applications of waste quarry dust

This thesis presents a study of the characterisation of fine aggregates manufactured from waste quarry material and their use in concrete supported by artificial neural network models of the fresh and hardened concrete properties. The reutilization of rock filler, a by-product of the sand manufacturing process, as a soil liming material is explored. A set of tests and techniques were identified to characterise fine aggregates manufactured from quarry dusts via a dry processing system. Granite, limestone, sandstone and basalt manufactured sands and their unprocessed counterparts “feed quarry dusts” were characterised with respect to their shape and texture, grading and quality of fines (presence of clays). The results showed that the reprocessing of quarry dusts improves the particle shape and grading irrespective of rock mineralogy. Plasticised and non-plasticised concrete mixes were developed and the fresh and hardened properties tested. Concrete consistency, compressive and flexural strength is correlated with the fine aggregate characterisation test results. The manufactured fine aggregates showed a higher water demand when compared with natural sand whereas compressive and flexural strengths were enhanced. Artificial neural network models were developed to enable the prediction of the consistency and compressive strength of concrete. These models used the fine aggregate properties and mix composition parameters as input variables and were validated using a separate testing dataset, additional concrete mixes and numerical evaluation. Artificial neural network models were shown to be able to predict fresh and hardened concrete properties based on the fine aggregate characteristics. The excess fillers created in the sand manufacturing process were evaluated for soil liming potential through standard tests and a soil incubation study. The main finding was that materials with high silicate content exhibit a potential for liming, however, a higher dosage is required when compared to the dosage of high purity limestone to achieve the same liming potential