Sixty mix-designs in concrete mixer corresponding to High Performance Concrete, Self Compacting Concrete or ordinary concrete were produced in the LCPC real scale mixing station. Forty-eight of these tests were already presented. A different analysis of the power consumption profile in time is given here.Henan Daswell Machinery Co., Ltd,is a professional manufacturer and trader specializing in the research, development and production of construction machinery for nearly 30 years. Our main products are as follows:mobile block machine, concrete batching plants,concrete mixer,blocking making machine,concrete pump,etc.
Concrete is batched in a 330-litre Couvrot planetary mixer at its nominal filling level. Solid components were loaded during first 15 to 18 s of operation time. Added water premixed with the HRWRA followed during about 6 s. The power consumption was measured every second. The fluctuation of the power curve was assessed here by calculating the standard deviation on 21 consecutive power measurements. The mixing time was chosen long concrete mixing plant, about 10 min, for the purpose of this study. This long mixing time permits an improved detection of the fluidity point and a fitting of the mixing behavior after the fluidity time.
Two levels of fine particles content were chosen, 425 and 550 kg/m3, respectively. In all batches these fine particles mainly consisted of cement, together with some silica fume or limestone filler. The cement was Lafarge, 52.5 CP2 from Saint Pierre Lacour or 52.5R from Le Havre. Two types of superplasticizer were alternatively used at 40% or 100% of the saturation threshold: polycarboxylictype and melamine-type. Other HRWRA contents were tested. Cohesion agent was employed for some SCC mixes. Coarse aggregates were crushed materials from two size fractions: 5/12.5 mm and 10/16 mm. The natural river sand was graded from 80 µm to 4 mm. All aggregates were from Lafarge — Les Pontreaux. For most batches used in the concrete plants, the packing density was maximized by using a sand/gravel ratio of 0.85. Other sand to gravel ratios were also tested.
Concrete fluidity after mixing is characterized by slump or slump-flow tests and by the rheology of the final mixture. The rheology is given as a Bingham model, measured using a concrete rheometer. Mixtures covers usual concrete rheology domains, with viscosity from very low up to 250 Pa s and yield stress from 100 to 2000 Pa.
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