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Edition:Final Report, Period: 5/01/16 – 7/31/19
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Abstract:The experimental work attesting the validity of the proposed mix design procedure was performed in both fresh and hardened states via a series of VFC (Vibration Free Concrete) mixes provided by other researcher in separate project. The test mixes were found to meet the necessary self-compacting and the compressive strength criteria, thus fully validating the proposed mix proportioning method. Therefore, this method reduces considerably the extent of laboratory work, the testing time and the materials used. Experimental study showed that the VFC has a lower viscosity comparing with conventional concrete due to the mix design criteria for the VFC which have smaller volume of coarse aggregates. The required force for VFC to flow is shown to be inversely proportional to its slump, and also the fines materials (slag) has significant effects on flow ability and shape-holding ability of VFC as shown clearly in results of the mixing design of SL-B-AC and AC, the results of SL-B-AC shows high compressive strength and slump comparing with AC mix design due to the slag material. “Increasing the filing material (slag) content of a cement-based material considerably increases its yield stress and viscosity”. The SL-B-1 mix design need to be redesign because of its result of the slump tests. Two different samples were made for this mix and in both cases the slump tests were 0 and 0.5 in. From this it was found the clay is has significant effects on flow ability. The compressive strength and rate of the strength development of VFC tend to be higher than those of conventional concrete due to the lower water-to-binder ratio. The elastic modulus of VFC is lower due to its low coarse aggregate content. The porosity and rapid chloride ion permeability of VFC are noticeably higher than those of conventional pavement concrete at 28 days, but they become comparable at the later ages, probably due to the extensive use of supplementary materials. The heat of cementations material hydration of VFC is comparable to or lowers than that of conventional pavement concrete. The freeze-thaw durability of VFC is also comparable to that of conventional concrete, which is primarily dependent upon durability of the aggregates used. Scaling resistance to deicing chemicals varies with VFC mixes, and addition of filling material generally provides VFC with a better scaling resistance to deicing chemicals. The AC mix was further modified to achieve high early strength by adding accelerator in the mixture and having different curing conditions. The optimum content of the accelerator to develop high early strength was to be 36 oz. Among the four different curing conditions with the AC mixtures having 36oz accelerator, oven dry condition is the best to achieve high early strength. A comparison analysis shows that the material cost of VFC is equal to or greater than that of conventional pavement concrete. The main contributors to the higher cost in VFC are the use of more cementations materials and admixtures/additives. The total costs, the sum of material and construction costs, of VFC mixes are comparable to those of conventional concrete.
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[PDF-12.48 MB]
