Wyniki 1-1 spośród 1 dla zapytania: authorDesc:"Ali M. Rajabi"

Effect of coarse grain aggregate on strength parameters of two-stage concrete DOI:10.15199/33.2019.03.01

  The Two-Stage concrete (TSC) is made by placing the gravel into the mold and then filling the empty spaces between them by the mortar of sand and cement. Usually, emptying spaces between gravel are performed in two ways: weighing and injecting. In the weighting method, the mortar is poured on top of the mold filled with grit and, with the help of a compacting or vibrating, mortar fills the empty spaces. This method can be used in concrete with a maximum height of 300 mm. In the injection method, by placing the injection tubes inside the mold, the mortar is injected into themold by the pump and the injection tubes are gradually increased [1]. TSC differs from conventional concrete (CC) in several aspects. First, all ingredients of conventional concrete are mixed together and then placed in the formwork, while in TSC the grout ingredients are mixed separately and then injected into the pre-placed aggregatemass as mentioned earlier. Second, TSC has a higher coarse aggregate content than that of conventional concrete. TSC can be considered as a skeleton of coarse aggregate particles resting on each other, leaving only internal voids to be filled with grout. Conversely, in normal concrete the aggregates are rather dispersed. Therefore, TSC has a specific stress distributionmechanismat which the stresses are transferred through contact areas between coarse aggregate particles. Coarse aggregate forms about 60% of the total volume of TSC,while coarse aggregate forms about 40% of the total volume of conventional concrete [2, 8]. Abdelgader [3], through some experiments, presented an algorithm for designing TSC. Additionally, he determined the optimalwater-cement and sand-cement ratios formanufacturingTSC, and concluded that a water-cement ratio of 0.47 and a cement-sand ratio of 1 produce the highest mortar quality [3]. Compared to conventional concrete, TSC is superior in economic and geomechanical aspects and is [...]

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