Concrete vacuum implementation and determination of the effects of steel fiber compound on concrete characteristics

Several factors affect the useful life of the concrete. On top of these the adverse weather and load conditions, inappropriate mixture designs and application methods are found. Nowadays, usually the additives are preferred in order to avoid the negative properties that can be seen in the concrete and the fibers are one of the most commonly used additives. It is preferred particularly due to the flexural strength of the concrete and to increase their energy absorption capacity. It is added to the concrete mostly in the field concretes, in order to prevent the breakages and fragmentations. One of the factors that mostly affect the strength of the concrete is the amount of water. Water is a mixture material, which is required for the workability and hydration reaction in the concrete. However, after the concrete takes the form of the mold, the task of the portion of the water that is required for the workability is finished. In this case some problems may be able to arise depending on the amount of water such as the deterioration of the homogeneity, segregation, sweating and shrinkage cracks. The vacuum concrete is an application carried out in order to avoid these problems and it is the process of removing back an amount of the mixture water from the fresh concrete which takes the shape of the mold. The parameters of this study are the steel fibers and the application of vacuum. The steel fibers are used in the normal and vacuum concretes in two different lengths and in three different ratios and in three different strength classes. The purpose of the study is to put forward the difference from the normal concretes of the length of the steel fiber, the ratio and the vacuum application by determining the energy absorption capacities with pressure, beam bending and plate tests. When all of the parameters of the study are evaluated all together, the steel fibers and vacuum application can be able to increase the concrete compressive strength up to 35%. In the beam flexural strengths, increases up to 38% were seen depending on the fiber ratio and increases up to 65% were seen together with the vacuum application. When considering the energy absorption capacities, the fibreless reference concretes were seen in the level of at least 1.7% and at most 13%. As a result, when the steel fibers are used in the limit range determined by TS 10514, they indicate a positive effect to the mechanical strength of the concrete. Keywords: Compressive Strength, Concrete, Steel Fiber, Beam Bending, Energy Absorption Capacity, Fiber Reinforcement Concrete, Slab Test, Vacuum Concrete