Tahir Çelik

Effects of crushed stone dust on some properties of concrete

Abstract Crusher dust is a fine material formed during the process of comminution of rock into crushed stone or crushed sand. This dust is composed by particles which pass 75 μm BS sieve. Effects of dust content in aggregate on properties of fresh and hardened concrete are not known very well. An experimental study was undertaken to find out the effects of various proportions of dust content on properties of fresh concrete and hardened concrete.

Effect of silica fume and steel fibers on some properties of high-strength concrete

Abstract The main disadvantage of high-strength concrete is its highly brittle behavior and this can beovercome by adding fibers to the concrete. This would also improve some other mechanical properties of high-strength concrete such as tensile strength and compressive strength. These properties are not very well established for high-strength steel-fiber reinforced concrete (HSFRC) yet. In this study the influence of silica fume on the properties of HSFRC were investigated by using silica fume of two different percentages and three different hooked-end fibers namely, 30/0.50, 60/0.80 and 50/0.60 length/diameter (mm/mm). Fibers were added to concrete in three different volume percentages of 0.5, 1.0 and 2.0 by volume of concrete. The results indicated that there is a linear function between splitting tensile strength (Fsplt) and volume percentage of fibers (Vf) [i.e. Fplt = A(Vf) + B, where A and B are correlation coefficients] as well as between splitting tensile strength (Fsplt) and compressive strength (Fc) of plain series A concrete [i.e. Fsplt = C (√Fc) + D, where C and D are correlation coefficients]. These relations can describe the development of splitting tensile strength of HSFRC containing no silica fume, 5% silica fume and 10% silica fume by weight of cement. On the other hand, although silica fume has an effect on compressive strength, volume percentage and aspect ratio of steel fibers has little effect.

Knowledge based-system for alternative design, cost estimating and scheduling

Abstract The traditional design, cost estimating and scheduling procedures focus on assessing costs and schedule after design decisions are made and conveyed to construction drawings and design that is, they do not have a mechanism that allow the designer to perform a rapid ‘what if’ analysis on design alternatives and cost analysis of different types of building materials and alternative schedule analysis at early stage of project without accompanying of detailed design and drawing. Moreover, the available scheduling tools are not integrated to design and cost estimating system and hence require manual input of activities lists, activities sequencing, resources, costs and durations to generate project schedule and they are unable to consider the effect of productivity factors and the resulting uncertainty inherent in each activity. This paper presents an integrated knowledge based system for construction cost estimating and scheduling. The knowledge based system supports an automated alternative design analysis with on line schematic drawing, material selection, crew selection and productivity analysis for generating activities sequencing, normal durations, productivity adjusted durations, cost estimate, list of materials selected and their respective quantities and list of assigned crew. An analysis of alternative design, cost estimating and scheduling for a residential building using the integrated system is presented.

Effect of coarse aggregate size on interfacial cracking under uniaxial compression

Abstract The effects of aggregate type and size are important parameters in the formation of interfacial transition zone (ITZ) structure and subsequently in the failure process of concrete. The influence of surface, rigidity and size of aggregates and water/cement (w/c) ratio of the matrix on bond strength at the ITZ and the interrelationship between the bond and the matrix in the failure process of concrete under uniaxial compression were studied. For this purpose a series of experiments were designed and carried out on mortars (with two different w/c ratios) containing single spherical steel aggregates. The ITZ properties and the failure process of concrete were investigated by means of tensile and compressive strength, and stress–volumetric strain measurements. It was observed that the effect of aggregate properties (high modulus of elasticity, smooth surface texture and size) on the weakness of ITZ and the failure process of concrete are of paramount importance for low w/c ratio composites. The effect of reduced bond properties was reflected in lowered critical stress levels for the low w/c ratio composites with larger aggregates.

An integrated web-based data warehouse and artificial neural networks system for unit price analysis with inflation adjustment

Abstract Estimating is a fundamental part of construction projects. Accurate cost estimate is the single most important element involved in the series of events that leads to a profitable completion of a contract in construction industry. The success or failure of a project depends on the accuracy of cost estimation. A cost estimate becomes more difficult and more complicated under inflationary medium. An unpredictable inflation rate and long progress payment delay during this period makes the budgeting function very difficult, if not impossible. The cost estimation process uses lots of data. The availability of the appropriate data at the appropriate time is one of the main factors affecting the accuracy of the cost estimation. As the complexity of the estimating task increases computerized system becomes increasingly important. The estimator should develop a good system of estimating forms and procedures that exactly meet the requirements of the pro- ject, and that is understood and accessible by all te...

Effects of Silica Fume and Steel Fibers on Some Mechanical Properties of High-Strength Fiber-Reinforced Concrete

There are many test methods to measure the impact resistance of fiber-reinforced concrete that are complicated, time consuming, and expensive. A practical test method has been developed to measure the impact resistance of high-strength fiber-reinforced concrete (HSFRC). The equipment developed can also be used for testing aggregate impact values by simply changing the base plate of the machine. A machine was developed to measure the surface abrasion resistance of HSFRC. Testing fiber-reinforced concrete for surface abrasion resistance was found to be extremely difficult if realistic and practical results were desired. In this study the influence of silica fume on the properties of HSFRC was investigated by using silica fume at two different percentages and with three different hooked-end fibers, namely, 30/0.50, 60/0.80, and 50/0.60 length/diameter (mm/mm). Fibers were added to concrete in three different percentages of 0.5, 1.0, and 2.0% by volume of concrete. The results show that including fibers in high-strength concrete improves impact resistance, surface abrasion, and splitting tensile strength.

A knowledge-based system for determination of marginal value of building projects

Abstract Marginal value of a building is the subjective part of the value of the constructed facility and depends on how the decisions made by the contributing parties at different stages of the implementation of the project of a building. To increase the marginal value of a building, decisions made during the stages of a project need to be in close agreement with the value criteria of the decisions. Traditionally, during the implementation of a building project designers and clients make decisions with a little knowledge of the effects contributed by the decisions on the value the constructed facility. Knowledge of decisions to be made during the stages of a building project, value criteria of the decisions and their effects on the value of the constructed facility are important for successful project implementation. Therefore, determination of marginal value of a construction project lends itself to a knowledge-based application. This paper presents a knowledge-based system called COMVOB for the determination of the marginal value of a building project. To the user COMVOB presents criteria of decisions together with their importance weights at stages of a building project and with the input and confirmation of the details of the decisions it reports anticipated positive and negative marginal values.