The test is performed to determine the fineness of cement i.e. whether the cement is properly grounded or not. Finer the particle, higher will be the rate of hydration and the development of strength will be quick. PROCEDURE: Take 1000 gm of cement and place it on 75µm sieve. The cement is sieved and the weight of cement-retained on the sieve is noted.
Regression equation for the determination of optimal tensile strength was also developed. The microhardness determination across the weld was done using Vicker?s microhardness tester. The specimens for microhardness examination were sectioned to the required size from the welded joints and polished using different grades of emery sheets and with alumina powder for final disc polishing. III. RESULTS AND DISCUSSION Friction welding experiments were conducted between each of the hollow head piece and solid stem piece.
In other words, the reduction in strain of reinforcement due to tensile stresses in concrete between cracks is termed as “Tension Stiffening”. Before cracking, the concrete tensile stress increases with load. When the stress in the concrete first reaches the tensile strength at a particular section, cracking occurs, Figure 1(a). When cracking occurs, the stress in the concrete at the crack, drops to zero. The concrete stress increases with distance from the crack, due to the steel-concrete bond, until at some distance from the crack, the concrete stress is no longer affected by the crack, as shown in Figure 1(b).
The breaking load (P) was noted. Young’s Modulus of Elasticity Test in accordance to ACI 318 The young’s modulus of concrete was computed using the method of Elastic Modulus provided by the code ACI 318. The compressive strength is the measured maximum resistance to axial loading, express as force per unit of cross sectional area in pounds per square inch (psi). Modulus of Elasticity can be estimated from compressive strength. Ec=Elasticity of Concrete fc=Compressive Strength of Concrete Wc=Unit Weight (Density) of the concrete Ec=33Wc1.5f1/2 (PSI lb/ft3) (ACI 318) Ec=.04.Wc1.5f1/2 (MPA kg/m^3) (ACI
Priestley (1997) and Hakuto et al. (2000) suggested the principle tensile stress approach to calculate the joint shear strength without joint shear reinforceemnt. Attalla (2004) presented a theorotical model considering the compression-softening phenomenon associated with the cracked reinforced concrete in compression. The effect of joint geometry and the presence of transverse beams are also consiered on joint shear strength. A fifth order polynomial equation was proposed by Tsonos (2002 and 2007) to find the ultimate joint shear strength.
A monolithic reinforced concrete floor is one unbroken solid mass, between 100 and 300mm thick, of in situ reinforced concrete. In this project, thickness of the concrete slab is 250mm. Formwork is required to support wet concrete for at least a week after it has been placed. The steel reinforcement is laid out on top of the support and raised 20mm or more above the formwork by means of small concrete blocks, wire chairs or plastic spacers, which are tied to the reinforcing bars with wire. The wet concrete is then placed and spread over the reinforcement and the formwork.
L Box Test: This test is also done for checking the passing ability of the concrete. The apparatus is in L shape and consist of a barrier through which the SCC is allowed to flow. The time taken by the concrete to pass the barrier and the height of the mix at the lower end of the apparatus is measured. Fig 2. L box apparatus 4.
For each mixture twelve specimens were casted, four each of beam, cube, and cylinder. Three percentages of nano-silica were used (0%, 3%, and 5%) with four percentages of partial replacement of river sand by crushed sand (0%, 33%, 67%, and 100%). Cube size of 70.6mm x 70.6mm x 70.6mm, cylinder of size 94mm x 47mm diameter and beams of size 160mm x 40mm x 40mm were casted. For the compressive strength test, four cubes were tested at the age of seven day, four cubes at the age of fourteen day and three cubes at the age of twenty-eight day. For split-tensile test, three cylinders were tested at the age of seven day, three cylinders were tested at the age of fourteen day, three cylinders were tested at the age of twenty eight day, three cylinders were tested for finding modulus of elasticity at the age of twenty eight day.
Cohesiveness is affected Aggregate grading and water content. c) Strength Strength of concrete is usually determined in terms of compressing strength. In cases where strength in tension or in shear is of primary importance the compressive strength is frequently used as a measure of this property. Factors affecting strength of concrete are as follows: • Water cement ratio: the strength of concrete depends upon strength of cement paste, & strength of cement paste depends upon dilution of paste. • Aggregate cement ratio :The strength may vary from different aggregate cement ratio.
Further, non preheated, 3000C and 7000C preheated specimen were selected for microstructural study and micro-hardness measurement from each sample. Before micro hardness measurement cross section of the welded specimen mounted and polished with 220, 600 and 1200 grit size polishing paper sequentially. Micro-hardness was measured with Vickers micro-hardness tester. Fig.3.5 Tensile test specimen 3.5 Chapter