DCP

Power Trowel  is widely used in surface of concrete raised paste and trowel and smooth out in high-standard workshop, warehouse, parking lot, square, airport and frame-style building.  Troweling with a steel trowel is done when a smooth, dense surface is desired, such as a warehouse or garage floor. Troweling is not recommend for external slabs in Florida, add water, a little mold, and someone wearing flip flops and you have a extremely dangerous situation. Be sure the surface has been floated before troweling. Bull floating or darbying alone are not adequate preparation. To save time the finisher can float the slab then trowel it as he moves across the slab on knee boards. During the first troweling use a wide trowel (at least 4 ½” wide) one that has been broken in, or a trowel that has the edges machined to give it a broken in feel. This will allow the finisher to work the trowel flat without digging into the surface. Move the trowel across the slab in...

Since the subject of repairs and  rehabilitation is very exhaustive and entails great complexities /  varieties in terms of types of distress / deterioration, materials and techniques available for repairs and rehabilitations, it has always been a daunting task for the authors to select aspects to be covered in this book.  Following sections gives the panoramic view of this book organized into six chapters: Chapter 1 (Introduction)  gives quick overview and relevance of repairs and rehabilitation of  structures besides outlining general scenario of prevalence of deterioration of concrete structures,  broad reasons for distress in structures explaining what can go wrong with structures, and a general  roadmap and steps to be followed for carrying out any structural repairs and rehabilitation. This section also defines some of the important terms that are used in this book. Chapter 2 (Distress in Structures- Serviceability and Durability...

Longitudinal steel bars have been provided to resist the tensile forces in the bottom of the beam due to bending (or flexure). Rectangular steel links would normally be provided to resist the tensile forces in the beam due to shear. In the beam shown in below video, shear links have not been provided. So, the beam experiences a sudden, brittle, shear failure as the applied load exceeds the shear capacity of the concrete. Also, n ote that how a diagonal crack forms suddenly between the left-hand support and the applied load.

Flexural strength also known as modulus of rupture, bend strength, or fracture strength, is a material property, defined as the stress in a material just before it yields in a flexure test. The flexural strength represents the highest stress experienced Within the material at its moment of rupture. It is measured in terms of stress. To overcome this type of failure, main steel is provided at the bottom/top of the beam. Flexural failure occurs at mid span of beam. There are many causes of flexural failure. The flexural failure is governed by concrete crushing after yielding of the steel. Indeed, the deformation capacity of the steel is normally not crucial.

The bend test is a simple and inexpensive qualitative test that can be used to evaluate both the ductility and soundness of a material. It is often used as a quality control test for butt-welded joints, having the advantage of simplicity of both test piece and equipment. No expensive test equipment is needed, test specimens are easily prepared and the test can, if required, be carried out on the shop floor as a quality control test to ensure consistency in production. The bend test uses a coupon that is bent in three point bending to a specified angle. The outside of the bend is extensively plastically deformed so that any defects in, or embrittlement of, the material will be revealed by the premature failure of the coupon. The bend test may be free formed or guided.

In a tensile test of mild steel specimen, usually a round or flat bar is gradually pulled in a testing machine until it breaks. Two points, called gauge points, are marked on the central portion. The distance between these points, before the application of the load, is called gauge length of the specimen. The extensions of the gauge length and the values of the corresponding loads are required at frequent intervals. The extensions are measured by an instrument called an extensometer. The strains corresponding to the recorded extensions are calculated by dividing the latter by the gauge length, while the stresses are calculated by dividing the loads by the original area of cross-section of the specimen. Stresses so arrived at is called nominal stress to distinguish it from actual stress which is obtained by dividing the load at a particular instant by the area of the cross-section at that instant. Actual stress is greater than nominal stress in a tensile test because the load in...

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