Paddy Engineering Consultant

In large work or in major construction works, cement is generally stored at site. The cement must be stored in such a manner so that, it can be easily accessible for proper inspection. The building in which cement is stored should be water tight in order to prevent dampness. The guidelines given below should be observed while storing the cement. 1. Cement should not be stored for a long period. During rainy season, the storage time period of cement should be as minimal as possible. 2. Dampness in godowns must be avoided. 3. Cement should not be piled against the wall. A minimum space of 60 cm all –round should be left between the exterior walls and the stacks. The distance between two consecutive stacks should be minimum to reduce circulation of air. 4. Cement should not be piled directly on the floor; instead it should be piled off the floor on wooden planks/crates so as to be clear off the floor by at least 10 to 20 cm. 5. There should not be more than 15 bags in one pile. This...

ADVANTAGES OF PRECAST CONCRETE Following are the advantages of precast concrete: 1. The concrete of superior quality is produced as it is possible to have better technical control on the production of concrete in factory. 2. It is not necessary to provide joints in the precast construction. 3. The labour required in the manufacturing process of the precast units can easily be trained. 4. The moulds employed for preparing the precast units are of steel with exact dimension in all directions. These moulds are more durable and they can be used several times. 5. The precast articles may be given the desired shape and finish with accuracy. 6.The precast structures can be dismantled, when required and they can then be suitably used elsewhere. 7. The transport and storage of various components of concrete for cast in-situ work are eliminated when precast members are adopted. 8. The work can be completed in a short time, when precast units are adopted. 9. When precast structures are to be ins...

The following properties of soil are taken into consideration while dealing with soil as a construction material. Cohesion  Angle of internal friction  Capillarity  Permeability  Elasticity  Compressibility  1. COHESION It is the internal molecular attraction which resists the rupture or shear of a material. Cohesion is derived in the fine grained soils from the water films which bind together the individual particles in the soil mass. Cohesion is the property of the fine grained soil with particle size below 0.002 mm. cohesion of a soil decreases as the moisture content increases. Cohesion is greater in well compacted clays and it is independent of the external load applied. 2. ANGLE OF INTERNAL FRICTION The resistance in sliding of grain particles of a soil mass depends upon the angle of internal friction. It is usually considered that the value of the angle of internal friction is almost independent of the normal pressure but varies with the de...

The choice of whether a structure should be built of concrete, steel, masonry, or timber depends on the availability of materials and on a number of value decisions. 1. ECONOMY Frequently, the foremost consideration is the overall cost of the structure. This is, of course, a function of the costs of the materials and the labour and the time necessary to erect them. Concrete floor systems tend to be thinner than structural steel systems because the girders and beams or joists all fit within the same depth, or the floors are flat plates. This produces an overall reduction in the height of a building compared to a steel building, which leads to a; a. Lower wind loads because there is less area exposed to wind b. And savings in cladding and mechanical and electrical risers Frequently, however, the overall cost is affected as much or more by the overall construction time since the contractor and the owner must allocate money to carry out the construction and will not receive a retu...

SUITABILITY OF WATER FOR CONCRETE MIXING OBJECTIVE To assess suitability of water for use in concrete mix. EQUIPMENT Measuring cylinder Cube moulds Trowel Tamping rod Vibrating table Testing machine PROCEDURE Analyse water for its chemical compositions as per  IS 3025-1964  and compare these with permissible limits given in  IS: 456-2000 .In case water does not satisfy the permissible limits or it is not possible to obtain chemical analysis data readily, the suitability of water is tested by making concrete cubes. Concrete of desired grade is prepared with available water with designed proportions and cubes casted for testing. Prepare the same concrete mix with distilled water and cast the cubes in exactly the similar manner as with water of unknown nature. Cure both the sample in respective water under exactly the same conditions. Test both the cube specimens after 7 and 28 days in exactly the same manner. Compare the test results of strength and cond...

DURABILITY OF CONCRETE PILES Properly mixed concrete compacted to a dense impermeable mass is one of the most permanent of all constructional material and give little cause of concern about its long-term durability in a non aggressive environment. However, concrete can be  attacked by sulphate and sulfuric acid  occurring naturally in soils, by corrosive chemicals which may be present in industrial waste in fill materials and by organic acids and carbon dioxide present in ground water as a result of decaying vegetable matters. Attack by sulphates is a disruptive process whereas the action of organic acids or dissolved carbon dioxide is one of leaching. Attack by sulphuric acid combines features of both processes. The severity of attack by soluble sulphates must be assessed by determining the soluble sulphate content and the proportions of the various cat ions present in an aqueous extract of the soil. These determinations must be made in all cases where the concentration of s...

DURABILITY OF BUILDING FOUNDATION A foundation is that part of the structure which is in direct contact with ground. Therefore foundations are subjected to attack by chemicals present in soil, water and by mechanical abrasion and erosion. The extent of deterioration depends on the concentration of chemicals, the level of and fluctuations in the ground water table or the variation in tidal and river level or on climatic conditions. The only way to increase the durability of foundation is to protect the foundation material from the above mentioned attacks. There are 4 types of material commonly used as foundation material, such as Timber foundation Metal foundation Concrete foundation Brick work foundation Let us discuss methods of protecting different foundation material from deterioration. 1. PROTECTION OF TIMBER FOUNDATION Timber piles are liable to fungal attack and termites, if kept in moist conditions. The protection of timber is best achieved by pressure treatment w...

FAILURE OF SHALLOW FOUNDATION & PREVENTIVE MEASURES The major causes of foundation failures are as follow Unequal settlement of sub soil Unequal settlement of masonry Presence of expansive soil below foundation Presence of mature trees Seasonal changes 1. UNEQUAL SETTLEMENT OF SUB SOIL This is one of the most important reasons for foundation failure. Unequal settlement causes cracks in the foundation and ultimately leads to failure of the whole structure. Unequal settlement of the foundation generally occurs for the following reasons The sub soil may not be uniform throughout the site. This means if some part of the site consist of compressible soil (such as clay) and some part consist of hard stratum (such as rock). The load coming from the structure may not be uniform. It may occur also on building constructed on sloping ground. REMEDIES The foundation should be designed in such a way that the pressure on soil on different portions of the structure and correspondi...

TYPES OF LOADS External loads on a structure may be classified in several different ways. In one classification, they may be considered as static or dynamic. 1. Static loads  are forces that are applied slowly and then remain nearly constant. One example is the weight, or dead load, of a floor or roof system. 2. Dynamic loads  vary with time. They include repeated and impact loads. 3. Repeated loads  are forces that are applied a number of times, causing a variation in the magnitude, and sometimes also in the sense, of the internal forces. A good example is an off-balance motor. 4. Impact loads  are forces that require a structure or its components to absorb energy in a short interval of time. An example is the dropping of a heavy weight on a floor slab, or the shock wave from an explosion striking the walls and roof of a building. External forces may also be classified as distributed and concentrated. 5. Uniformly distributed loads  are forces that are, o...

GRADING In case of sands, it has been found that materials having a large deficiency or excess of any size fraction adversely affect the workability of concrete. The most important size fraction in a concrete sand are those passing the 0.30, 0.15 and 0.075 mm sieves. If these fractions are too low the concrete tends to be prone to segregation. A rule of thumb guideline for optimum percentage is 30%, 15% and 7.5% respectively passing the 0.30 mm, 0.15 mm and 0.075 mm sieves. The percentage passing the 0.075 mm sieve may be used as a first estimate of the concrete’s tendency to bleed -the greater this fraction the lower the bleeding. BULK DENSITY Bulk density is a measure of aggregate packing capacity and therefore influences water requirement and mix proportioning. It does not have a direct influence on workability, provided the mix is correctly proportioned. PARTICLE SPECIFIC GRAVITY Because bleeding and settlement are driven by the force of gravity, the higher the specific g...

The following properties of aggregate affect the properties of hardened concrete. 1. GRADING Aggregate grading has no significant effect on the properties of hardened concrete. 2. BULK DENSITY This has no direct effect but has an indirect effect on drying shrinkage. Bulk density is an indicator of packing capacity, which influences water requirement, which in turn influences drying shrinkage of hardened concrete. For a given particle specific gravity, the higher the bulk densities of sand and stone, the lower the water requirement and hence the lower the drying shrinkage. 3. PARTICLE SPECIFIC GRAVITY Because aggregates make up about 80% of the mass of concrete, particles specific gravity of aggregates significantly affects the density of the concrete. 4. PARTICLE SHAPE Angular, flat and elongated stone particles tend to increase the flexural strength of concrete. The effect of particle shape on compressive strength is negligible. 5. SURFACE TEXTURE Rou...

CHECKING OF CONCRETE SLAB 1. Check all the concealed electric conduit work, junctions and electrical points, the positions of fan points, and MS boxes as per your electrical layout plan. 2. Check the reinforcement and get an approval from your RCC consultant. 3. Check the standby arrangements made for water in case of power failure. 4. Consult your RCC consultant before you decide the position of concrete joints in case of a big slab. 5. Ensure that wooden pieces, paper, nails, etc. are removed from the beam before casting. 6. Ensure that the shuttering, supporting, and the scaffolding are firm and proper. 7. Ensure that all joints in the formwork are properly sealed. This helps avoid slurry leakage.It is better to use putty made of grease and cement (50:50) instead of using mud, jute, paper, etc. This putty effectively seals joints and remains intact during the vibration of concrete. You can also use strips of aluminium foil to cover the gap.Place wooden planks and steel chairs...

PROPERTIES OF MORTAR Properties of mortar which are sought for use in masonry are: workability, water retentivity, rate of stiffening, strength, resistance to rain penetration and durability. These properties have been discussed below explaining their effect on masonry. Choice of masonry mortar is governed by several considerations such as: Type of masonry unit and its properties, Degree of exposure to weather and environments, Strength requirements, etc. 1.  WORKABILITY Workability is the property of mortar which enables it to be spread and applied to masonry unit with ease. It also facilitates proper filling of joints in masonry. A good mortar would hang from the trowel and will flow down readily when lightly jerked. This property of mortar depends on properties of various ingredients used for making mortar and on the method of mixing adopted. As a general rule, a mud mortar prepared from fine clay soil has better workability than one prepared from sandy soil and a lime mort...