Category: Project managment

Category: Project managment Handling and fixing steel reinforcement

In best engineering practice the engineer will produce complete bar-bending schedules for use by the contractor. The engineer may not guarantee that such schedules are error free and may call upon the contractor to check them. But, as often as not, the contractor will fail to do this, so it is advisable for the resident engineer to check the schedules so that he can

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Category: Project managment Concrete finish problems

The skill required by carpenters to make and erect formwork for concrete is seldom fully appreciated. The formwork must remain ‘true to line and level’ despite substantial loading from the wet concrete. Column and wall faces have to be strictly vertical, and beam soffits strictly level, or any departure will be easily visible by eye. Formwork for concrete which is to remain exposed to view

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Category: Project managment Construction and other joints

The resident engineer must agree with the contractor where construction joints should be placed; but he should not require them to be placed in impracticable positions and must allow for the manner in which formwork must necessarily be erected. There are positions for construction joints which are ‘traditional’ even though the position may not seem to be the most desirable from a structural point of

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Category: Project managment Conveyance and placing of concrete

Specifications often contain clauses dealing with the transport of concrete, requiring re-mixing after transport beyond a certain limit, limiting the height through which concrete can be dropped, and requiring no concrete be placed when more than a certain time has elapsed since mixing. In practice, problems of this sort seldom prove significant. Sometimes it may be necessary to insist that a contractor uses a closed

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Category: Project managment Site checks on concrete quality

until some days after the concrete has been placed. If weak concrete appears to have been placed in a structure a difficult situation arises. The resident engineer can ask for the offending concrete to be demolished and re-built but this may pose such difficulty and delay that the decision ought not to be made on site without first discussing the

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Category: Project managment Some causes of unsatisfactory concrete test results

The two most common kinds of failure are: • failure to get the required strength, the concrete being otherwise apparently good; • structural failures, such as honeycombing, sandy patches, and cracking. Failure to get the right strength in cubes taken from a concrete pour can sometimes have a very simple cause. Among such causes are the following: • the cube was not

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Category: Project managment Practical points in producing good concrete

Provided certain simple rules are followed good concrete can be achieved by methods varying from the ‘bucket and spade’ hand-labour method to use of the most sophisticated weigh-batching and mixing plant. The following shows the principal matters that should receive the resident engineer’s attention. First, choose good aggregates. The best guide is to use well-known local aggregates that have been and are being used

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Category: Project managment Workability of concrete and admixtures

Workability requirements for a concrete mix tend to conflict with requirements for maximum strength, density and economy, since workability increases with increased fines, cement, or water in a mix, but increased fines and water reduce density and strength, while increased cement may increase shrinkage and liability to cracking as well as adding to the cost of a mix. It is

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Category: Project managment Grading of aggregates and their suitable mixing

The 1981 edition of BS 5328 (referred to in Section 19.1) provided a useful table showing the amount of aggregate per 100 kg cement in what were then termed (see Section 19.2), Ordinary prescribed mixes as shown in Table 19.3, and the percentage of fine aggregate to total aggregate in these mixes as shown in Table 19.4. The grading of the fine aggregate was

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Category: Project managment Practical compliance with concrete standards

It can be seen that although designing a trial mix to meet a given grade can be done within a reasonable time using recommended minimum S values, the proving of a mix by statistical analysis of cube strengths is a lengthy business. At least 20 batches of concrete would have to be made up (preferably 30 or more) and at least two cubes

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