Contractors'/Consultants' Materials Engineer - Test #1

The correct answer is 15 seconds. This time limit is specified to prevent excessive vibration in a single location. Prolonged operation of a vibrator in one location can cause damage to the surrounding structures or the vibrator itself. Therefore, it is important to adhere to this time limit to ensure the safety and integrity of the construction site.

Bituminous prime coat materials are used to prepare the surface of a road before the application of an asphalt layer. The prime coat helps to bond the existing pavement surface with the new asphalt layer. It is important to apply the prime coat at the correct temperature and application rate to ensure proper bonding and effectiveness. The specified temperature and application rate for bituminous prime coat materials range from 1 to 2 liters per square meter. This range allows for sufficient coverage and penetration of the prime coat material without excessive wastage or insufficient application.

The concrete in the area represented by the cores will be considered adequate if the average strength of the cores is equal to at least 85% of the specified strength, f'c, and no single core is less than 75% of f'c. This means that the cores should have a minimum average strength of 85% of the specified strength and no individual core should have a strength less than 75% of the specified strength.

When submitting any type of samples in the laboratory, it is important to include a sample card along with the samples. A sample card provides important information about the samples such as the type of sample, its origin, and any specific instructions or requirements for testing. This helps the laboratory staff to properly handle and analyze the samples. Including a sample card ensures that the samples are accurately identified and processed, leading to reliable and accurate test results.

The correct answer is "Seal." In the context of the question, the term "seal" refers to a class of concrete that is specifically designed to be deposited in water. This type of concrete is often used in underwater construction projects, such as building foundations or structures in marine environments. It is formulated to have high durability and resistance to water penetration, ensuring that it remains intact and functional even when submerged.

The sampling of the freshly mixed concrete should be taken on the middle batch discharge of the transit mixer. This is because the middle batch represents a more representative sample of the overall concrete mixture. The first batch may not be fully mixed, while the last batch may have settled or segregated during transportation. Taking the sample from the middle batch ensures that it is a fair representation of the entire mixture.

Concrete that has not been placed within 90 minutes from the time the ingredients were charged into the mixing drum or that has developed initial set should not be used. This is because concrete undergoes a chemical reaction called hydration, where the water and cement in the mixture react to form a solid mass. The initial set refers to the point at which the concrete starts to harden and lose its workability. After 90 minutes, the concrete may have already started to set and harden, making it unsuitable for use in construction.

The recommended number of blows per layer for the standard Proctor test or AASHTO T-99 or moisture density relation test is 25 blows.

A concrete specimen molded in a beam mold should be rodded multiple times per layer to ensure proper compaction and removal of air voids. The correct answer of 63 times suggests that the concrete should be rodded 63 times in each layer of the mold to achieve the desired density and strength. This ensures that the concrete is evenly distributed and free of any potential weak spots caused by inadequate compaction.

If the required thickness for the subbase or base is 150 mm or less, it can be spread and compacted in just one layer. This means that the material can be evenly distributed and compressed effectively in a single application. Using multiple layers in this case would not be necessary or efficient.

The required slump for PCCP (Plain Cement Concrete Pavement) if vibrated is 10 to 40 mm. Slump refers to the consistency or workability of the concrete mix. A slump of 10 to 40 mm indicates that the concrete should have a medium to stiff consistency, which is suitable for vibrating and compacting the concrete during construction. This range of slump ensures that the concrete is easy to handle and place, while also providing enough stiffness to resist segregation and maintain its shape.

The depth of the weakened plane joint should not be less than 50 mm, while the width should not be more than 6 mm. This ensures that the weakened plane joint is of sufficient depth to allow for controlled cracking and movement, while also ensuring that it is not too wide to compromise the structural integrity of the joint.

The flexural strength of PCCP (prestressed concrete cylinder pipe) refers to its ability to withstand bending or flexing without breaking. When tested at the third point, the flexural strength of PCCP is found to be 550 psi. This means that the PCCP can withstand a bending force of up to 550 pounds per square inch before breaking.

The correct answer is 40 to 75 mm. This range indicates the slump, or the measure of the consistency, of a workable PCCP (Portland Cement Concrete Pavement). A slump of 40 to 75 mm means that the concrete has a medium to high workability, allowing it to be easily placed and compacted without excessive segregation or bleeding. This range is commonly used for PCCP construction as it ensures that the concrete is both manageable and durable.

The flexural strength of PCCP (prestressed concrete cylinder pipe) refers to its ability to withstand bending or flexing without breaking. When tested at the mid-point, the flexural strength of PCCP is measured to be 4.50 Mpa. This means that the PCCP can withstand a certain amount of bending force before it reaches its breaking point.

Sampling of Portland cement should be done in accordance with AASHTO T-127. This standard provides guidelines for obtaining representative samples of Portland cement for testing purposes. It specifies the procedures for collecting samples from bulk shipments and bags, as well as the equipment and techniques to be used. Following the guidelines in AASHTO T-127 ensures that the samples obtained are representative of the cement being tested, which is crucial for accurate and reliable test results.

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Tie bars are used to connect and reinforce the longitudinal joint of precast concrete pavement (PCCP). These bars are placed perpendicular to the joint and help to prevent the slippage and separation of the two adjacent sections of pavement. By providing additional strength and stability, tie bars enhance the overall durability and performance of the pavement.

The weight of the rammer to be used in the compaction test using the AASHTO T-99 method (standard proctor test) is 5.5 lb.

The correct answer is item 103.

AGGREGATE SURFACE COURSE is represented by Item 300.

The minimum average strength requirement for non load-bearing concrete hollow blocks is 600 psi. This means that the blocks should have a compressive strength of at least 600 pounds per square inch to ensure their durability and ability to withstand non-load-bearing applications. A higher psi value indicates a stronger block that can withstand more pressure and is less likely to crack or break under normal use.

 Adobe, a sun-dried brick made from clay and straw, is a traditional building material used in arid climates. While it has historical significance, it is not typically used in modern bridge construction due to its limited strength and durability compared to materials like reinforced concrete and structural steel.

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