Lec 2 mcqs hard

What is the percentage weight of the soil passing through the 4.75 sieve size?

9.71%

What is the range for Fine Medium (FM) grading according to the text?

2.3 - 2.5

What is one of the aspects that the optimum combined aggregate grading can help control in concrete?

Shrinkage

How does the reduction of voids occur when different sizes of aggregates are combined?

Decreases voids Signup and view all the answers

Why is it important to determine the absorption and surface moisture of aggregates?

To control total water content in concrete Signup and view all the answers

What is the maximum size of aggregate according to the information provided?

4.75 Signup and view all the answers

What percentage of aggregate should pass through the 2.36 sieve for the ASTM C33 grading limits?

80% Signup and view all the answers

What is the purpose of the Nominal Maximum Size for aggregates?

To control the spacing between rebars and forms Signup and view all the answers

How is the Nominal Maximum Size calculated based on the provided information?

1/5 the narrowest dimension between sides of forms Signup and view all the answers

Which sieve size should have 0% retained aggregate for an ideal gradation?

29 Signup and view all the answers

Why is particle size important in concrete mixtures?

To assess the surface area and its impact on properties Signup and view all the answers

How does the surface area of aggregates impact the cement requirement in concrete mixtures?

Higher surface area requires more cement Signup and view all the answers

What is the impact of larger coarse aggregate on water requirement in concrete mixtures?

Less water is required Signup and view all the answers

What does the Fineness Modulus (FM) in aggregates indicate?

Particle size distribution Signup and view all the answers

How does combined grading of aggregates help in reducing voids in concrete mixtures?

By optimizing gradation Signup and view all the answers

What is the primary influencing factor for Alkali-Carbonate Reaction (ACR)?

Clay content in the range of 5% to 25% Signup and view all the answers

Which test method is NOT used for investigating Alkali-Carbonate Reaction (ACR)?

Mortar bar expansion test (ASTM C 1260) Signup and view all the answers

What is the recommended limestone sweetening practice to control Alkali-Silica Reaction (ASR)?

Replacement of 50% of reactive aggregate with crushed limestone Signup and view all the answers

What is the main purpose of Lithium-based admixtures in concrete?

Reduce the risk of Alkali-Carbonate Reaction (ACR) Signup and view all the answers

Which factor plays a crucial role in controlling Alkali-Carbonate Reaction (ACR) according to the text?

Calcite-to-dolomite ratio of approximately 1:1 Signup and view all the answers

Why is Alkali-Silica Reaction (ASR) more concerning than Alkali-Carbonate Reaction (ACR)?

ASR occurs more frequently due to the common occurrence of aggregates containing reactive silica minerals. Signup and view all the answers

What are the visual symptoms associated with Alkali-Silica Reaction (ASR)?

Network of cracks and fragments breaking out of the surface (popouts) Signup and view all the answers

What is the mechanism behind Alkali-Silica Reaction (ASR)?

Alkali hydroxide expansion and reactive silica with moisture forming Alkali Silica Gel Signup and view all the answers

Which testing method can be used to detect Alkali-Silica Reaction (ASR) in concrete?

Petrographic Examination (ASTM C 295) Signup and view all the answers

How can Alkali-Silica Reaction (ASR) be controlled?

Use chemical additives that inhibit the alkali-silica reaction Signup and view all the answers

What is the main cause of D-cracking in concrete pavements?

Freeze-thaw deterioration of the aggregate within concrete Signup and view all the answers

What makes aggregates potentially harmful if they react with portland cement?

All of the above Signup and view all the answers

What is a popout in concrete caused by?

Internal pressure leading to breaking away of concrete surface Signup and view all the answers

Which aggregate property is most likely to cause harmful alkali-aggregate reactivity?

Presence of active mineral constituents Signup and view all the answers

How does combined grading of fine and coarse aggregate contribute to reducing voids in concrete?

By optimizing the particle distribution for better packing Signup and view all the answers

What is the purpose of grading an aggregate?

To measure the particle-size distribution of the aggregate Signup and view all the answers

Which sieve size range is considered fine aggregate according to ASTM standards?

150 μm to 9.5 mm Signup and view all the answers

Why is it important to have a proper distribution of different aggregate sizes in concrete?

To increase the strength and durability of concrete Signup and view all the answers

In concrete, what does combining fine and coarse aggregates help control?

Workability Signup and view all the answers

What is the significance of ASTM C 33 in evaluating aggregate characteristics?

It sets standards for grading aggregates based on sieve analysis Signup and view all the answers

How does the reduction of voids in concrete affect its strength?

Increases strength by reducing porosity Signup and view all the answers

Which type of aggregate represents a normal weight and falls under fine aggregate classification?

Sand Signup and view all the answers

What role does combined aggregate gradation play in reducing segregation during concrete placement?

Decreases segregation by providing a balanced mix Signup and view all the answers

What impact does proper grading of coarse aggregate have on concrete?

Increases workability and increases strength Signup and view all the answers

Why is it important to control the gradation of aggregates in concrete mixes?

To achieve desired workability and strength in the concrete Signup and view all the answers