Concrete Aggregates

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What is the primary role of aggregates in concrete?

To provide dimensional stability of concrete

To increase the strength of concrete in resisting abrasion loads and weathering effects (correct)

To act as a cheap filling material

To react with the cement

Which type of aggregate classification includes natural and artificial sources?

Source (correct)

Surface Texture

Size

Shape

What does the term 'bulking of fine aggregate' refer to?

Decrease in the volume of fine aggregate due to moisture content

Increase in the volume of fine aggregate due to moisture content (correct)

Decrease in the weight of fine aggregate due to moisture content

Increase in the weight of fine aggregate due to moisture content

What does bulk density mainly depend on in the context of aggregate properties?

Aggregate shape and surface texture (A) Signup and view all the answers

What is the bulk density range for gravel aggregate?

$1600 - 1800$ kg/m3 (B) Signup and view all the answers

Which type of aggregate has a surface texture that is described as 'honeycombed'?

Lightweight aggregate (A) Signup and view all the answers

What property does the term 'soundness' relate to in aggregate properties?

Resistance to weathering (D) Signup and view all the answers

What is the function of aggregates in concrete when combined with cement?

To increase the strength of concrete by resisting abrasion loads and weathering effects (A) Signup and view all the answers

What does the term 'lean mix' typically refer to in the context of concrete proportions?

A concrete mix with a low water to cement ratio (C) Signup and view all the answers

Which type of aggregate size includes gravel and crushed stone?

Coarse Aggregate (A) Signup and view all the answers

What is the formula for calculating bulk density?

M/V (C) Signup and view all the answers

What is the purpose of tamping the aggregate layers 25 times in the bucket?

To remove air voids and achieve a consistent density (B) Signup and view all the answers

What is the apparent specific gravity used for in concrete mix design?

To determine the volume of the solids including impermeable pores (A) Signup and view all the answers

How can the voids between aggregate particles be determined?

Using the bulk density and specific gravity of the aggregate (D) Signup and view all the answers

What is the purpose of determining the absorption capacity of an aggregate?

To understand its ability to absorb water (D) Signup and view all the answers

What is affected by the presence of moisture in fine aggregate?

The volume of a given mass of sand due to bulking (A) Signup and view all the answers

What does bulking of fine aggregate result in?

An increase in volume due to water films pushing sand particles apart (C) Signup and view all the answers

What does the term 'soundness of aggregate' refer to?

The ability of the aggregate to resist excessive changes in volume (D) Signup and view all the answers

What standard tests are used to determine the soundness of aggregate?

BS 812: Part 121 and ASTM C-88 (C) Signup and view all the answers

What is the maximum limit of salt contamination (% by weight) for fine aggregate after the soundness test?

12% for Na2SO4 and 18% for MgSO4 (D) Signup and view all the answers

What is the chloride ion content limit (expressed as a percentage by mass) for combined aggregate used in prestressed concrete?

0.01% (A) Signup and view all the answers

What is the purpose of limiting chloride and sulfate salts in aggregate according to different codes?

To prevent deleterious effects on concrete and its reinforcement (B) Signup and view all the answers

Which physical conditions can cause changes in volume and impact the soundness of aggregate?

Freezing/thawing, thermal changes, and wetting/drying cycles (A) Signup and view all the answers

What is the maximum limit on total sulfate content in concrete as per BS 882?

4% by weight of the cement mass (C) Signup and view all the answers

What destructive reaction may result from the alkali aggregate reaction?

Destruction of the bond between the aggregate and the cement paste (A) Signup and view all the answers

How can the reactivity of aggregate be detected?

Through chemical analysis of the aggregate (A) Signup and view all the answers

In the context of grading of aggregate, what does Sieve No.4 (4.75 mm) represent?

The dividing line between fine and coarse aggregate (A) Signup and view all the answers

What is the purpose of using supplementary cementing materials (SCM) in limiting alkali aggregate reaction?

To reduce alkali content in the concrete mix (D) Signup and view all the answers

What is the function of a sieve shaker in grading of coarse aggregates?

To separate particles based on size using vibration (A) Signup and view all the answers

Why should aggregate samples be oven dried before testing during sieve analysis?

To eliminate moisture which may affect test results (D) Signup and view all the answers

What does the term 'grading curves' represent in the context of sieve analysis?

The relationship between sieve size and cumulative passing percentage (B) Signup and view all the answers

What is the purpose of arranging sieves in descending order during sieve analysis?

To facilitate accurate grading by size (D) Signup and view all the answers

What is the primary function of Alkali-Silica Gel or Alkali-Carbonate-Gel in concrete?

To cause destruction of bond between aggregate and cement paste (D) Signup and view all the answers

Concrete Aggregates - I

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