NETTCP Material Specifications 4

Question 1

Which AASHTO soil classification group is generally considered unsuitable as a subgrade material without treatment?

Accepted Answer

A-7-6

Answer

A-7-6 soils are highly plastic clays with poor load-bearing characteristics and are generally unsuitable as subgrade without stabilization or replacement.

Question 2

For structural steel used in highway bridges, which ASTM grade is most commonly specified for rolled W-shapes?

Accepted Answer

ASTM A709 Grade 50

Answer

ASTM A709 Grade 50 is the bridge-specific structural steel specification most commonly used for rolled W-shapes in highway bridges.

Question 3

What is the purpose of specifying a maximum water-to-cementitious-material (w/cm) ratio in bridge concrete?

Accepted Answer

To limit permeability and improve durability against chloride intrusion

Answer

A lower w/cm ratio reduces concrete permeability, limiting chloride ion penetration and protecting reinforcing steel from corrosion.

Question 4

According to AASHTO M 29, what is the standard specification for fine aggregate (sand) used in bituminous mixtures?

Accepted Answer

It covers natural sand, manufactured sand, and screenings meeting specific gradation and quality requirements

Answer

AASHTO M 29 covers fine aggregate from natural or manufactured sources used in asphalt mixtures, including gradation and quality limits.

Question 5

Fly ash used as a supplementary cementitious material in concrete must conform to which ASTM standard?

Accepted Answer

ASTM C618

Answer

ASTM C618 specifies requirements for natural pozzolans and fly ash used as supplementary cementitious materials in concrete.

(NETTCP) New England Transportation Technician Certification Program Practice Test

(NETTCP) New England Transportation Technician Certification Program Practice Test

NETTCP Material Specifications 4