Civil Engineering PE Exam Flashcards

In a Critical Path Method (CPM) project schedule, the critical path is defined as:

Answer: The longest path through the project network, which controls the project duration

The critical path is the longest sequence of dependent activities from project start to finish; any delay on this path directly delays project completion, and all critical activities have zero total float.

In concrete mix design per ACI 318, the water-to-cementitious materials ratio (w/cm) primarily governs:

Answer: Both compressive strength and durability (permeability resistance)

A lower w/cm produces higher compressive strength and lower permeability, improving both strength and durability; this is why ACI 318 specifies maximum w/cm ratios for different exposure conditions.

A cohesive soil with a liquid limit (LL) of 55 and plasticity index (PI) of 25 plots above the A-line on the Casagrande plasticity chart. Per the Unified Soil Classification System (USCS), this soil is classified as:

Answer: CH — high-plasticity clay (fat clay)

Above the A-line means clay (C); LL = 55 ≥ 50 indicates high plasticity (H); the A-line value at LL = 55 is PI = 0.73(55 − 20) = 25.6, and PI = 25 is close but the soil's position above the line confirms CH classification.

The modulus of elasticity (Young's modulus) used for all grades of structural steel in AISC design is approximately:

Answer: 29,000 ksi (200 GPa)

E = 29,000 ksi (200 GPa) is the modulus of elasticity for all structural steel grades per the AISC Steel Construction Manual; this value is independent of the steel's yield strength.

In a project CPM schedule, 'total float' for an activity is defined as:

Answer: The amount of time an activity can be delayed without delaying the project completion date

Total float = Latest Start − Earliest Start (or equivalently, Latest Finish − Earliest Finish), representing how much an activity can slip before it impacts the project end date.

Per ACI 318, the minimum clear concrete cover required for deformed reinforcing bars #5 and smaller in a cast-in-place slab not exposed to weather is:

Answer: 3/4 inch (19 mm)

ACI 318-19 Table 20.6.1.3.1 specifies a minimum clear cover of 3/4 inch for #5 bars and smaller in cast-in-place slabs and walls not exposed to weather or in contact with the ground.

A geosynthetic geotextile placed as a separation layer between pavement subgrade and aggregate base primarily functions to:

Answer: Prevent migration of fine-grained subgrade soils into the coarser aggregate base under traffic loading

A separation geotextile acts as a filter and physical barrier, preventing the upward intrusion of fine subgrade particles into the aggregate base under traffic-induced pumping, preserving the drainage and load-spreading capacity of the base.