CLA Hardscape & Materials Flashcards

What does 'compressive strength' measured in PSI indicate for a hardscape material like concrete?

Answer: The force per unit area the material can withstand under compression before failure

Compressive strength (PSI) is the maximum compressive load per square inch a material can sustain; concrete for walkways is typically specified at 3,000–4,000 PSI.

Which surface treatment for concrete improves slip resistance for pedestrian areas?

Answer: Exposed aggregate or broom finish

Broom finishing or exposed aggregate creates surface texture that increases friction coefficients and reduces slip hazard, especially when wet.

What is the purpose of 'control joints' (contraction joints) in a concrete slab?

Answer: Create weakened planes that guide crack formation to controlled locations

Control joints are saw-cut or tooled grooves that create planes of weakness, directing inevitable shrinkage cracks to predictable, aesthetically acceptable locations.

What is the typical recommended base depth for a permeable interlocking concrete pavement (PICP) system designed for stormwater infiltration?

Answer: 6–12+ inches of open-graded aggregate

PICP requires a deep open-graded aggregate reservoir (often 6–18 inches) to store and infiltrate stormwater, unlike traditional pavements that simply convey runoff.

What is 'efflorescence' in masonry and concrete hardscape materials?

Answer: White salt deposits that leach to the surface as water migrates through the material

Efflorescence is the migration of soluble salts to a masonry or concrete surface where they crystallize as white deposits when water evaporates.

Which hardscape material is valued for its high thermal mass, durability, and natural variation in color and texture in landscape design?

Answer: Natural cut stone (granite, limestone, bluestone)

Natural cut stone offers exceptional durability, natural beauty, and color variation that improves with age, making it a premium landscape paving choice.