CLARB - Council of Landscape Architectural Registration Boards Materials and Construction Methods Questions and Answers — Questions and Answers
Question 1: A landscape architect is specifying materials for a public plaza where slip resistance is a primary safety concern, especially in a climate with frequent rainfall. Which of the following concrete finishes is MOST suitable for this application?
- A hard trowel finish, creating a smooth, dense surface.
- An exposed aggregate finish, revealing the texture of the coarse aggregate. (Correct answer)
- A polished finish, ground to a high-gloss sheen.
- A salt finish, which creates small, subtle indentations on the surface.
Correct answer: An exposed aggregate finish, revealing the texture of the coarse aggregate.
An exposed aggregate finish provides a highly textured surface with excellent slip resistance, making it ideal for wet conditions. A hard trowel or polished finish would be too smooth and become very slippery when wet. A salt finish offers some texture, but the small pits are generally less effective for slip resistance in high-traffic public areas compared to the robust texture of exposed aggregate.
Question 2: When designing a freestanding seat wall using brick, which type of mortar joint is recommended for the greatest durability and resistance to water penetration?
- Raked joint
- Flush joint
- Extruded (squeezed) joint
- Concave joint (Correct answer)
Correct answer: Concave joint
The concave joint is formed by tooling the mortar into a curved, indented shape. This profile effectively sheds water and is tightly compacted, making it the most resistant to weather and water penetration. Raked, flush, and extruded joints can create ledges or surfaces where water can collect, leading to accelerated deterioration.
Question 3: A landscape architect is specifying wood for a series of benches and a pergola in a park. The client wants to avoid chemical treatments and desires a material with high natural resistance to rot and insects. Which of the following wood species is the best choice?
- Douglas Fir
- White Pine
- Black Locust (Correct answer)
- Red Oak
Correct answer: Black Locust
Black Locust is a North American hardwood known for its exceptional density and natural compounds that make it highly resistant to rot and insects, often used for applications like fence posts due to its longevity in ground contact. While Douglas Fir, White Pine, and Red Oak are common construction woods, they do not possess the same high level of natural decay resistance and would typically require chemical treatment for long-term exterior use.
Question 4: In the construction of a flexible pavement system, such as for an interlocking concrete paver walkway, what is the primary function of the aggregate base course?
- To provide a perfectly smooth surface for laying the pavers.
- To act as a waterproof barrier to prevent moisture from reaching the subgrade.
- To distribute structural loads from the surface to the subgrade. (Correct answer)
- To prevent weed growth between the paver joints.
Correct answer: To distribute structural loads from the surface to the subgrade.
The aggregate base course is the main structural component of a flexible pavement system. Its primary role is to evenly distribute the loads (e.g., from pedestrian or vehicular traffic) over a wider area of the subgrade soil, preventing deformation and failure of the pavement surface.
Question 5: A detail for a custom steel railing specifies a 'hot-dip galvanized' finish. What is the primary purpose of this specification?
- To provide a smooth, paint-ready surface.
- To increase the tensile strength of the steel.
- To apply a sacrificial zinc coating for corrosion protection. (Correct answer)
- To create a dark, weathered appearance similar to Corten steel.
Correct answer: To apply a sacrificial zinc coating for corrosion protection.
Hot-dip galvanizing involves immersing the steel in molten zinc. The zinc bonds metallurgically to the steel, creating a durable coating that provides corrosion protection by acting as a physical barrier and a sacrificial anode, meaning the zinc corrodes first to protect the underlying steel.
Question 6: During the construction of a segmental retaining wall, a non-woven geotextile filter fabric is specified for placement behind the drainage aggregate. What is the main function of this fabric?
- To add structural strength to the retaining wall blocks.
- To prevent the migration of fine soil particles into the drainage aggregate. (Correct answer)
- To act as a waterproof liner to keep the backfill dry.
- To create a root barrier preventing landscape plants from damaging the wall.
Correct answer: To prevent the migration of fine soil particles into the drainage aggregate.
The primary function of a non-woven geotextile in this application is filtration and separation. It allows water to pass through into the drainage aggregate but prevents fine soil particles from the retained earth from migrating and clogging the aggregate, which would compromise the drainage system's effectiveness and increase hydrostatic pressure.
CLARB - Council of Landscape Architectural Registration Boards Materials and Construction Methods Questions and Answers
A landscape architect is specifying materials for a public plaza where slip resistance is a primary safety concern, especially in a climate with frequent rainfall.
Which of the following concrete finishes is MOST suitable for this application?