Regarding the use of Recycled Concrete Aggregates (RCA) in road construction, which of the following is a primary technical challenge compared to natural aggregates?
- ARCA typically has higher water absorption due to the presence of adhered mortar.Correct
- BRCA is significantly heavier than natural basalt aggregates.
- CRCA cannot be compacted using standard vibratory rollers.
- DRCA is chemically inert and does not bond with bitumen.
Solution
Concept
Recycled Concrete Aggregate Properties
Formula
N/A
Step-by-step solution
1. Recall that Recycled Concrete Aggregates (RCA) contain adhered mortar from crushed concrete. 2. Recognize that this porous adhered mortar significantly increases the aggregate's water absorption rate. 3. Compare with the choices and select Option (a) as the primary technical challenge.
Explanation
Recycled Concrete Aggregates (RCA) are made from crushed old concrete, which still has leftover cement mortar sticking to the stones. This attached mortar is porous and acts like a sponge, causing RCA to absorb significantly more water than natural aggregates.
Shortcut
To remember the primary technical challenge of Recycled Concrete Aggregates (RCA), use the memory hook "RCA = Sponge Mortar": - Sponge Mortar: Adhered old mortar on recycled aggregates makes them porous, causing significantly higher water absorption compared to natural aggregates.
Common mistake
A common mistake is selecting options B or C by assuming RCA behaves radically differently in weight or compaction mechanics compared to natural aggregates. In reality, RCA is lighter than natural basalt aggregates due to the lower density of adhered mortar, and it can be compacted using standard vibratory equipment. The main technical challenge is its significantly higher water absorption caused by the porous attached mortar.
Correct answer: A) RCA typically has higher water absorption due to the presence of adhered mortar.