The document discusses the use of manufactured sands and high cote aggregates in concrete paving from the Texas Department of Transportation's perspective. It highlights the impact of using specific materials on concrete durability, referencing the significant costs incurred in addressing spalling in continuously reinforced concrete pavements over the past 25 years. The findings suggest that adhering to cote requirements has greatly reduced spalling issues in recent years.

1. Two Lift Concrete Paving
TxDOT Perspective
Andy Naranjo, P.E.

2. • Use of Manufactured Sands
• Use of Coarse Aggregates with High CoTE
values
Use of Local Materials

3. Use of Manufactured Sands

4. Manufactured Sands
Natural River Sand
Depletion

5. TxDOT Spec Limits
• Concrete subject to direct
traffic requires the use of
fine aggregates or blends
to have a A.I. greater than
60%.
• Limits the use of Man.
Sands

6. Use of High CoTE Concrete

7. High CoTE
Aggregates

8. CoTE Data
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
CoTE, microstrain/F
Coarse Aggregate CoTE Values
25% above Limit
Acceptable for
use in CRCP
Unacceptable for
use in CRCP

9. San Antonio ACI June 27, 2012
Spalling in Concrete Pavement

10. Classification of TxDOT CRCP Distresses
0‐6274 Project Level Performance Database for Rigid Pavement in Texas, Phase II
San Antonio ACI June 27, 2012

11. Money Spent to Solve Problem
• Research
– Over $2 million for the past 25 years
• Maintenance
– The Houston District has spent:
• $41+ million to repair CRCP spalling
• $400+ million to place bonded overlays
• Spalling virtually eliminated since the CoTE
requirement began use in HOU ~10 years ago
–Restricts the use of local aggregates

12. Lower CoTE Concrete
Or
Concrete with Natural
Sands
Higher CoTE
Concrete
Or
Concrete with Man.
Sands

13. Questions