SESSION 9 Construction Considerations

Objectives  Describe key aspects of: Prepaving operations Paving operations Postpaving operations  Understand effects of pavement texturing  Identify benefits of initial pavement smoothness

Prepaving Activities  Subgrade preparation  Base preparation  Joint layout

Subgrade Preparation  Mixing in coarser material or stabilizer (as needed)  Fine grading and compaction  Accurate trimming to establish grade  Setting grade stakes

Base Placement

Joint Layout

Paving Activities  Mixing and transporting concrete  Placing concrete  Consolidating concrete

Mixing and Transporting Concrete  Optimize workability Mixing time and temperature Mix design (water, cement, gradation) Air content  Optimize finishability Fines content  Avoid segregation In every step of mixing, handling, transporting

Placing Concrete

Consolidating Concrete  Remove entrapped air  Distribute concrete uniformly around the dowels and reinforcement  Avoid under / overconsolidation Honeycombing Bleeding

Postpaving Activities  Finishing  Texturing  Curing  Joint sawing and sealing  Opening to traffic

Finishing  Screed off concrete surface level to desired height  Machine float to fill in low spots  Minimize hand finishing  Finishing too soon or too much will produce a surface with poor durability

Texturing  Initial texturing by burlap or astroturf drag behind paver  Tine texturing as soon has sheen of bleed water has disappeared  Separate machines used for tining and applying curing compound

Tine Texturing

 Important for surface friction and acceptable noise levels  Transverse tining most common procedure  For reduced noise levels, grooves: 3 to 5 mm deep 3 mm wide Variably spaced 10 to 40 mm apart

Curing  Enhance hydration and strength gain  Retain moisture and heat immediately after placement and finishing  Most common method: liquid membrane- forming curing compound Retains moisture, but not heat Blanket insulation may also be needed

Curing Compound

Joint Sawing and Sealing  Saw to establish contraction joints  Conventional sawcut dimensions: Depth: D/4 to D/3 typical Width: 3 mm (0.12 in)  Lightweight saws permit shallower cuts  Widening cuts for sealant reservoir

Sawcut Timing Time Concrete Set Sawcutting “Window” Too Late: Random Cracking Too Early: Excessive Raveling

Joint Sawing

Sawcut

Lightweight Sawing Equipment

Joint Preparation and Sealing

HIPERPAV Computer Program  Evaluates potential for uncontrolled cracking  Uses job-specific inputs for: Mix design Pavement design Construction Environmental factors

HIPERPAV Mix Design Inputs

HIPERPAV Pavement Design Inputs

HIPERPAV Construction Inputs

HIPERPAV Environmental Inputs

HIPERPAV Output

Initial Pavement Smoothness  Riding comfort  Improved long-term performance  Smoothness specifications: Improved initial smoothness levels Total roughness per unit length “Must-grind” bump Incentives/disincentives California profilograph

California Profilograph

Lightweight Profiler

Opening to Traffic  Time requirements  Strength requirements Beam or cylinder testing Maturity methods

Summary  Prepaving  Paving  Postpaving  Smoothness Subgrade preparation Base preparation Mixing and transporting Placing Consolidation Finishing Texturing Curing Joint sawing and sealing