Overview

Subgrade is the backbone of the road. Pavement is just icing on the cake. The City has several types treatments of soils that can be used in producing a durable subgrade. Those processes include flyash, lime stabilization, geogrid and compacted aggregate base. The subgrade also has features to protect itself longterm such as drainable base coarse, underdrains and blanket drains. Protection of the subgrade during construction is vital to a stable roadbed.

See Sections 2204 and 2205 of the Design and Construction Manual.
HMA, Hot Mix Asphalt is considered a durable driving surface material that allows for some bending/flexibility in
movement according to traffic loading. Asphalts quality requires the composite materials to be superior to all others in kind, properly handled controlled when used. The loading, transport, dumping, placement, and finishing of the HMA is critical to the life of the product. The inspection of the process from material to placement is the only way to ensure that quality has been achieved.

Section 2208 in the Design and Construction Manual refers to Portland Cement Concrete Payment. The subgrade construction can change from that of Asphalt streets and the subgrade specification will need to be followed and usually quality control and quality assurance is done by independent labs during construction.

Specifications/Contract Documents

Hot Mix Asphalt:
HM Asphalts have a project specific “design mix” that is submitted before work has begun. Projects can vary on items such as aggregate; recycled or clean/virgin rock. Contract documents will define any differences from what the industry standards are, as it needs to relate to the unique requirements of each project.

Portland Cement Concrete Payment:
PCCP (concrete) follows the KCCMB mix design and a predetermined joint detail is followed to insure proper reinforcement of the pavement. Special attention is given to weather, traffic and continuous service from suppliers for the pour. Sawing of joints shall follow finishing as soon as possible.

Submittals

Both Asphalt and Concrete pavements will have batch design for product. Concrete does have items like tie bars and dowels.

Field Observations

Inspection of the materials is most often assumed to be unnecessary at the production plant, as the mix design submitted has already been produced and tested for compliance and conformity, but as a quality assurance check the inspector should schedule the mixed materials to be collected and sampled by a qualified and reputable testing lab.

Observation of equipment use while placing HMA is needed, improper techniques and procedures can produce a thin surface,segregated aggregate, or other things that lend to a pavement deteriorating or showing signs of failure before the life span of the overall pavement.

Concrete pavement requires testing at specified intervals and attention to subgrade stability if under load from trucks. In addition to marking out for saw cuts to insure contraction joints are cut over center of dowels, the tie bars should be drilled in the next day, whenever an addition lane will be required. Hand poured sections require a stinger vibrator that the laborer is skilled in how to vibrate without segregation. Cure (usually white and at a rate of 150 to 200 square feet to the gallon) surface as finishers have completed their phase of the work.

Documentation

Material tickets are to be collected and stored. Identification of Measurement and payment methods are documented, this can be confusing since asphalt companies order by the ton(Type III surface and Type I base is 1.98 and 2.00 tons per cubic yard respectively) and most projects measure placement by the square yard. Temperatures and weather observations are documented should concerns arise at a later date.

Concrete pavement is usually paid by the square yard and check against the cubic yard tickets. Overages of cubic yards are not uncommon due to testing, waste and subgrade running lower than plan. That is why most contracts are given a specific depth and pay per square yard. A cubic yard of concrete weights approximately 3300lbs depending on batch designs.