by Peter van Niekerk
On the Atlantic side of the isthmus of Panama stands the city of Colon, aptly named for Columbus, who laid the cartographic groundwork for Vasco Nunez de Balboa to discover in 1513 that there were only 18 miles (30 km) of land separating the world's largest oceans. Begun in 1904, the Panama Canal was the pet project of U.S. President Theodore Roosevelt. The massive US$375 million public works project took 10 years to construct. Today, there is talk of widening the jammed canal so that the largest container ships can fit through it.
It is the western hemisphere's premier shipping lane, and the Panama Canal requires substantial support from the development of container yards to increase efficient transfer of goods at the world's crossroads. One such transfer point is the Manzanillo International Terminal (MIT) in Colon whose owners decided to construct a 830,000 sf (77,000 m2) of interlocking concrete pavement in an extension to their container terminal.
V.K. Kumar, P.E. who designed the pavement is a principal and Vice President of Berger/ABAM, a civil and structural engineering firm based in Seattle, Washington. He was assisted by Roy McQueen, P.E. of Roy D. McQueen & Associates from Sterling, Virginia. Mr. McQueen's firm wrote and reviewed publications for the Interlocking Concrete Pavement Institute.
Mr. Kumar used a combination of locally manufactured and inported 4 x 8 in. (100 x 200 mm) by 3 1/8 in. (80 mm) thick concrete pavers set on a 1 in. (25 mm) layer of bedding sand. This was placed over a cement-treated base. A key design consideration was that Panama only has two seasons - wet and dry with the rainy season extending from April until November. Almost continual rainfall during that period would slow paving, particularly in the earthmoving phase, and could compromise the integrity of the pavement if water infiltrated the base after the pavement was commissioned.
The design was further complicated by minimal grades constrained by preexisting invert levels over the large area of pavement. This meant grades could not exceed 1% over much of the pavement. For these reasons, the concrete paver surface should restrict water infiltration as much as possible. This was addressed by ensuring that the joint sand well consolidated in the joints, and by using a proven joint sand stabilizer to ensure that the sand would be permanently bonded together in the joints. Another reason for using the joint stabilizer was to achieve early stabilization of the sand in the joints to practically reduce any risk of loss of joint sand during operations on the pavement.
Implementation of the deisgn by Berger/ABAM was facilitated by the Port's own in-house team of civil engineers. They supervised and monitored the general contractor to ensure that every phase of the operation was installed acording to the design intent. They were led in their first experience with interlocking concrete paving by an experienced Panamanian civil engineer named Cesar Pinzon, Construction and Faciliites Manager. Mr. Pinzon was educationed in Panama and has a master's degree in civil engineering from a leading British university. He did much research on the construction of interlocking concrete pavements and focused on the crucial component - inspection for quality control.
Headed by Mr. Pinzon, his team developed a training program to enable them to critically assess the quality of every phase of the construction. They developed a detailed set of quality controls with a manager in charge of inspecting each aspect of the installation. Particular attention was given to the earthworks and a very high set of standards was developed for systematically checking the grades and density after compaction of different layers.
About a third of the pavers were manufactured by an ICPI member based in the U.S. and shipped to the terminal. The remaining pavers were produced by a Panamanian company to ICPI standards and specifications. Pavers were installed using mechanized installation machines supplied by an ICPI contractor member. The installation contractor supplied the bedding sand and jointing sand locally with the appropriate gradations. The bedding sand passed the required degradations tests recommended by IPCI for port, airport, and for heavily trafficked streets.
The installation of the subgrade and bases proceeded in spite of some rain interruptions. Even with almost daily rainfall, each operation was meticulously inspected during construction and upon completion by an individual trained for making such checks. They then divided the concrete paver installation work into key elements such as screeding bedding sand, installing and establishing the correct lines and levels of the concrete pavers, and installation of the joint sand and liquid stabilizer.
Before any sections were proof-rolled with a 10 T rubber-tired roller, a team checked and corrected each completed area for spalled, chipped, or misaligned blocks. Once proof-rolling was completed, an additional check for joints full with sand was done prior to placing the joint stabilizing sealer. This material was pumped from 55-gallon (200L) containers to the pavement surface, squeegeed into the joints, and allowed to soak into the sand to bond the particles together.
An unusual feature of the pavement was that MIT used yellow paving blocks to demarcate the lines and stop signs. This eliminated painted striping. As a section was completed, it was opened for use, enabling income to the owners even while remaining areas were being completed. Initial feedback from Mr. Pinzon indicates tha the pavement is performing as designed. Additional areas of concrete pavers are planned for future phases thanks to the experience gained by the Port, the installation contractor, and concrete paver suppliers.
