Joint Sand Stabilization -- A Case Studyby Peter van Niekerk
Editor's note: Peter van Niekerk has worked extensively in the concrete paver industry in South Africa and is contributing to its growth in southern California. He has consulted on many paver projects and carried a wealth of experience on how to rectify problems and, more importantly, how to avoid them in the first place. He has this story to tell about a highly visible municipal project in Palm Springs.
About four years ago I was retained for a technical paving consultant by one of the major manufacturers of interlocking concrete pavers in California. David Barakian, P.E., City Engineer of Palm Springs, California asked me to help them with some of their pavers. We met on Palm Canyon Drive where approximately 100,000 sf (10,000 m2) of pavers had been installed two years prior on sidewalks and main streets in the tourist area of the city.
The main intersection at Tarquitz Canyon Drive was particularly distressed. There were two reasons. One was caused by the loss of joint sand being removed by the sucking action from tires. This resulted in the pavers rocking under the heavy traffic which further caused the units to pump out the bedding sand. The pavers were subsiding and the edges were becoming spalled and chipped.
Second, the continuity, interlock and strength of the installation had been compromised by a large, colored, poured-in-place concrete starburst pattern covering about a third of the four-lane wide intersection. The pavers had to be cut into a variety of segments adjacent to this star. This was causing some of the smaller pieces to become dislodged from the edges around this irregular-shaped concrete star. The paving pattern was opening the edges, causing the pavers to loosen and fail.
Apparently, the designer -- or contractor -- was not aware of ICPI guidelines that recommend keeping cut pavers to less than a third of a paver in vehicular areas. The best approach when possible is to arrange the pattern so that there is little or no cutting along edges subject to constant vehicular traffic. My initial reaction in Palm Springs was to recommend removal of all the loose pavers and the concrete starburst. The repairs would be costly. However, this approach could eliminate much of the smaller cut pieces of pavers.
The City of Pam Springs didn't have the funds to do this work. Moreover, they were not willing to close a major intersection of the city for the three to four weeks for repairs. They decided initially to carry out necessary repair as needed from time to time.
About two years later, David Barakian heard about joint sand stabilization materials through one of his friends in the building industry. He contacted me to discover my successes (after our initial meeting) in stabilizing joint sand with SB-1300 on large paver installations elsewhere in California. As a result of my presentation, the city issued a contract for the cleaning, replacement of damaged pavers, reinstallation of the missing joint sand, sealing and joint sand stabilization of the pavers in streets and sidewalks.
Work commenced in mid-summer of 1998. The city carried out replacement of all the broken and chipped pavers, and then turned the site over to the contractor for cleaning and joint stabilization. Due to the intense daytime heat at that time (Palm Springs is in the desert), cleaning was done during the night and sand was brushed into the joints the next day when the pavers dried. This was immediately followed by an application of joint sand stabilization material using high-volume, low-pressure sprayers. The excess was squeegeed into the joints and allowed to soak into and bind the sand. The work was completed in six days.
The transformation was dramatic. As with most sealer applications, the pavers took on a richer, brighter appearance. They have stayed cleaner since the material applied to the surface of the units helps repel dirt. The amazing aspect is that not a single paver or a cut piece loosened around the concrete sunburst, even after a full year of traffic in this major intersection. The smallest of cut pieces is still firmly in place functioning perfectly. The performance of the joint stabilization material exceeded even our own best predictions.
As a result of success in the City of Palm Springs, other large paver projects have their joint sand stabilized with SB-1300 and SB-1370. These include California sites at Long Beach Rainbow Harbor, Huntington Beach pier, Anaheim Convention Center, Anaheim Baseball Stadium, Legoland and the Oakland Civic Center. Joint stabilization has been successfully applied in Columbus Ohio downtown streetscapes, various high profile developments in Las Vegas including the Venetian Hotel and Casino, and as far away as major waterfront projects in the cities of Wellington and Auckland, New Zealand.