Portal: General

In this section of the fall issue of ASA™s Shotcrete, I introduced some aspects of pool finishing. I receive many calls, questions, and comments from people about the new finishing tools. Since this issue is on architec-tural shotcrete and finishing, I thought it would be interesting to further develop the topic of finishing techniques for shotcrete.

For effective communication and interaction among groups in this industry, the knowledge and use of the Spanish language in the American construction industry has been increasingly recognized as a growing requirement, rather than an exception. According to U.S. Census Bureau reports for the year 2000, of the 281 million inhabitants in the United States, 35 million (12.5%) are Hispanic, which is actually slightly higher than the black population (12.3%). A large increase in the Hispanic population was observed in the last decade. This group has grown by almost 40% since 1990, with much of this growth being attributed to new jobs in construction. To date, it is estimated that Hispanic workers account for up to 15% of the workforce in the construction

It’s 5:30 in the morning in our yard. All of the compressors, trucks, shot-crete pumps, and related equipment are on their way out of the yard for the day™s operations. It™s important that the equipment gets to the various jobsites, which could be anywhere from 10 to 150 miles away, on time and without incident. But what can be done to assure that everything is road-worthy?

I remember doing a job in San Francisco, CA, about nine or ten years ago. The job consisted of building a basement in an existing commercial area. There were buildings on both sides of the new proposed basement. The construction called for the new basement walls to be built on the property line with a 2-in. foam spacer”the perfect shotcrete job!

In 2000, ACI, in cooperation with ASA, estab-lished a formal certification program for certifying shotcrete nozzlemen. Prior to that date, ACI had a guideline document for certifying nozzlemen, but it was not being uniformly applied, it contained outdated features and appli-cations, and it was not being universally accepted nor endorsed.

Where a section of shotcrete is left incom-plete at the end of a shooting shift, some provision must be made to ensure that the joint will not develop a plane of weakness at this point. According to the American Concrete Institute™s œGuide to Shotcrete1 and the œUnified Facilities Guide Specifications,2 construction joints should be tapered to a shallow edge form, about 25 mm thick. (1 in.) Therefore, in North America, contract specifications will typically require that shotcrete construction joints be tapered to a 45-degree edge and be thoroughly cleaned and wetted prior to the application of additional shotcrete. When welded wire mesh re-inforcement is used, some contractors will also overlap two layers of mesh at the expected location of construction joints in the antici-pation that the shotcrete at the joint may be weaker than the unjointed portions of the shotcrete.

The use of calcium aluminate cement as the binder in refractory systems in general, and refractory shotcretes in particular, is widely approach to high-performance refractory shotcrete involves the use of calcium aluminate aggregates along with the calcium aluminate cement. The addition of this unique aggregate imparts enhanced properties to shotcretes, enabling them to endure the toughest of industrial environments.

After a brief history of different installation modifications, this paper introduces a novel installation technique, which enables form-free placement of low cement and fully dispersed castable compositions. The method does not require the typical wet pumping equipment, as is needed for shotcreting, but delivers similar lining properties.

Whenever possible, try to pre-site all construc-tion projects before scheduling personnel and equipment. A little extra planning ahead of the actual work can save a lot of headaches later on.