Sprayed Concrete – Use and Certification

The large construction projects at CTRL, Heathrow Terminal 5, Hindhead Tunnel, the Natural History Museum and soon Crossrail are all recent examples of the use of sprayed concrete to provide a solution to complex engineering challenges. The sprayed concrete process is being universally recognised as one of the most effective means of concrete placement in a wide range of applications, by virtue of the methods’ unique characteristics to be able to meet a variety of application requirements.

It has also long been recognised that the quality of in-situ sprayed shotcrete is always dependent on the skill of the nozzleman, who must have the necessary site experience together with theoretical and practical skills to be able to apply sprayed concrete ensuring the products’ overall quality.
With the acceptance of the process and the current increase in sprayed concrete being specified within the UK, the need for industry wide recognition of competent nozzlemen and their work methods has never been greater.

The Sprayed Concrete Association was formed in 1976 by a group of sprayed concrete contractors and whilst the Association has grown considerably, one of the Associations’ main aims has been the recognition of sprayed concrete operative training, record keeping and certification as being a fundamental and essential requirement for the continued acceptance of the process. The Association has always maintained that it is vital that training and certification within the industry is supported and sustained.

Working closely over many years with industry bodies such as CITB, CSCS and the NVQ scheme, the Sprayed Concrete Association introduced the UK’s first recognised Certification Scheme covering Health & Safety, machine operation and manual sprayed concrete application. The desired result being a fully trained workforce, understanding the technicalities of the process, being capable of spraying concrete and able to create test pieces for testing.

As part of this work the Sprayed Concrete Association liaised with EFNARC (European Federation of National Associations Representing producers and applicators of specialist products for Concrete) to jointly produce the European Specification for Sprayed concrete (1996), together with Guidelines (1999) and The Specifier’s and Contractors Checklist (2002).

Following the publication of these industry recognised documents, the EFNARC Sprayed concrete Technical Committee was tasked with the undertaking of the Nozzleman Project to concentrate on a single objective – the nozzleman – the key link in providing high quality sprayed concrete.
This project culminated in the launch of the EFNARC Nozzleman Certification Scheme in September 2009 and has been developed in recognition that the construction industry requires a means of identifying expert nozzlemen applying sprayed concrete by the use of robotic nozzle manipulators.
The scheme offers certification to nozzlemen who have already gained the necessary experience and can demonstrate their technical knowledge and practical ability to produce wet, robotic applied sprayed concrete.

The certification scheme operates through National Examiners who assess nozzlemen for their theoretical and practical skills at their workplace. The first stage of the scheme is to identify and accredit suitable examiners through the attendance of the two and half day EFNARC Assessment Course run by CUC - International Centre for Geotechnics and Underground Construction in the underground Hagerbach Test Gallery in Switzerland.

After successful completion of the course, examiners receive the EFNARC Examiner tool package which includes the necessary nozzleman course notes, pre-defined theory exam questions and answers, theory and practical assessment forms and checklists that also define the minimum criteria and skills for the nozzleman.

The nozzleman accreditation course consists of a theory presentation and subsequent examination which takes one full day, on successful completion of which a practical competence assessment is undertaken during the course of a shift on a fully operational site.

The accreditation course notes contain all the information that the nozzleman should know in order to pass, whilst during the practical assessment the emphasis is placed on pre-spraying tasks, start-up procedure, spraying application, shut-down procedure, troubleshooting and HSE issues. The practical assessment is completed with the on-site spraying of large test panels which are cored. The cores are examined for integrity and tested by an independent laboratory to determine as-sprayed compressive strength. The weighting of the course is such that the practical assessment is given greater importance than the theoretical examination in the overall assessment.

The EFNARC certificates for both examiner and nozzleman are valid for three years after which they must be revalidated.

To date there are 23 EFNARC Examiners world wide from the UK, Europe, South Asia, Australia, North America and South America whose contact details are available from the EFNARC website - www.efnarc.org

With the examination and certification of sprayed concrete nozzlemen being available through the EFNARC scheme, the experience and skill of the most important link within the sprayed concrete application process – the nozzleman, can be assured.

Article courtesy of Concrete -April 2011