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2015SpringShotcreteEMag

Nozzleman Knowledge Evaluating Ready Mix Suppliers By Mark Bradford Oshotcrete in the past few “Nozzleman Know- • Willingness to work with you to get to aplacementrequirespecificationsjobthewithin 90 minutes of batching);scar Duckworth has covered the keys of theequipment necessary for successful wet-mix ledge” articles. This article discusses the impor- desired mixture design; tance of the material supplier in the equation. • Flexibility of schedule (availability of trucks); One of the most critical pieces to what we do, • Quality and cleanliness of their trucks; as wet-mix shotcrete contractors and nozzlemen, • Knowledge and demeanor of their drivers is monitor the quality and consistency of the and staff; concrete that we are placing. As we all know, • Extra (sometimes hidden) costs; and shotcrete is a method of placing concrete. The • Price per yd3 (m3). ingredients in concrete vary in dosages, but with Notice that price was the last on my list of key the right mixture design, the concrete should factors. That is because we have found that most provide good quality with long-lasting results. suppliers are very competitive on price. What sets Let us discuss a key variable in the equation the suppliers apart for our specific needs in the that is often overlooked: the ready mix supplier. shotcrete industry is service. Service includes The supplier consists of the dispatcher, the batch several different items. plant, the delivery truck, and the truck driver. Starting with the mixture design, it is crucial A good concrete supplier can help make your that the plant is willing to provide a mixture day of shotcreting very smooth. A bad supplier design to meet your needs/specifications. can make your day or job a nightmare. Shotcrete mixtures can be very different in com- To begin with, you need to determine where position compared to cast-in-place concrete the job is located. Then determine which sup- mixtures. The ingredients are not different but the pliers service that particular area. Some areas amounts of each ingredient are usually very dif- are serviced by several suppliers; some areas are ferent. It is not uncommon for a supplier/batch only serviced by one or two. In conjunction with plant to have never seen or produced a shotcrete- determining who services that area, you should specific mixture. Several times we have gotten ask around to get a feel for the performance of pushback from suppliers saying that a mixture each supplier. Generally, other contractors, design will not work. That is where previous engineers, and architects should be able to give experience and documentation become important. you input on the choices available in that par- We do our best to keep on file each mixture design ticular area. that we use and the compressive strength cylinder The majority of this discussion will be based tests that are taken (Fig. 1). We share this informa- on ready mix suppliers, not mobile mix trucks. tion with the supplier so that they have documen- However, mobile mix trucks can be a great alter- tation for the future. Admixtures are critical in native for certain jobs based on parameters, such making a good shotcrete mixture and the sup- as location (usually more remote jobsites) and plier’s ability to provide the correct admixtures amount of concrete needed. A mobile mix truck’s in the correct dosages is very important. quality and consistency is heavily dependent on Once a mixture is chosen, it is critical that the the skill and experience of the driver operator. mixture is consistent from truck to truck. That is A few key decision points for choosing a ready where batch recordings are necessary. Make sure mix supplier are: the supplier can and will provide batch records for • Proximity to the jobsite (if one supplier is the specific quantities in every load. Not only do 5 minutes away and another is 45 minutes batch records give you the complete picture of away, that is a huge difference, especially if what is in the truck but they also give you the 44 Shotcrete • Spring 2015


2015SpringShotcreteEMag
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