Guide for Use of Volumetric-Measuring and Continuous-Mixing Concrete Equipment

Description

This document offers guidance on volumetric-measurement and continuous-mixing (VMCM) concrete production. The original and most common use of VMCM equipment is as mobile (either truck- or trailer-mounted) equipment. Because of its compact size, ability to produce mixed concrete, and versatility, a significant number of stationary units have been produced. This configuration provides a free-standing base and is typically powered by electrical circuits normally found in a precast plant or other industrial facility. Unless specifically noted, the information in this document applies to all VMCM equipment.

This guide contains background information to be considered when using the VMCM method. A discussion of other types of continuous-measurement equipment (conveyor belt scales or weigh-in-motion scales) is outside the scope of this report. Volumetric measurement and continuous mixing have along history in the production of concrete. For many years, the concept of “one shovel of cement, two shovels of sand, and three shovels of stone” was used to produce concrete. Patents on continuous mixers date back at least to 1913. It was not until volumetric measurement and continuous mixing were successfully combined in the early 1960s that general field use of this type of equipment began.

The first commercial unit was delivered in 1964. Because of the detail of original patents, there was only one manufacturer of VMCM units until the early 1980s, when other manufacturers began to offer this type of equipment for concrete production. By the mid-1970s, there were over 4000 VMCM machines in operation in the United States that were generally used to produce small volumes of concrete. During the late 1970sand early 1980s, specialty concretes needed for bridge-deckrenovation and highway repair, which were difficult to produce in conventional transit mixers, were produced successfully with VMCM equipment. This application gave the equipment credence by proving that it could consistently produce close-tolerance, high-quality concrete. VMCM equipment was previously thought to be limited to producing special mixtures or small volumes; however, VMCM may be suitable for almost any concrete requirement.