Solution Summary: Pre-Blended Mortar and Grout Delivery Equipment
A pre-blended mortar and grout delivery system is an engineering control to help reduce musculoskeletal disorders (MSD) from manual material handling and stressful hand and wrist activities. It is an equipment that utilizes gravity to deliver grout into the masonry wall. After the grout has been delivered or mixed on site, it is poured into the hopper. The system is then lifted by crane or forklift to the work area. The grouting material flows with gravity down the attached hose, to the desired location. This system allows grouting to be done with two laborers: one laborer guides the hose to the block cell and the other maneuvers the forklift.
The following photos provide examples of how the equipment is used:
Figure 1. A Grout Hog being loaded
Figure 2. A Grout Hog being lifted above the work site
The grout hog has a swivel base that allows a 17-foot reach, an 8-foot dispensing hose, and an automatic shut-off valve that allows precise control of grout flow. The contractor can choose between two models: one powered by forklift hydraulics and the other with a 13-hp motor. The grout hog is a gravity feed system, as opposed to system that pump the grout into the block. In contrast, grout pumps are prone to mechanical failure, and the grout bucketing is labor intensive and physically demanding for the masons.
As the wall goes up, the labor crew will work behind the bricklayers and pour the grout in the block cell with the aid of the grout hog. There are two ways to do grouting, the low-lift and the high-lift grouting. The low-lift process is usually done in lifts up to about 4 feet, and sometimes every two or three courses of block. The high-lift can go as high as 24 feet using large pours of grout. The choice of lift type is dependant on the type of block used, the type of construction and location of the job site. The grout hog is ideal on any wall that is accessible with a forklift.
Heavy lifting and carrying and stooped postures can cause low back disorders, such as muscle strain or a disc herniation (“slipped disc”), which is bulging of disc material possibly pressing on the spinal cord or nerves that go into the leg. Using a pre-blended mortar and grout delivery system decreases the need for workers to manually carry materials and reduces the risk of developing low back and/or hand injuries.
How Risks are Reduced:
The grout hog is a delivery system that relieves the operator from lifting and supporting the weight of grout. There is no need to manually lift or carry heavy buckets of grout repeatedly.
Bucket handling is eliminated. Because bulks of grout are handled mechanically, with either a forklift or a crane, there is no need to manually lift or carry heavy buckets of grout repeatedly. Masons will not need to lift or carry buckets, thereby reducing the risk for developing a musculoskeletal disorder of the back and shoulders.
High hand forces are eliminated. In grout hoses, a pump is used to push grout up from ground level to the mason's work height. The mason who is directing the hose must therefore exert high hand forces to hold and control the grout hose. Because grout hogs are gravity fed from a height above the mason's work area, the pumping forces are eliminated. The high hand forces required by the mason are eliminated. Grout hogs will also reduce the mason's need to lift the grout hose from the ground.
There have not been independent published studies measuring the effect of a grout hog on reducing musculoskeletal disorders. Regardless, safety and health experts believe that masons will be less likely to develop musculoskeletal disorders if they use grout hogs instead of bucket handling on the jobsite, reducing the exposure of continuous lifting.
Effects on Productivity:
Some contractors prefer to use a "bucket brigade" to deliver the grout. This process is labor intensive and time consuming requiring several masons to do the job. The amount of time and energy spent during grouting will decrease production in other tasks at the worksite.
Using a truck to pump grout is another common method used for delivering grout. However, grout pumps are prone to mechanical failure, plug easily, and are time consuming to clean-up.
The grout delivery system (grout hog) allows grouting to be done with only two masons: one mason guides the hose to the block cell and the other maneuvers the forklift. Also, because the grout hog hose is shorter than the hose of a grout pump, it takes less time to clean the grout hog hose. Multiple grout hogs may be used simultaneously to increase productivity.
There is a new product called self-consolidating grout (SCG) which has a flowable consistency due to the addition of polycarboxilates (chemical admixtures) to the composition. SCG fills those difficult spaces of the core and prevents the presence of voids. Also, the time to place the grout is greatly reduced compared to conventional grout. The SCG is delivered to the job site with a truck.
Dan Anton, PT, PhD, ATC and Alysha Meyers, PhD – University of Iowa