Safety in Road Construction
In this text we will focuses on the main activity of road construction, the most expensive, the most delicate, and the one where everybody take a look at the end. It is the asphalt layer. This layer comes after the base and sub-base and other soil layers, and can be divided in other layers according with the project, usually designed as Binder course layers and Wearing course layers. Depending on the region, these names could be different.
The asphalt layers are the ones where the traffic roles on, and are the ones that gives safety and comfort to the drivers.
The Asphalt layers are composed by a mix of materials, usually called as Hot Mix Asphalt (HMA) that is the most common in road construction, and also the most dangerous if the safety rules are not accomplished and workers don’t take care because of the high temperatures of the mix at the moment of laying these types of pavement.
To understand a little more all the process, in a quick resume, lets see how a Hot Mix Asphalt is done and a brief process to the final pavement:
The components of Hot Mix Asphalt a mix of stone aggregates (usually crushed rocks divided in several grain sizes intervals, sand, filler) and liquid bitumen. All these components are mixed in asphalt plants at temperatures usually higher than 140 ºC, sometimes around 200 ºC ore more if some types of modified bitumens are used. Depending on the type of Asphalt plant, it requires a certain number of workers to give support and inspection and heavy machinery to load the materials to the plant, usually it’s a very busy place when is working with several works going at the same time. Because of this, it’s crucial to have strict and well defined safety rules to avoid accidents, casualties and losses. These rules should include the use of all the Personal Protection Equipments (PPE) needed as Safety Helmets, Safety Boots, visibility jackets, eye glasses and masks for dust protection, temperature gloves for those who work directly in the plant, fire extinguishers, etc., and should be clear concerning the behavior of all personnel involved.
The next step, load and transport the HMA with specific trucks to the site on the ongoing project. Once in the site, the truck will be part of a kind of pavement convoy, that is a predefined sequence of equipments used to do the asphalt pavement layer. This convoy begins with the prime/tack truck that sprays a bituminous liquid used as a glue for the asphalt to bonds the base (usually this is prime/tack coat could pass in 24h or 48h before); after comes the trucks from the Asphalt plant carrying the HMA; then de Paver machine that is used to place the HMA in the base and assures the thickness and smoothness of the pavement; after comes the compaction equipments, rollers, could be tyre rollers, steel rollers, or a mix of steel and tires, each company has his own way of use these rollers, the objective is to achieve the right compaction and guarantee the quality of the pavement.
You can imagine all these equipments running all at the same time, in a constant movement.In this area there is what is usually called as the Paving Crew, that is a team of workers (on foot) like paving superintendent, paver operators (minimum three), dump person, a couple of people to lute and take care of the joints and mat repairs, in total could be more than 10 workers. These persons are located between the convoy of equipments most of them on top of the hot recent layer, with temperatures above 140ºC that comes from the bottom of the paver machine. Is very frequent these workers to have special safety equipment to protect from heat, like Safety Boots designed for hot surfaces, gloves for heat, safety masks to prevent inhalation of the hot asphalt vapors, and safety eyeglasses. The safety rules concerning this activity should be also very strict concerning the behavior and rotation routine of the workers.
During all these processes, is always present the quality assurance crew, taking sample for lab and monitoring all the steps. They also have very strict safety rules according with the locations they are in the project.
This was a quick resume of all the activity of the Asphalt pavement works, hope you like it, and hope to see you soon.