Portland cement is the world’s most prevalent manmade material, with approximately 1,200 pounds produced annually for every person on earth. Its primary use is to bind concrete, which is used to construct much of the built environment.
Nearly 5% of global greenhouse gas emissions come from cement production, according to the World Business Council for Sustainable Development’s Cement Sustainability Initiative, making the industry among the largest contributors to climate change. Fortunately, wireless devices connected to control software can save time and money while significantly reducing the carbon footprint.
Same Resources, Better Product
One such platform is VERIFI®, a system of interconnected devices and software tied into the ready-mix truck’s batch panel and concrete producer’s dispatch systems to ensure water doesn’t have to be added at the jobsite to meet slump specifications.
Sensors on the truck measure and transmit temperature, load size, age, water, admixture, drum speed, and revolutions to a central processor mounted on the truck, which uses the data to calculate slump and automatically add water (and/or admixtures) based on a calibrated curve for the mixture’s design. Whenever water’s added, the software mixes the batch for 30 revolutions as required by ASTM C94, Standard Specification for Ready-Mix Concrete. The data’s also used to give the driver mixing instructions, including number of drum rotations and speed, so the drum rotates only as often as necessary to maintain specified slump.
Together, these functions optimize energy expenditures to deliver concrete that meets specifications immediately upon arrival, minimizing waste associated with rejected loads and increasing efficiency by reducing the need to retemper at the jobsite. The resulting environmental benefits can be broken into three categories:
- Cement reduction. Concrete mixes are routinely overdesigned to compensate for water added upon delivery to achieve specified slump. In addition to wasting cement, the practice can weaken concrete to the point where placements fail compressive strength tests and must be removed and replaced. More wasted resources. A conservative estimate is that 5% of the cement in a mix is there only to hedge against these issues. By tracking and managing the quality of a shipment from the ready-mix plant to the jobsite, a platform like Verifi reduces the overdesign needed to consistently meet a given performance specification.
- Waste reduction. The National Ready-Mixed Concrete Association (NRMCA) estimates 5% of deliveries are rejected at the jobsite, typically because they fail to meet the specified slump. The returned concrete is either crushed and used as road base, made into blocks, or simply discarded, solutions that expend time and fuel. Software that monitors consistency in transit and controls precise injections of water or admixtures en route ensures concrete is delivered more consistently within performance specifications. Data from ready-mix plants that have begun using Verifi indicate this could reduce rejection rates from 5% to 3.8%, saving time, money, and materials. Because a typical concrete load represents 5,500 pounds of carbon dioxide emissions, reducing concrete waste also benefits the environment.
- Fuel efficiency. Approximately 23% of the fuel consumed in a concrete delivery is for high-speed drum rotations that mix the concrete. Rotation timing is usually controlled by the truck driver, who has minimal information about mix consistency or fuel efficiency.In contrast, real-time feedback gives the driver instructions on the optimal number and timing of rotations. When the Verifi system is installed at a producer’s site, it runs for some time in “ghost mode” to benchmark the producer or plant. This allows the producer to compare the ghost data to a later time when the trucks are running in live mode. Early data suggests the number of high-speed revolutions can be reduced by 10%, representing significant cost reductions and associated environmental benefits. In addition, drivers have less need to climb a ladder next to a spinning drum—a clear an important safety benefit.
Real-World Results
Based on an NRMCA survey, from 2013 to 2016 eight concrete producers documented a 10% reduction in the energy used for drum rotation, compared with pre-Verifi estimates. By using 450,000 fewer gallons of fuel, they kept 4,000 metric tons of carbon dioxide from being released into the atmosphere – equal to taking 856 passenger vehicles off the road. At the prevailing diesel price of $3 per gallon, they saved about $1.4 million.
These customers represent about 1% of the U.S. ready-mix market, so imagine the impact of widespread adoption.
