Works with foundation systems to improve overall building design Finally, ESCS lightweight aggregates have a predictably low density and high internal angle of friction, which can exceed 35 degrees, to significantly reduce lateral earth pressure and dead loads by up to 50 percent. This characteristic is why ESCS is often used to increase the stability of soils in previously unusable or difficult-to-build-on project sites. That said, the reduced dead loads and lateral forces also help facilitate more sustainable construction practices when a project is assessed as a complete whole. Due to its ability to stabilize soils, ESCS lightweight aggregate can reduce the material demands of retaining walls, piles and foundations. For example, when designing a new terminal at Port Ca- naveral, engineers used lightweight aggregate to reduce the diameter and gauge of pipe piles. While several factors drove this decision, it resulted in fewer materials consumed to build the terminal and less construction waste overall. Therefore, ESCS also addressed the high energy input and emission of other construction materials like concrete and steel. Additionally, the lighter gauge foundation systems also contributed to reduced fuel costs to transport materials to the site. Similar results can be seen in highway stabilization projects, projects on riverfronts that need soil remediation and more. ESCS lightweight aggregates alleviate the strength require- ments of neighboring systems to reduce material use and waste—a benefit that increases as foundation size and complexity increase. Sustainable building aggregates impact every part of a project From extraction to placement, ESCS lightweight aggregates can help reduce the environmental impact of construction. Taking fewer materi- als from the earth, reducing fuel consumption for transportation and mitigating material use and waste across the entire structure, geotech- nical fills made from ESCS help mitigate the environmental cost of a project. Therefore, the material can be a viable option for engineers when ground retainment or improvement is necessary for a project and sustainable construction is a goal. While fill material may not be the most talked-about part of sustainable construction, it nevertheless can contribute to more ecologically con- scious building practices. Its role will become necessary as developers look to marginal sites with soft or suspect soils for new construction. However, the shift toward sustainable development highlights the ap - plication of ESCS in all projects concerned with public health, safety and well-being. DR. FARIBORZ M. TEHRANI, PH.D., PE, ENV SP, PMP, SAP DSW, F.ASCE is a Full Professor in CSU and the Director of ESCSI with expertise in sustainable and resilient SEMM. Fariborz is a voting member of ACI, ASTM, and TRB, EMI’s Liaison in ASCE STC, and EMI ORC Vice Chair. He is the recipient of ASCE Region 9 Outstanding Faculty Advisor, CHESC Best Practice, and Fresno and San Francisco ASCE Research Awards. Fariborz received BSc from SUT, MSc from AUT, and MS, Deg. of Eng., and PhD from UCLA.
Figure 2. The overall fuel, energy, emissions and freshwater savings of ESCS use are significant. Photo: Courtesy of ESCSI
Not only does this minimize the number of trucks, railcars, or ships needed to transport the material (thereby streamlining construction schedules), but it also reduces the amount of fuel needed to get the aggregates from manufacturer to site by 50 to 67 percent. That is, while the heavy weight of normalweight aggregates prevents reaching even a struck capacity of many hauling bodies, the low density of ESCS allows heaped capacity and, therefore, facilitates better fleet manage - ment with less cost of wear and tear on hauling carriers. On the one hand, this can positively impact a project’s bottom line since lower loads result in higher fuel efficiency, and less fuel generally reduces overall construction costs. Moreover, it drives sustainable practices as reduced fuel consumption translates to fewer nonrenewable resources consumed and less greenhouse gasses emitted. Supports long-term soil stability without contaminating local ecosystems While ESCS is substantially less dense than other quarried materials, it is not the lightest geotechnical fill available. However, unlike other, lighter geotechnical materials, its ability to reduce the environmental impact of transportation is bolstered by its chemical inertness, easy compactibility, and ability to reduce material needs of overlapping systems. When a project site requires ground improvement, it is crucial that the geotechnical materials used do not leach harmful or potentially harmful chemicals into soils and waterways or contain them within their bod- ies. ESCS, as a geotechnical fill, is chemically inert, non-degradable, non-corrosive, and free draining, all of which ensure the material can handle strain from areas below the water table and locations prone to flooding from heavy rainfall. Likewise, ESCS can be easily compacted to save fuel costs as well as reduce fuel and energy needed, greenhouse gasses emitted, and freshwater used in compaction efforts. Lightweight ESCS aggregates can use lighter compacting machines with higher fuel efficiency while achieving 95 percent compaction rates.
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April 2023 csengineermag.com
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