Notes on Fiber-Reinforced Lightweight-Aggregate Structural Concrete and Concrete Masonry

by Dr. Fariborz M. Tehrani, Ph.D., PE, PMP, ENV SP, SAP

Structural and masonry lightweight aggregate concrete are common materials in modern construction with established guidelines, such as ACI Committee 213 documents [‎1]. Further, rotary-kiln produced lightweight aggregates, as reported by Ries et al. (2017), contribute to preservation of natural resources and reduction of environmental footprints due to their low density, insulation, and durability characteristics [‎2]. For instance, expanded shale, clay, and slate (ESCS) aggregates have less environmental impact during mining of raw materials, need less energy and emissions for transportation, and enhance durability of concrete through reduction of cracks as ingredients of internally cure concrete [‎3]. Hence, increased demands for reducing cost, energy, and emissions associated with development of infrastructure [‎4] have prompted many scholars and practitioners to take advantage of the life-cycle performance of these materials. Furthermore, advancements in fiber-reinforcement [‎5] have introduced new opportunities to develop and deploy fiber-reinforced lightweight aggregate concrete (FRLWAC) products [‎6].

A review of literature by Hassanpour et al. (2012) indicates that lightweight aggregate concrete with fiber reinforcement shows substantial increase in toughness, ductility, and energy absorption; while reducing vertical and lateral demands on structures due to the lower density; and maintaining high strength values of concrete [‎7]. In this area, enhancement of shear capacity is a specific benefit of fiber reinforcement that is essential for performance of composite structures, and thus, contributes to the increased capacity of lightweight composite floors up to 100% as reported by McComb et al. [‎8]. Such characteristics are also beneficial in masonry applications, where ductile lightweight systems can replace brittle normal-weight systems [‎9]. The state-of-the-art report by Rico et al. (2017) indicates that joint application of lightweight aggregates and fibers do not require specific means and methods of construction beyond the current standard practice. This report calls for research in areas of mixture proportioning and investigation of structural performance in respect to shear strength of masonry piers [‎9]. Proportioning masonry mixtures has potential to optimize the shear response of structures during extreme loads, such as earthquakes and hurricanes. A recent experimental investigation has shown that fiber-reinforced lightweight-aggregate concrete-masonry (FRLWACM) piers have superior shear ductility over conventional systems by a ratio of 3.3 [‎10]. Hence, FRLWACM are promising materials for performance-based design of earthquake-resisting structures with lower loading demands and higher resistance capacities. Associated enhancements in the service life of buildings utilizing FRLWACM, as well as savings in embodied energy and emissions of these materials will further align the development of infrastructures with sustainability objectives. Such alignment is crucial to future economy as it facilitates the closure of the gap between infrastructure investment and funding.

1. ACI Committee 213. (2014). “Guide for structural lightweight-aggregate concrete,” ACI 213R-14. American Concrete Institute (ACI), Farmington Hills: MI. []
2. Ries, John P., and Thomas A. Holm. (2017). “A holistic approach to sustainability for the concrete community,” Information Sheet 7700.1. Expanded Shale, Clay, and Slate Institute (ESCSI), Chicago: IL. []
3. Weiss, Jason. (2016). “Internal Curing for Concrete Pavements,” Tech Brief FHWA-HIF-16-006. Federal Highway Administration (FHWA), Washington: DC. []
4. Economic Development Research Group. (2016). “Failure to act: closing the infrastructure investment gap for America’s economic future.” American Society of Civil Engineers (ASCE), Reston: VA. []
5. ACI Committee 544. (2009). “Report on fiber reinforced concrete,” ACI 544.1R-96. American Concrete Institute (ACI), Farmington Hills: MI. []
6. Gao, Jianming, Wei Sun, and Keiji Morino. (1997). “Mechanical properties of steel fiber-reinforced, high-strength, lightweight concrete.” Cement and Concrete Composites. 19(4):307–313. []
7. Hassanpour, Mahmoud, Payam Shafigh, and Hilmi Bin Mahmud. (2012). “Lightweight aggregate concrete fiber reinforcement – A review,” Construction and Building Materials. 37: 452-461. []
8. McComb, Chris and Fariborz M. Tehrani. (2015). “Enhancement of Shear Transfer in Composite Deck with Mechanical Fasteners.” Journal of Engineering Structures. 88(1): 251-261. []
9. Rico, S., R. Farshidpour, and F. M. Tehrani. (2017). “State-of-the-art Report on Fiber-reinforced Lightweight-aggregate Concrete Masonry.” Journal of Advances in Civil Engineering. (8078346). []
10. Tehrani, F. M., S. Rico, and R. Farshidpour. (2018). “Shear Ductility of Fiber-Reinforced Lightweight-Aggregate Concrete Masonry.” Proc. The 11th US National Conference on Earthquake Engineering, Earthquake Engineering Research Institute (EERI), Los Angeles, CA, June 2018, Paper 1112. []

Photo Gallery

  • Ductile shear failure of FRLWACM Pier (Tehrani et al. 2018, courtesy of EERI 11NCEE, Los Angeles, CA)