Experimental study of a noise reducing barrier made of fly ash

Abstract

Although fly ash is commonly used as an additive to cement, large amounts of this material are disposed in landfills. To mitigate, it would be interesting to develop new products in which fly ash can be easily used and required in large quantities. In this work, fly ash is added to manufacture eco-friendly materials with acceptable acoustic and non-acoustic properties and a low cost. We built a barrier composed of fly ash (60 wt.%), type II Portland cement (25 wt.%), vermiculite (14.5 wt.%) and polypropylene fibers (0.5 wt.%). The barrier complied with the mechanical requirements of European standards. The sound absorption coefficient and the airborne sound insulation were determined in a reverberation room, and the barrier was classified as A2 and B3. No leaching problems were observed.

Sound Absorption Properties of Porous Concrete Layers for Noise Barrier

“…Aggregate. The use of lightweight aggregate, such as expanded clay [31], arlite [32] and vermiculite [9], [32] outside the aggregate composition is recommended by ASTM C33 and ACI 522R-10 due to its porous, water absorbent and light properties (figure 7 & table 2). PCs produced with expanded clay (PC EC), arlite (PC AR) and vermiculite (PC VER) have similar trends of SAC curve (figure 6).…”

“…In addition, aggregates of larger size such as 3-8 mm show a significant decrease in NRC, probably due to a larger channel path, and thus a lower viscous heat loss that occurs during the sound propagation process, but there is no relevant study yet with pore sizes conducted by researchers on PC containing expanded clay. In addition, the use of vermiculite with a size less than 1.14 mm [9] and fibers in PC VER using fly ash binder increases the porosity of PC (figure 7d). The open pore size is relatively small (between 2 and 4 mm) with a total porosity of 40% compared to normal PC (with coarse aggregate between (5-10 mm) with a total porosity of 43% but has a larger main pore size than 8.5 mm [8] Vermiculite has exfoliating properties that allow it to retain small air particles that absorb sound and reduce the reverberation time in various frequencies, to increase the amount of absorption even when the open porosity is low.…”

“…Commercial concrete barriers usually consist of a combination of two layers: one made of PC with a thickness between 50-100 mm to absorb noise, and a hard backing layer of non-PC also 50-150 mm that has a high transmission loss index. The materials are classified according to EN 11654 standard traffic noise barriers [9].…”

A Novel Green Alternative for a Room Prototype Constructed with Entire Recycled PET Bottles and a Green Roof Composed of Waste Materials

“…Global fly ash production is an ever-growing problem, mainly due to the amount of land required for its disposal. This type of waste has been used in construction but with different approaches, such as direct addition to cement and concrete in various proportions, favorably increasing compression strength and workability while reducing costs [44,45]. Nonetheless, coal fly ash is an environmental potential pollutant because of the leaching of toxic heavy metals, such as As, Hg, and Se [46][47][48], depending on the coal surrounding soil [49,50].…”

“…Countless alternative materials have been proposed for use in buildings, including composites [51]; resources renewable in the short term [22]; waste materials, such as tires, ferrous and aluminum slags, fly ashes, plastics, and sawdust; and others [44,45,51,52]. All are required to provide structural safety and durability in the long term.…”