Abstract
The sound absorption performance of porous ceramisite is determined by its pore structure, which is mainly governed by a foaming agent and heating rate during a foaming process. By tuning the heating rate and foaming agent concentration, ceramisite with different pore structures was prepared by using flyash, cement, quick lime, and plaster as raw materials as well as ammonium acetate as a low-temperature decomposition foaming agent in this work. The phase composition, microstructure, and sound absorption performance of the prepared porous ceramisite were investigated. Results demonstrate that the apparent porosity and the pore diameter increased with the increase of foaming agent concentration, accompanied with the broadening of the pore diameter distribution. The apparent porosity is positively correlated with heating rate until the temperature is higher than 20 °C·min−1, while the pore diameter is negatively correlated. The pore diameter distribution becomes narrow as a function of the heating rate. The sound absorption performance is positively correlated with the apparent porosity. An optimal pore diameter might exist, meaning diameter sizes that are larger or smaller than the optimal diameter are not conducive to the optimization of the sound absorption performance of the overall frequency band. It was determined that the curing time was not a key factor for optimizing the pore structure.
Highlights
The noise pollution caused by urban railway transit (URT) is becoming increasingly serious due to large-scale construction of urban railway transit and the increasing of train velocities
In order to study the effect of foaming agent concentration on the microstructure of the ceramsite, the samples treated at a heating rate of 20 ◦ C·min−1 with various foaming agent concentrations were selected as a probe for SEM and mercury intrusion porosimetry measurements
With a heating rate of 3 ◦ C·min−1, flocculent hydration products of fly ash are observed ammonium acetate concentration, a larger amount of bubbles is provided in comparison with low attaching to the surface (Figure 6a), which indicates that the hydration degree of fly ash is relatively foaming agent concentration
Summary
The noise pollution caused by urban railway transit (URT) is becoming increasingly serious due to large-scale construction of urban railway transit and the increasing of train velocities. A sound barrier and/or track acoustic panel made of porous ceramsite, which is a kind of foaming cement-based aggregate, is quite suitable for sound absorption as both possess remarkable features, such as high sound absorption, fire-resistance, anti-seismic abilities, being weather-proof, anti-corrosiveness, a light weight, and non-toxicity [2,3]. They have been widely used to abate the noise pollution caused by URT in recent years [4,5,6]. For the decomposition mechanism of ammonium acetate in cement-based materials to be understood thoroughly, Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) techniques were used
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