United States Department of Transportation
i
Processing of Cenosphere-Cement/Asphalt Composite Materials and Evaluation of Their Mechanical and Acoustic Properties
-
2004-04-01
-
[PDF-288.59 KB]
Details:
-
Creators:
-
Corporate Creators:
-
Corporate Contributors:
-
Subject/TRT Terms:
-
Resource Type:
-
Geographical Coverage:
-
Corporate Publisher:
-
Abstract:Cenospheres are hollow, aluminum silicate spheres, between 10-300um in diameter. Their low specific gravity (0.67) make them ideal replacements for fine sand for producing low density concrete. In this research, the moisture uptake and loss by cenospheres, and water uptake and loss in cenosphere/concrete composites have been studied. The equilibrium moisture content of cenospheres exposed to air of 85% relative humidity is 0.15 kg moisture / kg dry cenospheres. This moisture content is about 18 times higher than that of sand, reflecting the porous nature of cenospheres. The temporal evolution of water penetration into the cenosphere/concrete is modeled using Washburn kinetics. The effective pore size using this model is of the order of several nanometers. The results imply a lack of connectivity within the pores, leading to a low permeability. SEM images of the concrete reveal pore sizes of the order of 2-5mm. When the "wet" cenospheres are exposed to air of 20% relative humidity at room temperature the drying flux shows a classical behavior - a constant rate followed by a linear falling rate period. Thus experiments done at these conditions can be used to predict drying times for wet cenospheres exposed to other environments. The drying of saturated cenosphere/concrete and the normal concrete material exposed to air at 20% relative humidity is compared at 23 degrees C, 30 degress C and 40 degress C. The flux of water vapor away from both the cenosphere/concrete as well as the normal concrete shows a non-linear change with moisture content throughout the drying cycle, implying that the pore structure within the concrete strongly influences the drying behavior. The acoustic behavior of different grades of cenosphere rich concrete has also been investigated experimentally. Properties such as absorption coefficient, reflection coefficient and acoustic impedance and their dependence on frequency have been measured. The effect of cenospheres on the acoustic properties including the complete acoustic frequency response characteristic of cenosphere rich concrete is reported. References, 21 figures, 27 p. (288 kb)
-
Format:
-
Collection(s):
-
Main Document Checksum:
-
Download URL:
-
File Type:
