Influence of Glass Additions on Illitic Clay Ceramics

Abstract

A mixture of an illitic clay and waste glass was prepared and studied during the sintering process. The illitic clay, from the Liepa deposit (Latvia), and green glass waste (GW) were disintegrated to obtain a homogeneous mixture. The addition of disintegrated GW (5-15 wt% in the mixture) led to a reduction in the intensive sintering temperature, from 900 to 860 °C, due to a significant decrease in the glass viscosity. The addition of GW slightly decreased the intensities of the endo- and exothermic reactions in the temperature range from 20 to 1000 °C due to the reduced concentration of clay minerals. GW reduced the plasticity of the clay and reduced the risk of structural breakage. The increase in sintering temperature from 700 to 1000 °C decreased the apparent porosity and water uptake capacity of the ceramics from 35% and 22%, down to 24% and 13%, respectively. The apparent porosities of all the sintered mixtures showed a decrease of between 6% to 9% after the addition of GW with concentrations from 5 up to 15 wt% respectively, while the water uptake capacities decreased from between 4% and 10%. The addition of GW led to an increase in the apparent density of the ceramic materials, up to 2.2 g/cm³. Furthermore, the compressive strength increased by more than two times, reaching a highest value of 240 MPa after the sintering of the 15 wt% GW-containing mixture at 1000 °C.

Keywords: ceramics; clay; compressive strength; glass; illite; specific strength; waste glass.

Figure 1

Particle size distribution of the clay and glass after the second milling/mixing.

Figure 2

Differential thermal analysis (DTA) results of the tested clay-glass ceramic materials in the temperature range from 20 up to 1100 °C. The content of glass in wt% is in the legend.

Figure 3

Thermogravimetric (TG) analysis results of the tested clay-glass ceramic materials in temperature range from 20 up to 1050 °C. Detected events (1, 2, and 3) are indicated. The content of glass in wt% is in the legend.

Figure 4

Dilatometric curves of the tested clay-glass ceramic materials in temperature range from 20 up to 1300 °C. Detected events are indicated. The content of glass in wt% is in the legend.

Figure 5

XRD pattern of the glass cullet (GC) (bottom curve) and GC treated at 1000 °C (upper curve).

Figure 6

XRD patterns of Liepa clay fired at 700, 800, 900, and 1000 °C (from the bottom to top).

Figure 7

XRD patterns of Liepa clay with 15% of GC fired at 700, 800, 900, and 1000 °C (from bottom to top).

Figure 8

Apparent porosity of tested clay-glass ceramic materials after sintering at temperatures from 700 up to 1000 °C. The content of glass in wt% is in the legend.

Figure 9

Apparent density of tested clay-glass ceramic materials after sintering at temperatures from 700 up to 1000 °C. The content of glass in wt% is in the legend.

Figure 10

Shrinkage of tested clay-glass ceramic materials after sintering at temperatures from 700 up to 1000 °C. The content of glass in wt% is in the legend.

Figure 11

Compressive strength of tested clay-glass ceramic materials after sintering at temperatures from 700 up to 1000 °C. The content of glass in wt% is in the legend.

Figure 12

Dependence of compressive strength on apparent density of tested clay-glass ceramic materials after sintering at temperatures from 700 up to 1000 °C.

Figure 13

The compliance of produced clay-glass ceramic materials with typical materials demonstrated in the Ashby classification diagram (adopted with permission from [43]).