# Study on Preparation and Properties of Sintered Brick from Multi-Source Solid Waste
## 3 Results and Discussions
### Influence Law of Compressive Strength
#### 3.1.3 Microwave Sintered MGS Sintered Brick  
(1) Microwave sintering temperature rise rate and holding time on the compressive strength of sintered brick influence law.  
In the microwave field, the internal polar molecules of the brick body are synchronously perturbed and resonate with the microwave frequency, which achieves rapid and uniform heating of the billet on a macroscopic scale, resulting in the high quality of the sintered brick. However, due to the high content of free water and bonded water inside the brick body, the excessive heating rate will cause a sharp increase in the pressure difference between the inside and outside of the brick, which eventually leads to the bursting of the brick body. The above problems can be seen in Table 10 and Figure 7a. This paper adopts the interval heating method, with room temperature\(\sim\)300 \({}^{\circ}\)C, 300-800 \({}^{\circ}\)C, and 800-1050 \({}^{\circ}\)C for three intervals; each temperature interval exerts independent control of the heating rate. When the microwave power is low, the highest temperature of the sintered brick interval does not reach the lowest temperature of the next interval, and its heating rate and sintering temperature are not enough to promote the continuous sintering of sintered brick and produce a jumping phenomenon. Different temperature rise types and holding times also have a significant impact on the compressive strength, and sintered brick compressive strength changes, as shown in Figure 7b, with three temperature rise types and different holding times. When the \"type 2\", holding time is 30 min, the maximum strength can reach 24.7 MPa, and a heating rate that is too fast or too slow will lead to a significant decrease in the strength of the sintered brick.  
Figure 6: Effect of sintering temperature on compressive strength of MGS sintered brick.  
(2) Effect of microwave sintering temperature on the compressive strength of sintered brick.  
From the experimental results of heating sintered brick using an electric furnace process, it is known that the best sintering temperature of the MGS-doped bricks is 1100 \({}^{\circ}\)C. However, the sintering temperature of the sintered brick may vary, due to different sintering mechanisms. Therefore, this paper initially chose to investigate the effects of sintering temperatures of 900 \({}^{\circ}\)C, 1000 \({}^{\circ}\)C, 1050 \({}^{\circ}\)C, and 1100 \({}^{\circ}\)C on the compressive strength of sintered brick under the conditions of 50% construction waste as the main raw material, 10% waste glass slag, and 16% Yellow River sedimentary sand as admixtures. The results are shown in Figure 8.  
As can be seen from Figure 8, with the increase in maturing temperature, the compressive strength of the MGS sintered brick increases, the compressive strength reaches its maximum value when sintered at 1000 \({}^{\circ}\)C, and when the maturing temperature reaches 1050 \({}^{\circ}\)C and 1100 \({}^{\circ}\)C, the strength of the sintered brick changes smoothly without significant growth.