## 1 Introduction
Further, light-weight aggregate concrete (LWAC) with excellent properties can be produced by using synthetic LWA, which can be applied to high-rise buildings and bridges to achieve the purpose of reducing self-weight and seismic force. LWA is porous, has a low density, and has high water absorption; it is fired in a rotary kiln to a high temperature above 1000 \({}^{\circ}\)C. As a result, it has a higher thermal stability and a lower thermal expansion coefficient. Therefore, LWA is essentially different from normal-weight aggregate, which will lead to differences in the mechanical behavior and refractory performance of LWAC and normal-weight aggregate concrete (NWC) [34; 35; 36; 37; 38]. [PERSON] and [PERSON] [37] investigated the thermal expansion of self-consolidating normal and lightweight aggregate concrete at an elevated temperature varying from 20 to 1000 \({}^{\circ}\)C. The results showed that lightweight aggregate reduced the coefficient of thermal expansion of self-consolidating concrete due to the fact of its porous structure. [PERSON] et al. [38] analyzed the mechanical properties degradation of LWAC after exposure to room temperature (20 \({}^{\circ}\)C) and high temperatures (up to 1000 \({}^{\circ}\)C). After exposure to 1000 \({}^{\circ}\)C, the LWAC lost no more than 80% of its strength, while the NWC lost its load-bearing capacity. Since LWA has many pores and a high water absorption rate, LWAC easily generates a high pore pressure inside it when it is exposed to a rapidly rising temperature environment. Coupled with a lower thermal conductivity, which contributes to a higher temperature gradient, LWAC members are more easily damaged under the action of a high temperature, which has a considerable impact on the fire safety of the structure [39; 40; 41; 42; 43; 44]. [PERSON] [44] pointed out that the presoaking degree of LWAC had a significant effect on the residual compressive strength and elastic modulus of LWAC after exposure to 800 \({}^{\circ}\)C.  
An overview of the above literature shows that concrete spalling at elevated temperatures is a complex phenomenon caused by the coupling of thermal, hydral, chemical, and mechanical processes. Under the standard temperature curve (ISO 834 standard fire resistance curve), the fire resistance of LWAC members (i.e., slabs, walls, and beams) is better than that of equivalent thickness members made with NWC. However, in the case of the hydrocarbon fire curve, fire tests showed the opposite result. This is because the factors that affect concrete's fire resistance include fire load (heat rate and maximum temperature), concrete properties (moisture content, permeability, and aggregate type), concrete strength grade (regular and high-strength concrete), and axial forces. Furthermore, relatively few studies have been conducted on the temperature and the pore pressure distribution of LWACs exposed to high temperatures. Therefore, this study aimed to investigate the temperature and the pore pressure distribution of LWAC slabs exposed to high temperatures. Thermocouples and pressure gauges were embedded in different positions of the slab specimens to measure their temperature and pore pressure, respectively. The test variables included the moisture content of the concrete specimen (oven-dried and air-dried), target temperature (600 and 800 \({}^{\circ}\)C), and heating rate (5 and 10 \({}^{\circ}\)C/min). In addition, NWC slabs of the same strength grade were used as a control group. The results of this study are helpful to understand the differences between LWAC and NWC in temperature and pore pressure distributions at elevated temperatures.