A Feasibility Study on Textile Sludge as a Raw Material for Sintering Lightweight Aggregates and Its Application in Concrete  
[PERSON]  
1 Department of Civil Engineering, National Chung-Hsing University, 145 Xingda Road, South District, Taichung City 40227, Taiwan; [EMAIL_ADDRESS] (H.-J.C.); [EMAIL_ADDRESS] (W.-T.C.) [PERSON]  
1 Department of Civil Engineering, National Chung-Hsing University, 145 Xingda Road, South District, Taichung City 40227, Taiwan; [EMAIL_ADDRESS] (H.-J.C.); [EMAIL_ADDRESS] (W.-T.C.) [PERSON]  
2 Department of Civil Engineering and Geomatics, Cheng Shiu University, No. 840, Chengching Road, Niaosong District, Kaohsiung 83347, Taiwan 2344  
With the raising of awareness in terms of environmental protection, the source of materials for the production of artificial lightweight aggregates (LWAs) has developed toward the direction of resource recycling. In addition to using industrial by-products such as slag [7] and fly ash [8], waste sludge, such as sewage sludge, is also used as raw materials for the production of LWAs [9; 10; 11; 12]. The authors' previous research has successfully used renewable resources, such as reservoir sediments, waste TFT-LCD glass powder, paper residue sludge, tile grinding sludge, and water purification sludge, in Taiwan to produce LWAs [13; 14; 15; 16; 17; 18]. Based on the aforementioned research results, this study continues to explore the feasibility of using textile sludge as a raw material for sintering artificial LWAs. At present, there are many ways to reuse textile sludge, including recycled bricks, concrete, compost, and biochar [19; 20; 21; 22; 23]. Some scholars have used textile silt to replace certain raw materials in order to manufacture various floor tiles, such as concrete floor tiles, pavement tiles, fired clay bricks, and fly ash bricks [24; 25]. It was found that the textile sludge itself contains organic matter, which can delay the setting time of cement and can affect the compressive strength. With the increase in its substitution amount, the slow setting phenomenon of the sample was particularly evident, and the compressive strength decreased accordingly [26; 27]. Certain scholars have reused textile sludge in cement mortar as a substitute for cement [28; 29; 30; 31; 32]. The test results of [PERSON] et al. [28] showed that when the replacement amount of textile sludge was too high, a more porous microstructure was observed, consisting mainly of ettringite, voids, and less CSH gel. [PERSON] et al. [32] explored the reutilization of textile sludge stabilized with low-grade MgO as a replacement of cement in mortars. The results of their experiments revealed that a replacement of up to 10% of the cement with stabilized textile sludge was found to be optimal without negatively affecting the properties of the mortar. Furthermore, the SEM images revealed the densification of the microstructure after the addition of stabilized textile sludge to the mixture. The sludge that is produced by the solid-liquid separation process in the tap water purification plant is water purification sludge. The chemical composition of water purification sludge will vary depending on the quality of raw water and the type of coagulant. The types of coagulants can be divided into iron series and aluminum series, which will lead to different contents of aluminum and iron in sludge. However, the water source of the water purification plant remains unchanged, and the other chemical components of the sludge will not change too much. Currently, water purification sludge is reused as raw materials for cement, raw materials for red brick, culture soil, construction materials, etc. [33; 34; 35; 36; 37; 38; 39; 40]. [PERSON] et al. [36] explored the effect of the water-binder ratio (w/b) on the strength, shrinkage, and microstructural characteristics of concrete containing drinking water sludge ash (DWSA). The results showed that recycling 10% DWSA in concrete improved the strength and shrinkage resistance of the samples.