Using Lime Mud Waste from Pulp Mill as an Additive in Brick Clay Srichalai Khunton 1,a , Siriphan Nilpairach 1,b , Supin Sangsuk 1,c, * 1 Metallurgy and Materials Science Research Institute, Chulalongkorn University, Phayathai Rd, Bangkok 10330, Thailand a Srichalai.k@chula.ac.th, b Siriphan.n@chula.ac.th, c Supin.t@chula.ac.th Keywords: Lime mud, Brick clay, Recycle, Additive Abstract. Lime mud from a pulp mill was used as an additive in brick clay from the southern part of Thailand. It was mixed with the clay from Cha-Aud district, Nakorn Si Thammarat province. The chemical composition of lime mud and the clay was characterised by X-ray fluorescence (XRF), and the mineralogical composition was measured by X-ray diffraction (XRD). The particle size distribution was also measured. The main composition of lime mud is CaO, and Cha-Aud clay consists of SiO 2 and Al 2 O 3 as major oxides. The lime mud contains calcite as a major phase when Cha-Aud clay is constituted by quartz, kaolinite, illite and goethite. Particle size distribution of lime mud is in the range of 1-50 μm. After the lime mud was neutralized using hydrochloric acid, it was mixed with Cha-Aud clay at 10 wt%. Samples with and without lime mud were sintered at 700, 800, 900 and 1000 o C for 1 hour. The results showed that lime mud can be used as an additive in brick clay. Both types of samples were similar in terms of physical properties when their linear firing shrinkage, water absorption and flexural strength were in the same range. Introduction Lime mud is a by-product produced in pulp mill as a part of the process that turns wood chips into pulp for paper. The main composition of lime mud is calcium carbonate [1]. It is very difficult to dry because of the tiny particle size of the suspended lime. Many paper mills have huge landfills full of lime mud [2]. In the past, calcium carbonate was used as an additive in pottery, for example in the Late Woodland period (AD 400-900) and in the Emergent Mississippian (AD 750-1000). A result showed that the samples with limestone temper were more resistant to mechanical stress than are grit or grog temper replicas fired at 600 o C [3]. There are at least two previous works that we studied about effects of adding limestone dust in pottery clay [4-5]. For the first work, we studied the effect of limestone dust mixing with pottery clay (Angthong clay) on the physical properties of ceramic. The result showed that the flexural strength increased by adding 50 wt% of limestone dust when the samples were sintered at 700 o C for 1 h. For the other work, limestone dust was mixed with various sources of pottery clay from the Northeast of Thailand. The study demonstrates that mechanical properties of the samples with limestone dust were improved by increasing flexural strength and decreasing linear firing shrinkage when the samples were fired at 700 o C for 1 h. Therefore the objective of this work is to investigate the possibility of using lime mud with brick clay from the southern part of Thailand and their physical properties. Experiment Brick clay from Cha-Aud district, Nakorn Si Thammarat, was used in this study. Lime mud waste was from a pulp mill. Because lime mud contaminated with strong alkaline, it was neutralized with 10 wt% hydrochloric acid solution. The chemical composition of clay and lime mud was characterised by X-ray fluorescence (XRF), Oxford ED 2000. The mineralogical composition of clay and lime mud was measured by X-ray diffraction (XRD), Philips PW3710 diffractometer (Cu-kα radiation). The Loss On Ignition (LOI) of Cha-Aud clay and lime mud was tested at 1000 o C. The particle size distribution was measured by laser particle size analyser (Mastersizer Malvern S). Mixture containing with 10 wt% of lime mud were prepared by mixing with water and were aged Key Engineering Materials Vol. 608 (2014) pp 3-7 Online available since 2014/Apr/17 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/KEM.608.3 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 161.200.12.148, Chulalongkorn University, Bangkok, Thailand-17/07/14,04:35:27)