Study on the soluble silica from palm oil clinker as partial cement replacement material

• Main Author: Lee, Tsu Yian
• Format: Undergraduates Project Papers
• Language: English
• Published: 2019
• Subjects: TA Engineering (General). Civil engineering (General)
• Online Access: http://umpir.ump.edu.my/id/eprint/28940/1/Study%20on%20the%20soluble%20silica%20from%20palm%20oil%20clinker%20as%20partial%20cement%20replacement.pdf; http://umpir.ump.edu.my/id/eprint/28940/

The growth of palm oil industry and construction industry have brought the issues of abundant dumping of palm oil clinker (POC) and carbon dioxide emission, respectively. Taking advantage of the high silica content in POC, the idea of extracting soluble silica from POC and using it to partially replace cement in mortar has been initiated. Therefore, this study aimed to investigate the feasibility of partially replacing cement in mortar with soluble silica extracted from POC, where the decision was supported by finding the suitable parameters for soluble silica extraction and evaluation of mortar in terms of compressive strength and porosity. The POC was ground into powder form called palm oil clinker powder (POCP) and then pre-treated with 0.1M hydrochloric acid. The acid-leached POCP was then used for soluble silica extraction. The Laine’s Method that consists of the water reflux and distillation steps was adopted to extract the soluble silica from the acid leached palm oil clinker powder (POCP). Based on the X-Ray Fluorescence (XRF) analyses, it was found that using longer distillation time and higher amount of POCP for soluble silica extraction resulted in the extracted soluble silica solution of higher silica concentration. The use of 480g of POCP and 12 hours of distillation in the extraction experiment resulted in 53.50% of dissolved silica, which was the highest gain among the trial experiments. The extracted soluble silica was used to replace cement at 0%, 2.5%, 5% and 7.5%. To evaluate the influences of replacement with soluble silica, compressive strength and porosity tests were conducted. It was found that all soluble silica-based mortars possessed rapid hardening properties, where high compressive strength was recorded during early age, due to the earlier taken place pozzolanic reaction. During early age, the highest compressive strength of 16.90MPa was recorded for the mortar batch with cement replaced by 5% of soluble silica (S5.0), where its compressive strength was 5.24% and 6.20% higher than that of reference mortar at day 3 and day 7, respectively. However, due to the slow strength development of all soluble silica-based mortars after early age, the targeted reference strength was failed to be achieved at day 28 and 56. Result of high porosity was obtained for all soluble silica-based mortars due to the reduction of cement amount. The reduction of porosity after early age was also slow, where the porosity of mortar batches with cement replaced by 2.5%, 5.0% and 7.5% only decreased by 1.7%, 0.8% and 1.7%, respectively from day 7 to day 28. The correlation between compressive strength and porosity of mortar was studied. It was found that during early age, the mortar compressive strength was independent to the porosity; however, mortar porosity became partial factor affecting compressive strength during later age. Since the reduction of cement amount in soluble silica-based mortar leads to high porosity and low later strength, reducing cement amount in mortar and replacing it with soluble silica is not recommended; however, due to the early strength properties displayed by soluble silica-based mortar, the potential of soluble silica to be used as additive for rapid hardening could further be explored.