This paper presents the synthesis of silica (SiO2) from rice husk at different firing temperatures. Due to the environmental awareness and to reduce air pollution, agricultural wastes specifically rice husk is used to produce SiO2. Silica was prepared by washing with clean water without any chemical treatment. The rice husk was fired at 700, 800, 900, 1000, 1100 and 1200°C. In order to determine the effect of firing rice husk at different temperature, X-ray Diffraction (XRD) analyses were conducted. Crystalline silica were obtained at 1100°C and 1200°C firing temperature. At 900°C and 1000°C firing temperature, silica was observed to be in a transitional phase of amorphous into crystalline or it called as semi crystalline. However, at 700°C and 800°C silica remains to be in amorphous phases.

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3D printing concrete is an alternative technology for construction industry that are gaining interest among the developers and contractors worldwide. 3D printing concrete requires a good quality printing material that are buildable, strong and durable to be used as construction material. This present study uses Rice Husk Ash (RHA) as cement material replacement in in 3D printing concrete. Initial investigation was carried out to assess the suitability of RHA as cement replacement by conducting basic cement test such as cement consistency, setting time and workability of the mortar. The amount of RHA was constant at 20% used as cement replacement. From this study, the appropriate water-binder ratio of RHA cement replacement was 0.45:1. As for setting time, the time required for mortar mix to be transport and delivered through the nozzles for 3D printing was achieved by implemented the 20% RHA as cement replacement which are initial time at 155 minutes and final time at 312 minutes. The flowability of the mortar with RHA were found to be printable and achieve the requirements of mortar for 3D printing. Hence, RHA exhibits promising material to be used as cement replacement in 3D printing construction.

The major cause for corrosion of steel reinforcement embedded in concrete due to chloride penetration has been the great research effort. The use of nano metaclay in UHPC increase the strength and helps the formation of micro pores by acting as a filler thus improve the chloride penetration resistance characteristic. The aim of this study is to evaluate the chloride diffusion of UHPC using RCPT and chloride penetration depth. Four (4) series of UHPC comprised of plain UHPC and a series of nanoUHPC incorporating 1%, 3% and 5% of nano metaclay were produced. It is reported that the compressive strength of nano UHPCl exhibits higher strength up to 10% compared to plain UHPC. The results showed that UHPC containing nano metaclay also significantly affect the chloride diffusion coefficient. As regards to the results, inclusion of 1% nano metaclay in UHPC led to noticeable benefit towards strength and chloride resistance.

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Abstract. Nowadays, the application of nano materials is getting attention to enhance the conventional concrete properties. The ultrafine particles of nano material also will help reducing the formation of micro pores by acting as a filler agent, produce a very dense concrete and will reduce the growth of micro pores in the UHPC structures. The introduction of nano materials in concrete is to increase the strength and durability of concrete. One of the most important factor affecting concrete durability is chloride penetrability. The purpose of this study was to evaluate the chloride permeability and chloride penetration depth by using rapid chloride permeability test (RCPT) and colorimetric method, respectively. The study was conducted for normal performance concrete (NPC), high performance concrete (HPC), ultra-high performance concrete (UHPC) and a series of UHPC (nano metaclayed-UHPC) incorporating different replacement levels of nano metaclay. All the tests were performed at ages of concretes from 3 up to 365 days. The results showed that the presence of silica fume in HPC and nano metaclay in UHPC reducing the Coulombs passed on the 56-days up to 365-days. The experimental results also revealed the depth of chloride ion penetration for nano metaclayed-UHPC concretes are much lesser than those concretes. As regards to the results, nano metaclay led to noticeable benefit in term of chloride resistance.

Abstract. The inclusion of Effective Microorganism (EM) lengthen the setting time of microbed cement paste with respect to the control cement paste. However, the investigation on the influence of EM ingredients to the setting time was not performed yet in the earlier study. Therefore, the test of X-Ray Diffraction (XRD) was performed on the EM product used in order to determine their ingredients. Further examination was carried out to analyse the pore characteristics in examining the effect of the pore size distribution to the setting time of microbed cement paste. Potassium Chloride (KCl) was detected in EM liquid using XRD test. It can be concluded, the ingredient of EM which is consist of the molasses influenced the setting time of microbed cement paste. The hardening rate of microbed cement paste was effected by the presence of KCl. The pore size of microbed cement paste recorded the lower pore volume (mL/g) with respect to the control cement paste. The larger intrusion of mercury was recorded at smaller pore diameter in microbed cement paste while control cement paste occupied at the bigger pore diameter. The microbed cement paste (16.5%) recorded the smaller porosity than cement paste without EM (20.3%). The smaller cement pore effects the delayed setting time of microbed cement.