Kartini Kamaruddin

Microorganism Precipitation in Enhancing Concrete Properties

Microorganism is an unique living element and has the ability to precipitate minerals through the process of biomineralisation. The precipitation process occured naturally and most of the precipitated products are very important compound composed of such as carbon, nitrogen, oxygen, sulphur, phosphorus and silica. So far, concrete incorporated with microorganism that able to precipitate calcium carbonate (calcite) was reported. However, little information on silica precipitation and its effect on concrete properties has been revealed. In this present study, the concrete specimens were incorporated with Bacillus subtilis silica adsorbed in their cell wall. Concrete specimens with five different concentration of Bacillus subtilis cell which are 104, 105, 106 and 107 cell/ml and control (without Bacillus subtilis) were cast. The experimental investigation aims to prove that the silica precipitated by this microorganism can enhance the concrete properties namely its compressive strength and resistance to carbonation. The microstructure of the concrete contained Bacillus subtilis was also examined. It appears that the inclusion of Bacillus subtilis into the concrete enhanced the compressive strength. The concentration of 106 cell/ml was found to be the optimum concentration to give most enhanced effect to the compressive strength. However the effect of including Bacillus subtilis to the resistance to carbonation of the concrete specimen is found to be insignificant.

The Effect of Bottom Ash on Fresh Characteristic, Compressive Strength and Water Absorption of Self-Compacting Concrete

Bottom ash is a solid residue produced through combustion process in a coal-fired power plant. It has been catogarized as a waste and usually disposed in the utility disposed site. With higher demand on the power energy, more coal-power plant are constructed and abundance of bottom ash are produced. Recently, the utilization of bottom ash in the construction industry has gained the interest of researches. Since it has similiar particle size distribution as normal sand, many attempt has been made in studying it potential use in mortar and concrete. In complementary to that, this paper presents the effect of bottom ash on fresh and hardened properties of self-compacting concrete (SCC). Bottom ash is used as fine aggregate replacing sand with replacement ratio range from 0% to 30% by volume. The effects of bottom ash on the SCC were investigated by comparing the test result of SCC mixed bottom ash with control specimens (0% of bottom ash). The test result on fresh properties of the concrete mixture revealed that, as the replacement level of bottom ash increased, the slump flow, L-box passing ratio and segregation resistance ratio (SR) decreased. Nevertheless, the slump flow time (T500) result increased with the increased of bottom ash content. The results show that the porosity and the irregular shape of the bottom ash particle has great influence on workability and viscosity of the fresh concete. The compressive strength and water absorption test are carried out on the sample at curing time of 7 and 28days. In terms of strength, the use of bottom ash in the production of SCC has increased the compressive strength of the concrete up to 15% replacement level. The increase in strength show the presence of the pozzolanic reactivity in a concrete with bottom ash particle. The water absorption rate was observed to be lower with a sample which having 10% and 15% replacement level.

The Strength Behavior of Self-Compacting Concrete Incorporating Bottom Ash as Partial Replacement to Fine Aggregate

Self-compacting concrete which commonly abbrevited as SCC is a special concrete that have the ability to consilodate fully under its own self-weight without any internal or external vibration. This paper presents the experimental investigation carried out to study the strength of self-compacting concrete incorporating bottom ash at different replacement level of natural sand. The composite cement was used and the replacement level of bottom ash to natural sand is set up to 30% by volume. The strength properties such as compressive strength, split tensile strength and flexural strength of the concrete at the age of 7 and 28 days of curing day were conducted. Results shows that the strength of the concrete with bottom ash increased up to replacement level 15% higher than control specimens. This show that bottom ash can be used as supplimentary cementitious materials, having the pozzolanic reactivty.

Evaluation on the Thermal Conductivity of Sand-Cement Blocks with Kenaf Fiber

Mechanical means of ventilation and air-conditioning system in Malaysian buildings are used continuously to provide and maintain the comfort of indoor environment to the occupants of the buildings. It was found that the system used led to higher rate of energy consumption. Hence, development of masonry units with high thermal insulation properties is a necessity. This paper represented the study on the thermal conductivity and the density of sand-cement blocks incorporated with different proportions of kenaf (Hibiscus cannabinus L.) fiber as additive. The amount of kenaf fiber inclusions were the main focus to observe the achievement of best results for both properties. It was found that kenaf fiber content had an advantage to reduce the self-weight of blocks whilst reducing the thermal conductivity property. Hence, it can be seen that there is a potential in developing masonry units for single wall components in Malaysian buildings with lightweight features and thermal insulator properties.

Enhancement of Thermophilic (Geobacillus stearothermophilus) Cement–Sand Mortar Properties

This study describes the incorporation method of Geobacillus stearothermophilus (ATCC 12978) inside the cement–sand mortar. Different cell concentrations of Geobacillus stearothermophilus were incorporated and the improvement in the properties of cement–sand mortar has been observed. Based on the study conducted, the involvement of Geobacillus stearothermophilus (ATCC 12978) has a positive impact to improve the performance of cement–sand mortar in terms of compressive strength and water absorption characteristic as compared to the controlled mortar. The incorporation of Geobacillus stearothermophilus has catalyst the occurrence of wollastonite (CaSiO3) that has proven capable to the enhanced concrete properties by modifying concrete pore structures. This study shows that the optimum concentration gives the most enhanced properties of the resulted cement–sand mortar as 1 × 109 cfu/ml. The current work demonstrates that the direct involvement of Geobacillus stearothermophilus in mortar has a great potential to enhance concrete performance in such natural way.

Compressive Strength and Density of Unfired Lightweight Coal Ash Brick

Coal-fired thermal power plant produces million tons of coal ash which constitute of fly ash and bottom ash annually throughout the world. They were by-product and significant to be developed as brick to substitute the existing widely used traditional material such as clay and sand brick which were produced from depleting and dwindling natural resources. In the present study, the coal ash from coal-fired thermal power plant was used as the main raw material for the fabrication of unfired lightweight brick. The blended binder comprising of Hydrated Lime (HL)-Ground Granulated Blastfurnace Slag (GGBS) and Portland Cement (PC)-GGBS were used to stabilize the coal ash in the fabrication process. Foam was used to reduce the weight of the brick. The compressive strength in accordance to BS EN 772-1 and ambient density in accordance to AS/NZS 4456.8 were evaluated on the brick samples. The results indicated that the coal ash brick incorporating PC-GGBS system achieved higher compressive strength compare to the HL-GGBS system. However, as the quantity of foam increase, the strength and density for both brick systems decreased.

Compressive Strength and Density of Cementless Unfired Lightweight Brick Utilizing Coal Ash from Coal-Fired Thermal Power Plant

Millions tons of coal ash which constitute of fly ash and bottom ash were produced annually throughout the world. They were significant to be developed as masonry brick to substitute the existing widely used traditional material such as clay and sand brick which were produced from depleting and dwindling natural resources. In the present study, the coal ash from coal-fired thermal power plant was used as the main raw material for the fabrication of cementless unfired lightweight brick. The binder comprising of Hydrated Lime (HL)-activated Ground Granulated Blastfurnace Slag (GGBS) system at binding ratio 30:70, 50:50 and 70:30 were used to stabilize the coal ash in the fabrication process of the brick. Foam was used to lightweight the brick. The compressive strength and ambient density were evaluated on the brick. The results indicated that the brick incorporating HL-GGBS system achieved higher strength of 20.84N/mm2 at 28 days compare to the HL system with strength of 13.98N/mm2 at 28 days. However, as the quantity of foam increase at 0%, 25%, 50%, 75% and 100%, the strength and density for the brick decreased.