Rice Husk Combustion Research Articles

Yields and heavy metal uptake of cocoyam (Xanthosoma sagittifolium) and effects on soil properties of different tillage practices and application of burnt rice husk dust in Abakaliki, south-east Nigeria

ABSTRACT Indigenous crops play a critical role in the socioeconomic growth of developing nations where there have been calls for exploitation of these staple crops. This study investigated the yield and heavy metal uptake of cocoyam and changes in soil physical properties in relation to different tillage practices and the application of burnt rice husk dust (BRHD). The experiment was arranged as a split plot in a randomised complete block design (RCBD) with six treatments and three replications. The treatments were: mound tillage (no BRHD); ridge tillage (no BRHD); mound + 10 t ha−1 BRHD; mound + 20 t ha−1 BRHD; ridge + 10 t ha−1 BRHD and ridge + 20 t ha−1 BRHD. The results showed that soil bulk density (at 45 days after planting, DAP) was lower when the tillage practices were combined with the amendment of burnt rice husk dust, while total porosity (at 45 DAP) and aggregate stability were higher. The yields of cocoyam corms were also higher for tillage practices combined with amendment with burnt rice husk dust. The concentrations of heavy metals (Cu, Fe, Pb and Zn) in the cocoyam corms were higher for plants grown in soil amended with BRHD, but the levels were still below the levels considered harmful in food crops. Burnt rice husk dust could be recommended for use as a soil amendment in the study area to improve soil properties and increase the production of cocoyam, without increasing the concentration of heavy metals in the corms to harmful levels.

Reduced Pollutant Emissions and Slagging Rate of Biomass Pellet Combustion by Optimizing the Multilayer Distribution of Secondary Air.

The utilization of coal and other fossil fuels is becoming increasingly restricted. Biomass, as a clean and renewable energy, plays a significant role in achieving zero carbon emissions. However, biomass is prone to slagging in the combustion process due to its high alkali metal content. The ash slagging rate and pollutant emission level of flue gas can be reduced by optimizing the air distribution, in order to decrease the fuel layer temperature in the combustion chamber. The results reveal opposite change trends of CO and NOx concentrations in the flue gas. The NOx emissions of corn stalk combustion under the multilayer secondary air distribution are obvious compared with those of rice husk combustion. The slagging rate of corn stalks is highly correlated with temperature T1 of the fuel bed. The silica ratio (G), alkali/acid ratio (B/A), Na content index (Na (index)), and alkaline index (Alc) cannot accurately predict the slagging tendency when temperature T1 changes. Therefore, the modified predictive index (Gt) was proposed to predict the slagging tendency of corn stalks with the combustion zone temperature T1 effectively. The experimental results can contribute to the efficient combustion and low pollutant emissions of biomass.

Particulate matter characterization of the combustion emissions from agricultural waste products

This research study examines the levels of particulate matter (PM) which result when two different unprocessed agricultural waste products were burned in a fixed bed combustor under varied air supply conditions. The properties of the PM emissions obtained are: 1) the overall number/mass concentration along with the emission factors (EFs), 2) the distribution of the number and mass size, and 3) the establishment of the morphology of the particles and the trace elements they contain. The findings indicated a total concentration of 3.1 ± 1.9×104 and 9.6 ± 4.5×104 particles/cm3 (or number EFs = 3.52×109–2.26×1010 and 1.88–5.65×1010 particles/kgfuel), whereas the total particle mass was found to be in the range of 5.51–10.4 and 1.45–6.08 mg/m3 (or mass EFs = 1.58–3.26 gPM10/kgfuel and 0.53–3.37 gPM10/kgfuel) in the case of rice husk and bagasse combustion, respectively. The distribution of the particle sizes was shown to be bimodal for rice husk combustion, but had only a single mode for bagasse combustion. For both fuel types, the predominant particle size emerging during combustion was 0.07μm. From the gravimetric perspective, the dominant sizes were 3.07, 5.13, and 8.09 μm. PM emissions are also affected by the properties of the fuel involved in the combustion process, with ash content, homogeneity of the fuel, and the mineral content all known to be influential factors. It is also understood that the air staging can affect PM emissions during the combustion of rice husks, so a rise in the ratio of secondary air to total air might reduce nanoparticle formation (PM0.1) through a shift to the accumulation mode (PM0.1-1.0). The results of assessment of the particle shapes and the evaluation of trace elements showed that the particles formed by the combustion of rice husks were predominantly spherical, which can be explained by the dominance of carbon. In contrast, irregular shapes of particle were obtained in coarse-sized particles and the most dominant element is calcium (Ca) and silicon (Si).

Enhancing Oil Palm Empty Fruit Bunch (EFB) Compost by Addition of Burnt Rice Husk as Carrier Material for Selected Nitrogen-Fixing Bacteria

The current interest in minimizing the use of inorganic fertilizers and the increasing demand for the combined action of beneficial microorganisms and agricultural wastes is considered to have a positive impact on soil, crop productivity and sustainable agriculture. The objective of this study was to prepare a series of combinations of empty fruit compost (EFBC) and burnt rice husk (BRH) as carrier materials for selected nitrogen-fixing bacteria, evaluate their suitability, and determine the ability of the inoculated EFBC-BRH carrier materials. Different ratios of EFBC and BRH were used to prepare the carrier materials for the selected N₂-fixing bacteria, namely strains Sb35 and Sb42 of Bacillus sp. Both coarse and fine EFBCs were used for the preparations. The suitability of the combinations of EFBC-BRH as a bacterial carrier was tested by inoculating the different ratios of organic material combinations with the N₂-fixing bacteria and incubating them at room temperature for eight weeks, after which the effects on the bacterial population, pH, moisture content, and contaminants were determined. The results showed that the fine-textured EFBC-BRH carriers’ formulation (T5 to T8) were better carriers compared to the formulation of coarse-textured EFBC-BRH carriers (T1 to T4). The inoculated carrier T6 (1 fine structured EFBC: 1 BRH) showed the best response with an increase in Sb35 and Sb42 populations of 7.34% and 7.47%, respectively. In conclusion, T6 as a carrier material for Sb35 and Sb42 is suitable to be developed as a biofertilizer.

An Applied Research of the Recycled Economic Model for Spirulina Algae’s Cultivation from Ion-Life Alkaline Water and 〖CO〗_2 Gas’s Boiler

This paper presents an investigation of Spirulina algae (S. platensis) cultivation from the research and application of the circular economy model for green production by combining Ion-Life alkaline water and the gas emitted from the combustion of rice husk. This circular economy model for green production is applied in using the optimal pH values and the in which S. platensis is much easier for using. The cost of prepared medium for S. platensis cultivation from the Ion-Life alkaline water is minimized thanks to the simplex algorithm. From this algorithm, the cost prepared medium for S. platensis cultivation from the Ion-Life alkaline water can be reduced approximately 71.86 VND/liter when comparing to the Zarrouk medium (nearly equal to 3.71 % of the cost for cultivation from the Zarrouk medium). Comparing the improved medium from Ion-Life alkaline water with the Zarrouk medium for cultivating S.platensis alge are at the same conditions as the temperature from 26 ¸ 40oC and pH value from 8.6 ¸ 10.6. During the first eight days of cultivation in improved medium from Ion-Life alkaline water, the concentration of biomass increases from 0.044 to 0.93 g/L. During the next eight days, the pH values are controlled to be from 8.5 to 9.5, which is suitable for Spirulina algae since feeding the gas from the combustion of rice husk with amount of 7.6 % with the 30 minutes a day. Finding a technology that blows from smoke of boiler to make the effect of stirring the environment for achieving objectives. First, it helps to add carbon-nutrient source in the form of . Second, it helps to maintain the pH of environment in the optimal range of 8.5-9.7. As a result, the biomass concentration increases to 1.4 g/L, while this value is 1.23 g/L in the case non-using from smoke of boiler. On the basis of the obtained results, it is basic to calculate equipment and to build a technology process for the green production of cultivation of Spirulina algae from by using the molecules emitted from the combustion of biomass combining alkaline water ion-life can be applied practically.

Influence of biomass on coal slime combustion characteristics based on TG-FTIR, principal component analysis, and artificial neural network

The development and utilization of solid waste is an effective way to solve the severe environmental and energy crisis. In this study, Thermogravimetry - Fourier transform infrared spectrometry (TG-FTIR) was used to carry out the co-combustion experiment of coal slime and rice husk under different mixing ratios. With the increase of the mass percentage of rice husk in the sample, the initial ignition temperature and burnout of the sample decreased, and the comprehensive combustion performance improved gradually. The dominant reaction in the co-combustion of coal slime and rice husk was determined by statistical method. When the mass percentage of rice husk in the mixture is between 30 and 90 %, it can inhibit the release of NOx and SO2. Taking Kissinger-Akahira-Sunose method as an example, the calculated average activation energies of coal slime and rice husk combustion are 105.66 and 148.93 kJ/mol respectively. With the increase of the mixing ratio of rice husk in the blend, the combustion mechanism of the sample changed. Finally, the mean absolute error, root mean square error and determination coefficient of the artificial neural network model are 0.52697, 0.67866 and 0.99941 respectively.

Experimental study and theoretical prediction of mechanical properties of ultra-high-performance concrete incorporated with nanorice husk ash burning at different temperature treatments.

This research aimed to investigate the effect of nanorice husk ash (NRHA) prepared using different thermal treatment methods on ultra-high-performance concrete (UHPC) behaviour. NRHA was prepared by two methods: (1) burning for 3h at 300, 500, 700 and 900°C and (2) burning for different durations (9, 7, 5 and 3h) at 300, 500, 700 and 900°C. NRHA was added to UHPC to make 25 mixtures with three dosages (1%, 3% and 5%). Density, compressive strength, tensile strength, flexure strength and ultrasonic pulse velocity tests were performed at the experimental level. Moreover, full microstructure analysis, including X-ray diffractometry, Brunauer-Emmett-Teller surface area analysis, thermogravimetric analysis, scanning electron microscopy and energy-dispersive X-ray spectroscopy, was performed. The best performances in in the first method (constant duration, different temperatures) were obtained by 1% NRHA burned at 900°C with 12.5% compressive strength and 1% NRHA burned at 700°C with increased ratio (10%). Moreover, the best performance in the second method (different burning durations and temperatures) was obtained by 3% NRHA with a ratio of 22.5% at 700°C for 5h. Burning rice husk ash improved the compressive strength. It also remarkably improved the splitting tensile strength and flexure strength by 32% and 47%, respectively, at 3% NRHA treated at 700°C for 3h. The microstructural analysis showed the efficient role of NRHA in the compactness of concrete sections. It improved the formation of new calcium silicate hydrate gel; decreased the cracks, voids, CaCO3 and Ca(OH)2; and increased the Ca/Si composition. The obtained experimental results were used to build an artificial neural network (ANN) to predict UHPC properties. The ANN model was used as a validation tool to determine the correlation between results. Results showed a remarkable improvement in the mechanical properties of UHPC incorporating NRHA for all mixtures. The ANN model indicated a reliable correlation between input and output variables. The R2 values for the training, validation and testing steps were all 0.99.

Synergy of RHA and silica sand on physico-mechanical and tribological properties of waste plastic-reinforced thermoplastic composites as floor tiles.

The usage of waste for the development of sustainable building materials has received an increasing attention in socio-eco-environment spheres. The rice husk ash (RHA) produced during burning of rice husk and the ever-increasing plastic wastes are useless causing detrimental effects on the environment. This research supports the idea of sustainability and circular economy via utilization of waste to produce value-added products. This research explores the potential of waste plastics, RHA, and silica sand as thermoplastic composite materials. The different composite samples were prepared through waste plastics which includes low- and high-density polyethylene and polypropylene with incorporation of RHA and silica sand in proportions. The study investigates the effect of filler/polymer in 30/70, 20/80, and 10/90 (wt. %) on the workability of the developed composite materials. The workability of the composites was found to improve with filler reinforcement. The experimental results showed the maximum density of 1.676g/cm3 and mechanical strength of 26.39, 4.89, and 3.25MPa as compressive, flexural, and tensile strengths, respectively. The minimum percentage of water absorption was 0.052%. The wear tests resulted in a minimum abrasive and sliding wear rate of 0.03759 (cm3) and 0.00692 × 10-6kg/m. The correlations between wear mechanisms and responses were morphologically analyzed. The developed composites verify the feasibility of RHA and plastics waste as a cost effective and environmentally competent product. The results and discussions provided a direction for the future research on sustainable polymeric composite materials.

Rice Husk Ash (RHA) Based Concrete: Workability and Compressive Strength with Different Dosages and Curing Ages

Abstract To reduce the consumption of cement in construction industry has been a hot area of consideration now days due to high evolution of CO2 gases during its production. Since decades efforts are made to replace cement with cementitious materials; minerals, agricultural, industrial by products etc. A few are fly ash, ground granulated blast furnace slag, silica fume, rice husk ash etc. These cementitious materials are often adopted as partial replacement of cement. However, their effectiveness and suitability as cementitious material depends upon their properties and the source of the production. Pakistan is an agricultural country and one of the major crops is Rice crop. It produces a substantial amount of rice husk during the processing g of the rice. A substantial amount of Rice Husk Ash (RHA) is produced on the burning of rice husk used as fuel in the rice mills while generating steam for parboiling process of rice grains. This ash causes the environmental problems also if not dumped properly. RHA is believed to have siliceous properties which may be used as supplementary cementitious material in concrete. As the suitability of supplementary cementitious materials is dependent upon the source of rice husk, temperature of burning of husk, its fineness and other properties. This study is focused on to determine the effect of rice husk ash produced by burning of the rice husk obtained from the local rice mills. Experimental investigation carried includes the determination of workability and compressive strength of concrete with different dosage of RHA from 5% to 30% with an increment of 5% tested at 1day, 3days, 7days and 28 days of the age of concrete. The results are compared with corresponding concrete without RHA and tested at the same ages. The results show the reduction in both the parameter; workability and compressive strength due to RHA particularly at its higher dosage beyond 10% by weight of cement.

Compressive strength prediction of rice husk ash using multiphysics genetic expression programming

Rice husk ash (RHA) is obtained by burning rice husks. An advanced programming technique known as genetic expression programming (GEP) is used in this research for developing an empirical multiphysics model for predicting the compressive strength of RHA incorporated concrete. A vast database comprising of 250 data points is obtained from the extensive and consistent literature review. Different parameters such as age, RHA content, cement content, water content, amount of superplasticizer and aggregate content are used as inputs. A closed-form equation solution was obtained to predict the compressive strength of RHA based on input parameters. The performance of GEP is evaluated by comparing it with regression models. Statistical parameter R2 is used to assess the results predicted by GEP and regression models. Statistical and parametric analysis is also carried out to determine the influence of inputs on the outcome. The GEP model performed better in all terms as compared to other models.

Potential Rice Husk Ash (RHA) For Clinker Substitute in K400 Concrete Compressive Strength Applications

Rice husk ash is a waste of rice husk combustion with pozzolanic properties and contains relatively high silica. Therefore, rice husk ash can be used as a cement substitute to manufacture concrete. This study aims to determine the performance of rice husk ash as a clinker substitute for the compressive strength of the K400 concrete produced. Rice husk ash used in this study was first ground to pass a 45 mm sieve. Then the K400 concrete mix design was made with three variations of adding rice husk ash: 0%, 10%, and 20% of the total cement consumption. The tests carried out on the test objects included slump testing and compressive strength testing for concrete aged 3, 7, 28 days. Slump flow testing is carried out to see the ease of work. At the same time, compressive strength testing is carried out to determine the quality of the concrete itself. Based on the Compressive Strength tool observing, adding rice husk ash, as much as 10% has a strength value that reached the standard compressive strength determined at 28 days. On the other hand, adding rice husk ash more than 10% produces a lower compressive strength of concrete than the standard.

Response of Cassava to Potassium Fertilization in a Tropical Sandy Typic Paleustult Amended with Burnt Rice Husk for Two-Consecutive Years

ABSTRACT A tropical sandy Typic Paleustult soil has low fertility status with low nutrient retainability. A field experiment was carried out in a farmer field, northeast Thailand for two-consecutive years (2018–2019). Split plot design with four replications was employed with main plot consisting of five rates (0, 3.125, 6.25, 12.5 and 25 t/ha) of burnt rice husk (BRH) and subplot comparing six rates (0, 25, 50, 75, 100 and 125 kg K2O/ha) of potassium (K) fertilizer. Amending the soil with 12.5 t/ha of BRH promoted the significantly highest fresh tuber yield (FTY) of 29.31 t/ha in the first crop and all amended plots significantly gave better FTY than did non-amended plot in the latter crop. Cassava significantly produced the highest FTY when received 125 kg/ha of K2O in both growing seasons. In the second year, the addition of 25 t/ha of BRH along with 125 kg/ha of K2O interactively gave the highest FTY which was 99.7% greater than that of the plot received no BRH nor K fertilizer. The waste, with increasing rates, evidently stimulated more N, P and K uptakes in all plant parts while N uptake in tuber and K in all plant parts were increased by increasing K fertilization. Two-consecutive year application of BRH significantly improved available P, K, Mg, Zn and Cu contents in the topsoil.

Potassium release during pulverized biomass combustion in a tubular burner investigated by TDLAS

The ignition and effect of different treatments of pulverized biomass on potassium release were monitored online using visible light detection and calibration-free TDLAS techniques in a tubular burner, with the following main conclusions. High-speed cyclonic flow enhanced the transport effect around the particles, allowing for the rapid separation and diffusion of volatile fractions from biomass particles, as well as the rapid but transient release of potassium. There were no visible envelope flames or trailing flames around the burning particles. High-speed photography also confirmed the homo-heterogeneous ignition. The release of water-soluble potassium was significantly postponed under an O2/CO2 atmosphere compared with the air atmosphere, shifting from a quick and instantaneous model to a continuous and slow-release one. In comparison, the O2/CO2 atmosphere had little suppression effect on the exchangeable and organic potassium release process. In both air and O2/CO2 combustion, the water-soluble potassium release was the fastest, followed by organic potassium and exchangeable state potassium. The release ratio of atomic potassium, the proportion of released atomic potassium in initial total potassium in particles, from water-washed and NH3Ac-washed rice husk is higher than that from rice husk combustion, under O2/CO2 and O2/N2 combustion conditions. The release process of potassium enriched in char takes a long time but has a low release rate. The inhibitory effect of the O2/CO2 atmosphere on the potassium release during rice husk char combustion was relatively weak compared with rice husk combustion.

High Purity Nano-Silica from Rice Husk Ash (RHA) via Chemical Method as Additive/Stabilizing Agent for CO<sub>2 </sub>Capture Application

This paper aims to synthesize high purity nano-sized silica from rice husk ash (RHA) by chemical method and investigate its physical and chemical properties. Through a controlled burning of rice husk, the white-colored RHA is obtained. Next, the RHA is subjected to the pre-treatment of acid leaching and thermal treatment. The synthesizing process has been done through the precipitation method. The EDX and FTIR analysis confirmed that the prepared powder consists of high purity silica particles through the detection of characteristic peaks of O and Si elements and the presence of primary bonds in silica, which are silanol groups and siloxane bonds. Meanwhile, the FESEM micrograph shows that silica particles in nano-scale had been obtained with an average diameter of 74.0 nm – 84.0 nm. The XRF and XRD analysis confirmed that the prepared powder yields 99.68% nano-silica in an amorphous structure.

Thermodynamics Simulation Performance of Rice Husk Combustion with a Realistic Decomposition Approach on the Devolatilization Stage

The high calorific value of rice husk and rich silica content in rice husk ash make its valorization becomes attractive. This study presents the thermodynamics simulation performance of rice husk combustion using a realistic decomposition approach. A non-ideal gas approach and fugacity coefficient were also considered in the calculation. In this study, devolatilization of rice husk is simulated to form gas (64.78%), liquid/tar (7.28%), solid/char (27.94%), and all of these are then oxidized with 100% excess air to form flue gas. From the calculation, about 2.6 MJ/kg of specific combustion energy is produced. The maximum combustion temperature in the furnace is up to 1457 °C for perfect insulation and up to 1400 °C if there is a 5% heat loss due to radiation. Furthermore, the thermodynamics simulation expressed that NOX emission amount from rice husk combustion is negligible and there is still a probability for CO and H2 to be produced at above 500 °C due to Boudouard reaction and homogeneous water gas shift reaction (WGSR). It is found that combustion equipped with larger excess air could quench the heat produced and reduce the combustion efficiency but could maintain the temperature at 700 °C. Supplying excess air of about 180–200% is advantageous to keep the combustion temperature at 700 °C to avoid silica crystalline formation which harms human health, as well as suppressing NOX emission and reducing CO emission from the simultaneous reaction of Boudouard-WGSR. Finally, the study concluded that a realistic decomposition approach could predict the rice husk combustion performance with reasonable and logical results.Graphical Abstract

The Effect of Different Growing Media on Physical Morphology of Rockmelon (Cucumis Melo Linn cv. Glamour) Seedling

Rockmelon (Cucumis melo L.) belongs to the Cucurbitaceae family, which can adapt to various soil and climate areas, especially in Malaysia. The production of rockmelon in Malaysia has highly declined, and for this reason, farmers have opted to use the concept of soilless cultivation due to it benefits accrued from soilless media such as cocopeat, perlite, and burnt rice husk. The study was carried out to determine the effect of different growing media on the physical morphology of rockmelon seedlings. This experiment was set up using RCBD arrangements with four replications. Different growing media used were: (i) 100% Black Soil (BS), (ii) 75% cocopeat + 15% burnt rice husk + 10% perlite (M1) and (iii) 75% cocopeat + 20% burnt rice husk + 5% perlite (M2). The parameters measured were plant height, number of leaves and total leaves area, and stem girth. The data were collected within two weeks after transplanting. The parameters measured were subjected to ANOVA and LSD was applied to compare means. In this study, rockmelon seedlings treated on BS showed significantly (P<0.001) the highest plant height, number of leaves per plant, and total leaves area and stem girth. Seedlings on soilless M1, however, grew in slightly good conditions, as it showed the insignificantly higher values on morphological parameters measured. Thus, BS is still suitable for better use of media for 15 days old rockmelon seedlings (after transplanting). It gives the optimum conditions for adapting seedlings to the new exposure environment.

Investigation of air and rice husk cold flow structures in the suspension furnace chamber through a simulation study

Rice husk combustion in the suspension furnace is not an easy matter. Until now, there are still many obstacles faced in its process as characterized by low combustion conversion. The main cause is the poor air-particle contact as well as the probability of particle elutriation out of the furnace chamber before combustion completely occurs. Thus, in-depth and detailed understanding of air and rice husk cold flow structures in the furnace chamber, as proposed in this study, becomes necessary. The simulation study was conducted using Reynold stress model (RSM) for fluid flow quantification whereas discrete phase model was utilized for particle flow quantification. The simulation results reveal that cylindrical chamber gives a more significant particle residence time rather than rectangular chamber for every similar excess air amount. Besides, providing burner with a tangential air inlet of 90o results in high turbulence, intense swirl phenomenon, and long particle residence time. Moreover, the furnace chamber equipped with a smaller burner diameter and longer burner length together will augment the air-particle contact in the furnace chamber. Despite providing the best condition for the furnace, the design must not forget to consider the economical aspect.

Simple mass transfer simulation using a single-particle heterogeneous reaction approach in rice husk combustion and rice husk ash extraction

Rice husk conversion to silica is usually carried out through combustion to produce ash and then continued with ash extraction to obtain silica. There is a model to simulate the single-particle combustion, which abandoned the simplification. However, the model is complex and seems complicated for early beginners. This study, hence, aims to discuss the simple mass transfer simulation using a single-particle heterogeneous reaction approach. The shrinking core model was targeted for rice husk combustion time prediction, whereas mass transfer effectiveness analysis was used in rice husk ash extraction simulation. According to this study, a shorter combustion time is reached under smaller particle diameter, more spherical particle, and higher oxygen concentration. The result showed that a combustion time of 133 minutes is obtained for oxygen diffusion to rice husk with diameter 5.8 mm, sphericity 0.5, and oxygen concentration 21%-vol. Besides, in order to improve the rice husk ash extraction overall mass transfer effectiveness from 0.01 to 0.1, extraction should be done under particle diameter of 0.2 mm, sphericity of 0.8, and agitator tip velocity of 5 cm/s. All of the parameters lessen the mass transfer limitation due to diffusion, and in consequence, intrinsic kinetic becomes a major factor.

Glass production from rice husk ash as an imitation gemstone products

The objectives of this research were study the amount of SiO2 content from naturally burned rice husk ash (RHA) for prepare rice husk ash glass (RHA-glass) from Phetchaburi Province, Thailand, for the development of gemstones and artificial jewelry from colored glass. The naturally burned RHA were re-burned RHA at 400, 500, 600, 700, 800, 900 and 1000 °C and analyzed the composition of various elements in RHA by distributed energy X-ray fluorescence spectrometer. The results found that re-burned RHA at 1000 °C had SiO2 element maximum, so the re-burned RHA at 1000 °C was prepared RHA-glass. In addition, glass sample from naturally burned RHA and re-burned RHA at 1000 °C have been studied density, refractive index and absorbance. For the colored glass samples were prepared using melt quenching technique by doped MnO2, CuO, Cr2O3, CoO and Er2O3 elements which according to glass formula 54SiO2: 1Al2O3: 6.3CaO: 0.2Sb2O3: 13B2O3: 4.5BaO: 20Na2O: 1A in mol% where A is the type of element added to cause color. The results exhibited that re-burned RHA glass which doped MnO2, CuO, Cr2O3, CoO and Er2O3 shown colored brown, light blue, green, deep blue and pink, respectively and potential to use as imitation gemstone which is increasing value of RHA.

Pengaruh Abu Sekam Sebagai Subtistusi Semen terhadap Slump Flow dan Berat Isi pada Flowing Concrete

In a construction project, the presence of dense reinforcement between reinforcement has its own problems when casting, namely when compaction it is very difficult to use a vibrator because of the density between the reinforcement. To minimize the negative impact of this, flowing concrete is made so that without using a vibrator, the concrete will self-compact properly. The constituent materials of flowing concrete are aggregate, cement and water. In the process of making cement production will produce carbon dioxide in the air, resulting in air pollution due to cement manufacture. To minimize the impact of air pollution due to cement, in this study, we tried one of the constituents of flowing concrete, namely partially substituted cement, so as to minimize air pollution. In this study, rice husk ash, which is the residue from burning rice husks, was used as a partial substitution of cement. The method used is conducting research in the laboratory. In this study, the variation of husk ash as a cement substitution was 0%, 5%, 7.5%, 10% and 12.5% with the addition of 1.5% superplasticizer. From the results of the study, the smallest diameter of slump flow was 53.17 cm in a mixture of 10% rice husk ash. The largest dry concrete density value is 2482.77 kg/m3 at 10% rice husk ash mixture. The conclusion that can be drawn is that based on slump flow and dry concrete density, the optimal substitution percentage for rice husk ash is 10 percent.