All praises and thanks be to Almighty Allah SWT, the only creator, guardian, sustainer, most merciful and efficient assembler of creation. The study on the development of durable cement mortar incorporating rice husk ash was carried out by several approaches. Purity of rice husk ash was determined based on different combustion systems, holding time and milling time.
The result of XRD confirmed the amorphous state of rice husk ash produced in the laboratory combustion system at 663.6°C. The findings of the present study will contribute to the sustainable development of cement mortar incorporating rice husk ash.
INTRODUCTION
SCOPE OF RESEARCH
STRUCTURE OF THE DISSERTATION
It also reviews the previous findings on the combustion process of rice husks, including the effect of rice husk ash on cement mortar. The results of the study on the combustion process of rice husks to produce amorphous, carbon-free siliceous ash. The effect of combustion techniques on the quality of rice husk ash was discussed here.
Mortar strengths were investigated at different ages using different types of sand, OPC, rice husk ash and water. The effects of rice husk ash on mortar were investigated in this chapter and RHAs suitable for mortar were identified.
LITERATURE REVIEW
GENERAL
CEMENT
- Cement 1-lydration
- Determination of Heat of Hydration
- Adiabatic and semi-adiabatic calorimeters
- Factors that Affect the Heat of I-Iydration
- Fineness of cement
- Water cement ratio
- Type of cement
- Sulphate content
- Blended cements
Energy consumption by the cement industry is estimated at 2% of global primary energy consumption (World Energy Council. 1995). The chemically bound water is the primary component of the cement gel and changes the reaction between the water and the cement paste (i.e. interlayer water). Powers and Brownyard (1 947) suggested that the degree of hydration of the cement can be calculated by measuring its non-evaporable water content.
However, tile volume of the hydration product is less than the total volume of the cement and water that reacted to form it. The relative importance of admixture use can be expressed by the cement to carbon (C/C) ratio of the cement production in a specific country.
RICE HUSK ASH
- Methods of Ash Analysis
- Factors Influencing Ash Properties
- Incineration temperature and duration
- Geographical location
- Characteristics of amorphous silica
- Uses ofRHA
Typically the ash will contain some unburned components, as well as inert components of the peels. The color of the ash generally reflects the completeness of the combustion process, as well as the structural composition of the ash. The combustion temperature and cooling rate indicate the amorphous property of the rice husk ash.
The form of silica after rice husk combustion depends on the temperature and duration of rice husk combustion. Maiiy researchers have already published on the properties of the mixed RHA concrete such as strength and durability.
PROPERTIES OF CEMENTITIOUS MATERIALS
- Workability
- Setting Times
- Strength
- Porosity
- Permeability
- Sorptivity
Sarawathy and Song (2007) investigated the effect of RHA addition with OPC cement on the porosity and water absorption of the concrete. The rate of entry of chlorides into concrete largely depends on the pore structure of the concrete. The permeability of concrete is clearly related to the pore structure of the cement paste matrix.
The rate of chloride penetration into concrete is affected by the chloride binding capacity of the concrete. Therefore, a sorptivity test will not provide direct information on the bulk properties of the concrete.
MATERIALS AND METHODS
GENERAL
MATERIALS
- Cement
- Fine Aggregate
- Water
- Rice Husk Ash
- Rice husk collection
- Rice husk ash production
- Ash collection
- Ash grinding
The burning of rice husk was allowed to start from the center of the pile. It was observed that the color of the burnt rice husk ash was blackish for 3. In the accelerated test method. the pH values and sulfate concentration throughout the test remained constant.
The timing device was started and the test surface of the sample was immediately placed on the support device, as shown in Figure 3.16. From the above discussion it is clear that the retention time has a significant effect on the Blaine fineness of the ash. The color of the ash was brighter with RHA I compared to RHA 2.
A blackish color indicates partially burnt rice husk and generally unburnt carbon was present in the ash. The fineness of this RHA 3 was found to be more than twice that of OPC. These results indicated that the rheological parameters (plastic viscosity and yield strength) of the cementitious material were probably changed due to the addition of rice husk ash.
Only the samples with 15% and 20% RFIA were maintained up to the 20 cycles of the test. According to Ali et al., (2004) and Kalifa et al., (2000), the effects of high temperatures on concrete are generally visible in the form of surface cracks. Demirbas from the paper 'Performance of rice husk ash produced using a new technology as mineral admixture in concrete' Cement and Concrete Research.
EXPERIMENTAL METI-IODS .................................................................... SI
- Specimen Identification
- Testing of Sample
- Workability
- Setting time
- Heat of hydration
- Compressive strength
- Fire performance
- Permeability test
- Resistance to sulphate attack
- Water sorption
- Loss on ignition
- Salt crystallization test
- XRD (X-ray Diffraction) test
- SEM (Scanning Electron Microscope) test
- FTIR (Fourier Transform Infra-Red) test
RESULTS AND DISCUSSIONS
RICE 1-IUSK ASI-I PREPARETION AND CHARACTERIZATION
- Fineness of RI-IA
- Particle Size of RI-IA
- Characterization ofRHA with XRD
MECHANICAL PROPERTIES AND PERFORMANCE OF MORTAR
- Water Requirement for Constant Workability
- Consistency and Setting Time
- Heat of Hydration
- Compressive Strength
The suitable type of RHA was selected based on compressive strength of 7, 28, 90 and 350 days. 1-lower, the trend of compressive strength for the samples with different percentage of RHA I did not follow the trend of compressive strength with Si. At later age (350 days) it is observed that samples with all replacement levels show lower compressive strength than 28 and 90 day results.
The variation of compressive strength of mortar prepared with varying percentage of RHA 2 is presented in Figure 4.19. It is observed that at 28 days strength the sample of 10% replacement shows maximum compressive strength among the samples with RHA 2 as a replacement material. In the case of RHA 3, the compressive strength of mortar with SI improved significantly compared to RHA 1 and RHA 2.
At this age, samples with 15% and 20% replacement rates show higher compressive strength than the control sample. It can be seen in Figure 4.20 that at 7 and 28 days the strength of the control sample showed higher strengths than samples with RHA 3 in different percentages and also for different types of sand. degrees of replacement of OPC with RHA 3 showed higher compressive strength than the control sample. After 350 days, the compressive strength with 15% and 20% RI-IA 3 showed higher values than the control sample.
At the age of 350 days, the compressive strength of all samples increased than the 90-day strength. The observed results with the addition of rice husk ash A3 in cement mortar had a positive effect on the compressive strength. The long-term performance of mortar with and without rice husk ash A3 based on compressive strength at 600 and 900 days is shown in Table 4.9.
DURABILITY OF MORTAR
- Permeability of Mortar
- Water Sorption
- Salt Crystallization Test
- Resistance to Sulphate Attack
- Performance under Elevated Temperature
- FT-IR Spectrum Analysis
From Figure 4.23 above, it can be seen that the charge passing through the control sample has less influence on the age of the samples compared to the rice 1-lusk ash (RHA) samples. Thus, for the calculation of the sorption coefficient, only the portion of the curves for an exposure period of 3 minutes to 60 minutes where the curves were consistently linear, from Figure 4.26, was used. The sorption of mortar with different levels of RI-IA addition is shown in Figure 4.27.
The loss of particles from the surface of the sample is shown in figure 4.29 (h). a) Crack observed (b) The surface was screwed up. Figure 4.29: Cracking and loss of sample particles due to salt crystallization. The durability of the mortar in crystallization tests and weight gain due to crystallization are shown in Figure 4.30. The heating rate for the mortar sample is shown in Figure 4.34 shows quite similar to ASTM El 19 up to 700°C. The strength of all samples heated to different temperature and cooled in free air and quenched with water are shown in Figures 4.37 and 4.38.
The compressive strength of A3 rice husk ash mortar at different temperature levels relative to the unheated open air cooled and water quenched control sample are shown in Figures 4.39 and 4.40. Figure 4.39 shows that 24.4% higher strength increased for the control sample at 200°C for open air cooling compared to the unheated sample (32°C). However, the highest strength of 20.1% was obtained from the 10% RHA sample for water quenching shown in Figure 4.40.
Figure 4.41 shows the effect of cooling conditions on the strength after heating to an elevated temperature. Figure 4.41 shows that at 200 °C and 400 °C, samples A3-10 and A3-20 show higher strength in water quenching and then in air cooling compared to outdoor cooling. In Figure 4.46, we see a sharp drop at wavenumber 2350, which indicates the unwanted presence of CO2 in sample A3-10.
CONCLUSIONS
Conversely, the final setting time of cement mortar gradually decreases due to the addition of RHA. The rheology of the cementitious materials was significantly changed due to the addition of RHA as a cementitious replacement material in mortar. The compressive strength of control samples shows higher values up to 28 days of curing than all other samples with RHA.
The mortar samples with RHA from conventional and pile firing show lower compressive strength than the control sample as well as the sample with RHA obtained from laboratory firing at all replacement levels. Moreover, the cement mortar with 1 5% RHA reveals the second highest compressive strength at the respective sample age. The compressive strength of mortar at 1 5% and 20% replacement is almost the same at the highest age.
The optimum replacement level of ordinary Portland cement with rice husk ash can be 15% or 20% by considering other parameters. The permeability of the mortar sample decreases with the increase of the RI-IA addition and also the age of the sample. The highest permeability is obtained for the control sample, while mortar with 30% RHA shows the lowest permeability from 28 to 350 days.
Samples with I 5% and 20% RHA exhibit the best performance against salt crystallization than any other percentage substitution levels. All specimens immersed in sulfate solution for 28 days after initial curing for 28 days provided higher compressive strength compared to the strength of specimens obtained after 28 days of normal curing.
RECOMMENDATIONS
The use of rice husk ash as a partial replacement material for cement in concrete mixtures. Particle size effect on the strength of rice husk ash mixed split-graded Portland cement concrete. Strength, porosity and corrosion resistance of ternary mixture of portland cement, rice husk ash and fly ash mortar.
Influence of fineness of rice husk ash and additives on the properties of lightweight aggregate. Use of sugarcane bagasse ash and rice husk ash as mineral admixture in concrete. Rice husk ash (RHA) as cement mixture for immobilization of liquid radioactive waste at different temperatures.
34;Properties of cement paste containing rice husk ash, fly ash, silica fume, slag and natural pozzolans in concrete-. Effects of silica fume and rice husk ash on the properties of heavy concrete. Strength properties of concrete incorporating highly reactive rice husk ash, Transaction of Japan Concrete Institute.
The relationship between temperature and duration of rice husk combustion in the development of amorphous rice husk silica.
