A sustainable calcined water treatment sludge and rice husk ash geopolymer

This paper tries to investigate the effect of replacing Ordinary Portland cement (OPC) with Metakaolin (MK) and Rice husk ash (RHA) on the physicomechanical properties such as consistency, setting times, soundness and mortar compressive strength of ternary cement up to 40 % cement replacement. The soundness of the blended cement pastes and compressive strength of the blended mortars were conducted using Le Chatelier apparatus and Tonic Technic compression machine while the initial and final setting times were conducted on the blended cement paste using Vicat apparatus. Nineteen ternary cement mortars were prepared to comprise of OPC, RHA MK at different proportions and tested at 2, 7, 28 and 60 days. Results indicated that as RHA was gradually increased up to 25% at constant MK content, the volume expansion of the ternary cement paste increased gradually. On the other hand, as MK was increased from 5-25% at constant RHA, the volume expansion diminished. The water consistency of ternary cement paste experienced a variation as MK was increased up to 25 wt% at constant RHA up to 10 wt%. However, at 10 wt% constant RHA as MK was increased the water demand gradually increased. Similarly, an increase in RHA at constant MK increased the water demands of the ternary blends. An increase in RHA from 5-25 wt% at 5-25 wt% constant MK resulted in an acceleration in the initial and final setting times of cement blends. These accelerations could be attributed to the pozzolanic activity leading in shorter setting time. Whereas a series of accelerations and retardations of both setting times were experienced as the MK was increased from 5-25 wt% at 5-25 wt% constant RHA. It was observed that increment in the MK or RHA up to 10 wt% at constant RHA/MK up to 10 wt% resulted in improved mortar compressive strength of the ternary blend in comparison with control. This improvement was attributed to the high silica/alumina contribution to the matrix by MK inclusion, the C/S ratio in the cement matrix and RHA pozzolanic reactivity despite its unburnt carbon. All mortar compressive strength of the cement blends and control experienced an increase as the curing days were lengthened from 2 to 60 days. The enhanced strength compared with the control especially beyond 28 days could be attributed to the slow pozzolanic reaction resulting from the formation of additional CSH and CAH from the interaction of the residual CH and the silica available in the MK and RHA. The best compressive strength at 60 days was obtained at cement replaced with 15 wt% and 20 wt% at MK 5 wt% RHA producing a mortar compressive strength of 40.5 MPa.

The use of pozzolanic materials to reduce carbon dioxide (CO2) emissions and enhanced properties of mortar and concrete has received increased interests in the last decades. In this study, admixtures such as metakaolin (MK), rice husk ash (RHA) and calcium carbide waste (CCW) partially replaced Portland cement (PC) at 5, 10, 20 % in multiple combinations of aforementioned admixtures as binders and the effect of setting times (initial and final) and standard consistency on the binders were evaluated. The Department of Environment (DOE) approach for mix proportions was employed. The mixes are in six groups consisting of control PC, each admixture replaced PC at 5, 10 and 20 % replacement level in binary mixes, then two of the admixtures replaced PC at same replacement level in ternary and the three admixtures replaced PC in quaternary mixes respectively. Results indicated that RHA significantly influenced the standard consistency of the binders incorporating the three admixtures as compared with CCW and MK. The requirement of water in the binder increased with increase in percentage replacement level of RHA within the binder due to its porous nature. At 5 % replacement level, it was 9 % above control value, 21 % and 39 % at 10 and 20 % replacement level subsequently. Similarly, setting times at the aforementioned replacement levels are 27 % and 6 % above the control value for initial and final setting time. For 20 % replacement level, it was 24 % and 38 % above the control value for the initial and final setting time respectively. This is due to reduction in PC content leading to less content of Tricalcium silicate aluminate (C3A) and amount of carbon content within the pozzolanic materials which retard the rate of reactions. By and large, the admixtures retard the setting times of quaternary binder, and increased its water of consistency which can be overcome by activation. However, they are useful in the construction of concrete structural elements or structures that requires longer time for placement. Furthermore, it will be worthwhile to investigate same properties at the nanoscale since these have been established at the micro level.

Water treatment sludge and rice husk ash to sustainable geopolymer production

Application of consistency-based water-to-binder ratio to compensate workability loss in concrete modified with rice husk ash

Development and characterization of eco- and user-friendly grout production via mechanochemical activation of slag/rice husk ash geopolymer

Performance evaluation on engineering properties of sodium silicate binder as a precursor material for the development of cement-free concrete

In this study, we investigated the feasibility of jarofix [a zinc (Zn) smelter by-product] as a potential geopolymer binder in soil stabilization for road applications. Different combinations of soil–jarofix (SJ) mixtures were prepared using sodium hydroxide (NaOH), sodium silicate (Na2SiO3), and a combination of NaOH + Na2SiO3 as alkali activators. Unconfined compressive strength (UCS) tests were performed to examine the mechanical performance of SJ mixtures, and the effects of the jarofix content, curing conditions, and curing time were investigated. Changes that occurred during the geopolymerization process were further corroborated using field-emission scanning electron microscope (FESEM) images and energy-dispersive X-ray spectroscopy (EDS) analysis. Durability tests were also performed to examine the weathering resistance of selected SJ mixtures against 12 cycles of alternating wetting and drying. Based on the experimental results, the compressive strength of bare soil was increased 8.8 times, from 0.31 to 2.75 MPa, under ambient curing (AC, at 27 ± 2°C) conditions and 6 times, from 1.1 to 6.55 MPa, under dry curing (DC, at 60°C) conditions. This increase in compressive strength was attributed to the formation of sodium alumino-silicate hydrate (N–A–S–H) gel structures during the geopolymerization process, which led to a compact soil matrix, as confirmed by the FESEM images. The specimens cured under DC conditions showed greater strength improvement than those cured under AC conditions owing to the faster rate of the geopolymerization reaction at elevated temperatures. In addition, the Na2SiO3 and NaOH + Na2SiO3 solutions were found to be the most efficient alkali activators for the SJ mixtures cured under AC and DC conditions, respectively. This durability study revealed that the alkali-activated SJ mixtures exhibit a significantly smaller loss in mass than bare soil when exposed to 12 cycles of alternating wetting and drying. Moreover, the specimens cured under DC conditions were found to be more resistant to weathering than those cured under AC conditions. Overall, soil amended with 15% jarofix (through alkali activation) satisfies the minimum strength and durability criteria recommended by Indian standards for its use as a subbase and subgrade material. The current study shows that jarofix has the potential to be used as a geopolymer binder for soil stabilization, which can help the mining sector in minimizing the volume to be stored in tailings storage facilities.

Malaysia possesses the distinction of being the ninth biggest expanse of peat soil land globally, hence encountering significant geotechnical challenges characterised by elevated moisture content, substantial organic composition, diminished shear strength, and reduced bearing capacity. The objective of this study is to investigate the fundamental geotechnical characteristics and strength of Batu Pahat peat that has been stabilised using Ordinary Portland Cement (OPC) and Rice Husk Ash (RHA). The application of Ordinary Portland Cement (OPC) in the process of peat stabilisation has the potential to enhance the mechanical properties and strength of the soil. Nevertheless, the extensive utilisation of cement might result in environmental degradation. Therefore, it is imperative to consider the incorporation of agricultural waste by-products as a partial substitute for cement. Hence, the objective of this research is to employ Rice Husk Ash (RHA) as a supplementary material in cementitious systems. An experimental investigation was undertaken to determine the ideal mix ratio by replacing cement with rice husk ash (RHA) in the range of 5% to 20%. The findings indicate that the peat under investigation can be classified as a hemic peat variety characterised by a high level of acidity. The experimental findings indicated that the peat treated with a 5% concentration of rice husk ash (RHA) (referred to as C95 RHA5) exhibited the maximum Unconfined Compressive Strength (UCS) value of 262 kN/m2. To validate the findings of the Unconfined Compressive Strength (UCS) test, an additional analysis was performed using the Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX) technique. This examination aimed to confirm the presence of calcium, which serves as evidence for the observed improvement in strength. In conclusion, it can be inferred that the utilisation of RHA as a substitute for cement at a proportion of 5% exhibits potential for application in Hemic peat.

Commercial sodium hydroxide (NaOH) and sodium silicate (SS) are commonly used as alkaline activators in geopolymer concrete production despite concerns about their availability and associated CO2 emissions. This study employs an alternative alkaline activator (AA) synthesized from a sodium silicate alternative (SSA) solution derived from rice husk ash (RHA) and a 10 M sodium hydroxide solution. The initial phase established an optimal water-to-binder (W/B) ratio of 0.50, balancing workability and structural performance. Subsequent investigations explored the influence of the alkali/precursor (A/P) ratio on geopolymer concrete properties. A control mix uses ordinary Portland cement (OPC), while ground granulated blast-furnace slag (GGBS)-based geopolymer concrete—GPC mixes (GPC1, GPC2, GPC3, GPC4) vary the A/P ratios (0.2, 0.4, 0.6, 0.8) with a 1:1 ratio of sodium silicate to sodium hydroxide (SS: SH). The engineering performance was evaluated through a slump test, and unconfined compressive strength (UCS) and tensile splitting (TS) tests in accordance with the appropriate standards. The geopolymer mixes, excluding GPC3, offer suitable workability; UCS and TS, though lower than the control mix, peak at an A/P ratio of 0.4. Despite lower mechanical strength than OPC, geopolymers’ environmental benefits make them a valuable alternative. GPC2, with a 0.4 A/P ratio and 0.5 W/B (water to binder) ratio, is recommended for balanced workability and structural performance. Future research should focus on enhancing the mechanical properties of geopolymer concrete for sustainable, high-performance mixtures.

The strength characteristics of two genetically different shales treated with both Rice Husk Ash (RHA) and Coconut Husk Ash (CHA) was evaluated to elucidate responses and effects, examine effectiveness of the additives with a view to ultimately provide economically viable and environmental friendly options for modification and hence stabilization. 2 to 20 % by weight of both RHA and CHA were separately added to Okitipupa (SW) and Enugu (SE) shales with the subsequent determination of Plasticity Index (PI), Maximum Dry Density (MDD), Optimum Moisture Content (OMC), Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR). RHA and CHA were found to possess pozolanic properties such that their addition to shale in modest amounts (not more than 10 % by weight) has beneficial effect on the strength characteristics. Addition of RHA produced shales with reduced PI, higher UCS, increased MDD and more pronounced reduction in OMC when compared with the CHA stabilized shales. However in general, addition of 10 % RHA and 6–10 % CHA brought about optimal effect on the geotechnical properties of shales and as such can be regarded as the optimum content. These materials can thus serve as suitable alternatives to modify and stabilize problematic shale and hence help reduce construction costs, environmental hazards and ultimately bring about shales with improved geotechnical properties.

Applications of agricultural by-product as substitute for non-renewable material in cement production are desirable in stimulating socio-economic development. In this study, Rice Husk Ash (RHA) blended cement was produced by replacing 5%, 7%, 11.25%, 15%, 20.25% and 25% by weight of Ordinary Portland Cement (OPC) clinker with RHA. The cement without RHA serves as the control. The chemical compositions of RHA, OPC-clinker and the blended cements were determined using X-ray fluorescence analyzer. The physical characteristics of RHA blended cements that were considered are fineness, soundness, consistency, initial and final setting times and compressive strength at 2, 7, 28, 56 and 90 curing ages. The results showed that RHA is a suitable material for use as a pozzolan as it satisfied the minimum requirement by having the sum of SiO2, Al2O3 and Fe2O3 of more than 70%. Incorporation of RHA led to an increase in the composition of SiO2 and reduction in that of CaO. An increase in RHA content showed a decrease in compressive strength at early ages and slightly increase at a later age (90 days). The blended cement produced with lower levels of RHA replacement conforms to standard specifications specified in BS EN 197-1:2000, NIS 439:2000 and ASTM C 150-02. The minimum Strength Activated Index (SAI) of 75% at the age of 28 days of curing as specified by ASTM C 618 was satisfied by RHA replacement of up to 15%. It was concluded that blended cement with the maximum of 15% RHA content is suitable for use for structural purposes.

Mechanical properties of soil reinforced by fiber and alkaline-activated rice husk ash, and rainfall erosion model tests.

Industrial wastes like ground granulated blast furnace slag (GGBFS) and rice husk (RH) ash were utilized to improve the strength of subgrade soil available locally in Vembakkam region of Thiruvannamalai district in Tamil Nadu. To improve the bonding between soil and industrial wastes, 4% quick lime was mixed with the soil along with the industrial wastes GGBFS and RH ash. Soil was identified as clayey sand (SC) based on its index properties. GGBFS was varied in proportions of 20–40% by weight of SC and RH ash was added in quantities of 10–50% by weight of SC, to decide the best dosage of GGBFS and RH ash to be mixed with SC so as to achieve maximum soil strength after curing for 3 days. Based on the unconfined compressive strength (UCCS) test and soaked CBR test, ideal percentage of GGBFS and RH ash was found to be 30% and 20%, respectively. For SC with 4% lime, 30% GGBFS, and 20% RH ash, UCCS was observed to increase by 3.36 times that of virgin soil and soaked CBR value was found to increase by 9.23 times that of virgin soil after 3 days curing period.KeywordsClayey sandQuick limeGround granulated blast furnace slagRice husk ashUnconfined compressive strengthSoaked CBR strength

Concrete is a material that is widely used in the construction world. The production of Portland cement in concrete leads to CO2 emissions that have an impact on global warming. Geopolymer Concrete is an eco-friendly material because it does not use Portland cement. Geopolymer cement is made from waste materials such as fly ash (FA) by alkali activation. In geopolymer, sodium silicate is a commonly used activator that is produced commercially. In this study, rice husk ash (RHA) from agricultural waste was used as an activator for geopolymer cement. The objective of this study is to review the chemical component of FCA and RHA and, to examine the effect of RHA in geopolymer concrete mixed design on the compressive strength. The geopolymer concrete binder is using 12 M NaOH and Na2SiO3, with variations for RHA 0%, 5%, 7.5%, and 10%. The specimens were treated for 28 days, curing in a 70oC oven for 24 hours then curing at ambient temperature. The result shows that geopolymer concrete has a higher compressive strength compared to ordinary Portland cement (OPC) as much as a 5.9 MPa difference with geopolymer concrete of RHA10% of 25 MPa.

Abstract: As a binder for infrastructure development, conventional Portland cement is currently the primary material that is used. However, cement production has a substantial impact on the environment, and many pozzolanic materials can reduce their carbon footprint with conventional Portland cement. In this experimental study, replacement of OPC (ordinary portland cement) is replaced with the ash produced from rice husk (An agricultural waste) and analyzed for durability and strength performance in concrete samples and mortar as well as chemical composition analysis and microstructure observation of rice hull ash according to X-ray differential test data were also conducted in the research analysis. it is produced by burning of husk (produced by rice barley waste) of oxygen for the production of rice husk ash. Its chemical composition is rich in silicates and aluminates which promotes the binding property of ordinary Portland cement and does not affect the IST(Initial setting time), FST(Final setting time) and does not increase the fineness of the cement particles hence it gives significant results with cement replacement. It was determined that 10% rice husk ash replacement was the optimum value for rice husk ash replacement based on the strength and workability criteria of the concrete quality assurance system.