The Influence of Rice Husk Ash on Mechanical Properties of the Mortar and Concrete: A Critical Review

Increasing the population and infrastructure in both emerging and developed countries requires a considerable amount of cement, which significantly affects the environment. The primary materials of concrete (‘cement’) production emit a large quantity of CO2 into the environment. Also, the cost of conventional building materials like cement gives motivation to find geopolymer waste materials for concrete. To reduce harmful effects on the environment and cost of traditional concrete substance, alternative waste materials like rice husk ash (RHA), ground granulated blast-furnace (GGBS), fly ash (FA), and metakaolin (MK) can be used due to their pozzolanic behavior. RHA waste material with a high silica concentration obtained from burning rice husks can possibly be used as a supplementary cementitious material (SCM) in the manufacturing of concrete, and its strong pozzolanic properties can contribute to the strength and impermeability of concrete. This review paper highlights a summary of the positive effect of using RHA as a partial substitute for cement in building construction, as well as its optimal inclusion of enhanced mechanical properties like compressive strength, flexural strength, and split tensile strength of mortar and concrete.

Rice Husk at a Glance:From Agro-Industrial to Modern Applications

Excessive waste production has led to the concept of a circular bioeconomy to deliver valuable by-products and improve environmental sustainability.The annual worldwide rice production accounts for more than 750 million tons of grain and 150 million tons of husk.Rice husk(RH)contains valuable biomaterials with extensive applications in various fields.The proportions of each component depend primarily on rice genotype,soil chemistry,and climatic conditions.RH and its derivatives,including ash,biochar,hydrochar,and activated carbon have been placed foreground of applications in agriculture and other industries.While the investigation on RH’s compositions,microstructures,and by-products has been done copiously,owing to its unique features,it is still an open-ended area with enormous scope for innovation,research,and technology.Here,we reviewed the latest applications of RH and its derivatives,including fuel and other energy resources,construction materials,pharmacy,medicine,and nanobiotechnology to keep this versatile biomaterial in the spotlight.

Effectiveness of Rice Husk and Sugarcane Bagasse Ashes Blended Cement in Improving Properties of Concrete

This paper emphasized the use of rice husk ash (RHA) and sugarcane bagasse ash (SBA) in improving concrete properties, and also their combined effects on workability, compressive strength, flexural strength, permeability and water absorption capacity. Thus, in this study, the water-to-cement ratio was kept constant (0.45), the binder materials content for conventional mix was kept constant at (350 kg/m3) and the partial replacement of cement with RHASBA used was 5%, 10%, 15%, 20%, 25%, and 30% by weight of cement. The maximum compressive strength was noted at a 5% replacement level of cement with RHASBA. The Results showed that the optimum replacement of cement with RHASBA in concrete was 5%, which was found to increase the compressive strength by 15%, flexural strength by 3.4%, lowered permeability by 50%, lowered sorptivity by 11.34% as compared with control concrete at 90 days of curing time. The micro-structural test results further established that RHA and SBA have a high content of SiO2 which enables them to be more reactive in concrete and also revealed that the presence of RHASBA depletes Ca(OH)2 crystals, converting it into CaH2O4Si (C-S-H gel) leading to the strengthening of bond within the concrete matrix.

Effectiveness of Rice Husk and Sugarcane Bagasse Ashes Blended Cement in Improving Properties of Concrete

This paper emphasized the use of rice husk ash (RHA) and sugarcane bagasse ash (SBA) in improving concrete properties, and also their combined effects on workability, compressive strength, flexural strength, permeability and water absorption capacity. Thus, in this study, the water-to-cement ratio was kept constant (0.45), the binder materials content for conventional mix was kept constant at (350 kg/m3) and the partial replacement of cement with RHASBA used was 5%, 10%, 15%, 20%, 25%, and 30% by weight of cement. The maximum compressive strength was noted at a 5% replacement level of cement with RHASBA. The Results showed that the optimum replacement of cement with RHASBA in concrete was 5%, which was found to increase the compressive strength by 15%, flexural strength by 3.4%, lowered permeability by 50%, lowered sorptivity by 11.34% as compared with control concrete at 90 days of curing time. The micro-structural test results further established that RHA and SBA have a high content of SiO2 which enables them to be more reactive in concrete and also revealed that the presence of RHASBA depletes Ca(OH)2 crystals, converting it into CaH2O4Si (C-S-H gel) leading to the strengthening of bond within the concrete matrix.

Properties of Geopolymers Made from Fired Clay Bricks Wastes and Rice Husk Ash (RHA)-Sodium Hydroxide (NaOH) Activator

High cost has been pointed among factors that limit the promotion of geopolymers. To contribute to the reduction of the use of costly industrial sodium silicate in activators for geopolymers, a gel obtained with RHA and concentrated sodium hydroxide was used in the present study to develop an alkaline activator with 8 M NaOH and to produce geopolymers with crushed fired clay bricks wastes (FCBW). Characteristics of the gel were compared to that of commercial sodium silicate which was also mixed with 8 M NaOH in the ratio 1:1 to produce geopolymers. Chemical and mineralogical analyses were done on raw materials. Fourier Transformed Infrared Spectroscopy (FTIR) was done on the gel, commercial sodium silicate and products. Biaxial four point flexural strength, bulk density, water absorption and scanning electron microscopy (SEM) tests were also done on products. Results showed that RHA-NaOH alkaline activator has good potential in consolidating FCBW powder through geopolymerization process which gave products that had characteristics not far from that when the commercial sodium silicate was used. The gel obtained by mixing RHA and NaOH can contribute to the reduction of the use of costly commercial sodium silicate in the production process of geopolymers. However, appropriate filtration process is needed for the RHA-NaOH gel to reduce its impurities as undissolved entities, which will consequently contribute to improve the flexural strength, the density and the microstructure of its products which were low compared to when commercial sodium silicate was used.

Economy of RHA （Rice Husk Ash） in Concrete for Low-Cost Housing Delivery in Nigeria

Delivery of housing units in adequate quantity and quality has been the pursuits of individuals and successive governments in Nigeria. Still, the gap between demand and supply is becoming wider on daily basis due to exorbitant cost of building materials that is beyond the reach of average Nigerians. Concrete being the most acceptable construction material is expensive due to high cost of cement. Efforts made to reduce the cost of cement were to no avail, thus there is need to look elsewhere. Past researches showed that substituting cement with 15% of RHA （rice husk ash） in concrete improves the performance of concrete and reduces global warming as a result of emissions from cement production. This paper looks into the effect of using RHA as partial substitute of cement on the cost of a low-cost housing unit. Results showed that cement based construction materials are responsible for 82.58% of the total cost in which cement is responsible for 42%. When 15% RHA was used to substitute cement over N90,000 was saved, amounting to about 7% of the total cost of the building. In addition, depletion of natural resources was reduced.

Effect of Partial Replacement of Ordinary Portland Cement (OPC) with Ghanaian Rice Husk Ash (RHA) on the Compressive Strength of Concrete

The cost of cement has made concrete production expensive such that the housing deficit in developing countries is on the rise despite all the efforts by governments and other stakeholders to produce affordable housing units for the populace. Ashes of agricultural products such as rice husk, known as mineral admixtures may have pozzolanic characteristics which would be more beneficial to the housing industry in terms of strength gain and economy than being pollutants to the environment. Rice Husk Ash (RHA), because of its finely divided form and very high silica content and amorphousness, proved to be useful for strength gain of Rice Husk Ash Concrete (RHAC). Rice husk ash was manufactured by uncontrolled burning, ground, sieved and replaced with cement at 0%, 5%, 10%, 15%, 20% and 25% in mass for the mixes C20, C25, C30 and C35 where their compressive strengths were verified at 3, 7, 14, 21, 28, 56, 90 and 180 days. The X-ray diffraction pattern list indicated amorphous as well as diffused peak of about 8000 counts of SiO2 representing crystalline structures identified as cristobalite. A physical examination of the RHA showed very fine appearance, grey color and specific gravity of 2.06. The chemical analysis also revealed the existence of oxide content to be 55.8% representing 0.78% of Fe2O3, 54% of SiO2 and 1.06% of Al2O3 representing 20.23% lower than the minimum value of 70% required for pozzolans. Generally, the compressive strength values decreased as the RHA content in the mixes increased but when compared to the control concrete the optimum replacement percentage of Ordinary Portland Cement (OPC) with RHA at 5% showed an increase above the control concrete for C20 mix. The increase in the RHA in the mixes resulted in the high demand for water in all the mixes.

Effect of grinding on chemical and physical properties of rice husk ash

The effect of grinding on the chemical and physical properties of rice husk ash was studied. Four rice husk ashes with different finenesses, i.e. coarse original rice husk ash （RHA0）, RHA1, RHA2, and RHA3 were used for the study. Ordinary Portland cement （OPC） was partially replaced with rice husk ash at 20% by weight of binder. The water to binder ratio （W/B） of the mortar was maintained at 110%±5% with flow table test. Specific gravity, fineness, chemical properties, compressive strength, and porosity test of mortars were determined. The differences in chemical composition of the rice husk ashes with different finenesses from the same batch are small. The use of RHA3 produces the mortars with good strength and low porosity. The strength of the mortar improves with partial replacement of RHA3 in comparison with normal coarse rice husk ash. The use of RHA3 results in a strong and dense mortar, which is due to the better dispersion and filling effect, as well as an increase in the pozzolanic reaction.

Preparation of fly ash and rice husk ash geopolymer

The geopolymer of fly ash （FA） and rice husk ash （RHA） was prepared. The burning temperature of rice husk, the RHA fineness and the ratio of FA to RHA were studied. The density and strength of the geopolymer mortars with RHA/FA mass ratios of 0/100, 20/80, 40/60, and 60/40 were tested. The geopolymers were activated with sodium hydroxide （NaOH）, sodium silicate, and heat. It is revealed that the optimum burning temperature of RHA for making FA-RHA geopolymer is 690oC. The as-received FA and the ground RHA with 1%-5% retained on No.325 sieve are suitable source materials for making geopolymer, and the obtained compressive strengths are between 12.5-56.0 MPa and are dependent on the ratio of FA/RHA, the RHA fineness, and the ratio of sodium silicate to NaOH. Relatively high strength FA-RHA geopolymer mortars are obtained using a sodium silicate/NaOH mass ratio of 4.0, delay time before subjecting the samples to heat for 1 h, and heat curing at 60oC for 48 h.

Hydration process of rice husk ash cement paste and its corrosion resistance of embedded steel bar

Thermogravimetric analysis and electrical resistivity were used to determine the hydration process of cement paste with rice husk ash(RHA)(0−15%)and water-cement ratio of 0.4 in this work.X-ray diffraction(XRD)method and scanning electron microscopy(SEM)were used to survey crystal composition and microstructures of specimens cured for 3 h,1 d,7 d and 28 d.Finally,electrical parameters(electrical resistance and AC impedance spectroscopy)of steel bars reinforced cement paste were investigated to study the effect of RHA on the corrosion resistance.Results showed that RHA could affect the cement hydration by hydration promotion and pozzolanic effect.The evaluation function for electrical resistivity and curing ages fitted well with linear increasing function.The addition of RHA higher than 5%demonstrated a decreasing role in the electrical resistivity of cement paste at earlier curing ages(3−7 d).Meanwhile,when at later curing ages(7−28 d)the result was the opposite.Moreover,RHA demonstrated positive effects on corrosion resistance of steel bars in cement paste.

Production of porous silica by the combustion of rice husk ash for tundish lining

In order to study the production of porous silica compacts by the combustion of rice husk ash （RHA） for tundish lining, the experimental design technique was used to evaluate the effect of firing temperature, soaking time and compaction pressure on controlling both the porosity degree and compressive strength of rice husk ash compacts. The results revealed that while the porosity degree of the compacts decreased with the increase in the entire studied parameters, the compressive strength exhibited another trend especially at a lower soaking time. At a lower soaking time, the increase in firing temperature led to a slight decrease in compressive strength and then increasing thereafter. The porous silica compacts having 30% porosity and 〉 2.5 MPa compressive strength suitable for tundish lining could be obtained from the combustion of rice husk ash compacts.

Performance evaluation of cement-stabilized pond ash-rice husk ashclay mixture as a highway construction material

This paper reports the results of an investigation carried out on clay soil stabilized with pond ash(PA),rice husk ash(RHA) and cement. Modified Proctor compaction tests were performed in order to investigate the compaction behavior of clay, and California bearing ratio(CBR) tests were performed to determine the strength characteristics of clay. For evaluation purpose, the specimens containing different amounts of admixtures were prepared. Clay was replaced with PA and RHA at a dosage of 30%e45% and5%e20%, respectively. The influence of stabilizer types and dosages on mechanical properties of clay was evaluated. In order to study the surface morphology and crystallization characteristics of the soil samples, scanning electron microscopy(SEM) and X-ray diffraction(XRD) analyses were carried out,respectively. The results obtained indicated a decrease in the maximum dry density(MDD) and a simultaneous increase in the optimum moisture content(OMC) with the addition of PA and RHA.Multiple linear regression analysis(MLRA) showed that the predicted values of CBR tests are in good agreement with the experimental values. Developed stabilized soil mixtures showed satisfactory strength and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, PA, RHA, and cement in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

Study on Preparation of Rice Husk Ash with High Specific Surface Area and Its Chemical Reactivity

Preparation of rice husk ash with high specific surface area and chemical reactivity of the product are reported in this paper. The amorphous rice husk ash with high specific surface area of 311 m2·g-1 was produced by heating acid treated rice husk at 700℃ for 4 h. The isotherms of rice husk ash are similar in shape to type Ⅱof Brunaner's classification with mesopores being predominant. The rice husk ash has a high chemical reactivity,especially that pretreated with acid. This chemical reactivity depends on ashing temperature and pretreatment conditions. There is an exponential relation between the specific surface area of rice husk ash and the change in the conductivity of saturated Ca(OH)2 solution with rice husk ash, from which the specific surface area can be known according to the conductivity change.

Fabrication of Rice Husk Ash/Natural Rubber Composites by the Latex Process

Rice husk ash/natural rubber composites were fabricated by modifying rice husk ash with the rare earth coupling agent DN-8102. The structure of the rice husk ash and the morphological dispersion of the rice husk ash in a rubber matrix were charactered by scanning and transmission electron microscopy, respectively.The mechanical properties of the composites were experimentally studied. The surface energy and the interaction between rice husk ash particles can be reduced by surface modification of rice husk ash with a rare earth coupling agent, which reduces the agglomeration of rice husk ash in both liquid and rubber matrices and enhances the interactions between rice husk ash and the rubber phase, and thus results in improved mechanical properties for the resulting rice husk ash/natural rubber composite. The modulus of the composites will increase as the loading level of modified rice husk ash increases. A maximum tensile strength of 25.96 MPa for the composites can be obtained when the modified rice husk ash loading level is 4%.

Development of high volume rice husk ash alumino silicate composites

The development of high volume rice husk ash （RHA） alumino silicate composites （ASC） was studied. RHA was used as the source of silica and aluminium in the ASC. The mass ratios of RHA：Al（OH）3 of 70：30 to 99：1 were tested. The results indicate that the obtained ASC mortars are not stable and disintegrate in water. Boric acid was introduced to the mixture to overcome this problem. Stable ASC mortars with high RHA：Al（OH）3 mass ratios of 90：10 to 97.5：2.5 were obtained with the use of boric acid and 115oC curing. The compressive strength of the mortar of 20 MPa was gained. The immersion test indicates that high volume RHA ASC mortars show good resistance in 3vol% H2SO4 solution, but is slightly less durable in 5wt% MgSO4 solution.

Combined Recycling of White Rice Husk Ash as Cement Replacement and Metal Furnace Slag as Coarse-Aggregate Replacement to Produce Self-Consolidating Concrete

According to empirical evidence,high levels of energy and considerable amounts of natural resources are used in the production of concrete.Given the context,this study explores self-consolidating concrete(SCC)that includes rice husk ash(RHA)and metal furnace slag(MFS)as an alternative to cement and the natural aggregates in standard SCC mixes.In this study,mixture designs are investigated with 20 wt.%of RHA,10–30 wt.%of MFS and water-to-powder material ratios of 0.30 and 0.40.Based on the findings regarding the fresh-state,hardened-state,and durability properties of the resulting SCC mixes,it is evident that the use of RHA and MFS can significantly improve the properties of concrete.The highest compressive strength was achieved for SCC with 20 wt.%RHA and 10 wt.%MFS.This outcome should be used as a basis for further investigations into the production of concrete materials that are both high-performance and sustainable.

Study of the Mechanical Behaviour of Mortars Modified with Rice Husk Ash

The purpose of this work is to study the influence of Rice Husk Ash (RHA) on the mechanical strength of mortars. For this purpose, ash was produced by calcining rice husk at 680°C for 5 hours to produce reactive pozzolan. The chemical and mineralogical composition studied by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and X-Ray Diffraction (XRD) showed that this ash is rich in amorphous silica. The ash presents a good pozzolanic activity with a lime fixation rate of 100% after only 7 days of treatment. The addition of RHA to cement contributes to the formation of calcium silicate hydrate (CSH) and calcium aluminate hydrate of C3ASH6 type. The presence of RHA in the mortars improves their mechanical strength. This improvement is due to the filler effect of RHA and to formation of the CSH resulting from the pozzolanic reactivity between the amorphous silica of the RHA and the portlandite released by hydration of the cement.

Rice Husk Ash:A New Silicon Source for Preparing SAPO-34 Catalysts Used in the Methanol-to-Olefins Reaction

SAPO-34 molecular sieves were synthesized directly by hydrothermal method with rice husk ash(RHA)used as the silicon source.The crystal structure,composition,surface morphology and acidity of the synthesized products weresieves had a high crystallinity,without any impure phase.Compared with the SAPO-34 prepared by the silica sol,RHA-SAPO-34 had similar acid properties in strength.The methanol to olefins(MTO)experiments showed that the SAPO-34molecular sieve synthesized from RHA exhibited both a good catalytic activity and ethylene selectivity.

Nanoindentation Characteristics of Cement Paste and Interfacial Transition Zone in Mortar with Rice Husk Ash

The nanostructure of cementitious materials has important effects on concrete properties. The effects of rice husk ash（RHA） on cement hydration product phases and interfacial transition zone（ITZ） in mortar were investigated from the nano-scale structure perspective. The experimental results indicate that, with the increase of RHA dosages of samples, the volume fraction of high-density calcium-silicate-hydrate（HD C-S-H） in porosity and hydration product phases increases. The volume fractions of HD C-S-H in C-S-H of samples show an increasing trend with the increase of RHA dosages. RHA decreases the thickness of ITZ and increases the matrix elastic moduli of samples, however, the RHA dosoges hardly affect the thickness and elastic moduli.

Characteristics of Rice Husk-Admixed Conplast SP 430 Concrete

Experimental work was mounted using 5.7 mL of the Conplast SP430 admixture and rice husk ash(RHA)at replacement levels of 0 to 50%at 10%intervals by wt.%of cement.It is on the performance of Conplast SP 430 admixture and its effects on concrete and concrete with rice husk ash.Concrete specimens were cast and cured for 3 to 90 days and subjected to slump and mechanical characteristics tests.Data generated from the experiments were analyzed and sensitivity analysis of the concrete mix was determined using the Minitab 18 Statistical Package.The results showed that CP with concrete improves the workability of the concrete and reduces water absorption.The reverse was the case when RHA was used with the admixture which may be an issue of compatibility.The statistical characteristics restrict good and within the specified limits.