Development of Ternary Concrete Utilizing Agricultural Waste Material

The present project proposes to utilize rice husk and maize cob husk ash in the cement to mitigate the adverse impact of cement on environment and to enhance the disposal of waste in a sustainable manner. Ternary concrete / MR concrete was prepared by using rise husk and maize cob ash with cement. For the present project, ve concrete mixes MR-0 (Control mix), MR-1 (Rice husk ash 10% and MR-2.5%), MR-2 (Rice husk ash 10% and MR-5%), MR-3 (Rice husk ash 10% and MR-2.5%), MR-4 (Rice husk ash 10% and MR-2.5%) were prepared. M35 concrete mix was designed as per IS 10262:2009 for low slump values 0-25mm. The purpose is to nd the optimum replacement level of cement in M35 grade ternary concrete for I – Shaped paver blocks. In order to study the effects of these additions, micro-structural and structural properties test of concretes have been conducted. The crystalline properties of control mix and modied concrete are analyzed by Fourier Transform Infrared Spectroscope (FTIR), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). The results indicated that 10% Rice husk ash and 5% maize cob ash replaced with cement produce a desirable quality of ternary concrete mix having good compressive strength. The results of SEM analysis indicated that the morphology of both concrete were different, showing porous structure at 7 days age and become unsymmetrical with the addition of ashes. After 28 day age, the control mix contained more quantity of ettringite and became denser than ternary concrete. XRD analysis revealed the presence of portlandite in large quantity in controlled mix concrete while MR concrete had the partially hydrated particle of alite. A scanning electron microscope is a tool to study the microstructure of concrete. The experiment was performed by a low vacuum SEM model JOEL JSM – LV/100 with an energy dispersive X-ray (EDS) detector. The splinted piece of concrete was xed in a sample holder with a carbon-coated with electrically conductive platinum material tape attached to the sampler in the machine. The study was conducted at 7, and 28 days of curing age for both controlled concrete and MR specimens. The X-ray diffraction test was used to establish the hydration peaks that appeared in the concrete at 7 and 28 days curing age. The collected samples were dipped in anhydrous ethanol to block the further hydration in concrete. The broken concrete pieces were grounded to a size fewer than 75 microns to use for XRD analysis. The mineralogy was studied with monochromatic Cu - K(cid:0) radiation at a scattering speed of 1.5 o (2(cid:0)) min-1. The powdered samples were axed to the sampler and the top surface of the sample was streaked by a glass slide to obtain a uniform surface. The samples were placed in the diffractometer and scanned in continuous mode from 10 o – 80 o with a scanning rate of 0.05 o / Sec. Concrete at 7 days of curing


Introduction
Ordinary Portland cement acts as a binder in concrete and is important building material for the construction of infrastructure. In 2019, global cement consumption has increased up to 2.9%, reaching nearly 10 billion tons per year, and responsible for 7% of the emission of carbon dioxide in the atmosphere. Production of one-ton cement releases 0.8 tons of carbon dioxide and responsible for 5% emission of global emission. The rise in carbon dioxide concentration has created a greenhouse effect and increased the atmospheric temperature on the earth. The dry manufacturing process of cement consumes 723 Kcal/kg of clinker and 82kWh/ tonne cement of thermal and electrical energy, PM emission 303kg/ tonne of clinker without APCD, NOx emission 3.1 -5.8 kg/tonne of clinker, SOx emission 4.9kg/tonne of clinker, CO 2 during calcination 0.57t -0.63t, fuel combustion -0.46 -0.57t, etc.
Therefore, cement manufacturing is not only responsible for CO 2 emission but gradually the depletion of fuel, energy, and natural resources of limited stocks. The requirement of sustainable development of binding material in the construction industry is the main issue to rectify the adverse impacts of cement manufacturing in the environment. To reduce demands and dependency on cement, emission of carbon dioxide, and other environmental problems, industrial and agro-waste by-products such as y ash, granulated furnace slag, and rice husk ash (RHA) have been used as a substitute for cementitious materials [ RHA is produced by the combustion of rice husk, which is extracted portion of paddy during de-husking operation. The husk production rate of paddy rice is 20 -25% while the ash production rate is 25% when burnt in the boilers. Organic compounds evaporate during combustion in the form of CO and silica remains as residue[xu et al 2016]. Kumar et al. (2012), concluded that the same can be used as fuel in the brick kiln, in the furnace and thermal power plant, and can produce 1MWh energy. Rao et al. (2014) and Zareei et al. (2017) found the speci c gravity of RHA varied from 2.06 to 2.3 depending upon the topography and geographic parameters and having pozzolanic properties. Mehta (1994) observed that the mesopores of RHA particles absorbed free water and allowed calcium ion to diffuse into internal parts which further enhanced the pozzolanic capacity of rice husk shell in concrete. While Zareei et al. (2017) found 20% increment in compressive strength with a 15% replacement of RHA, Habbeb et al. (2010) observed 30.8% enhanced compressive strength of the concrete with 10% replacement . Asonja et al. (2017) and Kyauta et al. (2015) suggested maize cob could also be used as fuel in power plant and 100g produce 600oC temperature depending upon the moisture content in it. Kamau et al. (2016) reported 25% silica content in corn cob ash and observed 20% enhanced compressive strength in concrete at 25% replacement levels .
Literature cite above corroborated the fact that the rice husk and maize cob can be used for the replacement of cement. The present project proposes to utilize rice husk and maize cob husk ash in the cement to mitigate the adverse impact of cement on environment and to enhance the disposal of waste in a sustainable manner.

Hydration Mechanism Of Rha And Mca
During the primary hydration reaction of cement, anhydrous calcium silicates react with water and produce CSH gel and calcium hydroxide (Ca(OH) 2 ). Calcium hydroxide, which further reacts with amorphous silica present in RHA and MCA in secondary hydration reaction and produces a type of CSH gel. The primary and secondary reactions are given below by Siddique  According to Boateng et al. (1990), Ca/Si ratio of CSH-1 produced from primary reaction and CSH-II gel produced from secondary may vary as shown below : The initial Ca-Si ratio at the surface of the particles is near 3. As calcium ions dissolve out of this C-S-H gel, the Ca-Si ratio in the gel becomes 0.8-1.5. According to Garg (2016)

Materials And Methods
In this study, Ordinary Portland Cement 43 grade of Ultra Tech brand was used has 3.16 speci c gravity and it con rmed the requirements of IS:8112 1989. The rice husk ash was collected from the rice mill near the area. The sum of main elements SiO 2 , Al 2 O 3 , and Fe 2 O 3 was corresponding to 88.97% of rice husk ash chemical composition and ful lled the requirements of ASTM 618C. Maize cob was collected from vendors and then converted into ash by burning at 1100 o C temp. The ash obtained was crushed in a ball milling machine and from chemical analysis, the sum of these main compositions was found to be 33.35%. The chemical analysis and physical properties of Cement, RHA, and MCA have been shown in Table 1. The physical properties of ne and coarse aggregates con rmed the requirements of the IS:383 2016 and have been briefed in Tables 2 and 3. proportions are given in Table 4. Further, these mix proportions were also used to produce concrete with and without rice husk ash and maize cob ash. Cement was partially replaced with 10% of rice husk ash and maize cob ash is 2.5%, 5%, 7.5%, and 10% varying ratio. Five various concrete mixes MR-0 (Control mix), MR-1 (Rice husk ash 10% and MR-2.5%), MR-2 (Rice husk ash 10% and MR-5%), MR-3 (Rice husk ash 10% and MR-2.5%), MR-4 (Rice husk ash 10% and MR-2.5%) were prepared.
A ternary concrete mixture was used to mix well all the ingredients in all mixes. The raw materials were mixed for one minute until homogenous color appeared. Firstly 60% water was added to the dry mixer and then 40% of water added. The prepared concrete was placed in greased I-shaped paver blocks moulds of 200 mm x 120mm x100mm size. The samples were demoulded after 24 hrs. and cured for 7, 14,28, and 56 days. Three specimens for each curing age were conducted to determine the average compressive strength. After crushing the specimens for compressive strength, the crushed sample was collected and microstructure analysis FTIR, XRD, SEM, and EDS were performed. The XRD and SEM techniques were used to determine the crystal structure of the paver blocks concrete.

FT-IR
Fourier -transformed infrared spectroscopy is used to obtain an infrared spectrum of absorption or emission of solid, liquid, or gas. It collects high -spectral-resolution data over a wide range. FT-IR is carried out on Perkin Elmer Frontier equipment using potassium bromide. The range is 4000 -400 cm −1 with 2 cm −1 resolution. This study was carried out to correlate the curing age with the development of special features in FTIR spectra during the hardened concrete. Concrete cured in portable water for 7day, 14 days, and 28 days and its wavenumbers and its functional groups of hydrated cement are given in Figures 2 and 3. was at the range of 1400 -1500 cm −1 wavenumber with a smaller and atter peak and shifted to more than 1500 cm −1 wavenumbers as has also been con rmed earlier [Lee and Deventer 2002]. This shift indicated the change in hydration products. While the sharp, strong peak and spiral of CaCO 3 at the range of 2875 -3000 cm −1 wavenumber was converted into a small peak within 7 and 14days but was sharper at 28 age curing age. When compared with controller concrete, it becomes obvious that hydration even at was the wavenumber. Ca(OH) 2 is present in CSH at this range. Maximum changes are found between 3000 to 4000 cm −1 where calcium hydroxide, gypsum, and capillary water decreased most probably with the pozzolanic reaction.

Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD)
A scanning electron microscope is a tool to study the microstructure of concrete. The experiment was performed by a low vacuum SEM model JOEL JSM -LV/100 with an energy dispersive X-ray (EDS) detector. The splinted piece of concrete was xed in a sample holder with a carbon-coated with electrically conductive platinum material tape attached to the sampler in the machine. The study was conducted at 7, and 28 days of curing age for both controlled concrete and MR specimens.
The X-ray diffraction test was used to establish the hydration peaks that appeared in the concrete at 7 and 28 days curing age. The collected samples were dipped in anhydrous ethanol to block the further hydration in concrete. The broken concrete pieces were grounded to a size fewer than 75 microns to use for XRD analysis. The mineralogy was studied with monochromatic Cu -K radiation at a scattering  Figure 4 shows the SEM image after 7 days of hydration of control mix concrete. During the hydration reaction, it has produced glossy quartz (SiO 2 ) low in quantity. White precipitation over particles of portlandite (CH) and CSH like cotton was observed in abundance around the anhydrous particle. In. Figure 5, EDS of microstructure analysis shows that the whitened area consists of the average Ca/Si ratio of 2.03 con rming the formation of portlandite. XRD analysis showed the minerals present and their contribution to the increase in strength and development of concrete. 1-Quartz low, 2 -Portlandite, and 3 -Sinnerite in XRD analysis. Since the age of concrete was 7 days, many voids could also be seen. The compressive strength of concrete is found to be 30.50 N/mm 2 . Figure6 (a) shows the SEM image of 7days Maize cob and Rice Husk Concrete. By adding rice husk and maize cob ashes in concrete, hydration reaction produced, the round dark porous structure, needles of silica (Quartz), and bright parts of anhydrous alite (Ca 3 O 5 Si) which covered more than 50% of the visible area. Figure 6(b) The XRD analysis showed that peaks of alite were very less and were in an amorphous state. 1-Quartz low, 2 -Alite (Ca 3 O 5 Si), 3 -As 8 Cu 12 S 18 in XRD analysis. The presence of calcium hydroxide is less quantum when compared with control mix concrete indicated the slow rate of hydration process of MR concrete due to a large amount of silica in ashes and pozzolanic reaction. Black spherical particles both hollow and solid of ashes were also clearly observed. Many voids at this age of 7 days as were in controlled concrete could also be observed. The 7 days compressive strength is found at 20.2 N/mm 2 . Figure 7, EDS analysis found Ca/Si ratio is 1.8 which was less than 2 indicated the formation of CSH gel.

Conclusions
Based on the above results and analysis presented following conclusions can be drawn: -The results show that the compressive strength of concrete increases with decreasing the Ca/Si ratio. The Ca/Si ratio of control mix concrete varies from is 2.03 to 1.5 while for MR concrete 1.8 to 1.3 in 7and 28 days respectively.
-Based on 28 day compressive strength, 10% RHA & 5% MCA was considered as optimum replacement level of cement in M35 grade concrete for I -Shaped paver blocks.
-The morphology of both types of concrete is very different and XRD analysis shows the presence of portlandite in large quantity in control mix concrete while MR concrete has the partially hydrated particle of alite.       EDS image of 28 days MR concrete