Investigating the effect of Manufactured sand and Silica Fume on the properties of Concrete

In the present era, concrete is one of the most commonly used construction materials worldwide. Consequently, the demand for natural river sand is increasing. Since the mining of natural sand has already been outlawed by the government in many regions, now it is essential to look into sustainable materials to control natural sand extraction. Hence, manufactured sand (MS) has been shown in numerous studies to be a more practical and environmentally responsible alternative to river sand (RS), which is normally used in the production of concrete. At the same time, the cement industry produces tons of greenhouse gases into the atmosphere, affecting atmospheric conditions. Now, it’s time to look into a suitable replacement material for cement. To investigate the feasibility of using manufactured sand & silica fume in place of river sand and cement under normal climatic conditions fresh, mechanical and durability properties were conducted in the laboratory. Twelve samples of M30 grade cubes and cylinders at desired M sand percentages of 0, 20, 40, 60, 80, and 100 & 0% and 5% variation of silica fume with cement are included in this study as a comparison to the control mix. After 28 days of water curing, a random variation in the properties of concrete was observed in the samples. In this experimental study, SF represents Silica Fume, MS represents manufactured sand, RS represents river sand, FA represents Fine aggregates and CA represents Coarse aggregates.


INTRODUCTION
Ordinary Portland Cement is the most frequently used building material in the world.Due to its application in the global expansion of the building sector, it's worth will not change in the future.Cement production requires a significant quantity of energy and raw resources.During the manufacture of cement, a significant amount of carbon dioxide (CO2) as well as various effluents are emitted into the atmosphere [1,2,3].The replacement of cementitious materials may reduce the production of cement and the emission of greenhouse gases into the atmosphere [4].Silica fume is a type of admixture that is commonly used as a cement replacement material and it is produced from the waste of ferrosilicon alloys [5].It is a pozzolanic material that combines with Ca (OH)2 and creates C-S-H, it avoids the voids or pores between concrete and enhances the strength and durability due to proper packing [5,6].The higher per cent of silicon dioxide in silica fume is the key factor of the binding property in concrete mixes and the particle size of silica fume is less than 1 micron.However, the high surface area of silica fume absorbs more water content compared to cement material [7].Sand is a vital raw material that is used in construction projects all over the world to create infrastructure and build homes.It is mostly used in concrete production and projects related to concrete, such as RMC plants, brickwork products, plastering, manholes, pipelines, and a range of other items [8,9].Sand can be used as a fine aggregate in the creation of asphalt, as a filter for water and other liquids, and as a filler in manufactured items [10].The demand for sand as a construction resource is quite high due to the expansion of the construction sector and significant infrastructure projects, which has increased the amount of illegal sand mining.Now more than ever, it is necessary to find a substitute for river sand in construction projects [11,12].Engineers and researchers have developed concepts for reducing the usage of river sand and for using many alternative materials instead, such as stone crusher dust, foundry sand, manufactured sand, and many other waste products [13].Most of the 1291 (2023) 012027 IOP Publishing doi:10.1088/1757-899X/1291/1/012027 2 research papers on manufactured sand are used as a partial replacement for concrete mixes up to M40 [7].In the present study, silica fume is used to partially replace cement and both partial and full replacements of natural sand with manufactured sand of M30 to demonstrate the properties of concrete.

Cement
OPC of grade 43 was used in this experiment and purchased from tulsi iron & cement traders, Jalandhar, Punjab having 3.13 specific gravity [14].The physical properties of cement are mentioned in Table 1

Silica Fume
The Silica fume used in our experimental study was produced by KGR Agro, Ludhiana, Punjab and the chemical properties of SF are mentioned in Table 2

Fine Aggregates
Locally available fine aggregates of grade IV were used in this experimental study.The properties of fine aggregates are shown in Table 3 2.4.Manufactured sand Manufactured sand of average particle size 150-micron meter was used in this experimental study and was procured from the Sri Syamala rock crushers, Hyderabad, Telangana.The properties of the same are mentioned in Table 3 2

.5. Coarse Aggregates
Coarse aggregates of a maximum size of 20 mm were used in this experiment [15].The properties are mentioned in Table 3 Figure 1 Figure 2 Figure 3 Silica Fume The production process of M sand M sand

EXPEIMMENTAL PROCUDURE
The tests were conducted using the M sand proportions of 0, 20, 40, 60, 80, & 100% and the replacement of 5% Silica Fume of cubes & cylinders specimens of 3 were casted.These specimens were tested after 28 days of the curing period.Until the specimen failed, a constant load of 200 KN was applied using the compression testing apparatus to put the specimen in the device so that the load was distributed across the cube's opposing sides and placed the specimen in the Centre of the machine's base plate.Gently turn the movable part by hand so that it touches the specimen's top surface until the specimen fails, gradually apply the load without sudden load and constantly at a rate of 200KN and note down the peak load.The concrete specimen of dia150 mm has a height of 300 mm specimen was cast and cured according to the relevant standard, the longitudinal axis of the specimen is aligned with the platens so that it is perpendicular to the direction of the applied load and until the specimen fractures, a compressive load is applied at a rate of 14 N/mm2/min.The specimen is then set on a flat surface, a steel plate with a 150mm diameter is set on top of the specimen, and the load at which the specimen fractures is noted as the concrete's compressive strength.Until the specimen is split in half, a compressive load of 0.7 N/mm2/min is given to the steel plate [16,17,18].The concrete's split tensile strength is measured as the load at which the specimen splits [19].As per the RCPT, the specimen was placed between two vessels of water-saturated, 5 cm thick, 10 cm dia concrete.For 6 hours, a 60-Hz (V) applied direct current voltage was delivered to the first vessel, which contained a 3.0 per cent NaCl solution, and the second vessel, which contained a 0.3 M Na (OH)2 solution.The entire charge that was discharged & measured and this value is used to calculate how quickly chloride permeates the concrete.For saturated water absorption, the specimens were weighed before being dried in a hot air oven at 105 degrees Celsius.Until an accurate measurement of the weight differential between the 2 following measures was conducted at 24-hour intervals, the drying process was continued.Before submerging the dried samples in water, they were warmed to room temperature.The samples were taken away at regular intervals.When the surface had been dried with a clean cloth, it was weighed.This process of adjusting the weights continued until they stabilized.Using the equation provided below, the water absorption was calculated [20,21,22].After the specimen was crushed, 10 g of the powdered mortar was obtained and, after being sieved through a 150-m sieve and ground, diluted in 100 ml of distilled water by stirring.We measure the alkalinity of each solution with a pH meter [22,23,24].In this experimental study, SF represents silica fume, MS represents manufactured sand, and RS represents river sand.

IS-10262, Table 4
For the appropriate workability (other than 50 mm slump), the needed water content may be adjusted by around 3% for every 25 mm slump increase or reduction, or it may be determined by trial and error.

RESULT AND DISCUSSION
In concrete mixes containing only river sand and manufactured sand (M1 to M6), the increment of manufactured sand in the control mix from 0 to 100% reduces the slump value due to the high-water absorption of M sand [21].From M1 to M6, decrement in slump value from 85mm to 73.5mm.Similarly, mixes from M7 to M12 containing the same variation of M sand with the replacement of 5% silica Fume in cement content decrease the slump value from 82mm to 70.The presence of both M sand and Silica Fume reduces the slump value of the concrete and it requires more water content at the initial stage of concrete so, a superplasticizer is suggested to maintain workability [16].The fineness of M sand and Silica Fume fills the voids between which led to increases in the strength of the concrete.Mixes containing only M sand (M1 to M6) represent the increment in compressive strength after 28 days of curing from 33.03Mpa to 42.19Mpa [21].Similarly, mixes incorporated with 5% Silica fume and 0 to 100% replacement of M sand (M7 to M12) increase the compressive strength of the concrete from 35.13Mpa to 44.81Mpa.Compared to the control mix, the mixes containing only M sand represent the increment in tensile strength from M1 to M6, parallelly the mixes from M7 to M12 show a greater increment in tensile strength from 3.42Mpa to 4.79Mpa.Chlorine ion permeability for the control mix (M1) shows high penetration compared to the mixes containing M sand and Silica Fume.It represents that, the presence of M sand and SF reduces the permeability of the concrete [20].Respective results of M1, M, M3, M4, M5, M6, M7, M8, M9, M10, M11 and M12 are 1827, 1695, 1517, 1269, 1087, 987, 1717, 1488, 1419, 1205, 964, 714.The initial stage of M sand and SF absorbs more water content but after 28 days of curing the saturated water absorption of the concrete reduces from M 1 to M6 mixes as well as M7 to M12 mixes.Respective results of M1, M2, M3, M4, M5, and M6 are 2.83, 2.79, 2.72, 2.61, 2.49, 2.35 similarly, the results of M7, M8, M9, M10, M11 and M12 are 2.71, 2.56, 2.40, 2,28, 2.13, 2.01.The concrete consisting of M sand and SF reduces the pH value of the concrete.For the first six mixes from M1 to M6 which are only M sand variations, pH was reduced by up to 2.31% (13.40 -13.09) and the next six mixes (M7 to M12) which are incorporated with both M sand variation & SF content reduces even more pH value by up to 2.91% (13.37 -12.98).The findings show that: • The increment of silica fume percentage from 0% to 5% in concrete mixes decreases the slump value of concrete by around 14%. • Compressive & Split tensile strength of concrete increases with the increment of manufactured sand from M1 to M6 mixes by up to 21% & 20% respectively.Similarly, mixes containing both manufactured sand and silica fume increase the strength of the concrete rapidly from M7 to M12 by up to 22% & 28% respectively.• The permeability of chlorine ions is decreased with the increment of manufactured sand, at the same time, the addition of silica fume with the same mixes reduces even more permeability compared to mixes without silica fume.• When compared to natural sand, manufactured sand initially absorbs more water, however after 28 days of curing, superior packing of the m sand reduces the water absorption from M1 to M6 by up to 17%.On the other hand, Mixes containing silica fume reduce water absorption from M7 to M12 by up to 22.14%.• The increase in M sand's percentage indicated a decrease in alkalinity from 13.40 to 13.09.It was discovered that concrete's alkalinity can be reduced to a certain extent by adding a higher percentage of M sand.Similarly, Silica Fume reduces even more alkalinity than normal mixes.Thus, the Silica Fume mixes contain less per cent of Cao to resist the carbonation effect.

Table 1 .
Physical properties of cement

Table 4
Mix proportions of all mixes (kg/m 3 )

Table 7 .
Durability test results of all mixesThe workability, strength, and durability of partial and full replacement manufactured with silica fume, the different mix proportions, were compared by Slump, Compressive, Split Tensile Strength, RCPT, Saturated Water Absorption, and Alkalinity tests to investigate the possibility of replacing natural sand with manufactured sand in concrete structures under normal environmental conditions.