AU2021101075A4 - Geopolymer concrete pavement construction materials and method thereof - Google Patents

Abstract

A composition for preparing geopolymer concrete, the composition comprises of an alkaline solution of sodium silicate and sodium hydroxide with water in a defined ratio, a definite amount of solution prepared from fine and coarse aggregate with water, a defined amount of fly ash mixed with a defined amount of ground granulated blast furnace slag, a first mixture prepared using the aggregate solution mixed with the solution of fly ash and ground granulated blast furnace slag, and a second mixture prepared using the alkaline solution with the first mixture and water. 27 102 110 SODIUM SILICATE AGGREGATE 104 112 GROUND GRANULATED BLAST SODIUM FURNACE SLAG HYDROXIDE 114 106 GEO POLYMER WATER CEMENT 108 116 FLY ASH ORDINARY PORTLAND CEMENT FIGURE 1 preparing the pavement by excavating soil up to a predefined depth using a soil excavator, wherein the soil excavator excavates the required quantity of soil 202 placinganaggregate in a motorized mixer for uniform mixing of aggregates, wherein a definite quantity of fly ash and ground granulated blast furnace slag is added to the aggregate and mixed for 204 a predefined interval of time preparing activator liquid before construction of pavement and mixing the activator liquid with the aggregator, wherein the activator liquid is a combination of alkaline elements mixed in a predefined ratio wherein the alkaline liquid comprises of: a) dissolving a predefined quantity of sodium hydroxide pallets with a defined amount of water; b) dissolving the mixture of sodium silicate with sodium hydroxide and water in a defined ratio. 206 FIGURE 2 Material A1203 Fe 20 3 SiO2 QqQ MgO Na20 K2O MgQ P205 SO TiO2 LOt Fly ash (Class-F) 25.08 4.56 58.23 2.87 1.21 0.41 0.87 2.94 0.2 1.16 0.83 1.59 GGBFS 12.14 1.10 32.25 44.7 4.23 0.87 - 1.96 - 0.84 - 1.98 Cement (OPC) 4.18 3.10 21.47 65.15 1.97 0.63 1.01 - - 1.96 - 0.37 FIGURE 3 Mix Binder Aggregate Solution S/B Extra Series Id FA GGBFS Cement Fine Coarse NaOH Na2SiO3 ratio* water Ml F90GIO-0.4 365.4 40.6 - 609 1218 46.4 116 0.4 14 M2 FtOG20-0.4 324.8 81.2 - 609 1218 46.4 116 0.4 22 M3 F70G30-0.4 284.2 121.8 - 609 1218 46.4 116 0.4 34 M4 F80G20-0.45 324.8 81.2 - 609 1218 52.2 130.5 0.45 11 M5 F70G30-0.45 284.2 121.8 - 609 1218 52.2 130.5 0.45 18 M6 OPC - - 406 609 1218 - - 0.42 FIGURE 4

Description

102 110 SODIUM SILICATE AGGREGATE

104 112 GROUND GRANULATED BLAST SODIUM FURNACE SLAG HYDROXIDE 114 106 GEO POLYMER WATER CEMENT

108 116 FLY ASH ORDINARY PORTLAND CEMENT

FIGURE 1

preparing the pavement by excavating soil up to a predefined depth using a soil excavator, wherein the soil excavator excavates the required quantity of soil 202

placinganaggregate in a motorized mixer for uniform mixing of aggregates, wherein a definite quantity of fly ash and ground granulated blast furnace slag is added to the aggregate and mixed for 204 a predefined interval of time

preparing activator liquid before construction of pavement and mixing the activator liquid with the aggregator, wherein the activator liquid is a combination of alkaline elements mixed in a predefined ratio wherein the alkaline liquid comprises of: a) dissolving a predefined quantity of sodium hydroxide pallets with a defined amount of water; b) dissolving the mixture of sodium silicate with sodium hydroxide and water in a defined ratio. 206

FIGURE 2

Material A12 0 3 Fe 20 3 SiO2 QqQ MgO Na 2 0 K2O MgQ P205 SO TiO 2 LOt Fly ash (Class-F) 25.08 4.56 58.23 2.87 1.21 0.41 0.87 2.94 0.2 1.16 0.83 1.59 GGBFS 12.14 1.10 32.25 44.7 4.23 0.87 - 1.96 - 0.84 - 1.98 Cement (OPC) 4.18 3.10 21.47 65.15 1.97 0.63 1.01 - - 1.96 - 0.37

FIGURE 3

Mix Binder Aggregate Solution S/B Extra Series Id FA GGBFS Cement Fine Coarse NaOH Na2 SiO3 ratio* water Ml F90GIO-0.4 365.4 40.6 - 609 1218 46.4 116 0.4 14 M2 FtOG20-0.4 324.8 81.2 - 609 1218 46.4 116 0.4 22 M3 F70G30-0.4 284.2 121.8 - 609 1218 46.4 116 0.4 34 M4 F80G20-0.45 324.8 81.2 - 609 1218 52.2 130.5 0.45 11 M5 F70G30-0.45 284.2 121.8 - 609 1218 52.2 130.5 0.45 18 M6 OPC - - 406 609 1218 - - 0.42

FIGURE 4

GEOPOLYMER CONCRETE PAVEMENT CONSTRUCTION MATERIALS AND METHODTHEREOF FIELD OF INVENTION

The present invention generally relates to a field of construction methods. More particularly, the present invention relates to geopolymer concrete pavement construction materials and method thereof.

BACKGROUND OF THE INVENTION

A large quantity of the rural roads in the world has been connected with all traditional concrete roads and has a low volume of traffic. The common problem for such kinds of roads is sustainability and durability. Geopolymer concrete (GC) roads offer an alternate to the traditional cement-based concrete roads. An acceleratory pavement track (APT) with six segments has been constructed to evaluate the practical approaches of fly ash-ground granulated blast furnace slag (GGBFS) based GC in the sustainable development of rural road network. This paper presents the non-destructive testing (NDT) on APT to check the quality of GC. Moreover, the mechanical, microstructural, and durability characteristics have been analyzed on samples prepared at the time of APT construction. In this paper, efforts have been made to elaborate on the corrosion resistance and chloride resistance of GC after 28 days of ambient curing. The highest compressive strength of 56.63 MPa was obtained for mix with 70% FA, 30% GGBFS, and 0.4 S/B ratio sample after 28 days of ambient curing, and this value is strengthened by rebound hammer result, i.e., 55.7 MPa, conducted on APT without load revolution. The increase in the number of load repetitions on APT found a decrease in rebound and ultrasonic pulse velocity (UPV) values. Geopolymer concrete mix with 30% GGBFS attained superior NDT behavior upon load repetitions on APT, and similar improved characteristics were identified on laboratory-based testing.

The major contributor to atmospheric carbon dioxide (C02) liberations is the production of ordinary Portland cement (OPC). Extensive usage of cement for the construction of rigid pavements along with some other construction fields would lead to an increase in global warming and thus ascend for sustainable issues. Further, the embodied energy related to concrete is modest; it can be reduced through the use of supplementary cementing materials (SCMs). The construction industry is mandated to use industrial by-products as a cementitious component in concrete. On the other side, geopolymer concrete (GC) has emerged as an alternative to cement concrete, which could potentially reduce emissions of C02 and utilize high volumes of industrial by-products such as fly ash (FA) and ground granulated blast furnace slag (GGBFS).

The existing composition of concrete emits a lot of carbon dioxide and causes pollution.

In order to overcome the above-mentioned limitations, there exists a need to develop a binding material that is strong enough for binding and causes less pollution to the environment.

The technical advancements disclosed by the present invention overcomes the limitations and disadvantages of existing and convention systems and methods.

SUMMARY OF THE INVENTION

The present invention generally relates to materials and methods for construction of roads and pavements.

An object of the present invention is to provide a sustainable material for construction of road.

Another object of the present invention is to construct a pavement by reducing carbon footprint.

Another object of the present invention is to estimate the characteristics of the material used for construction of pavement and roads.

According to an embodiment of the present invention, The compositions comprise of a sodium silicate, sodium hydroxide, water, fly ash, aggregate, and ground granulated blast furnace slag.

An alkaline solution of sodium silicate and sodium hydroxide with water in a defined ratio. The solution is prepared in the ratio of 2:5:1. the alkaline solution of sodium silicate and sodium hydroxide is prepared at least before 24 hours of use in concentration. A definite amount of solution prepared from fine and coarse aggregate with water.

A defined amount of fly ash mixed with a defined amount of ground granulated blast furnace slag. A first mixture prepared using the aggregate solution mixed with the solution of fly ash and ground granulated blast furnace slag and a second mixture prepared using the alkaline solution with the first mixture and water.

The aggregate along with water is mixed for at least 2 minutes, wherein the solution of fly ash and ground granulated blast furnace slag is mixed for at least 1 minutes. The first mixture solution of aggregates and water is mixed thoroughly with the solution of fly ash and ground granulated blast furnace slag for at least 3 minutes.

According to an embodiment, the first Step depicts about preparing the pavement by excavating soil up to a predefined depth using a soil excavator, wherein the soil excavator excavates the required quantity of soil.

The second Step depicts about placing an aggregate in a motorized mixer for uniform mixing of aggregates, wherein a definite quantity of fly ash and ground granulated blast furnace slag is added to the aggregate and mixed for a predefined interval of time; and

The third step depicts about preparing activator liquid before construction of pavement and mixing the activator liquid with the aggregator, wherein the activator liquid is a combination of alkaline elements mixed in a predefined ratio; wherein the alkaline liquid comprises of:

a) dissolving a predefined quantity of sodium hydroxide pallets with a defined amount of water;

b) dissolving the mixture of sodium silicate with sodium hydroxide and water in a defined ratio.

According to an embodiment, the table represents different oxide compounds used in variable quantities for preparation of fly ash, ground granulated blast furnace slag (GGBFS) and ordinary Portland cement (OPC) used as binders. The specific surface area of Fly ash, GGBFS, and cement were 478m2/kg, 670m2/kg, and 310m2/kg, respectively. The specific gravity of FA, GGBFS, and cement are 2.31, 2.80 and 3.14, respectively. The table shows the oxides used for manufacturing of fly ash are aluminum oxide 25.08, ferrous oxide 4.56, silicon oxide 58.23, calcium oxide 2.87, magnesium oxide 1.21, sodium oxide 0.41, potassium oxide 0.87, manganese oxide 2.94, phosphorous oxide 0.2, Sulphur trioxide 1.16, titanium oxide 0.83, LOI 1.59.

The table shows the oxides used for manufacturing of GGBFS are aluminum oxide 12.14, ferrous oxide 1.10, silicon oxide 32.25, calcium oxide 44.7, magnesium oxide 4.23, sodium oxide 0.87, manganese oxide 1.96, Sulphur trioxide 0.84, titanium oxide 0.83, LOI 1.98.

The table shows the oxides used for manufacturing of OPC are aluminum oxide 4.18, ferrous oxide 3.10, silicon oxide 21.47, calcium oxide 65.15, magnesium oxide 1.97, sodium oxide 0.63, potassium oxide 1.01, Sulphur trioxide 1.96, LOI 0.37.

The data shows the different series of geopolymers having different quantities of fly ash, cement, GGBFS, fine aggregates, coarse aggregates, sodium hydroxide, sodium silicate, solution to binder ratio and water.

The solution to binder ratio for the Mix ID M1, M2, M3 is found to be similar i.e., 0.4 for a fixed quantity of fine and coarse aggregate, sodium hydroxide and sodium silicate such as 609, 1218, 46.4 and 116 respectively by varying the proportion of fly ash and GGBFS.

The solution to binder ratio for the Mix ID M4, M5 is found to be similar i.e., 0.45 for afixed quantity of fine and coarse aggregate, sodium hydroxide and sodium silicate such as 609, 1218, 52.2 and 130.5 respectively by varying the proportion of fly ash and GGBFS.

The solution to binder ratio for the Mix ID M6 containing OPC is found to be similar i.e., 0.42 for a fixed quantity of fine and coarse aggregate such as 609, 1218 respectively by adding cement.

According to an embodiment, the planned circular pavement path with outer and inner radius 3.6m and 1.2m, respectively, to get the 2.4m width of the GC test track.

According to an alternate embodiment, the radius of the path may vary.

The soil was excavated up to 0.20m depth, and the sub-grade was prepared with 40mm metal ballast spread over the soil with a depth 0.05m. However, the dimensions are not restricted to the specified depth. The ballast compaction with a 2ton vibratory roller.

The APT is separated into six equal portions with FA bricks and geopolymer mortar, each portion consists of different mix grades with a thickness of 0.15m. However, the number of dimensions is not restricted to six equal portions.

According to an embodiment, the alkaline sodium of sodium silicate is formed with sodium hydroxide and left for 24 hours before the construction of APT. Initially, a definite amount of NaOH pellets is dissolved in the water depends on the required molarity and kept for 2 minutes. Meanwhile, a definite amount of fly ash and GGBFS is mixed in a required amount to form the mixture and kept for 1 minute.

Further, the Na2SiO3 and NaOH liquids is mixed with water in a ratio of 2.5:1. While construction, the aggregates were initially placed in a motorized mixer. Then, FA and GGBFS is added to the aggregate mixture and mixed for 3-4 min. After, the alkaline liquid is added and allowed for another 3 min. The formation of the mixture leads to the formation of fresh geopolymer concrete and the samples are tested.

According to an embodiment, shows the preparations for the wheel in the workshop. To simulate tire pressure, the rim of the prop isfixed with a pre-determined load arrangement (Dead). The tire assembly is like a cantilever with a prop end, where the tire plays a prop role, and the other end was fixed to a gear-box, which helps in controlled rotation of the total wheel and load arrangement.

According to an embodiment, the arrangement for rotation of wheel. To rotate the entire wheel system, the 3 HP mortar was fixed to the gear-box, and to regulate speed, a pulley was also arranged to the mortar. With the help of an electric mortar, the wheel assembly can rotate on the APT at the rate of 12 RPM. The wheel arrangement was provided with a carrier on which a suitable load was applied to maintain standard tire pressure on the APT.

According to alternate embodiments, the power and rotation of the wheel may be varied.

According to an embodiment, different methods are used for evaluating the performance of the geopolymer concrete. The geopolymer binder is prepared by blending the alkaline liquid with FA and GGBFS of each mix. The slump cone test is conducted as per ASTM C143-15 to estimate the consistency of GC. A slump test was held in the field at the time of APT construction with 5 GC mixes and one OPC mix.

The compressive strength test is conducted on 150mm cube molds with respect to BS EN 12390 3-09 standards. A split tensile test is performed on 150x300 mm cylindrical samples, according to ASTM C496/C496M-17. The flexural test was conducted on 100x100x500 mm samples with three-point loading according to ASTM C78/C78M-18. A broken piece from GC samples is taken to investigate the microstructural characteristics like XRD, SEM, and EDS. All the specimens is tested after 28 and 60 days of ambient temperature at a Relative Humidity (RH) of 44-47% to determine the mechanical properties.

The Pundit 200 Proceq UPV test equipment is used to evaluate the time of travel of an ultrasonic pulse through the GC based APT according to IS 13311 (part-I): 2004. The UPV apparatus mainly consists of three components: 1) Two transducers (50 kHz each), 2) Pulse receiver kit, and 3) Data acquisition system. Standards are available for estimating velocity using the direct method of transmission.

In common, an indirect approach is preferred when only one of the concrete structures is accessible. On the other hand, BS 1881 stated that the indirect velocity of UPV is 5-20% lesser than direct velocity. ASTM C597 has not suggested an indirect method of UPV, except when only one surface of the concrete is measurable. One surface of the APT is only accessible to measure the properties of GC properties with UPV so that indirect transmission is adopted.

Initially, the pavement surface is cleaned with paper stone to get the even surface. Grease is applied to both pavement and transducers to avoid space between the transducers and the pavement surface. On each segment of GC based APT, 54 indirect measurements are made.

According to an embodiment, the indirect readings are taken from a grid coordinate system drawn on the APT surface. The coordinate system is chosen for the primary grid at 250mm stretch and a secondary grid within the primary grid at 50mm stretch. The primary gridlines are labeled along the width of the APT as axes X, Y, and Z and along the length of the APT as axes 1, 2, 3, 4, and 5. The secondary grid lines are drawn within the area bounded by axes X, Z, 2, and 4.

The secondary grid labels along the length of APT is 6, 7, 8, and 9, and along the width of APT are a, b, c, d, e, f, g, and h. The indirect UPV readings are taken by placing the transducers at the grid nodes along the axes X, Y, and Z. After every reading, the receiving transducer is shifted from the transmitting transducer opening from the center-center division of 100-500 mm at roughly 50 mm increments. Further, a set of readings is taken before and after loading with several revolutions.

James W-M-250 manual test hammer is used to find the compressive strength of GC (obtained from the graph attached with the apparatus). The readings are sensitive to local differences of the concrete, mainly aggregates close to the surface of the pavement. Thus, several readings at one location is taken and to find their average among four readings taken over an area not more than 300 mm2 with the impact points not less than 20 mm from each other.

The graph shows the setting times in minutes in Y-axis and mix proportions in X-axis. The initial and final setting increases from 0.4 to 0.45.

The X-axis represents mix proportion IDs and the Y- axis represents the slump cone value in mm. The value of M6 is treated to have highest slump cone test value nearly about 150mm and minimum for M3 nearly about 60.

According to an embodiment, the graph represents mix proportions on X-axis and compressive strength MPa on Y-axis.

The compressive strength variance of FA-GGBFS based GC under 28 and 60 days of ambient temperature. The S/B ratio played a significant role in the strength variance. With the increase of the S/B ratio from 0.4 to 0.45, the strength is gradually decreased. The mix M3 contains 30% GGBFS and 0.4 S/B ratio attained elevated strength value under ambient curing. The amount of leached aluminosilicate typically governed the development in strength from the binders. In the structure of the geopolymer, the OH- ion from the alkaline liquid plays as a catalyst in the polymerization process and stimulates the Si4+ and A13+ ions dissolution from the binders. Besides, the Na+ balances the charge deficit of the geopolymer matrix.

However, the extent of Na+ ion required to form a polymeric matrix fulfilled at 0.4 S/B with 8M NaOH concentration. Beyond this alkali content, a surplus OH- ion, although it increases the rate of dissolution but lowers the polymerization process by precipitation of C-A-S-H gel, this decreases the compressive strength of GC. In geopolymer matrixes, aluminosilicate gel is the primary binding phase that provides inter-particle bonding. This improves the compressive strength and become the main reason for the strength increase in geopolymer concrete. The Mix M3 attained higher compressive strength values as 56.63 and 58.8 MPa at 28 and 60 days of ambient curing. SEM images depicted compressive strength values by showing denser microstructure and additional formation of C-A-S-H gel.

According to an embodiment, the X-axis represents the Mix proportions and the Y-axis represents the flexural strength in MPa. The flexural strength of GC at different S/B ratio mixes with FA and GGBFS under ambient temperature. There exists a considerable improvement in flexural strength with the GGBFS replacement level from 10% to 30% at ambient curing. Mix M1 with 10% addition of GGBFS attained 6.36 and 6.98 MPa flexural strength under 28 and 60 days of ambient curing, respectively. Further increase of GBBFS level from 10 to 20% (mix M2), the strength was 8.26 and 9.07 MPa for 28 and 60 days of ambient curing, respectively. However, the highest flexural strength attained at 30% replacement of GGBFS in mix M3 i.e., 11.22 and 11.87 MPa under 28 and 60 days of ambient curing. On the other hand, this has noticed that the increase of the S/B ratio from 0.4 to 0.45 the strength attainment was decreased due to slower geopolymer reaction with poor microstructural characteristics. The experimental results of compressive and flexural strengths have shown a significant correlation by showing higher strength values for mix M3. The increase in GGBFS replacement level refines the pore structure, thus improves the flexural strength of GC at 0.4 S/B ratios.

According to an embodiment, the table represents the GGBFS replacements caused significant reductions in chloride ion permeability of geopolymer concrete. The total charge passed for the %, 20%, and 30% GGBFS replaced 0.4 S/B ratio-based GC samples in terms of coulombs are 3670, 2953, and 1876 respectively. There is a decrease in the charge passed for 30% GGBFS replaced sample when compared to the control mix (M6). This implies that the mix M3 has a better resistance against chloride ion permeability. Mix M3 has shown higher compressive strength value and the same mix showed lower chloride permeability. The experimental results on geopolymer concrete reveal an excellent correlation between compressive strength and RCPT.

On the other hand, the mixes contain 0.45 S/B ratio has shown poor resistance against chloride permeability. The charge passed through the mixes M4 and M5 are 3862 and 3431 coulombs, respectively. This has been recognized that GC contains 0.4 S/B ratio samples exhibited excellent chloride ion resistance compared to 0.45 S/B ratio mixes, which thus gives the best durability characteristics to the GC with the chloride presence.

According to an embodiment, the X-axis represents the time delays and the Y-axis represents the current passed (mA). The current passage profile is stable at the start and that declines with time. This is due to the formation of an inert layer by the geopolymer, which holds the effect of the current to accelerate the corrosion process. After a certain period, the current passage is rapidly increased. This particular point of time is the corrosion instigation time, which shows the beginning of the corrosion process in concrete.

The rapid increase of current is observed due to the rise in the migration of chloride ions with time and result in de-passivation. The initiation period of the mix M1 (contain 10% GGBFS and 0.4 S/B ratio) was 14 days and showed the first crack at the 17th day.

Similarly, the initiation time for mix M2 (contain 20% GGBFS and 0.4 S/B ratio) was 17 days and crack identified on the 23rd day. Further, mix M3 contains 30% GGBFS and 0.4 S/B ratio initiation period identified after 24 days and first crack observed on 30th day. However, excessive alkaline content has a negative effect on corrosion prevention as it retards the improvement of a stronger polymer matrix.

As a result, the active layer around the reinforcement is damaged. The initiation time for mix M4 (contain 20% GGBFS and 0.45 S/B ratio) was at 11 days, and the first crack observed on the 16th day. Similarly, the initiation period for mix M5 (contain 30% GGBFS and 0.45 S/B ratio) was after 15 days, and the initial crack detected on the 22nd day.

The XRD patterns are shown both amorphous and crystalline phases. The major crystalline phases, like quartz, calcite, and hematite, are detected in FA-GGBFS based mixes. Besides, mullite and alumina are also noticed due to unreacted particles from FA. An additional phase of the C-A-S-H complex is noticed in mix M3, which is reported to form in extra C-A-S-H gel in FA-GGBFS based GC.

The expected hybrid gels are formed through the process of alkali activation of GGBFS and fly ash. The strong peak detected in mix M3 at approximately 30 (20) was the C-A-S-H phase, which is one of the leading products of alkali-activated fly ash-GGBFS. Peaks of calcite (calcium carbonate) are also detected, resulting from the amalgamation of C02 from the atmosphere when the specimens were analyzed. According to an observation, that the amount of geo polymerization matrix enriches with the increase of GGBFS. GGBFS has been stated to include a more significant amount of soluble calcium oxide, which could improve the geo-polymerization products and produce more gel.

In addition, a strongly alkaline medium is essential to enhance the leaching of Si4+, A13+, Ca2+, and other minor ions to some extent, which is reported to be significant for the generation of geo polymeric gel and the improvement of mechanical properties of the geopolymer concrete.

On the other hand, the mixes M4 and M5 shown less crystalline phases such as quartz, calcite, and mullite are observed due to the higher content of an alkaline solution. Further, the amount of C-A-S-H gel decreases, which could be observed from their intensity from the XRD peaks.

According to an embodiment, the microstructure of GC is the homogeneous matrix, geo polymeric gel, unreacted FA, and semi-reacted FA particles. The unreacted reacted particles are observed with the mixes contain more FA content like Ml, M2, and M4, due to lower FA reactivity. This judgment strongly supported by strength results, which indicates the greater quantity of geo-polymerization matrix, produced in the GGBFS rich specimens.

However, increasing the amount of FA in GC leads to the looser matrix. Figure 16 a & b illustrates the low denser structure and few non-reacted FA particles embedded in the geopolymer matrix.

On the other hand, the denser microstructure is observed in mix M3 (contain 30% GGBFS and 0.4 S/B ratio) samples with additional C-A-S-H gel formation. A noticeable difference was observed with the sample M3 compared to that of M5.

The more solution to binder ratio (0.45) has not shown proper geo-polymerization products; it is the reason the strength properties are less compared to M3 samples. This is mainly because of the slow geo-polymerization process, due to more alkaline content in the mixes M4 and M5. As more C-A-S-H gel is formed from the reaction of FA-GGBFS and 0.4 S/B ratios, which modified the microstructure of geopolymer concrete.

The SEM images from Figure 16 d & e are evident that the formation of cracks was found on the surface of the samples. According to the observation, the surface cracks on the pavement, and these observations are supported by UPV results also. These are the major drawbacks that the mixes contain greater alkaline solution has not shown proper denser microstructure, leads to lower mechanical properties compared to other mixes of GC. The delay in the geo-polymerization process in the mixes M4 and M5. Moreover, poor C-A-S-H gel formation is also found in Figure 16 d & e.

According to an embodiment, the data shows the different mixes from M1 to M6 having different element. The significant element obtained from the analysis are 'Si,' 'Al,' 'Na,' 'Mg,' and 'Ca'. The data obtained from EDS is in high conformity with the XRD analysis. The major elements identified in GC are Si and Al, whereas in control mix Si and Ca are detected.

According to the data obtained from the rebound hammer for APT are most comparable to cube test results. The downfall of rebound readings with the increase of no-load revolutions on the APT. There is no much variance observed in the field applications of geopolymer concrete with rebound values. As like enhanced cube compressive strength for mix M3, the higher rebound value is found for the same mix segment of APT. The strength reduction under 500 kg load with ,000 revolutions was around 5-9%.

Similarly, for 1,00,000 rotations, the strength reduction is observed from 14-19%. Compared to the control mix (M6), all the GC mixes have shown good results against the rebound hammer test. It is also noticed that there is no much strength variance that is found at different places on the APT segment (like Centre, interior, and exterior corners).

According to an embodiment, the UPV results of geopolymer concrete based APT with and without loading after 28 days of ambient temperature. In Tables 19a-19c, the indirect UPV values are determined as the ratio of path length to the time of flight of the waves between two transducers in 'km/sec'. Table 19a reveals the UPV results after 28 days of ambient curing and without any load revolutions.

Compared to all other mixes, the mix M3 depicted better UPV results in all cases like with and without loading. These values are also strengthened by cube compressive strength and rebound hammer results. According to the observation, after 1,00,000 revolutions of wheel arrangement with 500kg loading, the UPV results are slightly decreased.

The results are indicating that the quality of concrete is decreased by increasing the no of revolutions. The poor UPV values are observed for the mix M4 because of minor crack formations on the surface. The UPV values for segment M4 have not been recommended for practical applications.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings

BRIEF DESCRIPTION OF FIGURES

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1 illustrates a block diagram of the different materials used in geopolymer concrete.

Figure 2 illustrates the construction method for preparing pavement, the method comprises of following steps.

Figure 3 illustrates the tabular representation of the oxide composition of different materials.

Figure 4 illustrates the tabular representation of the mix proportions of geopolymer and OPC concretes.

Figure 5a, 5b, 5c and 5d shows the exemplary view of the different preparation steps carried out during the construction of pavement track.

Figure 6 illustrates the block diagram for the preparation of geopolymer concrete.

Figure 7a, 7b illustrates an exemplary embodiment of the wheel arrangement by preparation of wheel and rotation of wheel respectively.

Figure 8 illustrates the different UV test coordinate system on APT surface.

Figure 9 illustrates the graphical representation of the Initial and final setting times of different concretes

Figure 10 illustrates the graphical representation of the different values obtained from the slump cone test.

Figure 11 illustrates the graphical representation of the compressive strength of geopolymer and OPC concretes.

Figure 12 illustrates the graphical representation of the flexural strength of the geopolymer and OPC concretes.

Figure 13 illustrates the tabular representation of the rapid chloride penetration test.

Figure 14 illustrates the graphical representation of the accelerated corrosion penetration test.

Figure 15 illustrates a graphical representation of the XRD patterns of Flt ash-GGBFS based Geopolymer concrete.

Figure 16a-16f represents a pictorial representation of the SEM analysis of five geopolymer concrete mixes and control mixes.

Figure 17 illustrates a tabular representation of the EDS analysis related to SEM analysis of geopolymer concrete.

Figure 18 illustrates the tabular representation of the test results obtained from the test results of rebound hammer on accelerated pavement track.

Figure 19a, 19b and 19c illustrates the tabular representation of the indirect UPV results with and without load revolution in Km/Sec.

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Figure 1 illustrates a block diagram of the different materials used in geopolymer concrete. The compositions comprise of a sodium silicate 102, sodium hydroxide 104, water 106, fly ash 108, aggregate 110, and ground granulated blast furnace slag 112.

An alkaline solution of sodium silicate 102 and sodium hydroxide 104 with water 106 in a defined ratio. The solution is prepared in the ratio of 2:5:1. the alkaline solution of sodium silicate 102 and sodium hydroxide 104 is prepared at least before 24 hours of use in concentration. A definite amount of solution prepared from fine and coarse aggregate 110 with water 106.

A defined amount of fly ash 108 mixed with a defined amount of ground granulated blast furnace slag 112. A first mixture prepared using the aggregate 110 solution mixed with the solution of fly ash 108 and ground granulated blast furnace slag 112 and a second mixture prepared using the alkaline solution with the first mixture and water 106.

The aggregate 110 along with water 106 is mixed for at least 2 minutes, wherein the solution of fly ash 108 and ground granulated blast furnace slag 112 is mixed for at least 1 minutes. The first mixture solution of aggregates 110 and water 106 is mixed thoroughly with the solution of fly ash 108 and ground granulated blast furnace slag 112 for at least 3 minutes.

In an implementation, the 8 molarity sodium hydroxide liquid is considered in the mixes to prepare an alkaline solution in the construction of geopolymer pavement.

In an implementation, the alkaline solution to binder ratios is considered as 0.4 and 0.45.

Figure 2 illustrates the construction method for preparing pavement, the method comprises of following steps:

Step 202 depicts about preparing the pavement by excavating soil up to a predefined depth using a soil excavator, wherein the soil excavator excavates the required quantity of soil.

Step 204 depicts about placing an aggregate 110 in a motorized mixer for uniform mixing of aggregates 110, wherein a definite quantity of fly ash 108 and ground granulated blast furnace slag 112 is added to the aggregate 110 and mixed for a predefined interval of time; and

Step 206 depicts about preparing activator liquid before construction of pavement and mixing the activator liquid with the aggregator, wherein the activator liquid is a combination of alkaline elements mixed in a predefined ratio; wherein the alkaline liquid comprises of:

a) dissolving a predefined quantity of sodium hydroxide 104 pallets with a defined amount of water 106; b) dissolving the mixture of sodium silicate 102 with sodium hydroxide 104 and water 106 in a defined ratio.

In an implementation, the fly ash replaced with GGBFS in different proportions for various mixes; there are as follows,

* 10% GGBFS and 90% fly ash * 20% GGBFS and 80% fly ash

* 30% GGBFS and 70% fly ash

Figure 3 illustrates the tabular representation of the oxide composition of different materials. The table represents different oxide compounds used in variable quantities for preparation of fly ash 108, ground granulated blast furnace slag (GGBFS) 112 and ordinary Portland cement (OPC) 116 used as binders. The specific surface area of Fly ash 108, GGBFS 112, and cement were 478m2/kg, 670m2/kg, and 310m2/kg, respectively. The specific gravity of FA, GGBFS 112, and cement are 2.31, 2.80 and 3.14, respectively. The table shows the oxides used for manufacturing of fly ash 108 are aluminum oxide 25.08, ferrous oxide 4.56, silicon oxide 58.23, calcium oxide 2.87, magnesium oxide 1.21, sodium oxide 0.41, potassium oxide 0.87, manganese oxide 2.94, phosphorous oxide 0.2, Sulphur trioxide 1.16, titanium oxide 0.83, LOI 1.59.

The table shows the oxides used for manufacturing of GGBFS 112 are aluminum oxide 12.14, ferrous oxide 1.10, silicon oxide 32.25, calcium oxide 44.7, magnesium oxide 4.23, sodium oxide 0.87, manganese oxide 1.96, Sulphur trioxide 0.84, titanium oxide 0.83, LOI 1.98.

The table shows the oxides used for manufacturing of OPC 116 are aluminum oxide 4.18, ferrous oxide 3.10, silicon oxide 21.47, calcium oxide 65.15, magnesium oxide 1.97, sodium oxide 0.63, potassium oxide 1.01, Sulphur trioxide 1.96, LOI 0.37.

Figure 4 illustrates the tabular representation of the mix proportions of geopolymer and OPC concretes.

The data shows the different series of geopolymers having different quantities of fly ash 108, cement, GGBFS 112, fine aggregates 110, coarse aggregates 110, sodium hydroxide 104, sodium silicate 102, solution to binder ratio and water 106.

The solution to binder ratio for the Mix ID M1, M2, M3 is found to be similar i.e., 0.4 for afixed quantity of fine and coarse aggregate 110, sodium hydroxide 104 and sodium silicate 102 such as 609, 1218, 46.4 and 116 respectively by varying the proportion of fly ash 108 and GGBFS 112.

The solution to binder ratio for the Mix ID M4, M5 is found to be similar i.e., 0.45 for afixed quantity of fine and coarse aggregate 110, sodium hydroxide 104 and sodium silicate 102 such as 609, 1218, 52.2 and 130.5 respectively by varying the proportion of fly ash 108 and GGBFS 112.

The solution to binder ratio for the Mix ID M6 containing OPC 116 is found to be similar i.e., 0.42 for a fixed quantity of fine and coarse aggregate 110 such as 609, 1218 respectively by adding cement.

Figure 5a, 5b, 5c and 5d shows the exemplary view of the different preparation steps carried out during the construction of pavement track.

According to an embodiment, the planned circular pavement path with outer and inner radius 3.6m and 1.2m, respectively, to get the 2.4m width of the GC test track.

According to an alternate embodiment, the radius of the path may vary.

The soil was excavated up to 0.20m depth, and the sub-grade was prepared with 40mm metal ballast spread over the soil with a depth 0.05m. However, the dimensions are not restricted to the specified depth. The ballast compaction with a 2ton vibratory roller.

The APT is separated into six equal portions with FA bricks and geopolymer mortar, each portion consists of different mix grades with a thickness of 0.15m. However, the number of dimensions is not restricted to six equal portions.

Figure 6 illustrates the block diagram for the preparation of geopolymer concrete. According to an embodiment, the alkaline sodium of sodium silicate 102 is formed with sodium hydroxide 104 and left for 24 hours before the construction of APT. Initially, a definite amount of NaOH pellets is dissolved in the water 106 depends on the required molarity and kept for 2 minutes. Meanwhile, a definite amount of fly ash 108 and GGBFS 112 is mixed in a required amount to form the mixture and kept for 1 minute.

Further, the Na 2 SiO3 and NaOH liquids is mixed with water 106 in a ratio of 2.5:1. While construction, the aggregates 110 were initially placed in a motorized mixer. Then, FA and GGBFS 112 is added to the aggregate 110 mixture and mixed for 3-4 min. After, the alkaline liquid is added and allowed for another 3 min. The formation of the mixture leads to the formation of fresh geopolymer concrete 114 and the samples are tested.

Figure 7a, 7b illustrates an exemplary embodiment of the wheel arrangement by preparation of wheel and rotation of wheel respectively.

Figure 7a shows the preparations for the wheel in the workshop. To simulate tire pressure, the rim of the prop is fixed with a pre-determined load arrangement (Dead). The tire assembly is like a cantilever with a prop end, where the tire plays a prop role, and the other end was fixed to a gear box, which helps in controlled rotation of the total wheel and load arrangement.

Figure 7b shows the arrangement for rotation of wheel. To rotate the entire wheel system, the 3 HP mortar was fixed to the gear-box, and to regulate speed, a pulley was also arranged to the mortar. With the help of an electric mortar, the wheel assembly can rotate on the APT at the rate of 12 RPM. The wheel arrangement was provided with a carrier on which a suitable load was applied to maintain standard tire pressure on the APT.

According to alternate embodiments, the power and rotation of the wheel may be varied.

According to an embodiment, different methods are used for evaluating the performance of the geopolymer concrete 114. The geopolymer binder is prepared by blending the alkaline liquid with FA and GGBFS 112 of each mix. The slump cone test is conducted as per ASTM C143-15 to estimate the consistency of GC. A slump test was held in the field at the time of APT construction with 5 GC mixes and one OPC mix 116.

The compressive strength test is conducted on 150mm cube molds with respect to BS EN 12390 3-09 standards. A split tensile test is performed on 150x300 mm cylindrical samples, according to ASTM C496/C496M-17. The flexural test was conducted on 100x100x500 mm samples with three-point loading according to ASTM C78/C78M-18. A broken piece from GC samples is taken to investigate the microstructural characteristics like XRD, SEM, and EDS. All the specimens is tested after 28 and 60 days of ambient temperature at a Relative Humidity (RH) of 44-47% to determine the mechanical properties.

The Pundit 200 Proceq UPV test equipment is used to evaluate the time of travel of an ultrasonic pulse through the GC based APT according to IS 13311 (part-I): 2004. The UPV apparatus mainly consists of three components: 1) Two transducers (50 kHz each), 2) Pulse receiver kit, and 3) Data acquisition system. Standards are available for estimating velocity using the direct method of transmission.

In common, an indirect approach is preferred when only one of the concrete structures is accessible. On the other hand, BS 1881 [56] stated that the indirect velocity of UPV is 5-20% lesser than direct velocity. ASTM C597 has not suggested an indirect method of UPV, except when only one surface of the concrete is measurable. One surface of the APT is only accessible to measure the properties of GC properties with UPV so that indirect transmission is adopted.

Initially, the pavement surface is cleaned with paper stone to get the even surface. Grease is applied to both pavement and transducers to avoid space between the transducers and the pavement surface. On each segment of GC based APT, 54 indirect measurements are made.

Figure 8 illustrates the different UV test coordinate system on APT surface.

The indirect readings are taken from a grid coordinate system drawn on the APT surface. The coordinate system is chosen for the primary grid at 250mm stretch and a secondary grid within the primary grid at 50mm stretch. The primary gridlines are labeled along the width of the APT as axes X, Y, and Z and along the length of the APT as axes 1, 2, 3, 4, and 5. The secondary grid lines are drawn within the area bounded by axes X, Z, 2, and 4.

The secondary grid labels along the length of APT is 6, 7, 8, and 9, and along the width of APT are a, b, c, d, e, f, g, and h. The indirect UPV readings are taken by placing the transducers at the grid nodes along the axes X, Y, and Z. After every reading, the receiving transducer is shifted from the transmitting transducer opening from the center-center division of 100-500 mm at roughly 50 mm increments. Further, a set of readings is taken before and after loading with several revolutions.

James W-M-250 manual test hammer is used to find the compressive strength of GC (obtained from the graph attached with the apparatus). The readings are sensitive to local differences of the concrete, mainly aggregates 110 close to the surface of the pavement. Thus, several readings at one location is taken and to find their average among four readings taken over an area not more than 300 mm2 with the impact points not less than 20 mm from each other.

Figure 9 illustrates the graphical representation of the Initial and final setting times of different concretes. The graph shows the setting times in minutes in Y-axis and mix proportions in X-axis. The initial and final setting increases from 0.4 to 0.45.

Figure 10 illustrates the graphical representation of the different values obtained from the slump cone test. The X-axis represents mix proportion IDs and the Y- axis represents the slump cone value in mm. The value of M6 is treated to have highest slump cone test value nearly about 150mm and minimum for M3 nearly about 60.

Figure 11 illustrates the graphical representation of the compressive strength of geopolymer and OPC concretes 116. The graph represents mix proportions on X-axis and compressive strength MPa on Y-axis.

The compressive strength variance of FA-GGBFS 112 based GC under 28 and 60 days of ambient temperature. The S/B ratio played a significant role in the strength variance. With the increase of the S/B ratio from 0.4 to 0.45, the strength is gradually decreased. The mix M3 contains 30% GGBFS 112 and 0.4 S/B ratio attained elevated strength value under ambient curing. The amount of leached aluminosilicate typically governed the development in strength from the binders. In the structure of the geopolymer, the OH- ion from the alkaline liquid plays as a catalyst in the polymerization process and stimulates the Si4+ and A13+ ions dissolution from the binders. Besides, the Na+ balances the charge deficit of the geopolymer matrix.

However, the extent of Na+ ion required to form a polymeric matrix fulfilled at 0.4 S/B with 8M NaOH concentration. Beyond this alkali content, a surplus OH- ion, although it increases the rate of dissolution but lowers the polymerization process by precipitation of C-A-S-H gel, this decreases the compressive strength of GC. In geopolymer matrixes, aluminosilicate gel is the primary binding phase that provides inter-particle bonding. This improves the compressive strength and become the main reason for the strength increase in geopolymer concrete 114. The Mix M3 attained higher compressive strength values as 56.63 and 58.8 MPa at 28 and 60 days of ambient curing. SEM images depicted compressive strength values by showing denser microstructure and additional formation of C-A-S-H gel.

Figure 12 illustrates the graphical representation of the flexural strength of the geopolymer and OPC concretes 116. The X-axis represents the Mix proportions and the Y-axis represents the flexural strength in MPa. The flexural strength of GC at different S/B ratio mixes with FA and GGBFS 112 under ambient temperature. There exists a considerable improvement in flexural strength with the GGBFS 112 replacement level from 10% to 30% at ambient curing. Mix M1 with 10% addition of GGBFS 112 attained 6.36 and 6.98 MPa flexural strength under 28 and 60 days of ambient curing, respectively. Further increase of GBBFS level from 10 to 20% (mix M2), the strength was 8.26 and 9.07 MPa for 28 and 60 days of ambient curing, respectively. However, the highest flexural strength attained at 30% replacement of GGBFS 112 in mix M3 i.e., 11.22 and 11.87 MPa under 28 and 60 days of ambient curing. On the other hand, this has noticed that the increase of the S/B ratio from 0.4 to 0.45 the strength attainment was decreased due to slower geopolymer reaction with poor microstructural characteristics. The experimental results of compressive and flexural strengths have shown a significant correlation by showing higher strength values for mix M3. The increase in GGBFS 112 replacement level refines the pore structure, thus improves the flexural strength of GC at 0.4 S/B ratios.

Figure 13 illustrates the tabular representation of the rapid chloride penetration test.

The table represents the GGBFS 112 replacements caused significant reductions in chloride ion permeability of geopolymer concrete 114. The total charge passed for the 10%, 20%, and 30% GGBFS 112 replaced 0.4 S/B ratio-based GC samples in terms of coulombs are 3670, 2953, and 1876 respectively. There is a decrease in the charge passed for 30% GGBFS 112 replaced sample when compared to the control mix (M6). This implies that the mix M3 has a better resistance against chloride ion permeability. Mix M3 has shown higher compressive strength value and the same mix showed lower chloride permeability. The experimental results on geopolymer concrete 114 reveal an excellent correlation between compressive strength and RCPT.

On the other hand, the mixes contain 0.45 S/B ratio has shown poor resistance against chloride permeability. The charge passed through the mixes M4 and M5 are 3862 and 3431 coulombs, respectively. This has been recognized that GC contains 0.4 S/B ratio samples exhibited excellent chloride ion resistance compared to 0.45 S/B ratio mixes, which thus gives the best durability characteristics to the GC with the chloride presence.

Figure 14 illustrates the graphical representation of the accelerated corrosion penetration test. The X-axis represents the time delays and the Y-axis represents the current passed (mA). The current passage profile is stable at the start and that declines with time. This is due to the formation of an inert layer by the geopolymer, which holds the effect of the current to accelerate the corrosion process. After a certain period, the current passage is rapidly increased. This particular point of time is the corrosion instigation time, which shows the beginning of the corrosion process in concrete.

The rapid increase of current is observed due to the rise in the migration of chloride ions with time and result in de-passivation. The initiation period of the mix M1 (contain 10% GGBFS 112 and 0.4 S/B ratio) was 14 days and showed the first crack at the 17th day.

Similarly, the initiation time for mix M2 (contain 20% GGBFS 112 and 0.4 S/B ratio) was 17 days and crack identified on the 23rd day. Further, mix M3 contains 30% GGBFS 112 and 0.4 S/B ratio initiation period identified after 24 days and first crack observed on 30th day. However, excessive alkaline content has a negative effect on corrosion prevention as it retards the improvement of a stronger polymer matrix.

As a result, the active layer around the reinforcement is damaged. The initiation time for mix M4 (contain 20% GGBFS 112 and 0.45 S/B ratio) was at 11 days, and thefirst crack observed on the 16th day. Similarly, the initiation period for mix M5 (contain 30% GGBFS 112 and 0.45 S/B ratio) was after 15 days, and the initial crack detected on the 22nd day.

Figure 15 illustrates a graphical representation of the XRD patterns of Flt ash-GGBFS based Geopolymer concrete.

The XRD patterns are shown both amorphous and crystalline phases. The major crystalline phases, like quartz, calcite, and hematite, are detected in FA-GGBFS 112 based mixes. Besides, mullite and alumina are also noticed due to unreacted particles from FA. An additional phase of the C-A-S-H complex is noticed in mix M3, which is reported to form in extra C-A-S-H gel in FA-GGBFS 112 based GC.

The expected hybrid gels are formed through the process of alkali activation of GGBFS 112 and fly ash 108. The strong peak detected in mix M3 at approximately 30° (20) was the C-A-S-H phase, which is one of the leading products of alkali-activated fly ash 108-GGBFS 112. Peaks of calcite (calcium carbonate) are also detected, resulting from the amalgamation of C02 from the atmosphere when the specimens were analyzed. According to an observation, that the amount of geo-polymerization matrix enriches with the increase of GGBFS 112. GGBFS 112 has been stated to include a more significant amount of soluble calcium oxide, which could improve the geo-polymerization products and produce more gel.

In addition, a strongly alkaline medium is essential to enhance the leaching of Si4+, A13+, Ca2+, and other minor ions to some extent, which is reported to be significant for the generation of geo polymeric gel and the improvement of mechanical properties of the geopolymer concrete 114.

On the other hand, the mixes M4 and M5 shown less crystalline phases such as quartz, calcite, and mullite are observed due to the higher content of an alkaline solution. Further, the amount of C-A-S-H gel decreases, which could be observed from their intensity from the XRD peaks.

Figure 16a-16f represents a pictorial representation of the SEM analysis offive geopolymer concrete mixes and control mixes.

The microstructure of GC is the homogeneous matrix, geo-polymeric gel, unreacted FA, and semi-reacted FA particles. The unreacted reacted particles are observed with the mixes contain more FA content like Ml, M2, and M4, due to lower FA reactivity. This judgment strongly supported by strength results, which indicates the greater quantity of geo-polymerization matrix, produced in the GGBFS 112 rich specimens.

However, increasing the amount of FA in GC leads to the looser matrix. Figure 16 a & b illustrates the low denser structure and few non-reacted FA particles embedded in the geopolymer matrix.

On the other hand, the denser microstructure is observed in mix M3 (contain 30% GGBFS 112 and 0.4 S/B ratio) samples with additional C-A-S-H gel formation. A noticeable difference was observed with the sample M3 compared to that of M5.

The more solution to binder ratio (0.45) has not shown proper geo-polymerization products; it is the reason the strength properties are less compared to M3 samples. This is mainly because of the slow geo-polymerization process, due to more alkaline content in the mixes M4 and M5. As more C-A-S-H gel is formed from the reaction of FA-GGBFS 112 and 0.4 S/B ratios, which modified the microstructure of geopolymer concrete 114.

The SEM images from Figure 16 d & e are evident that the formation of cracks was found on the surface of the samples. According to the observation, the surface cracks on the pavement, and these observations are supported by UPV results also. These are the major drawbacks that the mixes contain greater alkaline solution has not shown proper denser microstructure, leads to lower mechanical properties compared to other mixes of GC. The delay in the geo-polymerization process in the mixes M4 and M5. Moreover, poor C-A-S-H gel formation is also found in Figure 16 d & e.

Figure 17 illustrates a tabular representation of the EDS analysis related to SEM analysis of geopolymer concrete 114. The data shows the different mixes from M1 to M6 having different element. The significant element obtained from the analysis are 'Si,' 'Al,' 'Na,' 'Mg,' and 'Ca'. The data obtained from EDS is in high conformity with the XRD analysis. The major elements identified in GC are Si and Al, whereas in control mix Si and Ca are detected.

Figure 18 illustrates the tabular representation of the test results obtained from the test results of rebound hammer on accelerated pavement track. According to the data obtained from the rebound hammer for APT are most comparable to cube test results. The downfall of rebound readings with the increase of no-load revolutions on the APT. There is no much variance observed in the field applications of geopolymer concrete 114 with rebound values. As like enhanced cube compressive strength for mix M3, the higher rebound value is found for the same mix segment of APT. The strength reduction under 500 kg load with 50,000 revolutions was around 5-9%.

Similarly, for 1,00,000 rotations, the strength reduction is observed from 14-19%. Compared to the control mix (M6), all the GC mixes have shown good results against the rebound hammer test. It is also noticed that there is no much strength variance that is found at different places on the APT segment (like Centre, interior, and exterior corners).

Figure 19a, 19b and 19 illustrates the tabular representation of the indirect UPV results with and without load revolution in Km/Sec.

The UPV results of geopolymer concrete 114 based APT with and without loading after 28 days of ambient temperature. In Tables 19a-19c, the indirect UPV values are determined as the ratio of path length to the time of flight of the waves between two transducers in 'km/sec'. Table 19a reveals the UPV results after 28 days of ambient curing and without any load revolutions.

Compared to all other mixes, the mix M3 depicted better UPV results in all cases like with and without loading. These values are also strengthened by cube compressive strength and rebound hammer results. According to the observation, after 1,00,000 revolutions of wheel arrangement with 500kg loading, the UPV results are slightly decreased.

The results are indicating that the quality of concrete is decreased by increasing the no of revolutions. The poor UPV values are observed for the mix M4 because of minor crack formations on the surface. The UPV values for segment M4 have not been recommended for practical applications.

The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.

Claims (10)

WE CLAIM

1. A composition for preparing geopolymer concrete, the composition comprises of:

an alkaline solution of sodium silicate and sodium hydroxide with water in a defined ratio;

a definite amount of solution prepared from fine and coarse aggregate with water;

a defined amount of fly ash mixed with a defined amount of ground granulated blast furnace slag;

a first mixture prepared using the aggregate solution mixed with the solution of fly ash and ground granulated blast furnace slag; and

a second mixture prepared using the alkaline solution with the first mixture and water, wherein 8 molarity sodium hydroxide liquid is considered in the mixes to prepare an alkaline solution in the construction of geopolymer pavement, and wherein the alkaline solution to binder ratios is considered as 0.4 and 0.45.

2. The composition as claimed in claim 1, wherein the alkaline solution of sodium silicate and sodium hydroxide is prepared at least before 24 hours of use in concentration.

3. The composition as claimed in claim 1, wherein the aggregate along with water is mixed for at least 2 minutes, wherein the solution of fly ash and ground granulated blast furnace slag is mixed for at least 1 minutes.

4. The composition as claimed in claim 1, wherein the solution of aggregates and water is mixed thoroughly with the solution of fly ash and ground granulated blast furnace slag for at least 3 minutes.

5. The composition as claimed in claim 1, wherein the alkaline solution is mixed thoroughly with the prepared solution of aggregates, fly ash, ground granulated blast furnace slag for at least 3 minutes.

6. The composition as claimed in claim 1, an Ultrasonic pulse velocity test is conducted to test the time of travel of an ultrasonic pulse through the geopolymer concrete, the components comprise of at least two transducers, a pulser receiver kit and a data acquisition module.

7. The composition as claimed in claim 1, wherein the solution of sodium silicate and sodium hydroxide is dissolved in ratio in the ratio of 2.5:1.

8. A construction method for preparing pavement, the method comprises of: preparing the pavement by excavating soil up to a predefined depth using a soil excavator, wherein the soil excavator excavates the required quantity of soil; placing an aggregate in a motorized mixer for uniform mixing of aggregates, wherein a definite quantity of fly ash and ground granulated blast furnace slag is added to the aggregate and mixed for a predefined interval of time; and preparing activator liquid before construction of pavement and mixing the activator liquid with the aggregator, wherein the activator liquid is a combination of alkaline elements mixed in a predefined ratio; wherein the alkaline liquid comprises of: a) dissolving a predefined quantity of sodium hydroxide pallets with a defined amount of water; dissolving the mixture of sodium silicate with sodium hydroxide and water in a defined ratio, and wherein the fly ash replaced with GGBFS in different proportions for various mixes as

* 10% GGBFS and 90% fly ash * 20% GGBFS and 80% fly ash

* 30% GGBFS and 70% fly ash.

9. The method as claimed in claim 8, wherein a wheel and load arrangement are made to create pressure on pavement, wherein the arrangement comprises of: a pre-determined load is applied to the wheel to create pressure; a gear box connected to at least an end of the wheel, wherein the gear box provides controlled rotation of the total wheel and load arrangement; and a pulley connected to the wheel to regulate the speed of the wheel.

10. The method as claimed in claim 8, wherein the construction of the pavement is divided into at least 6 divisions, wherein at least 5 divisions have different proportion of the mixture with a geopolymer concrete and at least one division is a mixture with a Cement concrete.

FIGURE 1

FIGURE 2

FIGURE 3

FIGURE 4

FIGURE 5

FIGURE 6

FIGURE 7A FIGURE 7B

FIGURE 8

Intitial Final 700 600 500 Setting Time (min)

400 300 200 2021101075

100 0 F90G10-0.4 F80G20-0.4 F70G30-0.4 F80G20-0.45 F70G30-0.45 OPC M1 M2 M3 M4 M5 M6

FIGURE 9 160 Slump cone Value (mm)

140 120 100 80 60 40 20 0 M1 M2 M3 M4 M5 M6 Mix proportions

FIGURE 10

60 28 Days 60 Days Compressive Strength (MPa)

50

40

30

20

10

0 M1 M2 M3 M4 M5 M6 Mix Proportions

FIGURE 11

28 Days 60 Days Flexural Strength (MPa) 10 8 6 4 2021101075

2 0 M1 M2 M3 M4 M5 M6 Mix Proportions

FIGURE 12

FIGURE 13

FIGURE 14

FIGURE 15

FIGURE 16A FIGURE 16B FIGURE 16C

FIGURE 16D FIGURE 16E FIGURE 16F

FIGURE 17

FIGURE 18

FIGURE 19A FIGURE 19B

FIGURE 19C