Efficient use of ceramic waste powder in Cementitious Grout for the Development of Sustainable Semi-Flexible Pavement Surfaces

Cement-based grouts are described as a liquid mixture with higher flowability that contains cement, additives, water, and a superplasticizer. Cement-based grouts can be utilized to fill minor voids and gaps in addition to repairing cracks in earthen structures to restore structural continuity. In most cases, structural grouting is used in conjunction with other strengthening methods like adding tie-rods or reinforcing meshes. Grout is usually used with semi-flexible pavement (SFP). SFP is a new pavement technology comprised of open-graded asphalt concrete with a high air void content that is filled by injecting special grouting materials. The goal of this research is to figure out what happens to the mechanical properties of grout when a proposed by-product is used as a supplement to cementitious materials. The specified grouts were made from cement, water, ceramic waste powder (CWP), and superplasticizer (SP). Scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) analysis were used to characterize the physical and chemical properties of the waste material after it had been crushed and finely ground. The pozzolanic behaviour of the material was evaluated by substituting ceramic waste for Portland cement at varying percentages (from 15% to 50%), and the modified grout was characterized through a variety of tests that included flow cone testing, as well as compression and flexural strength tests Based on the results of these tests, the best amount of CWP to use as a replacement for cement in terms of its mechanical properties is 20%.


1.Introduction
Environmental pollution is a severe issue that must be carefully solved in Iraq and worldwide.Recently, waste material is one important source of pollution in the atmosphere, water, and soil due to the growth of the industrial world [1,2].Cement dust is one of the causes of pollution in the environment, there are many cement factories in Iraq, such as Basra, Kufa, Muthanna, Kirkuk, Babel, and Karbala.etc. Increased demand for cement plants results in higher CO2 emissions, which circulate in the atmosphere as particles and block sunlight from reaching the Earth which circulates in the atmosphere as particulate and prevent sunshine from reaching the Earth, contributing to current global warming.To maintain the global trend towards sustainable construction materials, the demand for cement plants must be reduced by using waste materials or by-product materials as supplementary cementing materials to reduce the demand for virgin materials and increase the solid waste management.Using 45% of west material in HMA has a benefit environmentally friendly mix with lower expected Global warming potential, Eutrophication potential, and Acidification potential values for a 60-year analysis period [3,4].For this reason, we need to partially replacement of cement with a sustainable material in various applications, such as (concrete constructions, masonry mortar, plaster, grouting injection technology, etc.), in order to reduce cement usage.Engineers frequently utilize cementitious grouts to solve foundation issues including filling voids and maintaining the water tightness of subsurface soil.The use of cement grouts 2 in environmental areas for securing harmful and reduced radioactive wastes has grown.According to published research, grout can be used to solidify and stabilize burial waste ditches [5,6].Cement-based grouts are described as a liquid mixture with higher flowability that contains cement, additives, water, and a superplasticizer.A significant component of cement-based grout is the water to cement ratio (w/c) [7].Cement-based grouts can be utilized to fill minor voids and gaps in addition to repairing cracks in earthen structures to restore structural continuity.Usually, structural grouting is used in conjunction with other strengthening methods like adding tie-rods or reinforcing meshes.Particularly, the behaviour of crack repair by grouting is difficult in earthy materials and necessitates certain specifications for the grouting mortar.Grouts require good workability, minimal shrinkage, strong adhesion to the original material, compatibility with chemicals and machines, and longevity [8].Grout improves a surface's ability to withstand fire, reduces noise, protects against intrusion, withstands blasts, keeps out pests, stores heat, and serves as an anchor [9].Cement-based grouts may also be used in semi-flexible pavement (SFP), a new pavement technique that comprises open-graded asphalt concrete with a high air void content that is filled by injecting specialized grouting materials.The SFP demonstrates great rutting and shoving resistance, and it is built without expansion, contraction, or construction joints.These innovative pavement materials have the flexibility of asphalt pavements as well as the high strength (hardness) of concrete pavements [10].Cement paste grout differs from conventional pastes in that its fluidity, workability, and strength are important properties that must be evaluated to obtain satisfactory SFP mixes.Cement and water are the two primary components of cementitious grouts, which may or may not also include sand and other substances.The admixtures are added to the grout to increase its flowability, permeability, and strength.Superplasticizer (SP) is the most commonly utilized component in grout mixtures.If you use sand, you'll need more water and a superplasticizer to obtain the best workability [8,9].Superplasticizers based on carboxylic acids or polymers are more effective at countering the fluidity introduced by the sulphonated naphthalene formulation, which depresses the cementitious particle.The amount of water in the grout has a significant impact not only on its fluidity but also on its strength [11] To test the fluidity of the grout, the flow cone method is commonly used; according to this method and previous researchers, the flow time should be between 11 and 16 seconds [12] Due to the high fluidity of the grouting material, flow times greater than 16 seconds may result in more voids in the SFP combination not being filled, whereas flow times less than 11 seconds may result in the impossibility of penetrating the grout material to voids in SFP mixture.In particular, the superplasticizer is one of the material types that is highly successful in enhancing grout fluidity.This study recommended a sustainable method in the design of SFP.A mixture of Portland cement, water, and superplasticizer with a portion of ceramic waste powder (CWP) as a partial replacement for ordinary Portland cement was proposed as a modified grout.The overuse of natural resources is posing problems for society and the environment.The use of alternative materials that were previously discarded as waste could help conserve natural resources.Around 11,200 million square meters of ceramic tiles were produced globally in 2011 and 2012 [13].According to life cycle analysis (LCA), landfilling materials rather than recycling or reusing them would result in significant environmental harm and a large carbon footprint.Globally, 75% of solid waste is made up of construction and demolition (C&D) waste, while 54% of it is made up of ceramic waste.This percentage covers ceramic floor tiles, wall tiles, bathroom tiles, and home ceramics.The process of dumping ceramic waste produces a lot of air emissions, which harm the environment and people's health by dispersing dust [14].It may be better to dispose of such garbage by using waste ceramic dust in cement grout.CWP can be used safely and cheaply cost to improve grout.As previously mentioned, employing ceramic dust has the advantages of being an affordable, ecologically friendly technique of collection and processing as well as a robust, long-lasting material in highway building facilities.Although there isn't a ceramic industry in Iraq that might produce a lot of trash tiles every day, many businesses import tiles from outside and sell them, which results in the production of broken tile waste during the entire process.In addition, a lot of tiles and ceramic trash is produced during the destruction of various buildings, and this garbage is not properly disposed-off.The environmentally responsible disposal of such garbage might be aided by the use of small amounts of ceramic in subway and road construction [13,14].As a result of this, the purpose of this study is to investigate the influence of the application CWP and SP on the mechanical properties of cementitious grout that are used in SFP.

Materials and Experimental Test Methods
Sustainable grout is made from the following materials:

Cement
Ordinary Portland Cement (OPC) (IQS 5 -CEM I 42.5 R ( 1)) has been used for this work.This cement was manufactured at the Al Samawah Cement Factory.Table 1 displays the results of ordinary Portland cement's physical and chemical properties.The results have been compared with the limits of (IQS No.5-19) [15] and (ASTM C150 / C150M-17) [16] specifications.

Super-plasticizer
The superplasticizer (SP)was procured by a construction manufacturer CONMIX in Najaf, Iraq (under the trade name "Mega Flow 2000").It is a high-performance concrete superplasticizer based on modified polycarboxylate ether.With a unique carboxylic ether polymer with long lateral chains, it is an effective cement dispersant and high-range water reducer compared to conventional superplasticizers.The recommended dosage is between (0.5-2) % by weight of cementitious material.Figure 1 shows the type of superplasticizer that it used in the study.

Ceramic Waste Powder (CWP)
Ceramic tile is the most prevalent kind of construction trash left behind from building and demolition projects.The ceramic waste was collected in Al-Diwaniyah, Iraq, from commercial companies and residential building waste.Broken waste tiles were placed in a plastic bag, collected, cleaned with a brush to remove any other contaminating minerals, and then hammered into little pieces.These pieces were then placed in a Los Angeles abrasion test machine to further reduce their size.After that, the waste was removed from the machine, grinding, and sieved through sieve #No.200.Figures 2 and 3 show ceramic tile powder and the preparation of ceramic waste powder, respectively The chemical and physical characteristics of CWP are displayed in Table 2. Figure 4 shows the scanning electron microscopy (SEM) results of irregularly shaped ceramic tile powder particles with smooth surfaces and sharp edges.Figure 5 shows the results of the energy-dispersive X-ray (EDX) analysis used to determine the chemical composition of the CWP.The CWP contains large concentrations of silicon dioxide and aluminum oxide (59.42 percent by weight), as seen in Figure 5, with lower calcium oxide, iron oxide, and antimony oxide concentrations.

Water
In the grout mixture, tap water is used as the liquid component.

Methods
The design of cementitious grout is summarized in three fundamental phases: the first phase identifies the optimal super-plasticize content, the second phase determines the optimal W/B content, and the third phase evaluates the effect of using CWP as a supplementary cementitious material.The first stage began with a W/B ratio of (30) % and SP percent values of (0.5, 1, 1.5, and 2) %, whereas the second stage began with a W/B ratio of (35, 40) %, and SP percent values of (1.5, 2) %.CWP is used as a cement replacement in the third stage at (15, 20, 30, 40, and 50) % with a W/B ratio of (40) %.The initial need for water is reduced because of the lower cement consumption and low water absorption capacity of CWP, resulting in a highly workable cementitious mix [17], the fluidity time decreases as the proportion of ceramics increases.The ceramic tile waste powder is useful for use with SFP surfaces because it does not cause initial hardening.As can be seen in Table 3, the fluidity decreases as the percentage of ceramic powder used to replace cement increases.Table 3 displays the results of the test matrix along with the identification of the grout mixture.

Preparation of grouts materials
The following procedures are used in the production of cementitious grout components: 1. Adding the superplasticizer to the water, mix it completely for 60 seconds and then allow it to rest for 30 seconds to obtain homogeneity.The dry materials (OPC and CWP) are well mixed by hand before being added to the mixture of (SP and water), which is then blended for an additional 60 seconds using a mixer.2. Testing the flow time of the produced mixture.
3. Prepare the molds by covering them with paraffin wax or glass paste to prevent grout material leakage.The grout is poured in two layers into a cube-shaped mold with dimensions of (50x50x50) mm and a prism-shaped mold with dimensions of (170x50x50) mm.To release trapped air, puddle each layer with a gloved finger five times.4. According to ASTM C 109/C 109M [18], the specimens are removed from the mold after two or three days, depending on their hardness.The curing of the specimens is done by spraying using material called "Set Seal 22" formerly known as "Setcrete 22,".It is a curing compound that is manufactured from chosen emulsified paraffin in order to generate a low-viscosity wax emulsion."Set seal 22" is a curing compound that is based on water.Set 22 is a milky white pigment with a milky liquid.It dries to a white coating that reflects between 60 and 80 percent of the sunlight, provided that the necessary coverage has been maintained.Set seal 22 is mostly used for cementitious surfaces, with the purpose of retaining enough moisture to ensure complete hydration of the cement.Figure 6 displays the steps of preparation for grout materials.

Grout test
To evaluate the cementitious grout in its fresh and hard states, two types of testing were proposed: 1.Fresh test (flow time test): The flow cone test, also known as the fluidity test, is used to determine the flow time of grout using a standard flow cone mold that conforms with ASTM C939 (ASTM, 2010b) [19].
2.Hard tests (hard-paste grout): Compressive strength tests at (7,14, and 28) days and flexural strength tests at (7,14, and 28) days according to ASTM C942-15 [20] requirements are adopted to evaluate the mechanical properties of the produced grout.Figure 7 displays the devices used to test the grout.

Results and discussions
The following results from tests for the flow cone, compressive strength, and flexural strength of fresh and hard grout are displayed: 8

Cementitious grout materials fluidity
Table 3 and Figure 8 show the flow time that was test used to evaluate the performance of the grout.According to previous studies, a flow cone test is conducted for several types of grouts to achieve a sufficient fluidity of (11-16) seconds [5,12] for appropriate grout injection into the SFP surface mixture.The presence of a superplasticizer has a substantial impact on the workability of cementitious slurries, regardless of the W/B ratio.The increase in the percentage of SP from (0.5 to 2) % increases the workability of cementitious grout.Increasing SP has a potent plasticizing impact that enhances grout mix flowability.These findings are consistent with previous studies [11,21].The acceptable flow time requirement for effective grout injection into the SFP mixtures is 11-16 sec., and none of the results from mixes 1-7 satisfy this criterion.The difference in the W/B ratio also affects the strength and flow characteristics of cementitious grouts.Table 3 illustrates that the high workability and fluidity of water in cement paste grout reduce the flow time from 32 seconds to 15 seconds when the water content is increased from 30% to 40%.The 40% of W/B can provide a more allowable flow time while still satisfying the limits of 11-16 seconds required for producing SFP grout in this study.In the third phase, the amount of ceramic tile waste powder affects how quickly fluidity occurs without requiring an increase in the W/B ratio.As shown in Figure 9, the higher CWP percentage improves the workability of cementitious grout due to the fineness of the CWP granules.

The grout's compressive strength
The results of the cubing test (50x50x50) mm at ages (7, 14, and 28) days for varying (W/B) are seen in Figure 10, and Figure 11 illustrates the results for various CWP replacement percentages.As seen in Figure 10, the grout with the maximum compressive strength for all ages was (40%) W/B grout, followed by (35%), (45%), and (30%) This might be connected to the quantity of water required for the cement hydration process, where the optimal value is 4 0%.It should be mentioned that the decrease in compressive strength with (0.3%) W/B in cement paste is due to insufficient water for appropriate cement hydration.Furthermore, the compressive strength decreased by (0.45%) W/B due to the presence of water, which will occupy the space if it does not dry out, and these voids will be obvious weak points in the cementitious grout.As a result, (0.4%) W/B can be used to produce cementitious grout in SFP.Figure 11 shows that CWP has replaced roughly half of the cement.Except for 50% replacement, all replacement percentages of CWP give a higher compressive strength than the control mix (the reference mix with 0% CWP).The compressive strength increased after 15% for the percentage of replacement (20% CWP followed by 30%), then the compressive strength decreased in percentage (40,50) % compared to the control mix.At 15%, the influence of the additional cementitious material remains negligible, and the pozzolanic reactivity remains low and incomplete.Figure 11 also shows that when CWP is substituted for 20% of the paste, the compressive strength increases.This may be due to the paste's denser microstructure as a result of the CWP effect.The formation of more calcium silicate hydrate (CSH) over time may also be responsible for the increased grout strength observed with (20 and 30%) CWP.This happens as a result of the hydration process of cement when reactionary pozzolan silica reacts with the calcium hydroxide crystals ''Ca (OH)2" (also known as portlandite) that are formed.
The CWP composition can react with the portlandite produced during the hydration of Portland cement to produce cementing compounds via the pozzolanic reaction, as suggested by previous research [22].The SEM image in Figure 12 shows a high concentration of CSH crystallite particles in the hard paste, which has colloidal dimensions and a tendency to cluster.The CSH makes up 50-60% of the volume of solids in a completely hydrated portland cement grout, and increasing it in the grout material leads to an increase in compressive strength.The ceramic waste powder accelerated the pozzolanic reactions, resulting in a large amount of CSH gels.With more CWP replacement, the compressive strength drops by more than 30% at curing ages.This could be because the compounds that make up CSH are diluted by the interconnected micropores that cause poor microstructure, which slows the setting and hardening of the cement composites.Along with this, a drop in compressive strength was seen to agree with [17,23,24].

The grout's flexural strength
Figure 13 displays the curing times for the (170x50x50 mm) prisms at 7, 14, and 28 days for different W/B ratios, and Figure 14 displays the curing times for the (170x50x50 mm) grout prisms at different water-to-binder (W/B) ratios and with different CWP substitutes.The results of flexural strength were similar to compressive strength when the percentage of CWP was changed.The presence of water caused a large number of voids in the grout structure, reducing its ability to withstand flexural loads.The correct CWP ratio simultaneously produces more CHS gels through its pozzolanic action, enhancing flexural strength and maintaining hydration products.The finer crushed ceramic granules compared to cement, as well as their uniform distribution inside the prism, improve grout fracture resistance and thus have a positive effect on the denser microstructure of cementitious grout, as shown in Figure 15.For all different replacement ratios (15%, 20%, 30%, 40%, except 50%), the flexural strength of CWP prisms indicated higher strength values as compared with control prisms (reference prisms).Therefore, the optimal grout for the SFP combination is created when SP is 2%, with a 40% W/B ratio and 20% CWP as a cement replacement.

Conclusions
The goal of this research is to determine the addition of CWP and SP affects the mechanical properties of grouts used as sustainable supplementary cementitious materials in SFP surfaces.The following is the primary conclusion: • Replacement of cement with CWP can lead to reduced CO2 emissions in the cement dust industry and simultaneously reduce environmental pollution.• The initial need for water is reduced because of the lower cement consumption and low water absorption capacity of CWP, resulting in a highly flowable cementitious grout.• The recommended acceptable range for grout fluidity, which is between (11) and ( 16) seconds for SFP was achieved in mixtures containing 2% SP and 0.4% W/B.• SEM revealed the CWP showed high pozzolanic reactions, which produced a large amount of CSH gels.• According to the results of the compressive and flexural strength test, 20% CWP substitution of cement is the optimum percentage in terms of mechanical characteristics.• Utilizing CWP to replace cement reduces costs and can avoid some environmental risks.and represent the best solution for the disposal by-product of ceramic waste by recycling it.

Figure 5 .
Figure 5. Outcomes of the energy-dispersive x-ray (EDX) analysis of CWP.

Figure 6 .
Figure 6.Steps of preparation for grout materials.

Figure 8 .
Figure 8. Results of flow time test of cementitious grout.

Figure 14 .
Figure 14.The flexural strength of grout with various percentages of (CWP)% replacements.

Figure 15 .
Figure 15.Section of the fractured prism at 7-day age.

Table 2 .
The chemical and physical properties of CWP.

Table 3 .
The fluidity test matrix.