A review of Enhancing Abrasion Resistance of Dry Geopolymer Ramie Fiber Composite Mortar in Hydraulic Structures

Hydraulic structures, such as dams, spillways, and tunnels, suffer from severe abrasion and erosion due to the continuous flow of water and particles carried away. Such damage will result in expensive operating and maintenance of hydraulic structures. The purpose of this review is to discuss various abrasion testing methods as well as various efforts enhancing abrasion resistance, such as adding silica fume, and fibers, improving quality, and using geopolymers. In conclusion, the development of dry geopolymer methods offers great potential for use because they are more practical than wet geopolymer systems, however, the brittle nature of geopolymers is a weak point, which can be addressed by adding composite materials, such as ramie fiber. With the expectation that the matrix of composite geopolymer mortar with ramie fiber will have good abrasion resistance. Further research and development are needed to address existing challenges and establish this innovative construction material as a viable solution for sustainable hydraulic applications.


Introduction
Bridge pillars, dams, spillways, piers, canal pipes, irrigation canals, tunnels, and stilling basins often receive high-speed streams of sedimentary water.Damage to the surface of concrete structures from sediment-containing streams over time can cause damage that can reduce service life [1].Understanding the various causes of abrasion on concrete surfaces is important to maintaining hydraulic structures.Water and sediment flow speed, angle of impact, exposure period, aggregate quality, and abrasion resistance of the concrete surface.Due to severe climate change causing large amounts of CO2 in the atmosphere, researchers are looking to reduce the use of Portland cement binders.After water, the second most common material used worldwide is Portland cement.Like steel and aluminium, OPC uses a lot of energy during its production, according to Akashi, OPC produces 325 kg/ton of CO2 gas from combustion, 525 kg/ton from lime calcination, and 50 kg/ton from electricity. 1 ton of OPC produces 0.8-1 ton of CO2 gas.Many researchers are looking for binders to replace Portland cement to reduce the impact of environmental damage and climate change.Geopolymers are potential binders that can be used, but their brittle nature requires further handling by adding composite fibers to the geopolymer matrix [2].

Erosion
According to ACI 210 R, cavitation, abrasion, and chemical reactions cause erosion [3].Cavitation occurs when steam bubbles rupture due to pressure changes in high-speed water flow into surface cracks, and abrasion erosion occurs where concrete in hydraulic structures collide with sand, mud, gravel, or sedimentary remnants in the water so that the surface becomes worn, is a major cause of erosion.Chemical attack results in worn hydraulic concrete surfaces.Hydraulic structures will have a long service life if properly designed, built, operated, and maintained.Abrasion erosion damage arises because the surface of hydraulic structures does not have good abrasion resistance to abrasive materials.A chemical reaction occurs when compounds included in Portland cement are exposed to saline and acid solutions.The presence of acidic conditions has the potential to cause damage to concrete or masonry surfaces as shown in Figure 1.The phenomenon of hydrogen sulfide corrosion, which can be classified as a type of acid attack, is often observed in septic sewage systems.

ASTM Standard test
According to the ASTM C1138 standard, Abrasion resistance testing is an underwater test type.It is done by simulating abrasion produced by sand and debris floating in water.The equipment used in the experiment consisted of a stirrer, a stirring rod, and a steel pipe.Seven steel abrasive balls of various sizes as a means of colliding with each other, causing wear on the subtract surface.The arrangement of distributed test equipment is shown in Fig. 2. A stirring mechanism is used to circulate water in the experimental tank; Its rotation is powered by an electric motor that rotates at 1200 rpm.The steel ball generates a frictional force against the concrete surface due to the movement of water in this rotary motion, which has an abrasive effect.There are a total of six timed parts for this test.
Abrasion evaluation using sandblasting method according to ASTM C418 is used to determine how well concrete will withstand abrasion.The purpose of the test is to determine how much damage is caused by particles in water and how much is caused by the movement of particles across the concrete surface.
ASTM C779 uses three independent methodologies to measure the degree of abrasive damage to horizontal concrete surfaces.The abrasive loads applied to concrete surfaces during the studied procedure range both in magnitude and composition.Using drill or cast samples, ASTM C944 standard provides a testing technique for determining the durability of concrete and mortar.The methodology used in this investigation is very similar to ASTM C779.This method has been put to good use in the assessment of concrete sleeper constructions that receive vehicle loads on roads and bridges.

Indonesian SNI 3419 2008
This standard test is used to obtain a standard abrasion coefficient.Concrete samples are cast with a size of 15x30x6 cm.Each sample test is carried out 6 samples The test is carried out with abrasion test equipment such as in the image with a speed of 85-90 rpm for an hour.Then the sample is dried and weighed.This step is done three times.The Indonesian apparatus SNI 3419 2008 as can be seen see figure 3.

Non-Standard Test
The waterborne sand test is a non-standard method developed by Liu et all [4] that measures the lost of concrete surface.The information presented shows that the test area measures 2500 mm x 1800 mm x 1500 mm and is made entirely of steel.One-third of the total volume of the reservoir is filled with water.Water mixed with abrasive sand particles (size 5 millimetres, density 400 kilograms per cubic meter).The rotating propeller always mixes the particles with water and then sucks them with a pump.The flow of water and particles is rotated continuously, using four existing pumps.A tube with a nozzle 200 mm x 10 mm in diameter receives the pumped mixture.The concrete test slab can be above or below the nozzle.A concrete test plate of 200 square mm, 50 mm thick is located 20 cm below the nozzle.Typically, a contact angle of 45 degrees is used between the combination of water and sand jets and concrete test plates.Sand waterborne apparatus as can be seen in Figure

Factors affecting abrasion resistance.
Many factors affect how resistant it is to abrasion on the surface of hydraulic structures.The characteristics and material composition of concrete, compressive strength, and tensile strength, as well as elements related to the properties of water particles, such as flow direction, angle of effect, shape, and hardness, can provide resistance to abrasive impacts on the surface of the structure [5].
Cavitation damage can be significantly reduced by optimal geometry design.Design of hydraulic structures capable of adjusting the flow of water by dividing energy due to collisions.
Increasing the Compressive strength of mortar is a potential approach to increasing abrasion resistance.Horszczaruk added Fibers to the mortar matrix to increase its resistance to abrasion.Related research on abrasion, test methods, material composition, and variations can be seen in Table 1.
Silica fume is a common material to improve the abrasion resistance of concrete.Silica fume is a pozzolan that fills the void in the matrix and completes the CSH reaction in Portland cement so that the mortar has a small porosity and increased strength as can be seen in Fig 5 .In addition, the use of aggregates with good hardness is a key component that affects the abrasion resistance of hydraulic structures.The addition of steel fibers can increase the impact resistance of concrete on concrete surface cracks.
[11] Concrete rotatingdrum abrasion device Short straight steel fibers and fibers with medium hook ends have good abrasion resistance to debris flow.
[12] Concrete Home-Made Test Apparatus A 3D scanner is used to obtain an abrasion cross-section.

Geopolymers
Geopolymers are solids that exhibit hardness like natural rocks.These materials are produced from abundant natural sources containing high concentrations of aluminosilicate, such as fly ash, slag, kaolinite, silica fumes, andalusite, mica, rice husk ash, and various other substances.Activator is an alkaline component containing hydroxide and sodium silicate, Previous studies have shown that certain raw materials, such as fly ash, and slag, have higher compressive strength compared to other materials The formation of this structure occurs as a result of the chemical bond between polyciliate (Si-O-Al-O)n and polysialate siloxo (Si-O-Al-O-Si-O)n, which is produced through hydrothermal processes.

Materials
Geopolymers are derived from reactive aluminosilicate precursor materials.Sources of these materials can include industrial waste and natural resources.Solid activators are used to produce alkali metal cations (Na + , K + ) or alkaline earth cations (Ca 2+ , Mg 2+).The cation in question initiates the degradation of the Si-O-Si and Al-O-Al bonds present in the precursor, causing the dissolution of silicon and aluminium.This process then goes to the bonding phase, which contributes to the overall strength of the material.Solid activators are widely used in the manufacture of geopolymer matrices of systems dry and derived from natural and manufactured sources.[13]

Mixing System
Geopolymer mixing techniques in general can be divided into two, namely wet system mixing which uses a combination of aluminosilicate as a precursor and alkaline solutions with a certain composition.
In another dry technique, silica-aluminium precursors and solid activators are combined and then crushed into a powder resembling Portland cement.According to previous research, the concepts of dry geopolymers and wet geopolymers can be seen in figure 6.

Fiber reinforcement Composite
The addition of Fiber to the geopolymer matrix significantly increased abrasion resistance.Mechanical degradation processes, such as concrete surface wear caused by water particles and matrix separation through cracks, can be effectively controlled by the addition of Fibers, Previous research has used a variety of Fibers, including basalt, carbon, PVA, steel Fiber, but no one has ever used ramie.Ramie fiber as a sustainable material has excellent tension strength as shown in Table 2 and Figure 7. Table 2. Ramie Fibers chemical and mechanical properties [15].

Material Preparation
According to the previous research, some aluminosilicate needed pretreatment steps.Such as Ball milling and calcination consistently produce the highest activation levels among the several common preprocessing techniques listed in Table 3.
Increase the reactivity of alumino silicate by destroying the particle structure by increasing the amorphous phase.

Thermal
Increasing the temperature alters the mineral's phase, causing the longrange ordered structure to collapse and giving rise to an amorphous state that enhances reactivity.

High reactivity, increases emission
Hydrothermal Alumina silica and activator heat up until 200 celsius and then crushed Low carbon emission

Mix Design Dry Geopolymer
The mixing design of dry geopolymers is almost the same principle as wet system geopolymers, considering variables: the water to binder ratio (liquid to solid), the ratio of activator to precursor, molar ratio of main elements (such as SiO2 / Al2O3, Na2O / SiO2) [16].In previous studies, normal geopolymers perform best when the molar ratio of SiO2/Al2O3 is between 3.3 and 4.5, while dry geopolymers are optimal when the ratio is between 0.75 and 6.02.The mixed concept of dry geopolymer design can be seen in Figure 8.Since water consumption increases both during the fresh time and during the hardening time by decreasing mechanical characteristics, the value of the air/binder ratio predominantly affects the paste's hardening properties.Even though the geopolymer hardening time decreases with increased alkali content, a greater a/b ratio will influence workability.Si, Al decomposes and polymerizes to produce a binder in a highly alkaline environment.

Compressive Strength
Predictive equation to calculate Compressive strength according to a study by K. H. Yang et al. [17], From equations 1 -5 we can predict the compressive strength of dry mixing geopolymer, but it's not overcome the necessary of actual research (QA is the quantity of alkali, fc is compression strength, fsp is split tensile strength, λ, A is Constanta): ( 5 )

Durability
The composition of geopolymer raw material will affect on the shrinkage behavior, permeability, and porosity of the composite materials.While geopolymers have demonstrated exceptional resilience to sulfate and carbonation attacks, their resistance to frost has not been adequately studied.According to the study, inadequate hydration and internal structural damage led to a noticeably lower level of frost resistance when geopolymers were subjected to a temperature of -20 °C.To create compact microstructures and enhance frost resistance, the hardening temperature is raised [18].Using materials with smaller pores is important to increase performance due to the resistance of mortar and concrete.The quantity of pores in concrete and mortar is directly connected to their permeability.The type of precursor, the amount of activator or reagent, and the amount of water present are all factors that affect how the pores are structured, according to earlier studies.Slag and fly ashcontaining mixtures frequently exhibit increased pore densities when compared to mixtures that merely contain those two components.According to previous research, the type of precursor used, the amount of activator or reagent used, and the water content all influence pore structure.In comparison to combinations that simply contain fly ash, slag mixtures often have a denser pore structure.

Conclusion and future research
The damage on the surface of hydraulic structures occurs due to erosion caused by abrasion, cavitation, and chemical attack.Damage due to abrasion is the main factor causing damage to hydraulic structures, and after that cavitation and chemical attack.Efforts to increase abrasion resistance have been widely studied, namely: the addition of silica fume, modification of constituent aggregates, optimization of structural design, variations in cement water ratio, variations in concrete quality, the addition of composite Fibers with various types of Fibers and variations in composition, and the use of geopolymers.However, there has never been a study using dry geopolymers with the addition of ramie composite Fibers to enhance the abrasion of hydraulic structure, so further research is needed on geopolymer composite with ramie Fiber to fill the gap.

Figure 1 .
Figure 1.Abrasion on surfaces of hydraulic structure.

Table 1 .
Abrasion test material and method.
WorkabilityFlow table tests on geopolymer mortar are used to determine how alkali-binder ratios (a/w) and airbinder ratios (w/b) affect the performance of geopolymers.The w/b ratio is the most sensitive parameter. )