A Review on Stabilizing Clayey Soil Using Waste Materials

Infrastructural development on unstable clayey soil has resulted to the damage of buildings and roads, the loss of lives, and financial instability in many projects including both vertical and horizontal structures due to the incapability of clayey soil to withstand certain magnitude of loadings. Furthermore, the deposit of materials that are left-over in open areas has also become an environmental challenge for residents in many communities. This review elaborates on the effect of waste materials—SDA (sawdust ash), FA (fly ash), and RHA (rice hush ash)—on the shearing strength of clayey soil as agents for stabilization. The study covers significant books on stabilizing clayey soil with additives as well as high indexed research articles that were published from 1998 to 2023. The findings show that, mixing the ash of sawdust with natural clay soil at the peak values of four (4) percent to seven point five (7.5) percent carries up the UCS (Unconfined Compressive Strength), the MDD (Maximum Dry Density), the CBR (California Bearing Ratio), and lowers the soil’s swelling, Optimum Water Content or OMC and Liquid Limit (LL). Similarly, the mixture of FA and clay soil at the optimum values ranging from 9 to 25%, raises the clayey soil’s UCS, MDD, and CBR while lowering its swelling potential, OMC, and LL. Additionally, the UCS, MDD and CBR increases, and the swelling, OMC, and LL reduce at the optimum value of added rice hush ash ranging from 10 to 20%. Thus, it is established that the addition of sawdust, fly, and rice hush can enhance clayey soil’s engineering properties.


1.Introduction
Soil is the accumulation of naturally occurring mineral subdivisions which mass may encompass water, air, organic materials and are readily detached in to relatively small fragments due to weathering [32].For engineering purposes, soil can be classified based on their grain size as course grainedcohesionless or fine grainedcohesive (Figure 1).Civil engineers around the world today are concerned about the improvement of cohesive soil because of its low strength behavior in terms of load bearing [36].Cohesive soils are sediments (clays or silts) that demonstrate shear softening behavior when subjected to load because of their water absorption and particle attraction which allowed them to deform plastically at varying water content [31].Clayey soils frequently have weak strength properties as shown in -Table 1, and present substantial building challenges that cause significant settlements that are harmful to structures built on top of them [1].Construction of infrastructures on un-stabilized expansive/clayey soil has contributed to the loss of properties, lives and causes financial instability in many homes today [2].In order to help mitigate some of those live threatening issues, engineers have introduced several methods of improvement or stabilization of cohesive/expansive soil by adding additives and bounding materials like cement, lime etc. for load bearing [3].The process of improving 1327 (2024) 012001 IOP Publishing doi:10.1088/1755-1315/1327/1/012001 2 the soil's qualities for numerous uses, including agricultural, geological, mining, different types of foundations, roads, etc., is known as soil stabilization, and this is considered when the available soil is not good enoughexpansive soilto with stand various conditions of loadings [33].However, this comprehensive review is done in order to elaborate on the usage of waste materials for stabilizing clayey soil.RHA, SA, and FA are the wastes used for stabilization for this paper.It is noted that those materials are preferable in terms of cost [4]; and they also save the environment from pollution in terms of their disposal [5].Sawdust are made from the processing of wood for construction and other industrial purposes, and increases the undrained shear strength of clayey soil when added [6] Saw dust is a byproduct of sawmills created when cutting wood.Loose debris or wood chips are produced when cutting wood into valuable pieces.They are created in different countries around the world due to the significant use of wood for construction and industrial purposes [13].It is then transformed into ash by burning at normal room temperature.The burning of sawdust and the resulting sawdust ash are shown in Fig. 2 [14].Fuel combustion process especially cool, produces fly ash (particle discharged) (fig.3), and it is considered as a material that is a non-plastic silt.It is used as a substitute to conventional materials in the erection of valuable buildings and roads in the field of geoenviromental and geotechnical engineering, and controlling swelling resulting after alkali-silica reactivity [8].With expensive landfill disposal and environmental health issues, FA is also an environmental danger that arises due to burning remnant fuels connected to the production of power [19].Nearly 50 million metric tons of fly ash are produced in the US annually.There is no doubt about the posed significance challenge on the environment due to fly ash disposal as it relates to possible environmental degradation and land use.Therefore, there are considerable economic and environmental advantages to using fly ash effectively [20].One of the most common agricultural remains and left-over products produced by agricultural processing corporations is RHA.The addition of this waste material may increase the soil's dry strength.The burning of rice hush produces RHA.It is a by-product of both out-of-date and modern rice mills, which can be found in metropolitan or rural areas [25].Rice hush (RH) is formed every year, and around 100,000,000 (tons) are available each year for use in developing countries alone, as 50% of said amount are rice produced there each year [40].Nearly twenty percent of RH is particularly high in ash, which is 92-95% silica, very porous, lightweight, and has a very large exterior surface area.However, because of its porous structure and difficulty in handling and transport, a significant portion of RH is disposed in landfill sites as garbage.Therefore, increasing RHA usage has a huge potential for waste management as well [26].The main mineral in rice hush ash that help increase the strength of soil is Silica [10].The black High-carbon ash, grey low-carbon ash, and white/pink carbon-free ash are the three different forms of RHA.The silica in the ash undergoes a transition that is related to the degree to which the burning process was completed at burning temperature and time [39].The ash's pale color indicates that it contains more silica and less carbon than usual.As opposed to crystallized silica, amorphous silica is better suited for pozzolanic reactions [27].Using those waste materials will help minimize the cost of construction on expansive soil, save the environment from the improper disposal of the mentioned waste materials and strengthen the load withstanding potential of the soil to enable both vertical and horizontal substructures to be constructed for the benefit of mankind.

2.Results and Discussion
With the indication of both physical and chemical properties in table 1, the natural engineering properties of clayey soil are not strong enough to help the soil bear certain loadings because of its high water holding capacity (about 70% -80%) when pressure is not applied [37], and this leads to a change in volume when load is applied and may cause expansion that leading to structural failure if not properly stabilized.Table 2 compares the natural clay soil with the addition of the optimum percentages of Sawdust Ash, Fly Ash, and Rice Hush Ash separately to the properties of natural clay soil.With the application of those materials, many authors have proven that they improve the UCS of clay soil which is a major parameter.2020) shows an increase in the UCS from 0.266 to 0.301 after the addition of ten percent of Rice Hush Ash as indicated in table 2. With those analysis, it is shown that the use of those waste materials are applicable in the stability of clayey soil for engineering construction both vertical and horizontal infrastructures, and improves the permeability of the clayey soil.Those materials have not only been noted academically but also they have been applied in the real-world civil engineering constructions.For example, the Kentucky Transportation Cabinet (KTC) worked to increase clay soils' bearing capacities when they were wet in the 1980s, and effectiveness in chemical stabilization was discovered.About fifteen years ago, Penn DOT District 3 demonstrated how to control fly ash fugitive dust by simply using a self-propelled asphalt paver with a crawler track to apply fly ash that had been moisture-conditioned.Applying 6% fly ash by dry weight soil and this technique produced a layer that was roughly 2 inches deep on Penn DOT SR-283 [38].

UCS N/MM2
the initial point -1.81 g/cm 3 with 4, 8, and 12% been added [17].The CBR also increases after observing the increase of sawdust at different percentages.The mixture of 2, 4, 6, and 8%, the CBR increases from 3.86% to 4.62, 5.45, 8.43 and 10.15% [18].This waste material is considered as a stabilizing agent because of its properties as shown in table 1 and 2.

Fly Ash
Fly ash is noted for the improvement of clayey soil by reducing the level of swelling [7]; moisture content [8]; and increase the soil's UCS [2].Not only that fly ash improves clay soil, using rice hush ash also increases the Unconfined Compressive Strength of clayey/expansive soil [9]; It decreases the MDD as well [10].It is recorded that the clay's geotechnical property mixed with FA content improves its strength for construction purposes [21].Combining 25% fly ash with the clay decreases the index of compression (Cc) and swelling index (Cs) from 0.270 and 0.046 at 28 days curing to 0.123 and 0.015 [22].On the other hand, the California Bearing Ratio increases with addition of 15% fly ash from 1.612 to 3.22 [1].The Angle of Internal Friction (AIF), UCS, and the Coefficient (Ce) were improved after combined mixture of FA and clay at 46%.The Ce and AIF of the soil increases to 0.395kg/cm 2 and 30 o 38' at mentioned 46%.When the FA content increases, it also gives rise to the increase in cohesion value [35].Not only that, 20% fly ash mixture increased the UCS -24.73Kpa to 63.38Kpa respectively and the maximum dry density -1.77g/cm 2 to 2.02g/cm 2 [23].Considering the above rice and fall in the geotechnical properties of the studied soil, it is clearly indicated that FA enhances the clay's shearing ability for construction purposes.

Rice Hush Ash
The MDD and the CBR are improved if RHA is added.With the mixture of 12.5% decreases the MDD and increases the CBR from 13.20 KN/m2 and 3.03% to 12.9 KN/m2 and 6.39% [28].Moreover, 5% RHA decreases the water absorption rate from 7.6% to 7.42 while some level of decrease was observed in the loss of ignition and the specific gravity -1.64% and 1.93% to 1.98% to 2.07% [29].It has been seem that utilizing this material on a broad perspective in the engineering field will aid considering the wellbeing of structures, increase its life span, lower cost for stabilization, reduce the ecological trouble that unused waste causes, and help farmers raise some funds as it aid the production processes [30].

3.Conclusion
SDA, FA and RHA increase the load bearing ability of clay considering the following perimeters; • The UCS increase greatly after adding 4% SDA and decreases the liquid limit at 5%.As more sawdust is incorporated into the soil, the treated soil's ability to swell decreases.The MDD was observed to have reduced as OMC increases seeing SDA content increment.• Looking at the load bearing ability, the improvement of the Ce and AIF of FA mixed soils was greatly aided at 46% FA.As indicated (Table 2), it is clearly shown that FA enhances the strength of clay soil for construction purposes.• It has been seem that applying RHA on a large scale in geotechnical properties of clayey soil upturns the CBR, UCS, MDD, OMC and drops the swelling potential; It aids considering the wellbeing of structures, increase its life span, lower cost for stabilization, reduce the ecological trouble that unused waste causes, and farmers raise some funds as it aid the production processes.
Hence, the usage of all the three waste materials are beneficiary the bearing capacity of clayey soil in terms of load bearing.However, the UCS of FA is seem to be higher as compared to SDA and RHA as indicated in fig 5.

Table 2
shows the outcomes of three major authors after adding optimum values of SDA, FA, and RHA to the engineering properties of natural clay soil.The result from Butt, W. A., et al (2016) as indicated in table 2 shows an increase in the Unconfined Compressive Strength from 0.248 to 0.313 after the addition of four percent Sawdust Ash, Phanikumar, B. R. (2009) result shows an increase in the UCS from 0.19 to 0.34 after the addition of ten percent of Fly Ash, and Oyediran, I. A., & Ayeni, O. O. (
Comparison of UCS of SDA, FA, and RHA mixed with clayey soil2.1 Sawdust AshMixing the ash of sawdust at an optimum percent improves the engineering properties of clay.It is noticed that the Unconfined Compressive Strength of the clay soil increase greatly after adding 4% SDA from 39.2KN/m 2 to 169.23 KN/m 2 .With the mixture of (two, four, six, eight and ten percent) SDA, the UCS fluctuated in increasing and decreasing orders -38.5, 169.23, 98.30, 52.43, and 74.92KN/m 2