ENHANCEMENT OF THE CLAYEY SOIL STABILIZATION PERFORMANCE OF BY USING OF POTASSIUM CHLORIDE

CONCLUSION

• Cast earth is a technique suitable to be applied for low cost building beside compressed earth and rammed earth, and requires less hand labor than compressed or rammed earth.
• Pourable earth properties for clayey soil such as flowability and expansion were improved with chemically treatment of soil with 7% KCl.
• KCl has additional function in increase the compressive strength values.

• 58Egypt. J. of Appl. Sci., 35 (3) 2020

  The old restriction for swelling clay content in soil for earth building must be removing as result of presence of chemical compound which can be inhibit clay swelling.

ENHANCEMENT OF THE CLAYEY SOIL STABILIZATION PERFORMANCE OF BY USING OF POTASSIUM CHLORIDE

Ahmed H. Hassan ¹

1Chemistry Department, Faculty of Science, Helwan University, Cairo, Egypt

E-mail address: hassannr90@gmail.com

Key Words: Pourable earth, clayey soil, clay swelling inhibitors

ABSTRACT

This paper is part of a series of investigation carried out on aspects related to the performance of cast earth with a clayey soil, the third option for construction with stabilized soil beside the compression and ramming. A soil composed of 14% clay, quartz and calcite, is stabilized with 10% Portland cementwith soda lime glass powder (GP) as cement replacement materials. Different dosages from polynaphthalene sulphonate superplasticizer are added to gain the soil pourable properties. The effect of potassium chloride (KCl) on the swelling properties of clayey soil is studied to enable the stabilization of the clay-bearing soil with cement.The results show that the 7% KCl clay-swelling inhibitors reduce the expansion of the soil by ~25% with a maximum increase in the 90-day compressive strength of 18%.

1- INTRODUCTION

Earth construction is well known since decades. It is common in regions with muddy soil stabilized by variable materials to reduce expansion while avoiding its exposure to water.Soil in desert areas is sandy and contains often swelling clays. Its stabilization with conventional cement or pozzolanic materials is limited due to the presence of clays [1]. Compressed earth blocks [2-3] and rammed earth [4-6] are available techniques for the erection of buildings with different types of soil; the methodology of cast earth was explored lately in a numberof works. It required less hand labor than compressed or rammed earth.  [7-13]. National codes are available for construction with compressed and rammed earth [14-15] but no specifications are yet published on cast earth.

The concept of cast earth was primarily explored in 1978 by Turkish researchers who stabilized soil with gypsum and called it the "ALKER” [7]. The concept was patented by Lowenhaupt in 1993 [8]. In general constructions with cast earth stabilized by gypsum are not common because of the susceptibility of gypsum to water [8-10]. The high solubility of theses phases in water makes their utilization risky and their application should be accompanied by strict precautions.

A new approach for soil casting was developed to obtain durable constructions similar to ready mix concrete. It deals with the production of water resistant building units from casting flowable soil stabilized by binders  preferably  containing  the  least  amount  of  Portland  cement  with  suitable  hydraulic and/or latent hydraulic wastes such as silica fumes, fly ash, rice husk ashes, or ground glass. The fluidity of the stabilized soil is gained from superplasticizers. Pourable earth produced in this way is durable, water resistant and cost effective with comparable properties to plain concrete while taking all precautions against chemical attack [11-13].

On other hand cast earth techniques is possible in presence of up to 5% clay but becomes unworkable with high clay content. Superplasticizers do not have significant effect in casting clay-bearing soil/cement mix [11].

Earth construction with clayey soil was stabilized by variable materials to reduce expansion, and exposure to water must be avoiding and need to specific arthritically design to protect them.

2- EXPERIMENTAL WORK

The clayey soil, used in the present work, was provided from MersaMatrouh, at the western side of Egypt. The as-received clayey soil was passed 2.5 mm sieve and its particle size distribution was determined using sieve analysis and hydrometer according ASTM C136-19 and ASTM C 837-81 respectively[16-17]. The X-ray diffractogram, Philips instrument model PW/1710 with monochromatic, Cu-Kα radiation (λ = 1.54056 A^°) at 40 KV, 30 MA and scanning speed 0.02^°/sec, is used to characterize the clayey soil. The sulfate and chloride contents in sandy soil were determined according to BS 1377 [18]. Its cation exchange capacity was measured using methylene blue method according to ASTM C 837 - 09 [19] as follows: 10 g of soil are placed in a 600 ml beaker. 300 ml distilled water are added and sulfuric acid up is used to adjust the pH 2.5 to 3.8. 5 ml of methylene blue indicator are added from a burette to the slurry, and stirred shortly. A drop of the slurry is placed on the edge of a filter paper. This procedure is repeated with 1.0 ml of the methylene blue solution until a light blue halo is formed around the drop indicating the end point.

A  soda–lime  glass  (GP)  obtained  from  broken  windows  was  used  as  cement  replacement material.  The  glass  was  crushed,  milled  in  a  porcelain  ball  mill  then  sieved  to  pass  80 microns. The chemical composition of the powder is shown in Table 1.

The clay swelling inhibitor reagent was supplied from Sigma Aldrishcompany: potassium chloride (KCl).1-9 wt. % of KCl was separately weighed relative to the weight of the clayey soil, and were dissolved in an amount of water equivalent to a water/soil ratio of 1:4. The reagent solution was gradually added to the soil while stirring in a mechanical mixer for 30 minutes. The resulting mixes were dried one day at 100^oC then finely ground in a porcelain mortar.

The optimum concentration of each reagent needed to inhibit the swelling properties of the clay for the investigation of the physical and mechanical properties of the soil were determined by two ways: 1) using the X-ray diffraction analysis technique to identify the effect of the inhibitor on the structure of the clay 2) by measuring the free swelling index according to the Indian standard (IS: 2720, Part XL, 1977) [20]. In this method 10 g of the dry as-received soil with particle size less than < 0.42 mm are added to a 100 ml graduate glass cylinder filled with distilled water and pouring an equal weight to a second cylinder filled with kerosene. The suspensions are stirred gently with a glass rod to remove the entrapped air, left 24 hours to attain the state of equilibrium and the volume of the soil in each cylinder is recorded. The percent of the free swell index is expressed according to equation 1. The procedure is repeated with the soil treated with the different concentrations of the swelling inhibitor reagents. The optimum concentration effective from the reagent used was the lowest value for the free swell index.

Free swell index (%)          (1)

Where;

V_d  = The volume of soil read from the graduated cylinder containing distilled water.

V_k= The volume of soil read from the graduated cylinder containing kerosene

A commercial polynaphthalenesulphonatesuperplasticizer (SP), Sika NN, was provided from the local market. Its pH-value was 7.1, had a density of 1.12 g/cm³ and a viscosity of 143 cps.

10 wt. % of cement replaced with 25% glass powder as cement replacement material was added to the as-received soil and to those treated with the optimum concentrations determined for the swelling inhibitors.The flowability of the mixes was measured in presence of 1, 2 and 3 mass%  superplasticizer  relative  to  the  weight  of  binder  by  means  of  the  flow  table  according  to  ASTM C230 / C230M  –  08 [21]; 2/3  of  the  water  was  shortly  mixed  with  the  solids  by  means  of  a  heavy  duty  mechanical  agitator  of  a  maximum  rotating  capacity  of  5000  RPM,  the  remaining  third  with  the  superplasticizer content were then added to the solid and further mixed for around 2 minutes.  The samples were allowed to stand for few minutes, remixed, poured to the cone of the flowtable and the cone was quickly emptied.  The initial slump was taken as the average flow diameter (in cm) and the slump loss with time was determined after 30, 60 and 90 minutes.  At the end of each time, the samples were remixed for 2 minutes, poured in the cone and the average flow diameters were recorded.

The length change was recorded at 3, 7, 14, 28, and 90 days according to ASTM C490-93a [22]. For this purpose, the cement/soil/superplasticizer mixes prepared from the as-received soil as well as from the soil treated with the optimum concentrations of the inhibitor reagents and the superplasticizer, were cast in 4x4x16 prisms, demolded after 2 days, and immersed in water throughout the measurements.

5x5x5 cm cubic molds were further used from these mixes to measure the compressive strength after 7, 28 and 90 days according to ASTM C109 / C109M–13 [23]. The samples were cured humid and kept covered up to the measurements

3- RESULTS

Figure 1 illustrates the X-ray diffractogram of the as-received soil and shows the presence of a significant amount of montmorillonite (M) with a main d-value line at 12.3 A. Calcium carbonate (CC) and quartz (Q) appear as main constituents in the diffractogram. The clay content in the soil determined by the hydrometer was ~14% and its cation exchange capacity was 23 meq/ 100 g of clay. The salt content was 1.32% SO₃ and 1% Cl. The particle size distribution is showen in figure 2.

Fig. 1: The X ray diffraction pattern for the as-received soil (M= Montmorillonite, Q= Quartz, CC= Calcium carbonate)

Fig. 2:The particle size distribution of the as-received soil

The oxide composition of the cement and glass powder (GP) as determined by means of X-ray fluorescence is given in Table 1, the respective phases evaluated according to Bogue equation are further shown in Table 2.

Table 1: The oxide composition of CEM I 42.5 N

Table 2: Phase content of CEM I 42.5N

Table 1 shows the chemical composition of OPC and glass powder. The result indicated that the glass is typical soda-lime type. In agreement with ASTM C618-12a [24], which requires a sum of SiO₂ + Al₂O₃ +Fe₂O₃ higher than 70% for good pozzolan, the sum for the investigated glass powder is higher than 75%. It can be classified as class N natural pozzolan and therefore, it is likely to produce good pozzolan. However, the chemical composition should not be used as the only criterion for prediction of the pozzolanic activity.

It has been confirmed by XRD, as shown in Figure 3, that waste glass powder is completely amorphous. Indeed, no peaks attributed to any crystallized compound can be identified except a broad diffraction halo, which is attributed to the glassy phase.

Figure 3: X-ray spectrum of glass

The pozzolanic reactivity of the glass powder was evaluated, Figure 4, as change in lime content over time. The lime-pozzolan mixture is prepared by mixing reactive lime and glass powder in ratio of 1:4 with few drops of distilled water and stored in well covered plastic bottles. The remaining portlandite content was determined chemically [25-26] in lime-pozzolan mixtures after several curing intervals.

The finger print infrared spectrogram of the PNS is shown in Figures 5. The bands appearing in the spectrograms can be described as follows: The sharp strong band present at the wave number ~3909 cm-1 is attributed to the vibration mode of free OH– group of water. The very strong broad band present at the wave number ~3454 cm-1 is attributed to the vibration mode of hydrogen bond of OH– group of water. The very  weak band present at the wave number ~2088cm-1 is attributed to an alkyne bond –C=C– bond. The appreciably moderate strong band appearing at~1634 cm-1 is attributed to conjugated band in naphthalene ring. The strong band appearing at ~1445 cm-1 is attributed to the -CH2 group. The medium band appearing at 1354 cm-1 is attributed to a mode of the alkyl sulfonatealk–SO3. The very strong and weak bands appearing at ~1122 and ~579 cm-1 are attributed to a mode of the inorganic sulfate group Na2SO4 present in the polymer. The very strong band present at ~1035 cm-1 is attributed to the S=O mode. The strong bands present at ~892 cm-1 and 829 is attributed to 1, 2, 4 tri substitution in benzene ring. The strong band appearing at ~685 cm-1 is attributed to =C-H bending.

Figure 4: Pozzolanic reactivity of the glass powder measured, as change in lime content over time.

         Figure 5: FTIR spectra of the polynaphthalene sulphonate superplasticizer

Figure 6 illustrates the effect of potassium chloride on the swelling index of the as-received soil. The results show a weaker inhibiting effect of the KCl. The minimum values recorded represent a decrease of ~20 upon treatment with 7% KCl and remain constant at higher dosages.

Figure 6: The effect of the KCl swelling inhibitor on the swelling index of as-received soil

Based on the previous results were obtained from swell index test, the soil treatment with 3, 7 and 9 wt.% potassium chloride (KCl) were chosen to be tested under X-ray diffraction device.

Figure 7 illustrates the change in the X-ray diffraction patterns of the as-received soil plotted beside those of the soil treated with the inhibitor reagents at a wider scale of the y-axis representing the relative intensity, to clarify the shift in the main d-value line of the montmorillonite phase.The d-spacing of the montmorillonite shifts from 12.3 A to 11.4 and 10.1 A⁰at 3 and 7% and remains unchanged at higher concentration of 9 wt.%. Treatment the soil with 7% potassium chlroide was found the optimum value for use in the following investigations.

Figure 6: The effect KCl on the X-ray diffraction pattern for as received soil

The superplasticizershows no significant improvement in the fluidity of the as-received soil/cement mix shown in Figure 7a; the initial flow diameter remains within 16 to 17 cm with increasing the superplasticizer dosage to 3%, and is retained for a maximum of 30 minutes.

On the other hand, the fluidity of the soil/ 7% KCl/ cement mix improves with increasing superplasticizer dosage [Figure 7b]. In this system, an increase of 18% is observed in the initial diameter with a highest value of 20 cm. The fluidity is well retained over 90 minutes undergoing a drop of 7%.

The length change of the as-received soil is seen to be clearly affected by 7% KCl and shows a decrease in of the expansion values by 25% after 90 days [Figure 8a]. The effect of 7% KCl on the length change and compressive strength of the soil is depicted in [Figure 8] KCl has the lower effect on the swelling property of the soil and the length change reduced by ~24% after 90 days (Fig. 7a). The compressive strength of the treated samples shows a maximum increase of ~ 20% with a value of3.3 N/mm² after 90 days. The rate of increase in strength declines slightly after 28 day

4- DISCUSSION

Cast  earth  is  realized  by  the  production  of  soil  with  enough  workability  to  allow  pouring. Stabilized soils are rendered fluid with suitable admixtures. This work deals with investingating some factors affecting the casting process of a clayey soil stabilized with 10% CEM I 42.5 N with glass powder as cement replacement materials; the fluidity being created by polynaphthalene sulphonate superplasticizers.

The soda lime glass powder type was chosen as cement replacement material because of its high pozzolanic reactivity and its low potential for alkali/silicate reaction[27-29].A maximum replacement level of the cement in the reference mix by glass powder was 25% to avoiding segregation which takes place at higher level [11].

In this system, the polynaphthalene sulfonate superplasticizer is more effective than the ploycarboxylate, due to presence glassy phase.Figure 3, postulated that waste glass powder is completely amorphous. Indeed, no peaks attributed to any crystallized compound can be identified except a broad diffraction halo, which is attributed to the glassy phase.It was suggested that the polynaphthalene sulphonate might adsorbed part of the admixture generating repulsion between cement and glass particles [11,30].

On the other hand, this paper represents a new approach for study the effect of swelling inhibitor reagent (potassium chloride) on clayey soil and studying their impact on pourable earth properties.

Clay minerals have a great influence on the chemical and mechanical stability of the soil stabilization.Most common clay mineral of semacite group is montmorillonite, the general chemical formula of which is (½Ca,Na)(Al,Mg,Fe)₄[(Si,Al)₈O₂₀](OH)₄.nH₂O. It is to be noted here that it contains nH₂O, which must be differentiated from the OH^-. While the former occupies the interlayer spaces, the latter occurs in the plane of non-bridging oxygens of t-sheets. Smectites can readily absorb water, and the H₂O molecules are accommodated in the interlayer vacant spaces. They form hydration shells around the interlayer cations. Single or multiple sheets of H₂O can occupy the interlayer spaces. As the number of H₂O sheets increases, the basal spacing also increases [30-31].

Osmotic swelling is the type of swelling for montmorillonite clay. Where the concentration of cations between unit layers in a clay mineral is higher than that in the surrounding water, water is osmotically drawn between the unit layers and the c-spacing is increased [32].

There are three ways to stabilize clay: ion exchange, coating of clay particles, and modification of surface affinity toward water. Due to small hydrated ion size and low hydrational energy, potassium ions can enter into the clay lattice and become fixed on the clay planar surface, and eventually reduce the interlayer spacing and ionically bonding clay layers together.Potassium salts ions penetrate into the interlayer space, creating a semi-permeable membrane, which prevents the water from entering the interlayer space [33-34].

In the present work, a d-spacing between the aluminosilicate layers of a hydrated montmorillonite appears at 12.3A due to the water uptake between the negatively charged layers. The d-value for montmorillonite with intercalated K⁺ion is shifted to 10.1A in accordance with the literature [34].

In the present system of cement stabilized soil using the polycarboxylate superplasticizer, both swelling inhibitor reagents used interact preferentially with the clay either through intercalation or physical adsorption giving space to the superplasticizer to increase the fluidity of the mixes. The absolute value of strength is moderate in this work due to the nature of the soil. Better improvement can be realized by partial replacement of the soil with sand or in soil of more siliceous nature.

5- CONCLUSION

• Cast earth is a technique suitable to be applied for low cost building beside compressed earth and rammed earth, and requires less hand labor than compressed or rammed earth.
• Pourable earth properties for clayey soil such as flowability and expansion were improved with chemically treatment of soil with 7% KCl.
• KCl has additional function in increase the compressive strength values.

• 58Egypt. J. of Appl. Sci., 35 (3) 2020

  The old restriction for swelling clay content in soil for earth building must be removing as result of presence of chemical compound which can be inhibit clay swelling.

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تحسین أداء تثبیت التربة الطفلیة بأستخدام کلورید البوتاسیوم

أحمد حسن عید حسن عوف

مدرس مساعد- کلیة العلوم -  جامعة حلوان

یعتبر هذا البحث امتداد لعدید من الدراسات المرتبطة بدراسة أداء التربة المصبوبة بالتربة الطفلیة والتى تعتبر الأختیار الثالث فى مجال تثیت التربة بجانب طریقة الضغط والدمج. تحتوى التربة المستخدمة على 14% طفلة بالاضافة الى الکوارتز والکالسیت ومثبتة بأستخدام الاسمنت مع الزجاج المطحون کمادة بدیلة للأسمنت. فى وجود نسب مختلفة من ملدنات البولى نفثالین الکبریتیة المسئولة عن تحسین سیولة الخلطة. تم دراسة تأثیر کلورید البوتاسیوم على الخواص التمددیة للتربة الطفیة لتمکین تثبیتها فى وجود الأسمنت. وأظهرت النتائج أن أستخدام  کلورید البوتاسیوم بنسبة 7% کمادة مثبتة للتمدد یؤدى الى أنخفاض تمدد التربة بنسبة 25% مع زیادة الصلادة عند 90 یوم بنسبة 18% .