DESIGN AND CHARACTERISTICS OF POLYMER BASED SODIUM SILICATE GROUT

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1 IGC 29, Guntur, INDIA DESIGN AND CHARACTERISTICS OF POLYMER BASED SODIUM SILICATE GROUT L.S. Thakur Lecturer, Applied Mechanics Department, Faculty of Tech. & Engg., M.S.U., Vadodara 391, India. K.S. Shah P.G. Student, Applied Mechanics Department, Faculty of Tech. & Engg., M.S.U., Vadodara 391, India. R. Murali PhD Student, Applied Chemistry Department, Faculty of Tech. & Engg., M.S.U., Vadodara 391, India. D.L. Shah Professor, Applied Mechanics Department, Faculty of Tech. & Engg., M.S.U., Vadodara 391, India. C.N. Murthy Professor, Applied Chemistry Department, Faculty of Tech. & Engg., M.S.U., Vadodara 391, India. ABSTRACT: Sodium silicate grouting improves ground stability by way of increase in strength and reducing permeability of treated soils. The present research intends to design an economical, non toxic chemical grout using sodium silicate, a watersoluble polymer and reactants/accelerators. Experimental study is carried out to find optimum dosages of chemicals employed to balance physical and engineering properties of grout. Unconfined and tri axial compressive strength test was carried out on selected raw grout, grouted mass and stabilized soil to study the stress-strain characteristics. The behaviour of different possible environment conditions on grout was studied by curing grout and grouted mass at different ph values, and also durability effect was studied by dry-wet cycles. Adherent wash out test was performed for optimum grouted mass to study permeability of sand after grouting. 1. INTRODUCTION The silicate grouts are best suited for treating fine sand with mean particle size ranging from 1 to.1mm, which cannot be handled by cement grout. The grouting technology has expanded with the addition of organic polymer solution and additives that can control the strength and setting characteristics of the injected liquid. The physico-chemical and mechanical properties of any chemical grout has been carried out considering characteristics of grout chemical permeancy, gel time control, temperature sensitivity, toxicity, low initial viscosity, water solubility and economic factor in addition to set strength. Engineering criteria to be used for grout evaluation are viscosity, setting time, penetrability, strength of set grout and grouted mass, durability and toxicity. Polymer based sodium silicate grout consists of sodium silicate, admixture and water. When the admixture is added into it, the condensation and polymerization starts. The admixture namely Polymer A, mineral acid and calcium carbonate which added to sodium silicate gave strength and solid gel. Gel time is controlled by adjusting the amount of admixture. 2. MATERIALS USED AND THEIR PROPERTIES The basic grout materials used in the investigation are: Sodium Silicate (SS) (Table 1) Polymer A (PA) Mineral acid (MA) Calcium carbonate (CC) The Bhadarpur sand passing through 425µ and retained on 75 µ is used for experiments. Soil used for the stabilization study is procured locally having properties as given in Table 2. The soil was dried, hand sorted to remove pebbles and vegetable matter being further dried, pulverized and sieved through a 425μ sieve for further use. Table 1: Properties of Sodium Silicate Constituents Percentage Na 2 O (% by wt.) SiO 2 (% by wt.) Na 2 O : SiO 2 1:

2 Table 2: Properties of Sand and Soil Property Value Sand (Fine Sand) Coefficient of Curvature.72 Uniformity Coefficient 2.17 Soil Liquid Limit 3% Plastic Limit 22% Optimum Moisture Content 14% Maximum Dry Density 1.81 gm/cc 3. GROUT PREPARATION Mix proportions selected for the present study are as shown in Table 3. Grout mixes are prepared at different concentrations and their physical and engineering properties are studied in detail. The grout mix which shows good strength and appropriate gel time is further studied for its durability at different environment conditions. The grouted samples are prepared in the laboratory by injecting grout under pressure in a cylinder filled with fine sand. The grouted mass in the cylinder is than cured till the grout sets. Grouted sand mass samples were then tested for unconfined and tri axial shear test at different time intervals. Stabilized soil samples were prepared by mixing the grout and pulverizing the soil in a tray and compacted in a mould at its maximum density. Unconfined compressive strength and CBR tests were performed on stabilized soil samples. Table 3: Proportions for Various Grout Mix Grout SS (%) PA (ml) MA (ml) CC (gm) A B C D RESULTS 4.1 Specific Gravity Figure 1 shows the plot of specific gravity with respect to various grout mix as mentioned in Table 3. It can be seen that the value of specific gravity increases as the concentration of sodium silicate increases. 4.2 Gellification Time Figure 2 shows the plot of gel time for various grout mixes used for the study. Carbonate and mineral acid concentration in the gel contributes to setting and hardening of the gel respectively. Variation of concentration of Polymer A did not show much change in the gel time. The polymer contributes towards the strength of the grout. Any further increase in sodium silicate concentration other than the suggested in Table 3 results in localized precipitation and causing the grout becoming unworkable. Figure 3 shows the variation of gel time with environment temperature for a given grout mix. Gel time (min) Gel time (min) Grout-A Grout-C Calcium carbonate (%) Grout-B Grout-D Fig. 2: Effect of Calcium Carbonate on Gel Time 38 C C 8 C Specific Gravity Fig. 1: Variation of Specific Gravity 389 Fig. 3: Effect of Temperature on Gel Time 4.3 Syneresis Syneresis is a measure of volume shrinkage of raw grouts under different conditions. Grout samples of the present research were cured under wet and dry condition for 28 days. Figure 4 shows the plot percentage shrinkage for various grout mixes. Dry condition shows higher percentage of shrinkage compared to wet curing for all the grout mixes. Grout D shows less shrinkage in wet and dry curing as compared with other grouts.

3 Percentage of Shrinkage 1% 8% 6% 4% 2% wet curing dry curing Grout-C % Fig. 4: Variation of Syneresis Fig. 7: Time-viscosity for Grout-C 4.4 Time Viscosity Characteristics Figures 5 to 8 shows time viscosity curve for all grout mixes. It is observed that for grout-a limiting injection time is 1 minutes with viscosity of 14cP and zero displacement time at 15 minutes with viscosity of 15cP, whereas for grout-d limiting injection time is 5 minutes at viscosity of 8cP and zero displacement time at 15 minutes with viscosity of 18cP Grout-D Fig. 5: Time-viscosity for Grout-A Fig. 8: Time-viscosity for Grout-D 4.5 Unconfined Compressive Strength Figures 9 and 1 shows unconfined compressive strength for grouted mass samples cured in dry and wet conditions. Samples were also cured under similar conditions as well as wet and dry cycles on samples cured using water at different ph values as shown in Figure 11. Peak ucs strength (kg/cm 2 ) Groutedmass-A Groutedmass-C Groutedmass-B Groutedmass-D 3 Days 7 Days 14 Days 28 Days Fig. 6: Time-viscosity for Grout-B Curing time (days) Fig. 9: Comparison of UCS Strength of Grouted Mass with Curing Time (Dry Cured) 39

4 Peak ucs strength (kg/cm 2 ) Fig. 1: Comparison of UCS Strength of Grouted Mass with Curing Time (Wet Cured) UCS strength (kg/cm 2 ) Groutedmass-A Groutedmass-C Groutedmass-B Groutedmass-D 3 Days 7 Days 14 Days 28 Days Curing time (days) Dry WET Alternate ph-7 ph-8.2 ph-9 Fig. 11: Comparison of UCS Strength for Grouted Mass-D at Different ph. 4.6 Time Strength Properties of Stabilized Soil Unconfined compressive strength of stabilized soil was carried out at different curing condition and is as shown in Figure 12. Dry cured samples show an increase in strength as compared to wet curing or alternate dry and wet curing. CBR test was also performed on stabilized soil in soaked and unsoaked conditions as reported in Figure 13. Virgin soil Dry cured Wet cured Alternate cured CBR Value mm 5 mm Virgin Soil Grouted Soil Virgin Soil Grouted Soil Soaked value Unsoaked value Fig. 13: Comparison of CBR Value of Virgin Soil and Stabilized Soil 5. CONCLUSION The polymer based sodium silicate grout shows improved properties compared to conventional grout. It improves flow and strength characteristics as well as durability of the grout at different environmental conditions. The polymer based grout shows higher performance due to the better gelling characteristics of the polymer that helps in the formation of network structures and thus improving the strength of the grout. Designed grout also shows good improvement in strength and CBR values when used as a stabilizing chemical. REFERENCES Graf T.E. (1982). Long Term Aging Effects on Chemically Stabilized Soils, Proc. Conf. Grouting in Geotechnical Engg., New Orleans, ASCE, New York: Koenzen J.P. (1977). Time Dependent Stress Strain Behaviour of Silicate Grouted Sand, Jl. of Geotechnical Engg. Div., Vol. 13, Aug. 77: Shah D.L. (1987). Time Viscosity and Strength of Newtonian & Binghamian Grouts, Ph. D. Thesis, M.S. University of Baroda, Vadodara Stabilized Soil-A Stabilized Soil-B Stabilized Soil-C Stabilized Soil-D Fig. 12: Comparison of Unconfined Compressive Strength of Virgin Soil and Stabilized Soil at Different Curing Conditions 391

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