Effect of Compaction delay Time on Soil-Lime Stabilization

Transcription

1 Paper ID: GE International Conference on Recent Innovation in Civil Engineering for Sustainable Development () Department of Civil Engineering DUET - Gazipur, Bangladesh Effect of Compaction Time on Soil-Lime Stabilization R.C. Pul 1 ; M.S. Mia 1 ; M. R. M. Raja 2, M.M. Rahman 3 Abstract This study is carried out an investigation to the strength development of lime stabilized soil under time compaction. Sample of different types of soil with varying lime content were prepared and compacted at 1 hr, 3 hrs, 6 hrs, 12 hrs, 24 hrs and 48 hrs after mixing. Unconfined compressive strength of stabilized soil was determined after soaking the specimen in water. Two types of soil were used for this study and slaked lime (3%, 4% and 5%) was used as a stabilizer. The prepared samples were tested to find out the effect of ed compaction on strength. The strength gain was found to depend on various factors, such as lime content, soil type, curing time, compaction energy etc. The unconfined compressive strength of soil was increased with higher percent of lime content and decreased with ed compaction periods for particular lime content. Initially the strength gain is high and decreased with time of compaction. For soil type-i, about 16% and for soil type-ii, about 10% of compressive strength of stabilized soil were reduced when they are compacted only for 1 hour to 48 hours ed after mixing. Keywords: Compressive strength, time compaction, soil- lime stabilization. 1. Introduction Soil is a load bearing construction materials. It is used to meet the engineering properties such as high bearing capacity, low plasticity, low settlement etc. to support the highly loaded structure. In early days engineers could avoid unsuitable site or construction materials whenever the required conditions do not fulfilled. Now-a-days engineers are concern about the stability of the soil and they practice the economy of the soil stabilization method. Foe better construction it is required to apply some techniques to improve the engineering properties of soil. Soil stabilization with various additives is one of the most important techniques to improve the strength and durability properties of soil. Cement, lime, bitumen, calcium chloride, fly ash etc. are the various additives used for soil stabilization. Soil stabilization is used in the building of roads, aircraft runway, earth dam, embankment in erosion control etc. One of the most common ways of stabilization is soil lime stabilization. In this method lime is used as a stabilizer and thoroughly mixed with soil at required moisture content and compact the soil mix to required density. Compaction time is the time interval between wet mixing and compaction of the soil mix. Compaction time is critical and its leads to a decrease in the strength of soil for a fixed compaction effort. In many cases compaction is unavoidable due to sudden raining, ing of compaction equipment, insufficient workers, poor transportation etc. These hours affect the strength of stabilized soils. Mitchell and Hopper (1961) observed that the strength of the lime stabilized soil decrease due to compaction time. Working with an organic clay mixed with 4% dolomitic hydrated lime, They found that at a of 24 hours between wet mixing and compaction results a loss of 8 lb/cu-ft from 1 M.Sc Student, Department of Civil Engineering, DUET, ratancpul@gmail.com 1 Lecturer, Department of Civil Engineering, DUET, suman105@duet.ac.bd 2 Lecturer, Department of Civil Engineering, DUET, raja_ce@duet.ac.bd 3 Professor, Department of Civil Engineering, DUET, mokhlesur.2005@gmail.com

2 473 the maximum dry density of 98.5 lb/cu-ft as was found by compacting specimen immediately after mixing. A loss of unconfined compressive strength of 30% was observed. Thompson (1966) and Mitchell (1981) however, revealed that the between wet mixing and stabilization of soil mix was of considerable importance in achieving high strength and durability. Townsend et al. (1970) observed that the compaction time of 24 hours can reduce the strength of the specimen up to 30% as compared to the specimen prepared by compacting immediately after mixing. Boominathan and Prasad (1992) stated that compaction of 24 hours can decrease the strength from 13% to 22%. This study is carried out to find out the nature of compaction effects on the strength of stabilized soil. 2. Materials To study the compaction time on the strength of lime stabilized soil, Soil Type-1 (A-6) and Soil Type-2 (A-7-6) were selected. Type-1 soil was collected from Noroshingdi and Type-2 was obtained from Gazipur beside the rail line. The index properties of the two types of soil are presented in table 1. Table 1: Index properties of soil used for stabilization Properties of soil Soil type-1 Soil type Texture: Sand (%) Silt (%) Clay (%) Atterberg limits: Liquid Limit (%) Plastic Limit (%) Plasticity Index (%) Soil Classification: AASHTO A-6(11) A-7-6(20) Optimum moisture content i.e. OMC (%) Maximum Dry Density i.e. MDD (pcf) Unconfined compressive strength i.e. qu (kpa) Only one type of lime was used for this study. After collection lime was kept sealed to prevent carbonation before use. The test of lime was done in laboratory according to ASTM standard ASTM C (1984).The result of the chemical composition of lime shown in table 2. Table 2: Constituent of lime from chemical analysis Name of the ingredient Quantity in % CaO MgO Fe, Al, Na, K etc 8.18 SiO Loss due to ignition 23.7 Drinking tube-well water was used in all the mixture of soil and lime to prevent the mixing of impurities from water. 3. Methodology 3.1. Mixing of soil and lime In this study one stage of mixing is used for mixing of soil and lime. After adding lime with soil, water was added and thoroughly mixed with water. Total water was applied on the soil lime mix at a time

3 Compaction of soil lime mixture Moisture density relationship was found using Standard proctor compaction test method (ASTM D , 1989).Test specimen for unconfined compressive strength test was prepared by trimming a specimen from this compacted soil lime mixed mould sample Preparation of soil specimen for unconfined compressive strength test To evaluate the strength of stabilized soil, test specimen was prepared for unconfined compressive strength. To perform this test on lime stabilized soil, diameter 1.5 inch and length 3 inch specimen was prepared. After mixing a period of 1hr, 3 hrs, 6 hrs, 12 hrs, 24 hrs and 48 hrs, completed compaction the soil lime mixture in the compaction mould, it was divided into two parts. After making the sample of about a size of 1.5 inch diameter, it was inserted in a block of 3 inch in height and 1.5 inch in diameter and the specimen was trimmed to get the block size specimen. After preparing the test specimen, it was tested. 3.4 Unconfined compressive strength test Unconfined compressive strength was performed according to ASTM D (1989) test procedure. The prepared specimen was placed on a plate of loading device. Loading device was adjusted carefully such that the upper platoon just makes contact with specimen. Reading of deformation indicator was made zero. The rate of deformation during test for stabilized soil was chosen 0.2% of the height of the specimen per minute. The axial deformation of the specimen and the corresponding load applied were recorded at frequent interval to define stress strain curve. The maximum load at which the specimen was failed was taken as the unconfined compressive strength of that soil mix specimen. 4. Result and discussions The properties of the collected soil were determined in laboratory to identify the soil and their characteristics. To evaluate the strength of stabilized soil, unconfined compressive strength test was performed on the prepared specimen. All the test results are presented in table 3. Table 3: Test results of soil used after lime stabilization Soil Type Type-1 (A-6) Type-2 (A-7-6) % of Lime OMC (%) MDD (pcf) 1hr Unconfined Compressive Strength, qu (kpa) for 3hrs 6hrs compaction 12hrs 24hrs 48hrs qu(48 hrs) /qu (1 hr) Water is an important factor for lime stabilization. Optimum moisture content for two types of soil was determined using Standard proctor compaction test. The relationship between dry density and moisture content at different percent of lime are shown in Fig. 1 and Fig.2. In figures, we can see that the dry density varies with the moisture content and maximum dry density attained at a certain moisture content known as optimum moisture content. For soil Type-1, optimum moisture contents are 11.9%, 12.6%, 13.1% and 13.4% for corresponding maximum dry density 102 pcf, 98.1 pcf, 97.5 pcf and 96.7 pcf of 0%, 3%, 4% and respectively. For Type-2, soil optimum moisture contents are 20.8%, 21.3%, 21.8% and 22.1% for corresponding maximum dry density pcf, 97.8 pcf, 97.1 pcf and 96.7 pcf of 0%, 3%, 4% and respectively. It is also observed that the maximum dry density decrease with the increase of lime content.

4 qu, kpa Dry Density, pcf Dry Density, pcf 475 Soil Type % lime Moisture Content, percent Fig. 1: Relationship between moisture content and dry density at various lime content Soil Type % lime Moisture Content, percent Fig. 2: Relationship between moisture content and dry density at various lime content Lime percent is an important factor for lime stabilized soil. The relationship between lime percent and unconfined compressive strength at different period are shown in Fig. 3 and Fig. 4 for both type of soil. It is seen that the strength of stabilized soil increase with the percent of lime for same period. Hilt and Davidsion (1960) suggested for use 2% to 8% lime for stabilization. 350 Soil Type-1 (A-6) Compaction Delay Time, hr Fig. 3: Unconfined compressive strength at different compaction time for soil type-1

5 qu, kpa 476 Soil Type-2 (A-7-6) Compaction Delay Time, hr Fig. 4: Unconfined compressive strength at different compaction time for soil type-2 To observe the effect of compaction time on lime stabilized soil, the soil lime mixture was left for 1 hr, 3 hrs, 6 hrs, 12 hrs, 24 hrs and 48 hrs before compaction. The specimens were prepared at the optimum moisture content of 3%, 4% and 5% soil lime mix. After compacting the soil mix using standard proctor compaction test methods, test specimen were prepared. The values of the unconfined compressive strength at different time for type-1 and type-2 soil are presented in Fig. 3 and Fig. 4. From figure it is seen that the in compaction period decrease the strength of stabilized soil. This study represents that for soil type-1, the decrease in strength about 21%, 18% and 16% for 3%, 4% and respectively at ing 48 hours with comparing 1 hour while for type-2 soil, the decrease in strength about 14%, 13% and 10% for 3%, 4% and respectively at ing 48 hours with comparing 1 hour. Initially the rate of change of strength of stabilized soil is high and it is decrease with the increase of compaction time. 5. Conclusions This study is conducted to observe the effect of compaction time on the strength of lime stabilized soil. From the present study following conclusion can be drawn: Soil type-2 is more suitable for lime stabilization than soil type-1 due to presence of clay content in type-2 soil. Strength of stabilized soil increase with the percent of lime for same period. Strength of stabilized soil decrease with the increase of compaction time. Initially the rate of change of strength of stabilized soil is high and it is decrease with the increase of compaction time. About 16% to 21% for soil type-1 and about 10% to 14% for soil type-2, strength decrease for varying lime 5% to 3% at ing 48 hours with comparing 1 hour time. 6. Acknowledgement The authors acknowledge the financial grants provided by the Department of Civil Engineering, Dhaka University of Engineering &Technology, Gazipur for this study.

6 References [1] Boominathan A. and Prasad S. R (1992) Laboratory investigation of Effectiveness of lime Treatment in Polluted Soils, Proceeding of Indian Geotechnical Conference, PP [2] Mitchell, J. K and Hooper D.R (1961), Influence of the time between Mixing and compaction on properties of Lime Stabilized Expensive Clay Highway Research Board Washtion D.C, bull.no, 304 pp, [3] Thompson, M.R (1966), Shear Strength and Elastic properties of lime soil Mixtures, Highway Research Board Washtion D.C, vol. no 139 pp, [4] Mitchell, J. K. (1981), Soil improvement, State of art report, proc. 10 th ICSMFE, Stockholm. [5] Townsend, D.L. and Klyn, T.W. (1970), Durability of lime stabilized soil, Highway research board, Washington D.C., vol. 315 pp [6] Hilt G.H and Davidson, D.T (1960), Lime Fixation in Clayey Soils bull. no 262, Highway Research Board, Washington D.C. [7] ASTM (1984) Annual Book of ASTM Standard, Section-4, Vol , Cement; lime; gypsum. [8] ASTM (1989) Annual Book of ASTM Standard, Section-4, Vol , Soil and Rock, Building stone; Geotextile.

7 478 Structural Engineering