EXPERIMENTAL STUDY OF EFFECTS OF POTASSIUM CARBONATE ON STRENGTH PARAMETERS OF CONCRETE. 3 Mehvish, Insha Bashir. J&K, India

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1 EXPERIMENTAL STUDY OF EFFECTS OF POTASSIUM CARBONATE Experimental Study of Effects of Potassium Carbonate on Strength Parameters of Concrete, ON STRENGTH PARAMETERS OF CONCRETE 1 Dr. Javed Ahmed Naqash, 2 Saiqa Nabi, 3 Mehvish, 4 Tehseena Ali, 5 Mahapara Firdous, 6 Insha Bashir Volume 6, Issue 6, June (215), pp Article Id: International Journal of Civil Engineering and Technology (IJCIET) IAEME: ISSN (Print) ISSN (Online) IJCIET I A E M E 1 Associate Professor National Institute of Technology Srinagar, J&K, India 2,3,4,5,6 UG Students, Department of Civil Engineering, S S M College of Engineering & Technology, J&K, India ABSTRACT This study presents the effects of Potassium Carbonate (K 2 CO 3 ) on plain concrete. Potassium carbonate as depressant admixture was added in different percentages by weight of cement. The concrete specimens were tested for compressive, flexural and split tensile strengths and the results obtained were compared with those of normal concrete. The optimum percentage of admixture that could be used without harming the properties of concrete was also assessed. The results concluded permissibility of using admixture (K 2 CO 3 ) up to 2.6% by weight of cement. Key words: Potassium Carbonate, Workability, Compressive Strength, Flexural Strength, Split Tensile Strength. I. INTRODUCTION Winter has some peculiarities that affect construction in general and concreting in particular. Its duration is different in different parts of globe, but cold weather with white frosts may also happen in spring and autumn- not just in winter only. In central part of Russia, the cold period including winter early spring and late autumn may be as long as five to six months reaching eight to ten months in north. The situation is same in Canada, Alaska, Northern China, Finland, Sweden and Norway. Kashmir is also a cold region and cold weather conditions prevail over a period of about four months. The cold weather conditions warrant special precautions to be taken while placing, finishing and curing of concrete, so as to protect concrete against the effects of cold weather. Concrete has to be protected from freezing until it reaches a minimum strength of 3.5 Mpa. If concrete freezes while it is still fresh or before it has developed sufficient strength to resist the expansive forces associated with the freezing water, ice formation results in the disruption of the cement paste matrix causing an irreparable loss in strength. Once the concrete has attained a compressive strength of around 3.5 MPa, it is generally considered to have sufficient strength to resist significant expansion and damage if frozen [2]. Concreting in winter conditions is quite difficult. It is possible to create favourable conditions for concrete to harden when the ambient air temperature is below C but that requires additional 24 editor@iaeme.com

2 energy, material and labour. The energy cost for thermal protection is estimated to be 8 million dollar in US alone. So, it is not only a technical problem but a problem of cost effectiveness. Stopping the process of concreting in winter is uneconomical due to long downtimes of equipment and workers. It is better to bear additional costs and trying to minimize them as much as possible. In some cases when construction schedule is very tight and project is to be completed in winter, the additional costs are inevitable. The simplest and the least expensive way is to use a chemical depressant like potassium carbonate. In order to study the effects of K 2 CO 3 on properties of concrete, to get the optimum percentage of the chemical and to compare the various properties of concrete; a number of castings were done with varying percentages i.e., 2%, 2.2%, 2.4%, 2.6% and 3% by weight of cement. Also cost analysis reveals that cold weather concreting using chemical depressants is cost effective and economical than any other conventional methods. II. MATERIALS USED 2.1) Cement: Ordinary Portland Cement (OPC) 43 Grade (Khyber cement) confining to IS: 431[4] has been used for this Work. The properties of the used cement are shown in Table ) Aggregates: Fine aggregates used throughout the work comprised of clean river sand with maximum size of 4.75mm conforming to zone II as per IS: [5] with specific gravity of 2.6 and Fineness Modulus of 2.6. Coarse aggregates used consisted of machine crushed stone angular in shape passing through 2mm I S sieve and retained on 4.75mm I S sieve with specific gravity of 2.7 and Fineness Modulus of ) Potassium Carbonate: K 2 CO 3 was used as depressant admixture and was obtained from local market. Potassium Carbonate was in white fine powder form so it was easy to add it in mix. Fig. 1 shows Potassium carbonate. Function of Potassium Carbonate as Admixture: When K 2 CO 3 is added as admixture, it depresses the freezing point of water by increasing the ions in the water. Also it accelerates the initial setting of concrete. It allows concrete to gain early strength at sub-freezing temperature. III. EXPERIMENTAL INVESTIGATION 3.1) Mix Proportion: The concrete mix design was proposed by using IS 1262 [6]. The grade of concrete used was M2 with water to cement ratio of.45.the ratio obtained from mix design was 1:1.6: ) Tests on Fresh Concrete: The workability of all concrete mixtures was determined through Slump test and Compaction factor test. The slump tests were performed according to IS: [9]. Compaction factor test works on the principle of determining the degree of compaction achieved by a standard amount of work done by allowing the concrete to fall from a standard height. The degree of compaction, called the Compaction Factor is measured by the density ratio i.e., the ratio of the density actually achieved in the test to density of same concrete fully compacted. 3.3) Tests on hardened concrete: From each concrete mixture, cubes of size 15mm x 15mm x 15mm, 15mm dia. 3mm cylinders and 5mm x 1mm x 1mm beams were cast for the determination of compressive strength, split tensile strength and flexural strength respectively. The concrete specimens were cured under normal conditions as per IS: [1] and were tested at 3 days, 7 days and 28days for determining compressive strength as per IS: [11], split tensile strength as per IS: [12] and flexural strength as per IS: [13] editor@iaeme.com

3 IV. RESULTS AND DISCUSSION 4.1) Fresh concrete: The values of slump and compaction factor (C.F) of all the mixtures are presented in Tables No considerable change in slump and C.F values was observed in fresh concrete samples containing potassium carbonate as admixture as compared to those of normal concrete. 4.2) Hardened concrete Compressive strength: The compressive strength test results are presented in Table 2. Compressive strength tests, split tensile strength tests and flexural strength tests were carried out at 3, 7 and 28 days. An increase in compressive strength was observed up to 2.6% addition of potassium carbonate as admixture and thereafter a decrease in strength properties was observed Split tensile strength: The split tensile strength tests are presented in Table 3. Split tensile strength witnessed an increase of 33%, 14% and 1% at 3, 7 and 28 days of age respectively, corresponding to concrete mix containing 2.6% of potassium carbonate by weight of cement Flexural strength: The flexural strength tests are presented in Table 4. Flexural strength witnessed an increase of 21%, 25% and 25% at 3,7 and 28 days of age respectively, corresponding to concrete mix containing 2.6% potassium carbonate by weight of cement. Both split tensile strength and flexural strength for concrete mix with 3% potassium carbonate by weight of cement was found to be less than that of reference mix. Fig. 4, 5 and 6 present compressive strength of all mixtures at 3, 7 and 28 days respectively. Fig. 7, 8 and 9 present flexural strength of all mixtures at 3, 7 and 28 days respectively. Fig. 1, 11 and 12 present split tensile strength of all mixtures at 3, 7 and 28 days respectively. Fig. 1 K 2 CO 3 Fig. 2 Test Samples Fig. 3 Curing Tank TABLE 1: Properties of cement Fineness % Standard Consistency (%) Initial Setting Time Final Setting Time Soundness (mm) Compressive strength(n/mm 2 ) hr 1 min 5 hrs 15 min editor@iaeme.com

4 A) Compressive Strength Test Results. TABLE 6.1: Compressive Strength using 2% K 2 CO 3 (Casting Month Nov.) Slump (mm) 26 Average Strength (Plain) N/mm Slump (mm) 25.5 Average Strength (Admixtured) N/mm TABLE 6.2: Compressive Strength using 2.2% K 2 CO 3 (Casting Month Nov-Dec) Slump (mm) 27.5 Average Strength (Plain) N/mm Slump (mm) 26.9 Average Strength (Admixtured) N/mm TABLE 6.3: Compressive Strength using 2.4% K 2 CO 3 (Casting Month Dec) Slump (mm) 25 Average Strength (Plain) N/mm Slump (mm) 24.5 Average Strength (Admixtured) N/mm TABLE 6.4: Compressive Strength using 2.6% K 2 CO 3 (Casting Month Jan) Slump (mm) 25.1 Average Strength (Plain) N/mm Slump (mm) 24.7 Average Strength (Admixtured) N/mm editor@iaeme.com

5 TABLE 6.5: Compressive Strength using 3% K 2 CO 3 (Casting Month Jan-Feb) Slump (mm) 25 Average Strength (Plain) N/mm Slump (mm) 23. Compaction Factor.81 Average Strength (Admixtured) N/mm B) Flexural Strength Test Results. TABLE 6.6: Flexural Strength using 2% K 2 CO 3 (Casting Month Nov.) Slump (mm) 26 Compaction factor.86 Average Strength (Plain) N/mm Slump (mm) 25.5 Average Strength (Admixtured) N/mm TABLE 6.7: Flexural Strength using 2.2% K 2 CO 3 (Casting Month Nov-Dec) Slump (mm) 27.5 Average Strength (Plain) N/mm Slump (mm) 26.9 Average Strength (Admixtured) N/mm TABLE 6.8: Flexural Strength using 2.4% K 2 CO 3 (Casting Month Dec) Slump (mm) 25 Average Strength (Plain) N/mm Slump (mm) 24.5 Average Strength (Admixtured) N/mm editor@iaeme.com

6 TABLE 6.9: Flexural Strength using 2.6% K 2 CO 3 (Casting Month Jan) Slump (mm) 25.1 Average Strength (Plain) N/mm Slump (mm) 24.7 Average Strength (Admixtured) N/mm TABLE 6.1: Flexural Strength using 3% K 2 CO 3 (Casting Month Jan-Feb) Slump (mm) 25. Average Strength (Plain) N/mm Slump (mm) 23. Compaction Factor.81 Average Strength (Admixtured) N/mm C) Split Tensile Strength Test Results. TABLE 6.11: Split Tensile Strength using 2% K 2 CO 3 (Casting Month Nov.) Slump (mm) 26 Strength of Cylinder 1 (Plain) N/mm Slump (mm) 25.5 Split tensile strength (Admixtured) N/mm TABLE 6.12: Split Tensile Strength using 2.2% K 2 CO 3 (Casting Month Nov-Dec) Slump (mm) 27.5 Strength of Cylinder 1 (Plain) N/mm Slump (mm) 26.9 Split tensile strength (Admixtured) N/mm editor@iaeme.com

7 TABLE 6.13: Split Tensile Strength using 2.4% K 2 CO 3 (Casting Month Dec) Slump (mm) 25 Strength of Cylinder 3 (Plain) N/mm Slump (mm) 24.5 Split tensile strength (Admixtured) N/mm TABLE 6.14: Split Tensile Strength using 2.6% K 2 CO 3 (Casting Month Dec-Jan) Slump (mm) 25.1 Strength of Cylinder 1 (Plain) N/mm Slump (mm) 24.7 Split tensile strength (Admixtured) N/mm TABLE 6.15: Split Tensile Strength using 3% K 2 CO 3 (Casting Month Jan-Feb) Slump (mm) 25. Strength of Cylinder 1 (Plain) N/mm Slump (mm) 23. Compaction Factor.81 Split tensile strength (Admixtured) N/mm Variation of Compressive, Flexural & Split Tensile Strengths with different %ages of Admixtures. Compressive strength Flexural Strength editor@iaeme.com

8 3 3 Split Tensile Strength Compressive Strength Flexural Strength Split Tensile Strength % 2% 2.2% 2.4% 2.6% 3% V. CONCLUSIONS On the basis of results obtained, following conclusions can be drawn: 1. The use of admixture K 2 CO 3 in cold weather increases the compressive, flexural and split tensile strength of concrete compared to plain concrete. The percentage of potassium carbonate which gives maximum strength is 2.6% beyond which the strength decreases. Beyond this dosage of K 2 CO 3 a decrease in strength parameters was observed % Potassium carbonate addition as accelerating admixture showed optimum increase in compressive strength, flexural strength and split tensile strength of concrete with respect to reference mix at 3, 7 and 28 days. 3. From the study of the characteristics of K 2 CO 3 it can be concluded that it does not corrode the reinforcement provided in the RCC sections. 4. For M2 mix having w/c as.45, 2.6% K 2 CO 3 by weight of cement is recommended as optimum dosage in cold weather editor@iaeme.com

9 REFERENCE 1. Cold weather concreting, reported by ACI committee 36, Nicholas J. Carino, Chairman, p. 36 R Annual book of ASTM Standards (1979), part 13, ASTM C : Standard test method for time of setting of hydraulic cement. ASTM Race St. Philadelphia, pa Concrete Technology, A. M. Neville and J. J. Brooks Grade Ordinary Portland Cement Specification. IS 8112:1989, Bureau of Indian Standards, New Delhi. 5. Specification for Coarse and Fine Aggregates from Natural Sources for Concrete. IS: , Bureau of Indian Standards, New Delhi. 6. Recommended Guidelines for Concrete Mix Design. IS: , Bureau of Indian Standards, New Delhi. 7. Concrete Technology, A. M. Neville and J. J. Brooks. 8. Concrete Technology, A. M. Neville and J. J. Brooks, p Methods of Sampling and Analysis of Concrete. IS: , Bureau of Indian Standards, New Delhi. 1. Methods of Tests for Strength of Concrete. IS: , Bureau of Indian Standards, New Delhi. 11. Methods of Tests for Strength of Concrete. IS: , Bureau of Indian Standards, New Delhi. 12. Split Tensile Strength of concrete Methods of test. IS: 5816: Methods of Tests for Strength of Concrete. IS: , Bureau of Indian Standards, New Delhi. 14. Khaza Mohiddin Shaik and Prof. Vasugi K, Partial Replacement of Wood Ash and Quarry Dust with Cement and Sand To Study The Strength Parameters of Concrete International Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 8, 214, pp , ISSN Print: , ISSN Online: Ananthayya M.B. and Prema Kumar W. P., Influence of Steel Fibers and Partial Replacement of Sand by Iron Ore Tailings on The Compressive and Splitting Tensile Strength of Concrete International Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 3, 214, pp , ISSN Print: , ISSN Online: Harish.L., The Permeability and Indirect Tensile Strength Characteristics of Porous Asphalt Mixes International Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 8, 214, pp , ISSN Print: , ISSN Online: editor@iaeme.com