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20320130406012 2-3
20320130406012 2-3
20320130406012 2-3
20320130406012 2-3
20320130406012 2-3
20320130406012 2-3
20320130406012 2-3
20320130406012 2-3
20320130406012 2-3
20320130406012 2-3
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20320130406012 2-3

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  • 1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME TECHNOLOGY (IJCIET) ISSN 0976 – 6308 (Print) ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December, pp. 116-125 © IAEME: www.iaeme.com/ijciet.asp Journal Impact Factor (2013): 5.3277 (Calculated by GISI) www.jifactor.com IJCIET ©IAEME HARMFUL EFFECTS OF RAPIDITE ON STRENGTH OF CONCRETE Sameer ul bashir, Shabbir Ahmad Parray, Syed Rizwan Shah B.Tech, NIT Hazratbal, Srinagar ABSTRACT This present paper presents the progress on research of use of rapidite in cold weather concreting. The project aims at making and studying various properties of cold weather concrete using admixture called rapidite which is locally available in oils and chemical industries of Kashmir. The actual compressive strength of concrete depends on the percentage of Rapidite used in the concrete. In recent years, concrete usage around the world is second only to water .Ordinary Portland cement is conventionally used as a primary binder to produce concrete. But, the progress of strength of concrete is a function of temperature. At relatively low temperatures, it gives low strength because of the freezing action. Thus, In winters, especially in Kashmir where the temperatures are below zero degree in winters some admixtures need to be added to nullify the effects of cold temperature on the strength of concrete. Considering the availability and cost of the admixture, Rapidite is mostly used admixture in Kashmir in winters. This project aims at finding the optimum amount of percentage of Rapidite at which the strength of concrete comes to be maximum. Keywords: Cold Weather, Concreting Rapidite, Compressive Strength. CONCRETE Concrete is a composite construction material, composed of cement (commonly Portland cement) and other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate made of gravel or crushed rocks such as limestone, or granite, plus a fine aggregate such as sand), water and chemical admixtures. Concrete is used to make pavements, pipe, architectural structures, foundations, motorways/roads, bridges/overpasses, parking structures, brick/block walls and footings for gates, fences and poles. Concrete is used more than any other man-made material in the world. As of 2006, about 7.5 cubic kilometers of concrete are made each year—more than one cubic meter for every person on Earth. 116
  • 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME Reinforced concrete, prestressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days. Concrete solidifies and hardens after mixing with water and placement due to a chemical process known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a robust stone-like material. PORTLAND CEMENT + H2O + ROCK = HARDENED CONCRETE + ENERGY (HEAT) COLD WEATHER CONCRETING In India certain regions experience sub-zero temperatures in winter. Concrete structures in such regions undergo cycles of freezing and thawing and there durability is affected due to frost action. Fresh concrete contains considerable quantity of fresh water which gets converted into ice lenses at freezing temperature. The ice formation in fresh concrete results in about 9% rise in volume and causes permanent damage to concrete and structural integrity cannot be recovered even if the concrete is made to harden later at high temperature. Even during hardening the concrete should be protected from extremely low temperature hence while concreting in cold weather ensure that the temperature of fresh concrete is maintained above 0 °C and temperature during first six hrs of casting should not be less than 5 °C. IS 7861 part II defines Cold Weather Concreting as Any operation of concreting done at about 5°C atmospheric temperature or below. ACI 306 “Cold Weather Concreting” defines cold weather concreting as a period when for more than three (3) consecutive days, the following conditions exist: • The average daily air temperature is less than 5°C (40°F) and, • The air temperature is not greater than 10°C (50°F) for more than one-half of any 24 hour period. What Happens When Concrete Freezes? • Pore water in concrete starts to freeze around -1°C (30°F) • As some water freezes the ion concentration in the unfrozen water goes up, further depressing the freezing point. • At around -3 to -4°C (25 to 27°F), enough of the pore water will freeze so that hydration will completely stop, and depending on the extent of hydration, and thus the strength of the concrete, the forces generated by the expansion of ice (ice occupies ~9% more volume than water) may be detrimental to the long term integrity of the concrete. Objectives of Cold Weather Concreting The objectives of cold weather concreting are to: • Prevent damage to concrete due to freezing at early ages • Assure that concrete develops the required strength for the safe removal of forms • Maintain curing conditions that foster normal strength development without using excessive heat • Limit rapid temperature changes in the concrete to prevent thermal cracking For every 10°C (18°F) reduction in concrete temperature, the times of setting of the concrete double, thus increasing the amount of time that the concrete is vulnerable to damage due to freezing 117
  • 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME Deleterious Effects Following deleterious effect may occur due to cold weather concreting • Hydration will be hampered • Setting time will be prolong • Disruption of freshly placed concrete because of freezing • Low workability • Freezing and thawing effect • Improper curing • Workmanship is affected • Deicing effect Recommended Practices and Basic Principles Curing and Protection: Where a specified concrete strength must be attained in a few days or weeks, protection at temperatures above 10°C (50°F) is required. Temperature Records: Temperature of the concrete determines the effectiveness of protection, regardless of air temperature. Maintaining temperature records of concrete in place is essential. Heated Enclosures: Must be strong enough to be windproof and weatherproof. Combustion heaters must be vented to the outside to prevent carbonation. Exposure to Freezing and Thawing: Concrete should be properly air entrained if it will be saturated and exposed to freezing and thawing cycles during construction. Slump: All else being equal, lower slump and/or lower water/cement ratio mixes are particularly desirable in cold weather for flatwork. This reduces bleeding and decreases setting time. Truck Travel Time: The distance from the plant to the point of placement can have a severe effect on the temperature of concrete. Hot Water: While hot water improves setting time of cold weather concrete, after the first few batches of concrete hot water heaters may not be able to maintain hot water temperature. Later in the pour, concrete may be cooler than at the beginning of the pour. Admixtures : Some admixtures, which act as accelerators ,can be used in cold weather concreting so to increase the rate of hydration and thus decreasing the effect of cold weather on concreting. RAPIDITE Rapidte is a commonly used admixture in Kashmir during winter to accelerate the strength gain of concrete. It falls under Type C on the basis of ASTM classification i.e., it acts as accelerator. It also acts as anti freeze, depressing the freezing point of water and hence protecting the fresh concrete. 118
  • 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME Description RAPIDITE 2 IN 1 is a specially developed Concrete Set Accelerator, a ready-to-use, liquid admixture. It accelerates initial setting time (cement-water chemical reaction HYDRATION) of normal mortar and concrete and acts as anti-freeze within cement concrete. It improves workability and strength while fastening the hydration of cement. It makes the mix easier to place and speeds construction by shortening the initial set and curing time. Time and labor are saved, because forms and other protection can be removed earlier, and finishing can be started. Uses RAPIDITE 2 in 1 is recommended for use during cool and cold weather to accelerate the set time and reduce the risk of frozen mortar and concrete mixes. Features/Benefits • Accelerates initial set time. • Increases compressive strength. • Provides Anti –freeze properties. • Speeds up hydration of cement. • Increases workability of concrete or mortar mix in colder temperatures. Properties Color : Lemon-Orange Appearance : Clear bright Liquid Relative Density (g/ml) :1gm/ml EXPERIMENTAL PROGRAM In total five castings were done at the Rapidte percentage of 0.5, 1, 1.25, 1.4 and 1.5% by percentage of cement and the minimum and maximum temperature during the first 24 Hrs after casting was observed. The Temperature during first 24 Hrs after casting along with the results of various tests are shown in tables below: Variation of Increase in 7 day strength and Compaction Factor with Rapidite % Temperature during 1st 24Hrs of Average increase in 7 Compaction factor casting (°C) day strength % Rapidite % 150mm 100mm Min Max Avg. plain Admixture cube cube -1 7 3 0.50 3.6 8 0.77 0.88 -1 6 2.5 1.00 8.3 16.8 0.74 0.81 -2 6 2 1.25 106.3 96.2 0.68 0.77 -4 7 1.5 1.4 -30.2 -26.6 -2.5 6.5 2 1.50 -22 -20 0.74 0.88 119
  • 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME Variation of Increase in 28 day strength and compaction factorwith Rapidite % Temperature during 1st 24Hrs of casting (°C) Average Increase in 28 day strength % Rapidite % Compaction factor 150mm cube 100mm cube ↑ in Split tensile strength ↑ in Flexural tensile strength plain Admixture Min Max Avg. -1 7 3 0.50 2.6 5.3 2.9 3.2 0.77 0.88 -1 6 2.5 1.00 5.2 10.4 6.4 6.7 0.74 0.81 -2 6 2 1.25 38 30.6 53.5 53.1 0.72 0.77 -4 7 1.5 1.4 -42.6 -26 -12 -21.1 0.73 0.8 -2.5 6.5 2 1.50 -18 -23 -17.4 -17.5 0.73 0.88 Variation of Compaction Factor for plain concrete and concret with admixture for different % of rapidite S. No Rapidte % Plain Admixture 1 0.50 0.77 0.88 2 1.00 0.74 0.81 3 1.25 0.72 0.77 4 1.4 0.73 0.8 5 1.50 0.73 0.88 DISCUSSIONS In order to study the variation in the rate of gain of strength with respect to the Rapidite percentage, a comparative study of the test results achieved at different Rapidite percentage is performed. Following Variations were studied: • • • • • • Variation of increase in 7 day strength with Rapidite % Variation of Increase in 28 day strength with Rapidite % Variation of split and flexural tensile strength with Rapidite % Comparison of Avg. Increase in 7 and 28 day strength for 150mm cube Comparison of Avg. Increase in 7 and 28 day strength for 100mm cube Variation of compaction factor on adding Rapidite. 120
  • 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME The results graphs and tables represent the comparative study: G1-Variation of 7 day strength with Rapidite % Percent increase in strength 120 100 80 60 40 150mm 20 100mm 0 -20 0 0.5 1 1.5 2 -40 -60 Rapidite % From the study of G1 it is clear that the by adding Rapidite the 7 day strength increases when compared to the plain concrete casted at the same temperature. Also it can be seen that the at the 1.25% there is maximum increase in strength, beyond this value there is a decrease in the strength of concrete with admixture ,when compared with plain one. Also the 100mm cube shows more increase in strength when compared with 150mm cube, except at the optimum amount, the increase in strength of 150mm cube is more than 100mm cube. G2-Variation of 28 day strength with Rapidite % percent increase in strength 50 40 30 20 10 0 -10 0 -20 -30 -40 -50 0.5 1 1.5 2 150mm 100mm Rapidite % 121
  • 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME The G2 also shows same trend i.e, the 28 day strength also goes on increasing upto the percentage of 1.25, beyond which it decreases.Also the 100mm cube shows more increase as compared to 150mm cube except at the optimum amount. percent increase in split and flexural strengths G3-Variation of split and flexural tensile strength with rapidite % 60 50 40 30 Split tensile strength 20 10 Flexural tensile strength 0 -10 0 0.5 1 1.5 2 -20 -30 Rapidte % G3 shows that there is an increase in both split and flexural tensile strengths up to the 1.25% of rapidite, beyond this value the strength decreases in both the cases. Also the two graphs almost coincide showing that both strengths increase by equal amounts, flexural strength increasing slightly more than split strength. G4-Comparison of Avg. increase in 7 and 28 day strength for 150mm cube 120 100 Syrength MPa 80 60 Avg.↑ in 7 day strength % 40 20 0 -20 0 1 2 -40 -60 Rapidite % 122 Avg. Average ↑ in 28 day strength %
  • 8. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME G4 shows that although both 7 and 28 day strength for 150mm cube increases and reaches there maximum at the Rapidite percentage of 1.25% , the increase in 7day strength is 180% more than increase in 28 day strength. G5-Comparison of Avg. increase in 7 and 28 day strength for 100mm cube 120 100 80 60 Avg. ↑ in 7 day strength % %↑ 40 20 Avg. Average ↑ in 28 day strength % 0 -20 0 1 2 -40 -60 Rapidite % G4 shows the same trend, that although both 7 and 28 day strength for 100mm cube increases and reach there maximum at the rapidite percentage of 1.25% ,the increase in 7day strength is 214% more than increase in 28 day strength.which is higher than in case of 150mm cube. G6-Variation of C.F for plain concrete and concret with admixture for different % of rapidite Plain 0.88 0.81 0.77 0.74 1 2 Admixture 0.72 0.77 3 0.73 4 0.8 0.88 0.73 5 G6 shows that the compaction factor always increases when compared with the plain concrete,thus workability increases by the addition of rapidite. 123
  • 9. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME CONCLUSION After analyzing the test results following important conclusions are drawn: • All the three strength parameters viz, compressive strength, split tensile strength and flexural tensile strength of concrete increase when compared with plain one. The increase in strength reaches the maximum value at the Rapidite percentage of 1.25%, beyond which it starts decreasing. It must be noted that the avg temperature during the 1st 24 hrs after casting is almost constant. • The increase in 7 day strength is much higher than increase in 28 day strength, in case of 150mm cubes former is 180% more increase and in case of 100mm cubes former shows 214% more increase. Thus increase in early strength is more significant than increase in lateral strength. • The increase in early strength shows that the freezing of fresh concrete was not there, as such the admixture also acts as a antifreeze, depressing the freezing point of water and protecting the concrete from the affects of freezing in early age. • Adding Rapidte has shown increase in the workability of mix with respect to the plain mix. Recommendations • The quantity of Rapidite to be added needs to be carefully controlled as there is a decrease in the strength of concrete if the value passes 1.25% by weight of cement. The manual which comes with the Rapidite recommends the percentage of Rapidite to be used in the range of 26%, which in excess of the optimum value of 1.25%. Thus the amount of the Rapidite should be limited to the 1.25%. • When concreting is to be done in the period from November to February, Rapidte should be used to accelerate the early gain of strength and protecting the fresh concrete from the effects of freezing, as Rapidite acts as Antifreeze cum accelerator. • When there is intention of using Rapidite during warm weather for the purpose of early removal of formwork, proper performance tests testing should be done to check the behaviour of rapidite at the high temperature, as the behavior of a admixture depends on the temperature. • Further proper testing should be done to check the compatibility of the Rapidite with the type of cement to be used in actual construction. • Admixture should be uniformly distributed throughout the mix, and this best achieved by dissolving the admixture in mixing water. • Trial tests should be carried out using the actual constituents of the mix to be used. Also, adequate supervision should be provided at the batching stage so as to ensure correct levels of dosage of the admixture. 124
  • 10. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME REFERENCES 1) 2) 3) 4) 5) 6) 7) 8) 9) M.S.Shetty, Concrete Technology, Chapters 1- 8,page nos. 1 – 330, IS 9103 : 1999, Admixtures : definition, Page nos (23,24). IS 456 : 2000, strength of concrete : tests, compressive strength .pages (2-7) Abbas S. Al-Ameeri, K.A.Al- Hussain and M.S Essa, “Constructing a Mathematical Models to Predict Compressive Strength of Concrete from Non-Destructive Testing”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 4, 2013, pp. 1 - 20, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. Alaa Abdul Kareem Ahmad, “The Effect of Gypsum Compensative on Mortar Compressive Strength”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 3, 2013, pp. 168 - 175, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. P.J.Patel, Mukesh A. Patel and Dr. H.S. Patel, “Effect of Coarse Aggregate Characteristics on Strength Properties of High Performance Concrete using Mineral and Chemical Admixtures”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 2, 2013, pp. 89 - 95, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. Dr. Shanthappa B. C, Dr. Prahallada. M. C. and Dr. Prakash. K. B., “Effect of Addition of Combination of Admixtures on the Properties of Self Compacting Concrete Subjected to Alternate Wetting and Drying”, International Journal of Civil Engineering & Technology (IJCIET), Volume 2, Issue 1, 2011, pp. 17 - 24, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. M.Vijaya Sekhar Reddy, Dr.I.V. Ramana Reddy and N.Krishna Murthy, “Experimental Evaluation of the Durability Properties of High Performance Concrete using Admixtures”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 1, 2013, pp. 96 - 104, ISSN Print: 0976-6480, ISSN Online: 0976-6499. Vinod P, Lalumangal and Jeenu G, “Durability Studies on High Strength High Performance Concrete”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 1, 2013, pp. 16 - 25, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. 125

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