TO STUDY THE PERFORMANCE M30 GRADE CONCRETE DUE TO CHANGE IN PH VALUE OF MIXING AND CURING WATER

Rajendra Prasad Singh 1 , K. Sunil kumar 2 , Ch. E. Vijay Kumar 3 and B. Teja 3 . 1. Asst. Professor, Dept. of Civil Engineering, MVGR College of Engineering, Vizianagaram, India. 2. M.Tech. Student, MVGR College of Engineering, Vizianagaram, India. 3. Graduate student, MVGR College of Engineering, Vizianagaram, India. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

The quality of water used in mixing and curing the concrete is the major factor which influences the strength of the concrete, As per IS 456-2000, it specifies the quality of water to be within the limiting range. The effect of variation of water quality on strength of concrete is not known. In the present work, the effect of pH value of the water used in mixing and curing of concrete in strength of concrete is studied by considering pH values as pH4, pH7, pH9 and pH12. This work was carried out for a mix of M30 grade concrete to study effect of the water of different pH values used in mixing and curing on the strength development of concrete at 7,28,56 and 90 days. From the results it is observed that concrete casted and cured using pH 9 shows the greater strength when compared with other pH values, pH 4 gives out the least of the strength. There was no homogeneity effect on concrete by changing in the pH values. Little change was seen on the concrete. when the compressive testing was done pH-4 was taking the load up to the crushing of concrete. There should be changing of water for the pH-4, pH-9and pH-12.

…………………………………………………………………………………………………….... Introduction:-
Concrete is one of the most commonly used construction materials in the world. Concrete has relatively high compressive strength, but lower tensile strength. However, when exposed to severe environments its strength can significantly decline due to degradation of concrete. Cement used in concrete is a mixture of complex mineral compounds. The reaction of these with water leads to setting and hardening of cement. The Tricalcium Silicate and Dicalcium Silicate are the most important compounds responsible for strength. Together they constitute 70 to 80 percent of cement. The average C3S content in modern cement is about 45 percent and that C2S is about 25 percent. The sum of the contents of C3A and C4AF has decreased slightly in modern cement. the hydrates rather slowly. The initial setting is attributed to hydration reactions. The C2S (Dicalcium Silicate) phase the reactions of C3A, C3 S and C,.AF (lea, 1956).
Impurities in water may interact with the of the cement and may adversely affect the strength of the concrete (Neville,1970). The chemical constituents present in water may participate in the chemical reactions and thus affect the setting, Hardening and strength development of concrete.

Material And Specifications:-
The water cement ratio is selected based on the desired compressive strength or the expected exposure conditions. The amount of mixing water is based on the maximum aggregate size and the desired slump range. The aggregate proportions are selected to provide for an economical mixture with the desired workability and finish ability characteristics. A different type of Portland cement allows some tailoring of strength grain characteristics or for additional resistance to chemical attach.
In practice mix proportions vary depending on the properties of the individual ingredients and on the desired properties of the concrete in service details of some actual mixes used in the past. Coarse aggregate:-Coarse aggregate was procured from local market. The specific gravity, moisture content, water absorption, crushing value and impact value of coarse aggregate were 2.744, 0.10%, 0.55%, 23.76% and 15.875% respectively. All the physical and mechanical properties of coarse aggregate were as per the standard limit of IS: 383-1970.

Cement:-
Chemicals used for maintaining desired pH:-1. Sodium hydroxide 2. Hydrogen chloride 3. Ammonia Solution The chemicals procured were manufactured by E. Merck India Limited were used in this research work.
2. Approximately 40 gm of sodium hydroxide (NaOH) was added in 1 litre of normal water and mixed thoroughly to obtain alkaline solution. 3. Finally, a digital pH meter was used to measure the pH value of the solution and which obtained the solution of pH 12.
Preparation of Alkaline water (for Ph-9):-4. Take 1 litre of deionised water. 5. Approximately 22ml of Ammonia solution (NH 3 ) was added in 1 litre of normal water and mixed thoroughly to obtain alkaline solution. 6. Finally, a digital pH meter was used to measure the pH value of the solution and which obtained the solution of pH 9.0.

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8. Approximately 2ml of hydrogen chloride (HCl) was added in 1liter of normal water and mixed thoroughly to obtain acidic solution. 9. Finally, a digital pH meter was used to measure the pH value of the solution and which obtained the solution of pH 4.

Methodology:-
The M30 grade of concrete is proportioned as per the mix design and the water to be used for mixing of water is made with different pH of waters. The four different mixes P-4, P-7, P-9 and P-12 were prepared for four different pH values (pH-4, pH-7, pH-9 and pH-12) in water.
The mix design is as shown in table I

Methods of curing:-
Curing is the process in which the rate and extent of loss of moisture from concrete to make hydration process of cement is done. Proper curing will maintain temperature of concrete in its early ages, as this directly affects the rate of hydration of cement and eventually the strength gain of concrete.
In the present work the effect of acids and basses mixing in water on the strength and durability of hardened concrete is studied. An experimental work is carried out in following curing conditions: -1. Normal water curing 2. Alkaline curing 3. Acid curing Normal water Curing:-Portable water is generally considered satisfactory for curing. The samples were tested for 7days, 28days, 56days and 90 days of proper curing.

Alkaline and Acidic curing:-
The solution used for alkaline and acidic curing of concrete samples was prepared using NaOH, NH 3 and HCL which was dissolved in water to obtain solutions with pH of 12, 9, 4. The concrete samples were tested after 7 days, 28 days, 56 days and 90 days of proper alkaline and acidic curing. There curing was done in different tubs with different pH values in each tubs. There should be change in water for changing of pH values in tubs. Every day check the pH values in tubs. Compressive strength test is done in compressive testing machine for M30 Grade concrete after 7, 28, 56 and 90days curing.
Schmidt Rebound Hammer test is done in the laboratory. Test is done by placing the concrete cube in compression testing machine and by applying 30% load required to that of the full strength of the specimen. The test was done for 28days only.
Ultrasonic Pulse velocity test was done to find the homogeneity of the concrete for every change pH values in the concrete. The test was done for 28days only.  The rebound hammer test for of M30 Grade concrete is observed that, the rebound compressive strength is reduced to all the pH of water except for pH 7, from which it can be concluded that the concrete has got surface disintegrated. The UPV test for of M30 Grade concrete is observed that, the pulse velocity is reduced to all the pH of water except for pH 7, from which it can be concluded that the concrete has lost its integrity.