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CHEMICAL ANALYSIS
Soil
DETERMINATION OF ORGANIC MATTER IS: 2720 (Part 22) 1972
  • This part deals with the method of test for the determination of organic matter content in the soil. Organic matter is an undesirable constituent of the soil from the engineering point of view since it causes swelling or shrinkage of the soil when the moisture content or the applied load changes. A wide variety of both dry and wet combustion methods are in use for the determining of the organic matter of soils.
DETERMINATION OF TOTAL SOLUBLE SULPHATES IS: 2720 (Part 27) - 1977
  • This deals with the presence of total soluble sulphates (in the form of sodium sulphate) in the soil which is easily hydrated and dehydrated under the influence of climate changes. There are enormous volume changes during this process, which influence the engineering properties of soil. However, the scope lays down the procedure for determining the total soluble sulphate content of soils by
  • Precipitation method
  • Volumetric method
  • Volumetric as turbidimetric method
DETERMINATION OF TOTAL SOLUBLE SOLIDS IS: 2720 (Part 21) - 1977
  • This deals with the presence of soluble solids in a soil which is one of the important aspects requiring examination since these water soluble solids greatly influence the engineering properties of the soil. Two methods for the determination of soluble solids are given.
  • The gravimetric method (designated as the standard method) for determining percentage of soluble solids accurately ln absolute term.
  • The conductimetric method (designated as the subsidiary method) for rapid assessment.
DETERMINATION OF pH VALUE
  • The acidic or alkaline characteristics of a soil sample can be quantitatively expressed by hydrogen ion-activity commonly designated as pH, which is conveniently expressed by the following:
  • pH = -log10 (H+) = log10 1/H+
  • Where H+ is the hydrogen ion-concentration in moles/litre
Admixture
USE OF ADMIXTURES IN CEMENT CONCRETE
  • t is defined as a material other than water, aggregate and cement that is used as an ingredient of concrete to modify the properties of fresh or hardened concrete.
TYPE:
  • Chemical admixtures
  • Mineral admixtures
FUNCTION OF ADMIXTURE
  • To improve workability of fresh concrete
  • To improve durability by entrainment of air
  • To reduce the water required
  • To accelerate setting & hardening & thus to produce high early strength
  • To aid curing
  • To impart water repellent / water proofing property
  • To cause dispersion of the cement particles when mixed with water
  • To retard setting
  • To improve wear resistance (hardness)
  • To offset / reduce shrinkage during setting & hardening
  • To cause expansion of concrete and automatic prestressing of steel
  • To aerate mortar / concrete to produce a light-weight product
  • To impart colour to concrete
  • To offset or reduce some chemical reaction
  • To reduce bleeding
  • To reduce the evolution of heat
  • Among the type of chemical admixture used are:
Accelerator
  • Added to increase the rate of hydration of concrete mix which then lead to the increases in the rate of development of strength and greater heat evolution.
  • And to shorten the setting time
  • More rapid gain of strength & rapid setting
  • Disadvantages is possible cracking due to heat evolution & possibility of corrosion of embedded reinforcement
Water reducing Admixture
  • Used to reduce the amount of water necessary to produce a concrete of a given consistency
  • To increase the slump for a given water content
  • To obtain specified strength at lower cement content
  • Increases workability with faster gain of strength
  • Disadvantages, it has the risk of corrosion
Superplasticizer
  • By adding to a hydraulic binder, gives very high workability and allows a large decrease in water content for a given workability
  • Allows the particles to be more workable where it enable working with low w/c ratio
  • Enhances hydration process, increases strength
  • Eliminate concrete segregation & allow good dispersion of cement particles in water, accelerating the rate of hydration
  • Uniform distribution of cement particles is partly responsible for the highly early strength in concrete made with superplasticizer.
  • Advantages of using Superplasticizers are:
  • Decreased time to place and finish
  • Accelerated curing period
  • Early removal of formwork
  • Excessive dosage may render concrete too fluid, causing severe segregation
Air Entraining Admixtures
  • By adding to a hydraulic binder, gives very high workability and allows a large decrease in water content for a given workability
  • An entraining concrete containing air in a rather special form of a bubble that trapped in concrete
  • Workability improved, increase in slump, easier placing, increased durability, better resistance to frost action
  • Able to reduce segregation tendency and control of bleeding
  • It is necessary to have a careful control of air content and mixing time
  • An entraining concrete containing air in a rather special form of a bubble that trapped in concrete
  • Workability improved, increase in slump, easier placing, increased durability, better resistance to frost action
  • Able to reduce segregation tendency and control of bleeding
  • It is necessary to have a careful control of air content and mixing time
  • Water mixes tend to result in higher air content while mixes rich in sand entrain less air as fine material competes for available waterIf air entrainment is to be used, sand content need to be reduced
  • Bubbles produced by air entrainment are quite different from entrapped air because:
  • They are sealed and wouldn't be filled with water during normal saturation of the concrete
  • They are very small and well distributed.
  • Used to increase concrete durability by protecting it against freeze-thaw cycle damage.
  • By entraining air in concrete to form a microscopic air-void system , the expansion is provided a relief valve system.
  • The air void system in the hardened concrete paste allows water to freeze, with the empty air voids providing room for the expansion that occurs as water changes to ice.
Retarding Admixtures
  • Prolong or delay the setting time of cement paste in concrete
  • Used in hot weather to reduce any premature stiffening of the concrete and consequent loss of workability
  • Often carried by ready mixed concrete vehicles to prevent the concrete setting in the drum in the event of brakdown
  • Disadvantage is, it may promote bleeding
Corrosion Inhibitors
  • Able to reduce the rate of corrosion to a level that major damage to concrete will be avoided or at least greatly reduced.
Alkali-Aggregate Reaction Inhibiting Admixtures
  • Lithium and Barium salts can reduce the expansion and cracking associated with alkali-silica reaction
Shrinkage Reducing Admixtures
  • Able to reduce the amount of shrinkage that occurs as hardened concrete dries.
Mineral Admixtures
  • Are natural pozzolanic materials or industrial by-products that are commonly used in concrete to replace part of the cement or sand.
  • Types of mineral admixtures are:
  • Flyash
  • Silica Fume
  • Blended hydraulic cement
Chemiacal Properties of Concrete Admixture(IS: 9103 - 1999)
Chloride Ion concentration:
  • The following methods of test for determination of water soluble chlorides in concrete admixtures:
  • Volumetric method
  • Gravimetric method
  • Turbidimetric method
Selection of method:
  • One of the three methods may be used appropriately depending on the concentration of the chlorides in the admixtures as per the declaration of the manufacturer.
  • The volumetric method may be used when the chloride concentration is nearly 1 percent or above. The gravimetric method may be used when the chloride concentration is more than 25 percent.
  • The turbidimetric method may be used when the concentration of chloride is as low as 2 ppm and above.
  • Where a choice is open between volumetric and gravimetric methods volumetric method is preferable as it is quicker and less laborious. Turbidimetric method may be adopted when the chloride concentration is very low.
pH Value:
  • pH is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the logarithm to base 10 of the molar concentration, measured in units of moles per liter, of hydrogen ions. More precisely it is the negative of the logarithm to base 10 of the activity of the hydrogen ion. Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. Pure water is neutral, being neither an acid nor a base. Contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively.
Water
pH VALUE (IS: 3025 PART11) 1983
  • In general, a water with a pH < 7 is considered acidic and with a pH > 7 is considered basic. The normal range for pH in surface water systems is 6.5 to 8.5 and for groundwater systems 6 to 8.5. Alkalinity is a measure of the capacity of the water to resists a change in pH that would tend to make the water more acidic. The measurement of alkalinity and pH is needed to determine the corrosivity of the water.
SUSPENDED MATTER
  • Non-filterable residue is determined by passing the sample through a weighed filter and drying the filter at 103-105C or 179-181C. Non-filterable residue is calculated from th e increase in mass of the filter.
VOLATILE AND FIXED RESIDUE (TOTAL, FILTERABLE AND NON-FILTERABLE)(IS:3025 PART18) 1984
  • A gravimetric method for the determination of volatile and fixed portions of total, filterable and non-filterable residues. The method is applicable to all types of water and waste water.
  • Terminology:-
  • Total Fixed Residue The dish with residue after completion of test for total residue is heated in a muffle furnace at 550C for 1 hour. Total fixed and volatile residue are calculated from loss in mass, on ignition.
  • Filterable Fixed Residue The dish with residue after completion of test for filterable residue is heated in a muffle furnace at 550C for 1 hour. Filterable fixed and volatile residue are calculated from loss of mass, on ignition.
  • Non-filterable Fixed Residue The filter with residue after completion of test for non-filterable residue is heated in a muffle furnace at 550C for 1 hour. Non-filterable fixed and volatile residue are calculated from loss in mass after ignition.
ACIDITY
  • Prescribes the indicator and potentiometric methods for determination of acidity. These methods are applicable to the determination of acidity in water and waste water. The applicable range is O-5 to 500 mg/l acidity as CaCO,.
  • Acidity of water is its quantitative capacity to react with a strong base to a designated pH. It may be defined as equivalent concentration of hydrogen ions in mg/l. The equation in its simplest form is as follows: Hf + NaOH = H,O + Na+
ALKANITY
  • Prescribes the potentiometric and indicator methods for determination of alkalinity. These methods are applicable to determine alkalinity in water and wastewater in the range of 0'5 to g 500 mgtl alkalinity as CaCO.. The upper range may be extended by dilution of the original sample.e
Sulphates (IS: 3025-PART24) 1986
  • for determination of sulphates in water and waste water there arethree methods as given below are prescribed:
  • Gravimetric method
  • Thorin method
  • Turbidity method
  • iv) The choice depends upon the concentration range of sulphate and degree of accuracy required. Dilution or concentration of sample will bring most waters into the desired range for any of the methods prescribed in the standard.
Chloride (IS: 3025-PART32) 1988
  • There are four methods for the determination of chloride.
  • The argentometric method is suitable for use in relatively clear waters when O-1 5 to 10 mg of chloride is present in the portion titrated. The end point of mercuric nitrate method is easier to detect Potentiometric method is suitable for coloured or turbid samples. The ferricyanide method is an automated technique. In case of any difference of opinion, the argentometric method shall be the referee method.
  • Argentometric Method:
  • Principle - In a neutral or slightly alkaline solution, potassium chromate can indicate tht end point of the silver nitrate titration of chloride. Silver chloride is precipitated before red silver chromate is formed.
  • interference - Bromide, iodide and cyanide register equivalent chloride concentrations, Sulphite, thiosulphate and sulphide ions interfere but can be removed by treatment with hydroger peroxide. Orthophosphates in excess of 25 mg/l interfere. by masking the end point. Iron in excess of 10 mg/l interferes
  • Apparatus:
  • Erlenmeyer flask - 250 ml.
  • Burette - 50 ml.
  • Reagents:
  • Potassium chromate indicator solution - Dissolve 50 g of potassium chromate in a little distilled water. Add silver nitrate solution until a definite red precipitate is formed. Let it stand for I2 h, filter and dilute to 1 litre with distilled water.
  • Standard silver nitrate titrant - 0.014 1 N. Dissolve 2.395 g of silver nitrate in distilled Nater and dilute to 1 litre. Standardize against 0014 1 N sodium chloride solution as prescribed n 2.5.1. 1 *OO ml = 500 pg of chloride. Store in a brown bottle.
  • Standard sodium chloride solution - 0014 1 N. Dissolve 824.0 mg of sodium chloride : dried at 140C ) in distilled water and dilute to 1 litre. 100 ml = 500 pg of chloride. 2.4.4 Special reagents for removal of interferences
  • Aluminium hydroxide suspension - Dissolve I.2 5 g of aluminium potassium sulphate >r aluminium ammonium sulphate [AIK ( SOa )~.12H20 or Al NH4 ( SOa )s.l2HsO ] in 1 titre If distilled water. with stirring. Warm to 60C and cldd 55 ml of concentrated ammonium hydroxide slowly additions. Let it stand for 1 h. transfer to a large bottle and wash precipitate by successive with thorough mixing and decanting with distilled water, until free from chloride. When reshly prepared, the suspension occupies a volume of about 1 litre.
  • Phenolphthalein indicator solution 2.4.4.3 Sodium hydroxide - 1 N. 2.4.4.4 Sulphuric acid - 1 N. 2.4.4.5 Hydrogen peroxide - 30 percent.
  • Procedure:
  • Use IO0 ml sample or a suitable portion diluted to 100 ml. If the sample is highly coloured. add 3 ml of aluminium hydroxide suspension, mix, let settle and filter. If sulphide, sulphite or thiosulphate is present, add 1 ml of hydrogen peroxide and stir for I minute. Directly titrate the samples in the pH range 7 to IO. Adjust sample pH to 7-10 with sulphuric acid or sodium hydroxide if it is not in the range. Add I.0 ml of potassium chromate indicator solution. Titrate with standard silver nitrate solution to a pinkish yellow end point. Standardize silver nitrate solution and establish reagent blank value by titration method.
  • Calculation:
    Chloride, mg/l =[ ( V1-V2)s ) x N x 35.450]/ v3
    where
  • VI = volume in ml of silver nitrate used by the sample
  • v2 = volume in ml of silver nitrate used in the blank titration
  • v3 = volume in ml of sample taken for titration, and N I normality of silver nitrate solution
Cement
CHEMICAL ANALYSIS OF CEMENT
  • This standard gives the procedure for the chemical analysis of the different types of hydraulic cement
  • Loss on ignition
  • Silica
  • Combined Ferric oxide and Alumina
  • Ferric oxide (Fe2O3)
  • Alumina (Al2O3)
  • Calcium Oxide (Cao)
  • Magnesia (Mgo)
  • Sulphuric Anhydride (So3)