Cement and Concrete Mix PDF

SAMPLING AND TESTING OF CEMENT AND CONCRETE MIX  Module II- SAMPLING AND TESTING CEMENT AND CONCRETE MIX OUTLINE: I. Introduction: Cement II. Definition: Portland Cement Hydraulic Cement Hydration Heat of Hydration III. Basic...

SAMPLING AND TESTING OF CEMENT AND CONCRETE MIX  Module II- SAMPLING AND TESTING CEMENT AND CONCRETE MIX OUTLINE: I. Introduction: Cement II. Definition: Portland Cement Hydraulic Cement Hydration Heat of Hydration III. Basic Composition of Portland Cement IV. Raw Materials Used in the Manufacture of Cement V. Manufacture of Portland Cement A. Basic Processes B. Steps VI. Principal Compounds Present in the Finished Cement VII. Types of Portland Cement/ Uses VIII. Pozzolan A. Types B. Uses IX. Blended Hydraulic Cement (Portland-Pozzolan Cement) A. Kinds B. Types C. Uses X. Sampling/Minimum Testing Requirements XI. Different Tests on Portland Cement A. Physical Tests B. Chemical Tests XII. Significance of Tests XIII. Specifications What is Cement? The term cement, in its broader meaning, applies to any materials that will bind two or more non- adhesive substances together. The cements to be considered here are those which have a limestone, oyster-shell, coquina shell or similar lime base and are used to form concrete. Composition of Concrete By Weight: By Volume: 1. Cement – 14% 1. Cement – 10% CA - 50% 2. Aggregates – 80% 2. Aggregates – 70% FA - 30% 3. Water – 6% 3. Water – 15% 4. Air – 5% Composition of Concrete is Classified into Two Groups: 1. Active Group – Cement and Water 2. Inactive Group – Coarse and Fine Aggregates Functions of Cement: 1. To bind CA and FA together. 2. To fill the voids in between CA and FA to form a compact mass. Cement + water = cement paste fill small voids in FA fill large voids in CA  What is Portland Cement? Portland Cement is defined as the product obtained by burning (calcining) to incipient fusion a properly proportioned mixture of argillaceous and calcareous materials and the burnt product which is called clinker is then mixed with Gypsum (CaSO42H2O), and pulverized to form Portland Cement. INCIPIENT FUSION Burning the materials to make it liquid by heating it into a very high temperature, at about 1480°C. At this temperature, the initial melting stage of the materials is reached known as the point of incipient fusion. Here sintering takes place and a clinker is formed. What is Hydraulic Cement? Portland Cement is a hydraulic cement, that is, it reacts or combined chemically with water (hydrates), one that will harden under water. The process is known as Hydration. The heat generated in the reaction of cement and water is called Heat of Hydration. The reaction produce a substance that is durable, resists the effects of water, and continues to gain strength as long as moisture is present. It will continue to gain strength even when completely submerged in water. HYDRATION: The process in which the cement reacts or combined chemically with water HEAT OF HYDRATION: ▪ The heat produced by the chemical reaction between cement and water. ▪ The amount of heat generated depends on the chemical composition of the cement. ▪ The rate of heat generation is affected by: the fineness of the cement, the chemical composition and the temperature during hydration.  Portland Cement Basic Composition 1. Lime (CaO) = 60 – 65% 2. Silica (SiO2) = 10 – 25% 3. Iron Oxide (Fe2O3) = 2 – 4% (gives the cement its grey color) 4. Alumina (Al2O3) = 5 – 10%  Raw Materials Used in the Manufacture of Portland Cement Most of the ingredients in Portland Cement are found in nature, but they cannot always be used in their natural form. Limestone, shale, clay, chalk, marl, oyster shells, silica sand, iron ore and blast furnace slag may be used as raw materials. Each cement plant may use a different combination of raw materials which when ground, blended, and tested under rigid control, produce a cement that is uniform in strength and quality. Depending on the location of the cement manufacturing plant, available raw materials are pulverized and mixed in proportions such that the resulting mixture will have the desired chemical composition. Argillaceous Raw Materials Those materials which contributes Silica (SiO2), Alumina (Al2O3) and Iron Oxide (Fe2O3) to the clinker, it includes clay, shale, blast furnace slag, iron ore, sand,etc. Calcareous Raw Materials Those material which contributes Lime (CaO) and Magnesia (MgO) to the clinker, it includes limestone, chalk, marls, marine (oyster shells), etc. Typical Sources of Raw Material Used in the Manufacture of Portland Cement COMPONENTS Lime Silica Alumina Iron Cement Rock Sand Clay Iron Ore Limestone Traprock Shale Iron Calcine Marl Calcium Slag Iron Dust Alkali Waste Silicate Fly Ash Iron Pyrite Oyster Shell Quartzite Copper Slag Iron Sinters Coquina Shell Fuller’s Earth Aluminum Ore Refuse Iron Oxide Chalk Staurolite Blast Furnace Flue Dust Marble Diaspore Clay Granodiorite Kaolin Source: Portland Cement Association GYPSUM (CaSO42H2O) A predetermined percentage of gypsum is added to regulate the setting time that will be required for a particular cement. The addition of small quantity of gypsum is of great importance because it can stabilize and control the rate of hydration. Although small in quantity, the addition of gypsum must be done with some care, as its prime purpose is to react with the tricalcium aluminate, the quantity added must correspond to the amount of tricalcium aluminate available. Small amount added will often increase the strength, too much amount leads to slow expansion of the set cement and may result in crumbling. Portland Cement is Manufactured by Two (2) Basic Processes: 1. Wet Process In the wet process proper proportions of raw materials are mixed with enough water to form a slurry, which is 30 to 35 % water. In this form the materials are further proportioned, mixed, ground and pulverized and then pumped to a furnace called a kiln. It is used for very friable materials such as chalk and clay, wet process are preferred because of more accurate control of the raw mix. 2. Dry Process The dry process is similar, except that the materials are proportioned, stored, ground, mixed, pulverized and fed into the kiln in a dry state. Preferred when raw materials are hard rocks, less fuel is required for burning than in the wet process. Steps in the Manufacture of Portland Cement 1. Raw materials is first reduced to 5 in. size (primary crusher), then ¾ in. size in secondary crusher, and stored separately and conveyed to grinding mill. 2. Raw materials are ground to powder and blended (incorporation of raw materials to form a homogeneous mixture). 3. The burning of the raw mix in a kiln to form a clinker (burning changes raw mix chemically into cement clinker). 4. The grinding or pulverizing the clinker with the addition of a small proportion of gypsum to a fine powder (Portland Cement). Three heating stages occurring in a Rotary Kiln: 1. @ 425°C - Drying – excess water is driven off 2. @ 875°C - Calcining – heating to a high temperature but below the melting or fusing point, causing decomposition of carbonates and other compounds (limestone breaksdown into CaO and CO2). CaCO3 CaO + CO2 Calcium Carbonate (limestone) MgCO3 MgO + CO2 Magnesium Carbonate Al2Si2O7 Al2O3 + 2SiO2 Aluminum Silicate (clay) Fe2O3 Hematite (Iron Ore) 3. @1400°C – 1480°C – Clinkering – initial melting stage of material, known as the point of incipient fusion, is reached sintering takes place and a clinker is formed. Oxides recombine to form cement compounds. Cement Compounds: C3S, C2S, C3A, C3AF where: C =CaO, S = SiO2, A = Al2O3, F = Fe2O3 C3S = 3CaO.SiO2, C2S = 2CaO.SiO2 C3A = 3CaO.Al2O3, C3AF = 3CaO.Al2O3.Fe2O3 Principal Compounds which are Present in the Finished Cement When lime and silica are heated to the sintering temperature in the presence of alumina and ferric oxide, four basic components of cement are formed. These clinker compounds that are formed by sintering are responsible for the hydration process: 1. Tricalcium Silicate, 3CaOSiO2 (C3S) 2. Dicalcium Silicate, 2CaOSiO2 (C2S) 3. Tricalcium Aluminate, 3CaOAl2O3 (C3A) 4. Tetracalcium Alumino Ferrite, 4CaOAl2O3Fe2O3 (C4AF) 1. Tricalcium Silicate (C3S) = 3CaO.SiO2 Responsible for the initial set and of the early strength development of the cement, high percent will give high strength, faster strength development. It has all the essential properties of portland cement, it undergoes an initial and final set within an hour after mixing and when properly prepared shows no unsoundness. Mixes of tricalcium silicate and water are less plastic, more water are required to obtained a workable paste, addition of gypsum to the mass render it more plastic and has some effect on setting time. Can be calculated as follows: C3S = 4.07(CaO) - 7.60(SiO2) - 6.72(Al2O3) - 1.43(Fe2O3) - 2.85(SO3) 2. Dicalcium Silicate (C2S) = 2CaO.SiO2 Also responsible for the strength development, high percent will give high strength but slow in development. Exhibits no definite setting time and mixed mass sets only slowly over a period of some days, addition of gypsum produces little change. It produces little strength at early ages but gains steadily in strength at later ages until it approaches equality with tricalcium silicate. Tricalcium silicate attains the greater part of its strength in seven (7) days. Added strength in the final hardening which may be prolonged over many months (slow), hardens the slowest, releases the least heat, and has a low shrinkage. Can be calculated as follows: C2S = 2.87(SiO2) - 0.754(3CaO.SiO2) 3. Tricalcium Aluminate (C3A) = 3CaO.Al2O3 Control the volume change of cement, aid in development of early strength of cement. Facilitate combination of lime and silica. It reacts the most rapidly, gaining an appreciable amount of its maximum strength at first day after mixing, it liberates the most heat, and undergoes the most shrinkage. Gives a flash set on mixing with water and this is accompanied by the evolution of so much heat as to lead to violent steaming, as cement, become finer, the setting rate is accelerated making the problem of flash set more prevalent, addition of small quantity of gypsum counteract this detrimental reaction. Weak resistance against sulfate attack. Can be calculated as follows: C3A = 2.65(Al2O3) - 1.69(Fe2O3) 4. Tetracalcium AluminoFerrite (C4AF) = 4CaO.Al2O3.Fe2O3 Must not be present in excess amount because it will displace the silicate which is responsible in strength development. Hydrates rapidly More stable than C3A Contribution to overall strength is insignificant Accelerate the hydration of silicates Can be calculated as follows: C4AF = 3.04(Fe2O3)  Typical Average Values of Compound of Portland Cements of Different Types Compound Composition, % Cement Free Loss on C3S C2S C3A C4AF CaSO4 MgO CaO Ignition Type I 59 15 12 8 2.9 0.8 2.4 1.2 6 Type II 46 29 12 2.8 0.6 3 1 (8 max.) 12 Type III 60 12 8 3.9 1.3 2.6 1.9 (15 max.) 30 46 5 Type IV (35 max.) 13 2.9 0.3 2.7 1 (40 min.) (7 max.) 4 Type V 43 36 12 2.7 0.4 1.6 1 (5 max.) The numbers in parenthesis are the maximum or minimum values specified by ASTM C 150-84  Schematic Representation of the Formation and Hydration of Portland Cement Component elements O2 Si Ca Al Fe Component oxides CaO SiO2 Al2O3 Fe2O3 Cement Compounds C3S C2S C3A C4AF Portland Cements Various Types Hydration products C-S-H gel Ca(OH)2  HYDRATION OF CEMENT At any stage of hydration, the cement paste consists of gel (a finely-grained product of hydration having large surface area collectively called gel), the remnant of unreacted cement, calcium hydroxide Ca(OH)2, and water, besides some other minor compounds. The reactions of compounds and their products may be symbolically represented as: 2C3S + 6H C3S2H3 + 3Ca(OH)2 Silicate phase 2C2S + 4H C3S2H3 + Ca(OH)2 C3A + 6H C3AH6 C4AF + 7H C3AH6 + CFH The product C – S – H represents the calcium silicate hydrate which is the gel structure. The above equations only refer to the processes in which the cement compounds (C3S and C2S, etc.) react with water to form a strong hydrated mass. The hydrated crystals are extremely small, varying from colloidal dimensions(less than 2um) to 10 um or more. The Ca(OH)2 liberated during the reaction of silicate phase crystallizes in the available free space. Types of Portland Cement For most construction purposes a standard type of Portland Cement is used. However, special types are manufactured for specific uses. The amount of the four (4) basic ingredients can be varied to produce different types of portland cement, each with some unique characteristics: 1. Type I (Normal Type) This is a standard portland cement used for general construction work when the special properties of the other types are not required. Uses It is normally used for reinforced concrete buildings, bridges, pavement and sidewalks where the soil conditions are normal, for most concrete masonry units, and for all uses where the concrete is not subject to special sulfate hazard or where the heat generated by the hydration of the cement is not objectionable. 2. Type II (Moderate-Sulfate Resistant) This cement has a lower heat of hydration than Type I and generally sets more slowly. It has a better resistance to the action of sulfate than Normal Portland and is used where sulfate concentrations in ground waters are higher than normal but not unusually severe It also generates heat at a slower rate than Normal Portland and is used in mass concrete works. Its use will minimize temperature rise, a property which is particularly important when concrete is being placed in hot weather.  Uses It is used in drainage structures, foundations and floor slabs, where the soil contains a moderate amount of sulfates. 3. Type III (Highly-Early Strength) This type develops approximately 190% of the strength of Type I at three (3)days and 90% to 130% at 28 days. It develops considerable heat during setting. Uses It is used where higher strengths are required at early periods usually of a week or less. It is particularly useful where it is required to remove forms as soon as possible or when the structure must be brought into service quickly. High-early strength makes it possible to reduce the period of protection for concrete during cold weather. 4. Type IV (Low-Heat of Hydration) This is a special cement for use where the amount and rate of heat generated must be minimized. Strength is also developed at a slower rate. Low-heat portland cement was first developed for use in the construction of the Hoover Dam. Its slow setting time is an advantage in large structures, where solid one-piece construction is desire.. Uses It is intended for use in massive concrete structures, such as large dams, where the temperature rise resulting from heat generated during hydration is a critical factor. 5. Type V (Sulfate - Resistant) A special cement intended to be used in structures to prevent damage from severe sulfate action of soils or high alkali content of waters. Uses Intended for use in structures subject to attack by sulfate concentrations in some waters, such as may be found in certain manufacturing plants or in the ground water in some areas. It is also resistant to the action of seawater.  Approximate Relative Strength of Concrete As Affected by Type of Cement Compressive Strength – Percent of Strength of Normal (Type I) Portland – Cement Concrete Type of Portland Cement 1 Day 7 Days 28 Days 3 Months I. Normal 100 100 100 100 II. Moderate 75 85 90 100 III. High-Early Strength 190 120 110 100 IV. Low-Heat 55 55 75 100 V. Sulfate-Resistant 65 75 85 100  Approximate Composition Limits of Portland Cement CaO ------------------ 60 – 70 SiO2 ------------------ 17 – 25 Al2O3 ------------------ 3–8 FeO3 ------------------ 0.5 – 6.0 MgO ------------------ 0.1 – 5.5 Na2O + K2O ------------------ 0.2 – 1.3 SO3 ------------------ 1.0 – 3.0 Oxide Composition of Type I or Normal Portland Cement Oxide Ingredient Range, % Lime, CaO 60 – 66 Silica, SiO2 19 – 25 Alumina, Al2O3 3–8 Iron Oxide, Fe2O3 1–5 Magnesia, MgO 0–5 Sulfur Trioxide, SO3 1-3 Source: Portland Cement Association Oxide and Compound Compositions of a Typical Portland Cement Typical Oxide Composition, percent CaO 63 SiO2 20 Al2O2 6 Fe2O2 3 MgO 1 – 1/2 SO3 2 K2O 1 Na2O Other 1 Loss on ignition 2 Insoluble Residue 1/2 Hence, Calculated Compound Composition, percent C3A 10.8 C3S 54.1 C2S 16.6 C4AF 9.1 Minor compounds -  POZZOLAN AND POZZOLANIC CEMENT POZZOLAN: A siliceous or siliceous and aluminous material, which in itself possesses little or no cementitious value but which will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide (lime at ordinary temperature to form compounds possessing cementitious properties.  Two (2) Kinds of Pozzolan 1. Natural Pozzolan Materials of volcanic origin (volcanic ash), it includes a number of natural materials such as diatomaceous earth, opaline cherts and shales, tuffs and pumicites, which is composed of a mixture silicates and contain both glass and crystalline particles. 2. Artificial Pozzolan Product obtain by heat treatment of natural materials such as clays and shales and certain siliceous rocks and pulverized fuel ash.  Pulverized Fuel Ash (Fly Ash) The most common artificial pozzolan, obtained by electrostatic or mechanical means form the flue gases of furnace in coal-fired power plant stations. The fly ash particles are spherical and of at least the same fineness as cement so that silica is readily available for reaction. A fly ash is a fine residue which results from the combustion of powdered coal and may contain various amounts of carbon, silica, sulfur, alkalis and other ingredients.  Uses of Pozzolan Use as a substitute for a proportion of the portland cement in concrete, but in some cases it is preferable to use it as an addition (admixture). These pozzolanic materials are generally substitute for 10 to 35 percent of the cement. This substitute produces concrete that is more permeable but much more resistance to the action of salt, sulfate or and water.  Blended Hydraulic Cement Hydraulic cement used for general construction and or some special application containing pozzolan , blast – furnace slag, limestone, or some combination of these with portland cement clinker or slag with lime in different porportions.  Blended Hydraulic Cement Kinds of Blended Hydraulic Cements for General Concrete Construction 1. Type IS - Portland - blast-furnace slag cement 2. Type IP - Portland - pozzolan cement 3. Type IL - Portland - limestone cement 4.Type IT -Ternary blended cement (consist of portland cement with either a combination of two different pozzolans, slag and pozzolan, a pozzolan and limestone, or a slag and a limestone.  Portland – Pozzolan Cement Defined as a blend of ordinary portland cement and pozzolan. These cements are made by intergrinding or blending pozzolans with portland cement A hydraulic cement consisting of an intimate and uniform blend of portland cement and fine pozzolan produced by intergrinding portland cement clinker and finely divided pozzolan, or a combination of intergrinding and blending, in which the amount of the pozzolan constituent is within specified limits, usually between 15 and 40 weight percent of the portland- pozzolan cement. Types of Portland - Pozzolan Cement 1. Type IP Portland-Pozzolan cement for use in general concrete construction. 2. Type P Portland-Pozzolan cement for use in concrete construction where high strengths at early ages are not required.  Uses of Portland-Pozzolan Cement Particular useful in marine and hydraulic constructions and other mass concrete structures. Use in large mass concrete works because of reduction in heat evolution, examples are the constructions of dams and bridges. Portland-pozzolan cement produces less heat of hydration and offers greater resistance to the attack of impurities in water than Normal Portland Cement. The original reason for the use of pozzolanic portland cement was the improved durability combined with some economy obtained in marine, hydraulic and underground structures. The portland-pozzolan cement can generally be used wherever ordinary portland cement is usable under normal condition. Use in concrete with low-heat characteristics and in concrete requiring good chemical resistance.  ITEM 311 – PORTLAND CEMENT CONCRETE PAVEMENT (as amended by D.O. No. 133, s. 2016)  ITEM 311 – PORTLAND CEMENT CONCRETE PAVEMENT (as amended by D.O. No. 133, s. 2016) ITEM 405 – STRUCTURAL CONCRETE  Sampling/Testing Requirements ASTM C183-SAMPLING AND THE AMOUNT OF TESTING OF HYDRAULIC CEMENT The cement may be sampled by any of the applicable methods: 1.1 From the Conveyor Delivering to Bulk Storage – Take one grab sample, having a mass of at least 5 kg (10 lb) at approximately 6-h intervals. “Grab Sample” – A cement sample secured from a conveyor, from bulk storage, or from bulk shipment in one operation, shall be termed a “grab sample.” A sample obtained during a 10-min interval using an automatic sampling device that continuously samples a cement stream may also be termed a grab sample. “Composite Sample”- Grab samples taken at prescribed intervals over a period of time may be combined to form a “composite sample” representative of the cement produced during that period of time. All samples, whether grab or composite, shall have a mass of at least 5 kg (10 lb).  Sampling/Testing Requirements 2. Transfer Sampling – Sample cement in storage while the cement is being transferred from one bin to another. Take one grab sample from the transfer stream for each 400 tons of cement, or fraction thereof, but take no less than two grab samples and combine them to produce a composite sample. 3. Other Sampling Methods – When neither of the above sampling methods is applicable, samples may, when authorized by the purchaser, be taken by one of the following methods: 1.From Bulk Storage at Point of Discharge – Withdraw cement from the discharge openings in a steady stream until sampling is completed. In sampling bulk storage at points of discharge , while the cement is flowing through the openings, take samples as such intervals so that at least two grab samples shall be secured for each 400 tons in the bin or silo. 1.3.2 From Bulk Storage and Bulk Shipment by Means of a Slotted Tube Sampler –When the depth of the cement to be sampled does not exceed 2.1 m (7 ft), obtain samples using a slotted tube sampler. Take samples from well-distributed points and various depths of the cement so that the samples taken will represent the cement involved.  Sampling/Testing Requirements Sampling 3. From Packaged Cement by Means of Tube Sampler – Insert the sampler diagonally into the valve of the bag and place the thumb over the air hole. Then withdraw the sampler. Take one sample from a bag in each 5 tons or fraction thereof. 4. From Bulk Shipment of Car or Truck: (a). Single Shipment – If only one car or truck is being loaded and the loading is continuous and all from the same source, take a 5-kg (10 lb) sample. If not continuous or unknown, combine five or more portions from different points in the load to form the test sample. (b) Multiple Shipment – When the shipment consists of several cars or trucks loaded from the same source and on the same day, sample the shipment at the rate of one sample for each 90 Mg (100 tons) of cement or fraction thereof, but take not less than two samples.  Sampling/Testing Requirements STORAGE OF CEMENT Cement, in bulk, can best be stored in bins of depth 2 m or more, usually a crust about 5 cm thick forms, and this must be removed before cement is taken for use. The bagged cement may also be kept safely for many months if stored in waterproofed shed with nonporous walls and floors, the wind being tightly shut. Once the cement has been properly stored it should not be disturbed until it is to be used. The practice of moving and restacking the bags to reduce warehouse pack only exposes fresh cement to air. DPWH STANDARD SPECIFICATION (BLUE BOOK) Item 311 : PORTLAND CEMENT CONCRETE PAVEMENT Item 405 – STRUCTURAL CONCRETE Subsection 311.2.11 – Storage of Cement and Aggregates All cement shall be stored, immediately upon delivery at the Site, in weatherproof building which will protect the cement from dampness. The floor shall be raised from the ground. The buildings shall be placed in locations approved by the Engineer. Provisions for storage shall be ample, and the shipments of cement as received shall be separately stored in such a manner as to allow the earliest deliveries to be used first and to provide easy access of each shipment for identification and inspection  Sampling/Testing Requirements Subsection 311.2.11 –Storage of Cement and Aggregates Storage buildings shall have capacity for storage of a sufficient quantity of cement to allow sampling at least (12) days before the cement is to be used. Bulk cement, if used, shall be transferred to elevated air tight and weatherproof bins. Stored cement shall meet the test requirements at any time after storage when retest is ordered by the Engineer. At the time of use, all cement shall be free-flowing and free of lumps. REJECTION Cement which for any reason, has become partially set or which contains lumps of caked cement shall be rejected. Cement salvaged from discarded or used bags shall not be used. Samples of cement shall be obtained in accordance with AASHTO T 127/ASTM C 183. Due to defective storage for long periods, cement is adversely affected. The cement remaining in bulk storage with the manufactures for more than six(6) months or cement in jute bags in local storage in the hands of dealers for more than three (3) months after completion of tests may be retested before use and rejected if they fail to conform to any of the requirements of the specification.  Sampling/Testing Requirements PROTECTION OF SAMPLES As samples are taken, place them directly in moisture-proof airtight containers to avoid moisture absorption and aeration of the sample. If the samples are placed in cans, fill the can completely and immediately seal. Use moisture-proof multiple-wall paper bags or plastic bags if they are strong enough to avoid breakage, and if they can be sealed immediately after filling in such a manner as to eliminate excess air in the sample and avoid moisture absorption and aeration of the sample. Samples shall be treated as described in the Preparation of Sample. PREPARATION OF SAMPLE (PHYSICAL TESTING) Before testing, pass each sample through an 850-um(No. 20) sieve, or any other sieve having approximately the same size openings, in order to mix the sample, break up lumps, and remove foreign material. Discard the foreign materials and hardened lumps that do not break up on sieving or brushing. Store the cement in airtight moisture-proof containers to prevent aeration or absorption of moisture prior to test.  Sampling/Testing Requirements SAMPLE PREPARATION (CHEMICAL ANALYSIS): 1.Before testing, pass representative portions of each sample through a No. 20 (0.850 mm) sieve, or any other sieve having approximately 20 openings/1 in., in order to mix the sample, break up lumps, and foreign materials. Discard the foreign materials and hardened lumps that do not break up on sieving or brushing. 2.By means of a sample splitter or by quartering, the representative sample shall be reduced to a laboratory sample of at least 50 g. Where the larger quantities are required for additional determinations such as water-soluble alkali, chloride, duplicate testing, etc., prepare a sample of at least 100 g. 3.Pass the laboratory sample through a U.S. No. 100 sieve (sieve opening of 0.150 mm). Further grind the sieve residue so that it also passes the No. 100 sieve. Homogenize the entire sample by again passing it through the sieve. 4.Transfer the sample to a clean, dry, glass container with an airtight lid and further mix the sample thoroughly. 5.Expedite the above procedure so that the sample is exposed to the atmosphere for a minimum time.  Sampling/Testing Requirements REQUIREMENTS FOR CEMENT MIXING ROOMS The temperature of the air in the vicinity of the mixing slab, molds, and base plates shall be maintained at 23 ± 4.0 °C and at a relative humidity of not less than 50 %. The temperature of the mixing water used to prepare cement paste and mortar specimens shall be 23.0 ± 2.0 °C. REQUIREMENTS FOR MOIST CABINETS AND MOIST ROOMS Maintain the atmosphere in the moist cabinet or moist room at a temperature of 23.0 ± 2.0 °C and a relative humidity of not less than 95 %. Maintain atmospheric conditions within a moist cabinet or moist room such that test specimens in storage are saturated with moisture to the degree needed to ensure that the exposed surfaces of all specimens in storage both look moist and feel moist. Equip all moist cabinets and moist rooms with a temperature recorder. The use of humidity recording devices is optional.  Sampling/Testing Requirements TEMPERATURE MEASURING DEVICES Reference Temperature Measuring Device – used to verify the temperature recorder, must be accurate and readable to 0.05 °C. A copy of the certificate or report which verifies the accuracy shall be available in the laboratory. Temperature Recorder – shall record temperatures every 15 min or less and shall be accurate and readable to 1 °C. The data from the recorder shall be evaluated at a minimum once each week.  Sampling/Testing Requirements QUANTITY REPRESENTED : One ( 1 ) Quality Test for every 2000 bags or fraction thereof. TESTING REQUIREMENTS : At least 10 kg of sample shall be submitted in an airtight container.  Different Tests on Portland Cement ASTM Standards Physical Tests 1. Fineness : Air Permeability Test (ASTM C 204) No. 325 Sieve (ASTM C 430) – Blended only 3. Normal Consistency (ASTM C 187) 4. Time of Setting by : Vicat Needle (ASTM C 191) Gillmore Needle (ASTM C 266) 5. Autoclave Expansion (ASTM C 151) 6. Compressive Strength (ASTM C 109) Different Tests on Portland Cement ASTM Standards CHEMICAL ANALYSIS OF HYDRAULIC CEMENT 1. Density/Specific Gravity (ASTM C 188) 1. Loss On Ignition (LOI) (ASTM C 114) 2. Insoluble Residue (IR) (ASTM C 114) 3. Sulfur Trioxide (SO3) (ASTM C 114) 4. Magnesium Oxide (MgO) (ASTM C 114)  Significance of Tests DENSITY/SPECIFIC GRAVITY : The test method covers the determination of the density of hydraulic cement. The density of hydraulic cement is defined as the mass of a unit volume of the solids. Its particular usefulness is in connection with the design and control of concrete mix. Specific gravity is not an indication of the quality of the cement. It is used in calculating mix designs.  Significance of Tests FINENESS: The test method covers the determination of the fineness of hydraulic cement. One of the important physical properties of cement is its fineness. Fineness affects the rate of hydration: the finer the cement, the faster strength development takes place. The effects of greater fineness on strength are particularly noticeable during the first 7 days. Also as fineness increases, the amount of water required for a constant slump concrete decreases, to the limits reached by the higher ranges of fineness in high-early-strength cement. Greater fineness not only improves the strength but also watertightness, workability, appearance and durability of concrete.  Significance of Tests NORMAL CONSISTENCY: The test method is intended to be used to determine the amount of water to prepare hydraulic cement pastes for testing. It determines the volume of water to be added in cement paste in order to reduce its in a certain state of plasticity. If insufficient amount of water is added in the mix, some particles of cement will not be chemically changed, if much water is used the excess water may be trapped in the cement paste, the resulting concrete will be weaker. The quality of the cement paste is determined by the proportion of water to cement, too much water prevents proper setting, too little water prevents complete chemical combination. At low water- cement ratio, cement pastes has a consistency of a thick cream (0.25 – 0.35), at high water cement ratio, the mix become increasingly fluid in its characteristics.  Significance of Tests TIME OF SETTING: The purpose of the test method is to establish whether a cement complies with a specification limit on setting time. A method of determining the time occupied in the process of setting, the time interval in which the cement must remain in plastic state. Setting time is an important characteristics of cement which must be regulated. It is necessary for concrete to remain plastic long enough for finishing operations to be carried out. A knowledge of the time of setting is of value since crystallization begins with the initial set and molding and placing of mortar should be complete before the cement begins to set. In practical circumstances, the length of time that a concrete mixture will remain plastic is usually more dependent on the amount of mixing water used and the atmospheric temperature than on the setting time of the cement.  Significance of Tests INITIAL SET : The time which elapses before the paste ceases to be fluid and plastic. Interval between the gauging and partial of plasticity. FINAL SET: The time required for the paste to harden to a certain degree. The time required for the gauged cement to acquire sufficient firmness to resist a certain definite pressure.  Significance of Tests FALSE SET : Grab Set, Premature Stiffening, Hesitation Set, is the rapid development of rigidity (hardness) in a mixed cement paste, mortar or concrete without the evolution of much heat which rigidity can be dispelled and plasticity regained by further mixing without the addition of water. QUICK OR FLASH SET: The rapid development of rigidity in a mixed cement paste, mortar or concrete, usually with the evolution of considerable heat, which rigidity cannot be dispelled nor can the plasticity be regained by further addition of water.  Significance of Tests AUTOCLAVE EXPANSION: The test method covers the determination of the autoclave expansion of Portland cement by means of a test on a neat cement specimen. This method of test is for determining the soundness of Portland cement, soundness is a physical property tested by determining the ability of a hardened cement paste to retain its volume after setting. Lack of soundness or a delayed destructive expansion is caused by too much hard-burned free lime or magnesia in the cement. Autoclave expansion test provided an index of potential delayed expansion caused by the hydration of CaO and MgO or both.  Significance of Tests AIR CONTENT: Air content of freshly mixed mortar is the volume of air (or other gas) voids in a freshly mixed cement mortar, usually expressed as a percentage of total volume of the mortar. The purpose of the test method is to determine whether or not the hydraulic cement under test meets the air-entraining or non- air-entraining requirements of the applicable hydraulic cement specification for which the test is being made.  Significance of Tests COMPRESSIVE STRENGTH: The test method provides a means of determining the compressive strength of hydraulic cement and other mortars and result may be used to determine compliance with specification. Compressive strength is the maximum load sustained by standard specimen when subjected to a crushing force. The ability of cement to develop compressive strength in a concrete mixture is one of its most important characteristics. Strength tests at various ages indicate the strength-producing characteristics of cement but should not be used to try to predict strengths accurately because of the great number of variable that may occur in a number of concrete mixtures.  Factors that Affects the Strength of Cement 1. Grading of the sand or aggregate 2. Proportion of water used 3. Degree of mixing 4. Temperature and humidity of the atmosphere in which it is conducted 5. Method in which the materials is placed in the moulds and the specimen made 6. Curing condition 7. Methods of testing and the age at which tests are carried out  Chemical Analysis of Portland Cement MAJOR COMPONENTS : SiO2 (Silicon Dioxide) Al2O3 (Aluminum Oxide) Fe2O3 (Ferric Oxide) CaO (Calcium Oxide) MgO (Magnesium Oxide) SO3 (Sulfur Trioxide) Loss on Ignition MINOR COMPONENTS : Na2O (Sodium Oxide) K2O (Potassium Oxide) TiO2 (Titanium Dioxide) P2O5 (Phosphorus Pentoxide) ZnO (Zinc Oxide) Mn2O3 (Manganic Oxide) Sulfide Sulfur SEPARATE DETERMINATIONS: Insoluble residue Chloroform-soluble organic substances Free calcium oxide Water-soluble alkali LOSS ON IGNITION (LOI) : A test carried out on Portland cement to determine how much weight a sample will lose when heated to 900 to 10000C. It determines the freshness of cement and the moisture content accumulated and present in the cement cause by free hydration and carbonation of cement. INSOLUBLE RESIDUE (IR) : To determine the acid-insoluble materials (inert) present in cement. SULFUR TRIOXIDE (SO3) : Oxide form from Gypsum (CaSO4.2H2O), it affects the strength and setting time of cement. MAGNESIUM OXIDE (MgO) : It causes unsoundness (volume change) on cement. SPECIFICATIONS - ITEM 700  ITEM 311 – PORTLAND CEMENT CONCRETE PAVEMENT (as amended by D.O. No. 133, s. 2016)  ITEM 311 – PORTLAND CEMENT CONCRETE PAVEMENT (as amended by D.O. No. 133, s. 2016) ITEM 405 – STRUCTURAL CONCRETE