Portland Cement CE 414 Materials PDF

MANUEL L. QUEZON UNIVERSITY School of Engineering CIVIL ENGINEERING DEPARTMENT CE 414 : CONSTRUCTION MATERIALS & TESTING PORTLAND CEMENT TESTING OF PO...

MANUEL L. QUEZON UNIVERSITY School of Engineering CIVIL ENGINEERING DEPARTMENT CE 414 : CONSTRUCTION MATERIALS & TESTING PORTLAND CEMENT TESTING OF PORTLAND CEMENT Portland cement is a non-bituminous cement or hydraulic cement considered as the basic binding material concrete. It is defined as the material produced by burning to incipient fusion a properly proportioned mixture of argillaceous and calcareous materials. The cement has hydraulic properties; that is, it combines chemically with water, and then hardens for indefinite period. The chemical reaction is called hydration. Basic Manufacture of Portland cement 1. The raw materials containing lime, silica and alumina, in appropriate proportions are ground separately to a fine grade and are then blended under carefully controlled proportioning either in a dry form or in a wet process. 2. The blended mixture is then placed in a rotary kiln essentially a cylindrical shell from 150 to 450 ft. long, and 8 to 13 ft. in diameter, rotating about an axis slightly inclined to the horizontal. The temperature inside the kiln is approximately 2,700°F. 3. The immediate product emerging from the kiln are called “clinkers” which are cooled and then ground to a very fine grade that the majority will pass through a sieve having 200 meshes to the lineal inch, or 40,000 openings in one square inch. 4. After formation of the clinkers. Four major compounds plus trace elements are produced. The relative proportion of these compounds determines which type of cement results. These compounds are: 4.1 Tri-calcium Silicate 4.2 Di-calcium Silicate 4.3 Tri-calcium Aluminate 4.4 Tetra-calcium Alumino ferrite 5. A small amount of Plaster of Paris of Gypsum is being added to regulate the setting time of the cement. At this stage, the cement is ready to be shipped for use. CONSTRUCTION MATERIALS & TESTING CONNIE A. BALISI  ASTM Types of Portland cement Type Name Purpose I Normal General-purpose cement suitable for most purposes. IA Normal-Air Entraining An air-entraining modification of Type I. Moderate Sulfate Used as a precaution against moderate sulfate attack. It will usually II Resistance generate less heat at a slower rate than Type I cement. Moderate Sulfate IIA Resistance- An air-entraining modification of Type II. Air Entraining Used when high early strength is needed. It is has more C3S than Type I cement and has been ground finer to provide a higher surface-to-volume III High Early Strength ratio, both of which speed hydration. Strength gain is double that of Type I cement in the first 24 hours. High Early Strength- IIIA An air-entraining modification of Type III. Air Entraining Used when hydration heat must be minimized in large volume applications IV Low Heat of Hydration such as gravity dams. Contains about half the C3S and C3A and double the C2S of Type I cement. Used as a precaution against severe sulfate action - principally where soils or ground waters have a high sulfate content. It gains strength at a slower rate V High Sulfate Resistance than Type I cement. High sulfate resistance is attributable to low C3A content. Handling Portland cement 1. Bulk Shipment 2. Non-bulk Shipment Ways of Storing Portland cement a. Warehouse or shed should be airtight as much as possible. b. Flooring or shed should be stocked together. c. Cement sacks should be stocked together. d. Warehouse doors and windows should be kept closed except when cement is taken out for use. CONSTRUCTION MATERIALS & TESTING CONNIE A. BALISI Physical Properties 1. Fineness Fineness, or particle size of portland cement affects hydration rate and thus the rate of strength gain. The smaller the particle size, the greater the surface area-to-volume ratio, and thus, the more area available for water-cement interaction per unit volume. The effects of greater fineness on strength are generally seen during the first seven days (PCA, 1988). Fineness can be measured by several methods:  AASHTO T 98 and ASTM C 115: Fineness of Portland Cement by the Turbidimeter.  AASHTO T 128 and ASTM C 184: Fineness of Hydraulic Cement by the 150-µm (No. 100) and 75-µm (No. 200) Sieves  AASHTO T 153 and ASTM C 204: Fineness of Hydraulic Cement by Air Permeability Apparatus  AASHTO T 192 and ASTM C 430: Fineness of Hydraulic Cement by the 45-µm (No. 325) Sieve 2. Soundness When referring to Portland cement, "soundness" refers to the ability of a hardened cement paste to retain its volume after setting without delayed destructive expansion (PCA, 1988).. ASTM C 150, Standard Specification for Portland Cement specifies a maximum autoclave expansion of 0.80 percent for all Portland cement types. The standard autoclave expansion test is: AASHTO T 107 and ASTM C 151: Autoclave Expansion of Portland cement 3. Setting time Cement paste setting time is affected by a number of items including: cement fineness, water-cement ratio, chemical content (especially gypsum content) and admixtures. Setting tests are used to characterize how a particular cement paste sets. For construction purposes, the initial set must not be too soon and the final set must not be too late. Additionally, setting times can give some indication of whether or not cement is undergoing normal hydration (PCA, 1988). Normally, two setting times are defined (Mindess and Young, 1981): 1. Initial set. Occurs when the paste begins to stiffen considerably. 2. Final set. Occurs when the cement has hardened to the point at which it can sustain some load. CONSTRUCTION MATERIALS & TESTING CONNIE A. BALISI  ASTM C 150 Specified Set Times by Test Method Test Method Set Type Time Specification Initial ≥45 minutes Vicat Final ≤375 minutes Initial ≥60 minutes Gillmore Final ≤600 minutes The standard setting time tests are:  ASTM C 191: Time of Setting of Hydraulic Cement by Vicat Needle  ASTM C 266: Time of Setting of Hydraulic-Cement Paste by Gillmore Needles 4. Strength Cement paste strength is typically defined in three ways: compressive, tensile and flexural. These strengths can be affected by a number of items including: water-cement ratio, cement-fine aggregate ratio, type and grading of fine aggregate, manner of mixing and molding specimens, curing conditions, size and shape of specimen, moisture content at time of test, loading conditions and age (Mindess and Young, 1981). Since cement gains strength over time, the time at which strength test is to be conducted must be specified. Typically times are 1 day (for high early strength cement), 3 days, 7 days, 28 days and 90 days (for low heat of hydration cement). When considering cement paste strength tests, there are two items to consider:  Cement mortar strength is not directly related to concrete strength. Cement paste strength is typically used as a quality control measure.  Strength tests are done on cement mortars (cement + water + sand) and not on cement pastes. 5. Compressive The most common strength test, compressive strength, is carried out on a 50 mm (2-inch) cement mortar test specimen. The test specimen is subjected to a compressive load (usually from a hydraulic machine) until failure. This loading sequence must take no less than 20 seconds and no more than 80 seconds. Table 3.15 shows ASTM C 150 compressive strength specifications. CONSTRUCTION MATERIALS & TESTING CONNIE A. BALISI  ASTM C 150 Portland cement Mortar Compressive Strength Specifications in MPa (psi) Portland Cement Type Curing Time I IA II IIA III IIIA IV V 12.4 10.0 1 day - - - - - - (1800) (1450) 12.4 10.0 10.3 8.3 24.1 19.3 8.3 3 days - (1800) (1450) (1500) (1200) (3500) (2800) (1200) 19.3 15.5 17.2 13.8 6.9 15.2 7 days - -- (2800) (2250) (2500) (2000) (1000) (2200) 17.2 20.7 28 days - - - - - - (2500) (3000) Note: Type II and IIA requirements can be lowered if either an optional heat of hydration or chemical limit on the sum of C3S and C3A is specified The standard cement mortar compressive strength test is:  ASTM C 109: Compressive Strength of Hydraulic Cement Mortars (Using 50-mm or 2- in. Cube Specimens)  ASTM C 349: Compressive Strength of Hydraulic Cement Mortars (Using Portions of Prisms Broken in Flexure) 6. Tensile Although still specified by ASTM, the direct tension test does not provide any useful insight into the concrete-making properties of cements. It persists as a specified test because in the early years of cement manufacture, it used to be the most common test since it was difficult to find machines that could compress a cement sample to failure. 7. Flexural strength Flexural strength (actually a measure of tensile strength in bending) is carried out on a 40 x 40 x 160 mm (1.57-inch x 1.57-inch x 6.30-inch) cement mortar beam. The beam is then loaded at its center point until failure. The standard cement mortar flexural strength test is:  ASTM C 348: Flexural Strength of Hydraulic Cement Mortars CONSTRUCTION MATERIALS & TESTING CONNIE A. BALISI  8. Specific Gravity Test Specific gravity is normally used in mixture proportioning calculations. The specific gravity of portland cement is generally around 3.15 while the specific gravity of portland-blast- furnace-slag and portland-pozzolan cements may have specific gravities near 2.90 (PCA, 1988). The standard specific gravity test is:  ASTM C 188: Density of Hydraulic Cement 9. Loss on Ignition Loss on ignition is calculated by heating up a cement sample to 900 - 1000 C (1650 - 1830°F) until a constant weight is obtained. The weight loss of the sample due to heating is then determined. A high loss on ignition can indicate rehydration and carbonation, which may be caused by improper and prolonged storage or adulteration during transport or transfer (PCA, 1988). The standard loss on ignition test is contained in:  ASTM C 114: Chemical Analysis of Hydraulic Cement CONSTRUCTION MATERIALS & TESTING CONNIE A. BALISI