Construction Testing Cement Testing

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Construction Testing Cement Testing

  1. 1. Construction Testing is ready to stand as your partner in concrete technology. Australian Standards for testing are fundamental to the laboratory’s operations Two NATA accredited laboratories at Darra. One for Chemical Testing and the other for Construction Materials Testing Testing can be integrated with your own quality assurance system CONCRETE Compressive Strength AS 1012.9 Method for the determination of compressive strength of concrete specimens. Purpose: The most important property of concrete is its very high strength in compression (crushing). Concrete is specified in terms of compressive strength and this test is a basic measure of compliance with specification. Air Content AS 1012.4 Methods of the determination of air content of freshly mixed concrete. Purpose: Entraining air into concrete can be helpful in enabling it to resist repeated freezing and thawing, such as occurs in floors in industrial freezers. Too much air can reduce strength while too little will reduce durability. This test is used to ensure that the air content is as specified, and can be used to test the efficacy of air entraining admixtures. Mass Per Unit Volume AS 1012.5 Methods for the determination of mass per unit volume of freshly mixed concrete. Purpose: Concrete is made by mixing weighed quantities of materials, but it is sold by volume. Mass per unit volume is the first stage in determining "yield". * Yield AS 1379 The specification and manufacture of concrete 1.7.2 Volume Of Plastic Concrete. Purpose: Yield is the calculation made using mass per unit volume, and establishes whether a weighed batch of materials achieves its intended volume. Setting Time AS 1012.18 Determination of setting time of fresh concrete, mortar and grout by penetration resistance. Purpose: Handling fresh concrete successfully involves winning a race against the clock – there is a finite length of time available to transport, pour and finish it. It is important to know just how long the concrete will remain workable, and this varies from mix to mix. This test measures the time from batching to setting – a crucial variable, which assists good planning. Flexural Strength AS 1012.11 Method for the determination of the flexural strength of concrete specimens Purpose: In addition to compression and splitting, concrete may have to resist bending forces, often imparted by point loads. These might be encountered on airport taxiways, container terminals aprons or warehouse floors. In these cases, the concrete must resist heavy wheel loads without fracturing. This test measures its ability to withstand this kind of load. Splitting Tension AS 1012.10 Method for the determination of indirect tensile strength of concrete cylinders. Purpose: In addition to its ability to resist compressive forces (eg. in a column), concrete may also have to resist shear forces (splitting). This force might be encountered at the junction of a column and a slab, and is resisted by a different type of strength. Bleed Water AS 1012.6 Method for the determination of bleeding of concrete. Purpose: After concrete is placed, water rises to the surface in a process known as bleeding. The amount of water involved affects the durability of the surface, and the ease of finishing. A mix design needs to provide for just the right amount of bleed water; weather conditions – wind, temperature, humidity and sunshine – are important variables.
  2. 2. CEMENT AS 2350 Methods of testing Portland and blended cements. Normal Consistency AS 2350.3 Normal consistency of Portland and blended cements Purpose: The workability of a concrete mix is partly determined by the workability of the cement/water paste. Cements will require slightly different quantities of water to achieve ideal consistency – the type, mineral content and fineness are the key variables. Water content will influence compressive strength and setting time; this test establishes the precise amount of water required to produce the optimum mix of properties. Setting Time AS 2530.4 Setting times of Portland and blended cements Purpose: The length of the workable life of fresh concrete is largely influenced by the setting time of the cement paste. This test determines the setting behaviour of cement in isolation from the other concrete materials, to assist in mix design. This test measures the setting time cement in a cement water paste. The cement paste is confined in a standard mould and its setting time is determined using a penetration needle. Fineness index by Air Permeability AS 2350.8 Fineness index of Portland cement by air permeability. Purpose: Cement fineness is an important process feature, varying according to the milling process. It will influence reactivity (the finer, the more reactive) and water demand. This test measures an average fineness for a given cement sample. Fineness by the 45 Micron Sieve Method AS 2350.9 Fineness of Portland Fly Ash cement by the 45 micron sieve. Purpose: Cement hydrates optimally when 2/3 or more of its particles are sized in the range 3-32 microns. This ratio can’t be determined from the fineness index, because its only a crude average of particle sizes. This test is used for measuring the coarse (poorly reactive) fraction produced in the cement mill – it is especially important when using blends of different clinkers. Expansion-Le Chatelier AS 2350.5 Determination of soundness of Portland and blended cement. Purpose: Two normal components of cement, free lime and magnesium compounds, are capable of causing cracks in concrete if their concentrations are too high. The Le Chatelier test provides an indication of the likely expansion of a sample, and thus its risk of cracking, by accelerated curing of a cement paste sample. Compressive Strength (ISO/CEN TEST) AS 2350.11 Compressive strength of Portland and blended cements. Purpose: This test determines the intrinsic strength of cement. Its value lies in the way it eliminates other variables which affect the strength of concrete – aggregates, water and admixtures. The test is carried out under internationally standardised conditions, using standard materials, in such a way that variations in test results are solely attributable to variations in cement quality. Drying Shrinkage AS 2350.13 Determination of drying shrinkage of Portland cement mortars. Purpose: Designers of concrete mixes are facing demand for ever finer tolerances in finished concrete as such structures as super-flat warehouse floors become more common. The two factors with the greatest bearing on drying shrinkage are aggregate type and cement. This test measures the shrinkage performance of cement. Sulphate Resistance AS 2350.14 Length of Portland and blended cement mortars exposed to a sulphate solution. Purpose: Vulnerability to attack by dissolved sulphates is an historical weakness of concrete. While a dense, impermeable concrete mix is a good start, the chemistry of the cement can also be manipulated to reduce the risk of attack. This test measures the precise properties of the cement. * Autoclave Expansion ASTM C151 Determination of Aautoclave Expansion. Purpose: This test emulates the process of steam curing used by concrete and indicates the extent of dimensional changes to be expected in moulded concrete products as they are cured. All concrete mixes respond somewhat differently to this treatment – it is important to understand the unique properties of a
  3. 3. cement before it is committed to a mix design. In particular, the test will reveal the presence of unhydrated MgO (Magnesium Oxide), the effects of which may appear only very slowly under ordinary curing conditions. * Relative Density ASTM C188 Determination of relative density. Purpose: The effect that Fly Ash will have on the yield of a concrete mix design must be understood in advance – since cement and Fly Ash have different relative densities, successful use of blended cements depend on knowing this relationship between mass and volume. FLY ASH AS 3583 Methods of test for supplementary cementitious materials for use with Portland cement Fineness by the 45 Micron Sieve Method AS 3583.1 Determination of fineness by the 45 micron sieve. Purpose: Fly Ash is graded according to its fineness as either Fine, Medium or Coarse, Like cement, reactivity of Fly Ash varies with fineness as a production control measure. Loss of Ignition AS 3583.3 Determination of loss of lgnition. Purpose: The most common cause of loss of ignition of Fly Ash is carbon content, indicative of incomplete coal combustion. High carbon content is undesirable in concrete because it is known to cause detrainment – the loss of air – resulting in loss workability and serious placement difficulties. In addition, carbon rises to the surface with bleed water causing unsightly black staining. This test is a routine process control, indicating high carbon content before it can become a problem in concrete. Moisture Content AS 3583.2 Determination of moisture content. Purpose: Fly Ash, like all concrete materials, must be kept dry during storage and distribution. If the material has become damp or wet during handling, this test measures the extent of the problem. * Autoclave Expansion AS 3583.4 Determination of autoclave expansion. Purpose: This test emulates the process of steam curing used by concrete and indicates the extent of dimensional changes to be expected in moulded concrete products as they are cured. All concrete mixes respond somewhat differently to this treatment – it is important to understand the unique properties of a cement before it is committed to a mix design. In particular, the test will reveal the presence of unhydrated MgO (Magnesium Oxide), the effects of which may appear only very slowly under ordinary curing conditions. * Relative Density AS 3583.5 Determination of relative density. Purpose: The effect that Fly Ash will have on the yield of a concrete mix design must be understood in advance – since cement and Fly Ash have different relative densities, successful use of blended cements depend on knowing this relationship between mass and volume. * Relative Water Requirement and Relative Strength AS 3583.6 Determination of relative water requirement and relative strength. Purpose: The addition of Fly Ash to a concrete mix should not significantly change its water demand, or its compressive strength. This test uses a comparison of a subject mortar sample with a control sample to determine the effects of a given Fly Ash on a standard Portland cement mortar. OTHER PRODUCTS Aggregates: Particle Size Distribution AS 1141.11 Particle size distribution by dry sieving. Purpose: Aggregates have an important influence on the strength, workability and water demand of concrete mix designs, and these effects can be understood to a large extent from the mix of particle sizes of which they are composed. This test divides the aggregate into size fractions, enabling judgements to be made about its suitability for the mix design under consideration. Ground Granulated Iron Blast Furnace Slag AS 3582.2 Supplementary cementitious materials for use with Portland cement. Part 2: Slag – Ground Granulated Iron Blast Furnace Three tests are NATA registered – Determination of Loss of Ignition; of Moisture Content; of Fineness by the 45 micron sieve. The testing methods are the same as for Fly Ash and are outlined in an earlier section.
  4. 4. Clay Bricks: Compressive and Transverse Strength AS 4456.4 Method for determining compressive strength. AS 4456.5 Method for determining transverse strength. Purpose: Bricks and blocks must perform under two kinds of load – ordinary compression, of the kind found in a typical brick wall; and in bending, when the product must act as a beam. These four tests determine standard strengths under the two types of load. Concrete Masonry Bricks and Blocks AS 2733 Appendix C: Method for determining transverse strength. As for AS 4456.5 for clay bricks (above). AS 2733 Appendix E: Method for compressive strength. As for AS 4456.4 for clay bricks (above). Admixtures for Concrete AS 1478 Chemical admixtures for concrete. Purpose: The intended and actual effects of admixtures on concrete mixes may not always be the same. It is important to understand just what admixtures can be expected to do, both from the manufacturer’s and the user’s perspective. * Grouts AS 2701 Methods for testing mortars for masonry constructions. CHEMICALS Loss of Ignition AS 2350.2 Determination of loss of ignition Purpose: The result of the LOI test can provide clues about the condition of cement – its age and exposure to moisture and other contamination which might occur through the storage and distribution system. LOI is a routine quality control test in the cement plant. Insoluble Residue As 2350.2 Determination of insoluble residue Purpose: Insoluble residue is unreacted silica or sand. The amount present in a cement sample is an indication of the extent of combination of clinker raw materials, and the correctness of their proportions in the kiln feed material. This is a routine process control test. Chloride Content of Portland Cement XRF (X Ray Fluoroscopy (dry powder) method; Wet chemical method. AS, BS, ISO and ASTM Standards are not available for XRF. Both methods are in-house, registered as such by NATA. Purpose: Chlorides in cement need to be strictly controlled; they can cause problems with kiln operations, and will also attack steel reinforcement in concrete if concentrations are too high. Free Lime (Free Calcium Oxide) Adapted from ASTM (American Society of Testing & Materials) C114.27. Purpose: The measurement of free lime in Portland Cement is a routine process control procedure, indicating the extent of combination of clinker raw materials, and the correctness of their proportions in the kiln feed material. Like the loss of ignition test, the measurement of free lime is also an indicator of age and quality of storage conditions. MICROSCOPY *Inspection of the microscopic crystal structure of cement, clinker, Fly Ash and other materials can provide insights into material properties which cannot be gained from other analytical methods. Modern stereo microscopes are used, and samples inspected at magnifications between x100 and x900. Microscopy is used for a wide range of analytical tasks: eg two clinker samples might be found that perform quite differently in cement, but yield identical chemical test results. Differences in microstructure may provide the explanation.

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