Misplaced Pages

#844155

52-587: Maros is the location of the Indonesian Cereals Research Institute, a branch of the Indonesian Agency for Agricultural Research and Development. In 2012, regional cement producer PT Semen Bosowa Maros began construction in Maros of a new clinker plant estimated to cost over $ 300 million. The clinker plant was expected to help the cement company increase production in the region in response to

104-408: A {\textstyle \sigma _{a}} changes according to the ratio ( d o / d 2 ) 2 {\displaystyle (d_{o}/d_{2})^{2}} . The parameters ( F , d 1 , d 2 , l {\textstyle F,d_{1},d_{2},l} ) obtained from a test result can be used with these formulas to calculate

156-427: A Compressometer is common. As per Indian codes, compressive strength of concrete is defined as: The compressive strength of concrete is given in terms of the characteristic compressive strength of 150 mm size cubes tested after 28 days (fck). In field, compressive strength tests are also conducted at interim duration i.e. after 7 days to verify the anticipated compressive strength expected after 28 days. The same

208-419: A rotary kiln at high temperature. The products of the chemical reaction aggregate together at their sintering temperature, about 1,450 °C (2,640 °F). Aluminium oxide and iron oxide are present only as a flux to reduce the sintering temperature and contribute little to the cement strength . For special cements, such as low heat (LH) and sulfate resistant (SR) types, it is necessary to limit

260-551: A difference in frictional forces. In either case this will cause the material sections to begin bending and lead to ultimate failure. Microcracks are a leading cause of failure under compression for brittle and quasi-brittle materials. Sliding along crack tips leads to tensile forces along the tip of the crack. Microcracks tend to form around any pre-existing crack tips. In all cases it is the overall global compressive stress interacting with local microstructural anomalies to create local areas of tension.  Microcracks can stem from

312-402: A few factors. The growth of microcracks is not the growth of the original crack or imperfection. The cracks that nucleate do so perpendicular to the original crack and are known as secondary cracks. The figure below emphasizes this point for wingtip cracks. These secondary cracks can grow to as long as 10-15 times the length of the original cracks in simple (uniaxial) compression. However, if

364-436: A given amount of deformation may be considered as the limit for compressive load. Compressive strength is a key value for design of structures . Compressive strength is often measured on a universal testing machine . Measurements of compressive strength are affected by the specific test method and conditions of measurement. Compressive strengths are usually reported in relationship to a specific technical standard . When

416-402: A high bulk modulus, such as metals, tend to form a barrel shape under axial compressive loading due to frictional contact at the ends. For this case the equivalent true compressive stress for this condition can be calculated using σ ´ = C σ a {\displaystyle {\acute {\sigma }}=C\sigma _{a}} where Note that if there

468-444: A specimen of material is loaded in such a way that it extends it is said to be in tension . On the other hand, if the material compresses and shortens it is said to be in compression . On an atomic level, molecules or atoms are forced together when in compression, whereas they are pulled apart when in tension. Since atoms in solids always try to find an equilibrium position, and distance between other atoms, forces arise throughout

520-465: A transverse compressive load is applied. The growth is limited to a few integer multiples of the original crack's length. If the sample size is large enough such that the worse defect's secondary cracks cannot grow large enough to break the sample, other defects within the sample will begin to grow secondary cracks as well. This will occur homogeneously over the entire sample. These micro-cracks form an echelon that can form an “intrinsic” fracture behavior,

572-476: Is a stub . You can help Misplaced Pages by expanding it . Clinker (cement) Cement clinker is a solid material produced in the manufacture of portland cement as an intermediary product. Clinker occurs as lumps or nodules, usually 3 millimetres (0.12 in) to 25 millimetres (0.98 in) in diameter. It is produced by sintering (fusing together without melting to the point of liquefaction ) limestone and aluminosilicate materials such as clay during

SECTION 10

#1732851092845

624-458: Is a hydraulic binder whose hydration requires water. It can perfectly set under water. Water is essential to its hardening and water losses must be avoided at the young age to avoid the development of cracks. Young concrete is protected against desiccation (evaporation of unreacted water). Traditional methods for preventing desiccation involve covering the product with wet burlap or use of plastic sheeting.. For larger projects, such as highways,

676-661: Is added to clinker primarily as an additive preventing the flash settings of the cement, but it is also very effective to facilitate the grinding of clinker by preventing agglomeration and coating of the powder at the surface of balls and mill wall. Organic compounds are also often added as grinding aids to avoid powder agglomeration. Triethanolamine (TEA) is commonly used at 0.1 wt. % and has proved to be very effective. Other additives are sometimes used, such as ethylene glycol , oleic acid , and dodecyl-benzene sulfonate. Upon addition of water, clinker minerals react to form different types of hydrates and "set" (harden) as

728-495: Is at least the beginning of the primary failure process under compressive loading.” For designers, compressive strength is one of the most important engineering properties of concrete . It is standard industrial practice that the compressive strength of a given concrete mix is classified by grade. Cubic or cylindrical samples of concrete are tested under a compression testing machine to measure this value. Test requirements vary by country based on their differing design codes. Use of

780-572: Is defined as the force divided by the area at the start of the experiment. This is known as the engineering stress, and is defined by σ e = F A 0 , {\displaystyle \sigma _{e}={\frac {F}{A_{0}}},} where A 0 is the original specimen area [m ]. Correspondingly, the engineering strain is defined by ε e = l − l 0 l 0 , {\displaystyle \varepsilon _{e}={\frac {l-l_{0}}{l_{0}}},} where l

832-414: Is done to be forewarned of an event of failure and take necessary precautions. The characteristic strength is defined as the strength of the concrete below which not more than 5% of the test results are expected to fall. For design purposes, this compressive strength value is restricted by dividing with a factor of safety, whose value depends on the design philosophy used. The construction industry

884-527: Is frictionless contact between the ends of the specimen and the test machine, the bulge radius becomes infinite ( R = ∞ {\textstyle R=\infty } ) and C = 1 {\textstyle C=1} . In this case, the formulas yield the same result as σ ´ = σ e ( 1 + ϵ e ) {\textstyle {\acute {\sigma }}=\sigma _{e}(1+\epsilon _{e})} because σ

936-657: Is impractical, as they would fail by buckling before reaching the material's true compressive strength. To overcome this, a series of tests can be conducted using specimens with varying aspect ratios, and the true compressive strength can then be determined through extrapolation. Concrete and ceramics typically have much higher compressive strengths than tensile strengths. Composite materials, such as glass fiber epoxy matrix composite, tend to have higher tensile strengths than compressive strengths. Metals are difficult to test to failure in tension vs compression. In compression metals fail from buckling/crumbling/45° shear which

988-429: Is incorporated into the final clinker product, and carbon dioxide which is typically released into the atmosphere. The second raw material (materials in the rawmix other than limestone) depend on the purity of the limestone. Some of the second raw materials used are: clay, shale , sand , iron ore , bauxite , fly ash and slag . Portland cement clinker is made by heating a homogeneous mixture of raw materials in

1040-525: Is measured on materials, components, and structures. The ultimate compressive strength of a material is the maximum uniaxial compressive stress that it can withstand before complete failure. This value is typically determined through a compressive test conducted using a universal testing machine . During the test, a steadily increasing uniaxial compressive load is applied to the test specimen until it fails.The specimen, often cylindrical in shape, experiences both axial shortening and lateral expansion under

1092-521: Is much different (though higher stresses) than tension which fails from defects or necking down. If the ratio of the length to the effective radius of the material loaded in compression ( Slenderness ratio ) is too high, it is likely that the material will fail under buckling . Otherwise, if the material is ductile yielding usually occurs which displaying the barreling effect discussed above. A brittle material in compression typically will fail by axial splitting, shear fracture, or ductile failure depending on

SECTION 20

#1732851092845

1144-502: Is negative, so the true stress ( σ ´ {\displaystyle {\acute {\sigma }}} ) is less than the engineering stress ( σ e {\textstyle \sigma _{e}} ). The true strain ( ϵ ´ {\displaystyle {\acute {\epsilon }}} ) can be used in these formulas instead of engineering strain ( ϵ e {\textstyle \epsilon _{e}} ) when

1196-455: Is no confining pressure, i.e. a lesser compressive load on axis perpendicular to the main applied load. The material now split into micro columns will feel different frictional forces either due to inhomogeneity of interfaces on the free end or stress shielding. In the case of stress shielding , inhomogeneity in the materials can lead to different Young's modulus . This will in turn cause the stress to be disproportionately distributed, leading to

1248-437: Is often involved in a wide array of testing. In addition to simple compression testing, testing standards such as ASTM C39, ASTM C109, ASTM C469, ASTM C1609 are among the test methods that can be followed to measure the mechanical properties of concrete. When measuring the compressive strength and other material properties of concrete, testing equipment that can be manually controlled or servo-controlled may be selected depending on

1300-460: Is the capacity of a material or structure to withstand loads tending to reduce size ( compression ). It is opposed to tensile strength which withstands loads tending to elongate, resisting tension (being pulled apart). In the study of strength of materials , compressive strength, tensile strength, and shear strength can be analyzed independently. Some materials fracture at their compressive strength limit; others deform irreversibly , so

1352-555: Is the current specimen length [m] and l 0 is the original specimen length [m]. True strain, also known as logarithmic strain or natural strain, provides a more accurate measure of large deformations, such as in materials like ductile metals ϵ ´ = ln ⁡ ( l / l o ) = l n ( 1 + ϵ e ) {\displaystyle {\acute {\epsilon }}=\ln(l/l_{o})=ln(1+\epsilon _{e})} The compressive strength therefore corresponds to

1404-698: Is the load applied just before crushing and l is the specimen length just before crushing. When a uniaxial compressive load is applied to an object it will become shorter and spread laterally so its original cross sectional area ( A o {\textstyle A_{o}} ) increases to the loaded area ( A {\textstyle A} ). Thus the true stress ( σ ´ = F / A {\displaystyle {\acute {\sigma }}=F/A} ) deviates from engineering stress ( σ e = F / A o {\displaystyle \sigma _{e}=F/A_{o}} ). Tests that measure

1456-412: The cement kiln stage. The Portland clinker essentially consists of four minerals: two calcium silicates , alite (Ca 3 SiO 5 ) and belite (Ca 2 SiO 4 ), along with tricalcium aluminate (Ca 3 Al 2 O 6 ) and calcium aluminoferrite (Ca 2 (Al,Fe) 2 O 5 ). These main mineral phases are produced by heating at high temperature clays and limestone . The major raw material for

1508-447: The Young's modulus for compression. In this region, the material deforms elastically and returns to its original length when the stress is removed. This linear region terminates at what is known as the yield point . Above this point the material behaves plastically and will not return to its original length once the load is removed. There is a difference between the engineering stress and

1560-540: The amount of tricalcium aluminate formed. The clinker and its hydration reactions are characterized and studied in detail by many techniques, including calorimetry , strength development, X-ray diffraction , scanning electron microscope and atomic force microscopy . Portland cement clinker (abbreviated k in the European norms) is ground to a fine powder and used as the binder in many cement products. A small amount of gypsum (less than 5 wt.%) must be added to avoid

1612-420: The clinker-making is usually limestone mixed with a second material containing clay as a source of alumino-silicate. An impure limestone containing clay or silicon dioxide (SiO 2 ) can be used. The calcium carbonate (CaCO 3 ) content of these limestones can be as low as 80% by weight. During the calcination process that occurs in the production of clinker, limestone is broken into Lime (calcium oxide), which

Maros - Misplaced Pages Continue

1664-418: The deformation is large. As the load is applied, friction at the interface between the specimen and the test machine restricts the lateral expansion at its ends. This has two effects: Various methods can be used to reduce the friction according to the application: Three methods can be used to compensate for the effects of friction on the test result: Round test specimens made from ductile materials with

1716-432: The directions perpendicular to the applied compressive stress. As defined by a materials Poisson ratio a material compressed elastically in one direction will strain in the other two directions. During axial splitting a crack may release that tensile strain by forming a new surface parallel to the applied load. The material then proceeds to separate in two or more pieces. Hence the axial splitting occurs most often when there

1768-399: The engineering stress at the point of failure in a material are often sufficient for many routine applications, such as quality control in concrete production. However, determining the true stress in materials under compressive loads is important for research focused on the properties on new materials and their processing. The geometry of test specimens and friction can significantly influence

1820-518: The entire material which oppose both tension or compression. The phenomena prevailing on an atomic level are therefore similar. The "strain" is the relative change in length under applied stress; positive strain characterizes an object under tension load which tends to lengthen it, and a compressive stress that shortens an object gives negative strain. Tension tends to pull small sideways deflections back into alignment, while compression tends to amplify such deflection into buckling . Compressive strength

1872-419: The equivalent true stress σ ´ {\textstyle {\acute {\sigma }}} at failure. The graph of specimen shape effect shows how the ratio of true stress to engineering stress (σ´/σ e ) varies with the aspect ratio of the test specimen ( d o / l o {\textstyle d_{o}/l_{o}} ). The curves were calculated using

1924-665: The flash setting of the tricalcium aluminate (Ca 3 Al 2 O 6 ), the most reactive mineral phase (exothermic hydration reaction) in Portland clinker. It may also be combined with other active ingredients or cement additions to produce other types of cement including, following the European EN 197-1 standard: Clinker is one of the ingredients of an artificial rock imitating limestone and called pulhamite after its inventor, James Pulham (1820–1898). Other ingredients were Portland cement and sand. Pulhamite can be extremely convincing and

1976-412: The formulas provided above, based on the specific values presented in the table for specimen shape effect calculations . For the curves where end restraint is applied to the specimens, they are assumed to be fully laterally restrained, meaning that the coefficient of friction at the contact points between the specimen and the testing machine is greater than or equal to one (μ ⩾ 1). As shown in the graph, as

2028-568: The growing demand for cement to support construction activities. Maros Water Park is in Maros. Nearby to Maros, in the area of the Maros Regency to the north of Makassar, are Pettakere cave and other prehistoric caves that contain significant rock art. Research suggests that the rock art is of considerable archaeological significance. 5°00′08″S 119°34′32″E  /  5.00222°S 119.57556°E  / -5.00222; 119.57556 This South Sulawesi location article

2080-418: The hydrated cement paste becomes concrete . The calcium silicate hydrates (C-S-H) (hydrates of alite and belite minerals) represent the main "glue" components of the concrete. After initial setting the concrete continues to harden and to develop its mechanical strength . The first 28 days are the most critical for the hardening. The concrete does not dry but one says that it sets and hardens. The cement

2132-783: The length of the specimen because there are no external lateral constraints. This condition represents an ideal test condition. For all practical purposes the volume of a high bulk modulus material (e.g. solid metals) is not changed by uniaxial compression. So A l = A o l o {\displaystyle Al=A_{o}l_{o}} Using the strain equation from above A = A o / ( 1 + ϵ e ) {\displaystyle A=A_{o}/(1+\epsilon _{e})} and σ ´ = σ e ( 1 + ϵ e ) {\displaystyle {\acute {\sigma }}=\sigma _{e}(1+\epsilon _{e})} Note that compressive strain

Maros - Misplaced Pages Continue

2184-446: The level of constraint in the direction perpendicular to the direction of loading. If there is no constraint (also called confining pressure), the brittle material is likely to fail by axial splitting. Moderate confining pressure often results in shear fracture, while high confining pressure often leads to ductile failure, even in brittle materials. Axial Splitting relieves elastic energy in brittle material by releasing strain energy in

2236-514: The load. As the load increases, the machine records the corresponding deformation, plotting a stress-strain curve that would look similar to the following: The compressive strength of the material corresponds to the stress at the red point shown on the curve. In a compression test, there is a linear region where the material follows Hooke's law . Hence, for this region, σ = E ε , {\displaystyle \sigma =E\varepsilon ,} where, this time, E refers to

2288-423: The nucleus of a shear fault instability. Shown right: Eventually this leads the material deforming non-homogeneously. That is the strain caused by the material will no longer vary linearly with the load. Creating localized shear bands on which the material will fail according to deformation theory. “The onset of localized banding does not necessarily constitute final failure of a material element, but it presumably

2340-675: The point on the engineering stress–strain curve ( ε e ∗ , σ e ∗ ) {\displaystyle \left(\varepsilon _{e}^{*},\sigma _{e}^{*}\right)} defined by σ e ∗ = F ∗ A 0 {\displaystyle \sigma _{e}^{*}={\frac {F^{*}}{A_{0}}}} ε e ∗ = l ∗ − l 0 l 0 , {\displaystyle \varepsilon _{e}^{*}={\frac {l^{*}-l_{0}}{l_{0}}},} where F

2392-426: The relative length of the specimen increases ( d o / l o → 0 {\textstyle d_{o}/l_{o}\rightarrow 0} ), the ratio of true to engineering stress ( σ ´ / σ e {\displaystyle {\acute {\sigma }}/\sigma _{e}} ) approaches the value corresponding to frictionless contact between

2444-426: The results of compressive stress tests. Friction at the contact points between the testing machine and the specimen can restrict the lateral expansion at its ends (also known as 'barreling') leading to non-uniform stress distribution. This is discussed in section on contact with friction . With a compressive load on a test specimen it will become shorter and spread laterally so its cross sectional area increases and

2496-457: The specimen and the machine, which is the ideal test condition. As shown in the section on correction formulas , as the length of test specimens is increased and their aspect ratio approaches zero ( d o / l o ⟶ 0 {\displaystyle d_{o}/l_{o}\longrightarrow 0} ), the compressive stresses (σ) approach the true value (σ′). However, conducting tests with excessively long specimens

2548-414: The surface is sprayed with a solution of curing compound that leaves a water-impermeable coating. As of 2018 , cement production contributed about 8% of all carbon emissions worldwide, contributing substantially to global warming . Most of those emissions were produced in the clinker manufacturing process. Compressive strength In mechanics , compressive strength (or compression strength )

2600-520: The true compressive stress is σ ´ = F / A {\displaystyle {\acute {\sigma }}=F/A} and the engineering stress is σ e = F / A o {\displaystyle {\sigma _{e}}=F/A_{o}} The cross sectional area ( A {\textstyle A} ) and consequently the stress ( σ ´ {\textstyle {\acute {\sigma }}} ) are uniform along

2652-433: The true stress. By its basic definition the uniaxial stress is given by: σ ´ = F A , {\displaystyle {\acute {\sigma }}={\frac {F}{A}},} where F is load applied [N] and A is area [m ]. As stated, the area of the specimen varies on compression. In reality therefore the area is some function of the applied load i.e. A = f ( F ) . Indeed, stress

SECTION 50

#1732851092845

2704-575: Was popular in creating natural looking rock gardens in the nineteenth century. Clinker, if stored in dry conditions, can be kept for several months without appreciable loss of quality. Because of this, and because it can be easily handled by ordinary mineral handling equipment, clinker is internationally traded in large quantities. Cement manufacturers purchasing clinker usually grind it as an addition to their own clinker at their cement plants. Manufacturers also ship clinker to grinding plants in areas where cement-making raw materials are not available. Gypsum

#844155