Monday, 08 August 2022

تاریخ بروزرسانی 1401/05/15




strength of materials lab

Mechanics of Materials Laboratory

1.    Measuring tensile strength of steel (reinforcing bars, steel sheets, bolts and nuts)
According to ASTM A370, AASHTO T244 Standards

One of the mechanical properties of steel is tensile strength and this test method is intended to determine this parameter. During this test, steel specimens are pulled by testing machine until rupture occurs. Yield strength, tensile strength and elongation in breaking moment are determined.
  Maximum capacity of the tensile testing machine is up to 60 tons and the machine has the ability to display stress-strain curve as well as to record yield strength, determine tensile strength, and calculate elastic modulus of steel.  

2.     Bend and re-bend test of steel reinforcing bars for use in concrete reinforcement
According to ASTM A370, AASHTO T244 and INSO 3132 Standards

These standards and test methods cover procedures to determine mechanical properties of steels. Bar and rebar, plate, nuts yield and tensile strength, extension under load, bend and re-bend test, as well as bend test with the bend angle of 180° for cold-finished rebars.

3.    Determining creep of concrete in compression
According to ASTM C512

Designing concrete structures involves the use of stress-strain relationships and the behavior of concrete. Concrete is not necessarily elastic. Inelastic deformations increase with time as the concrete experiences a sustained load. These inelastic deformations, also known as creep, increase at a decreasing rate during the loading period.
This test method (ASTM C512) covers the determination of the creep of molded concrete cylinders subjected to sustained longitudinal compressive load. This test measures the load-induced time-dependent compressive strain at selected ages for concrete under an arbitrary set of controlled environmental conditions.

4.    Determining of the permeability of concrete to Oxygen gas
According to Camburea Method and UNI Standard

Permeability of concrete is an important performance value Permeability of concrete is the principal factor that provides their durability. Permeability indicates the movements of fluids into porous concrete area. This property of concrete gives information about microstructure and quality of the material. Considering the fact most of the chloride ion and aggressive sulphate ions that affect the durability of concrete permeate from outside the concrete, determination of permeability is essential for designing and construction of concrete structures. Air permeability of concrete results from this test in m2 unit.
In the concrete structures, concrete cover on rebar is considered as a protecting layer against rebar corrosion. This shallow area of concrete cover is exposed to penetration of oxygen, carbonic gas, and water. Penetration of carbonic gas and water may change concrete microstructure so that both of them are not suitable for repeatability of the test; therefore oxygen gas is considered the most suitable fluid for doing Permeability test.  

5.    Determining water Permeability of hardened concrete
According to CRD-C48 Standard

Permeability refers to the amount of water migration through concrete when the water is under pressure, and also the ability of concrete to resist penetration of any substance, liquid, gas, or chloride ion. Permeability is considered as the durability measure of concrete. One example is evaluating the amount of passing water through the concrete hydraulic structures (e.g. concrete dams) which indicates the necessity for determination of water permeability of concrete. It was based in Darcy’s law equation to calculate permeability values. This test covers the laboratory determination of the Darcy’s coefficient of water permeability of hardened concrete in m/s units.

6.    Determining  dynamic  modulus of elasticity from fundamental resonant frequency test
According to ASTM C215 Standard

The dynamic modulus of elasticity is used to compute durability factor of concrete specimens that are subjected to freezing-thawing cycles and weathering conditions. Durability factor is the ratio of the dynamic modulus at N cycles to the dynamic modulus at 0 cycles. This test method is intended primarily for detecting changes in the dynamic modulus of elasticity of laboratory or field test specimens that are undergoing exposure to weathering or other types of potentially deteriorating influences. The test method may also be used to monitor the development of dynamic elastic modulus with increasing maturity of test specimens. This test covers measurement of the fundamental transverse, longitudinal, and torsional resonant frequencies of concrete prisms and cylinders for the purpose of calculating dynamic Young’s modulus of elasticity, the dynamic modulus of rigidity (sometimes designated as “the modulus of elasticity in shear”), and dynamic Poisson’s ratio.      

7.    Determining resistance of concrete to rapid freezing and thawing
According to ASTM C666 Standard

The decrease in durability can be evaluated by several methods. The most common is measuring the changes in dynamic modulus values. Reducing modulus values after cycles of Freezing and Thawing indicates reduction in concrete durability. In the ASTM C666 method, usually Freezing and Thawing cycles continue up to 300 cycles or until dynamic modulus of concrete specimen reduces to 60 percent of its initial value (whichever occurs first).

8.    Determining electrical indication of concrete’s ability to resist chloride ion penetration
According to ASTM C1202 Standard

Penetration of ions from concrete surface into the inner parts of concrete is one of the most important factors affecting durability of concrete structures exposed to various conditions like marine environments chloride migration through concrete is a very slow process. This test method accelerates this migration. An electrical current is applied to a concrete specimen, it increased and accelerate the rate at which the chlorides migrate into concrete. Based on FHWNRD-81/119 and the Iranian code for concrete durability in Persian Gulf and Oman sea, some criterions are presented to evaluate performance of concrete specimens exposed to penetration destructive ions, especially chloride ion permeability. This test method covers the laboratory evaluation of the electrical conductance of concrete samples to provide a rapid indication of their resistance to chloride ion penetration. The result report in coulombs (the integral of current vs. time plot) that were passed through the concrete sample. This test method does not measure concrete permeability. It does measure concrete resistivity and chloride permeability under 60 volt potential.

9.    Measuring tensile strength of concrete
According to CRD C164 Standard

Concrete is much weaker in tension than in compression. This test determines direct tensile strength of hardened cylindrical concrete specimens with different dimensions by dividing the maximum load carried by the specimen during test by the cross-sectional area.

10.    Determining the depth of penetration of water under pressure in hardened concrete
According to BS EN 12390-8 Standard

This test method can be used to determine the depth of water penetration in hardened cylindrical and cubic concrete specimens after applying water pressure to their surface. The maximum depth of penetration under the test area is measured and recorded to millimeter.

11.    Determining of flexural strength of concrete
According to ASTM C78, C293 Standards

Common method for determining flexural strength of concrete is bending test. When the concrete beam specimen is loaded under bending mode, tensile stresses are created at the bottom fibre of test beam and compressive stresses are created at the top fibre of the test beam. Since tensile strength is lower than the compressive strength, failure starts from the area in tension and therefore breaking load is dependent to the tensile strength. The maximum capacity of the machine used for determining flexural strength is up to 40 tons, and both 2 points and 3 points modes of loading can be performed. Based on the standard method used, flexural strength at middle or other parts of the specimen can be determined.

12.    Measuring tensile strength of  Waterstop and  Wiremesh
According to ASTM A370, AASHTO T244 and ASTM D412 Standards

One of the tests used for characterizing waterstop and wiremesh materials is tensile strength test. Similar to steel bars, specimens are pulled by tensile testing machine until rupture and yield strength, tensile strength and elongation at breaking moment is determined.
The tensile testing machine used for pulling wiremeshes, waterstops and steels which are wire shape has the maximum capacity of 5 tons and the machine can display stress-strain curve and determine mechanical properties of the tested materials.

13.    Waterstop quality control tests

The following standard methods are used to determine mechanical properties of waterstop materials.
1-    Determining tensile strength and ultimate elongation according to ASTM D412 standard
2-    Determining specific gravity according to ASTM D792 Standard
3-    Determining water absorption according to ASTM D570 Standard
4-    Determining hardness (Shore A) according to ASTM D2240 Standard
5-    Determining tear strength according to ASTM D624 Standard
6-    Determining effect of Alkalis according to CRD C572 Standard
7-    Determining bending modules according to ASTM D747 Standard
8-    Determining weight loss according to ASTM D1203 Standard
9-    Determining accelerated extraction according to CRD C572 Standard
10-    Determining brittleness at low temperature according to ASTM D746 Standard

14.    Determining the bending strength (modulus of rupture) of Terrazzo tiles
According to INSO 755-2 Standard

The main use of Terrazzo tiles is flooring the sidewalks and the other public places. One of the most important reasons for Terrazzo tile destruction is its weakness in bending mode of loading. Thus, determining the bending strength of Terrazzo tile will be necessary for quality control of this product.


Determining the Flexural Creep Stiffness of Asphalt Binder
Using the Bending Beam Rheometer (BBR)

This test method covers the determination of the flexural creep stiffness and m-value of asphalt binders by means of a bending beam rheometer. It can be used with unaged material or with materials aged using Rolling Thin Film Oven and Pressure Aging Vessel aging procedures.
The bending beam rheometer measures the midpoint deflection of a simply supported prismatic beam of asphalt binder subjected to a constant load applied to its midpoint. A prismatic test specimen is placed in the controlled temperature fluid bath and loaded with a constant test load for 240 s. The test load and the midpoint deflection of the test specimen are monitored versus time.
The low-temperature thermal cracking performance of asphalt pavements is related to the creep stiffness and the m-value of the asphalt binder.

Determining the Rheological Properties of Asphalt Binder
Using a Dynamic Shear Rheometer

This test method covers the determination of the dynamic shear modulus and phase angle of asphalt binders when tested in dynamic shear using parallel plate geometry. During the test, one of the parallel plates is oscillated with respect to the other at preselected frequencies and angular deflection amplitudes. The required amplitude is selected so that the testing is within the region of linear behavior.
The test temperature for this test is related to the temperature experienced by the pavement in the geographical area for which the asphalt binder is intended to be used. The complex shear modulus is an indicator of the stiffness or resistance of asphalt binder to deformation under load.

Determining the Fracture Properties of Asphalt Binder in Direct Tension (DT)

This test method covers the determination of the failure strain of asphalt binders test specimen pulled at a constant rate of elongation by means of a direct tension tester. It is used with materials aged using RTFO and PAV aging procedures.
A displacement transducer is used to measure the elongation of the test specimen as it is pulled in tension at a constant rate of 1.0 mm/min. The load developed during the test is monitored and the tensile strain in the test specimen when the load reaches a maximum is reported as the failure strain.

Test Method for Effect of Heat and Air on a Moving Film of Asphalt
(Rolling Thin Film Oven Test)

This test method is intended to measure the effect of heat and air on a moving film of asphalt binders. The test indicates approximate change in properties of asphalt during conventional hot-mixing. For testing, a moving film of asphalt binder is heated in a rolling thin film oven for 85 min at 163°C. The effects of heat and air are determined from measurement of asphalt properties, before and after the test. A procedure is also provided for determining the change in asphalt binder mass.

Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel

This practice covers the accelerated aging of asphalt binders by means of pressurized air at elevated temperature. This test simulates the changes in rheology which occur in asphalt binders during in-service oxidative aging. Asphalt binder residue from the RTFOT is placed in standard steel pans and aged at the specified temperature for 20 hours in a vessel pressurized with air to 2.1 MPa. Residue from this practice is used to estimate the physical or chemical properties of asphalt binders after several years of in-service aging in the field.

Viscosity Determination of Asphalt at Elevated Temperatures Using a Rotational Viscometer

This test method covers a procedure for measuring the apparent viscosity of asphalt binders using a rotational viscometer and a temperature controlled thermal chamber for maintaining test temperature. The torque on the apparatus-measuring geometry, rotating in the sample of asphalt, is used to measure the relative resistance to rotation. The torque and rotating speed are used to determine the viscosity of the asphalt in pascal seconds.

Measuring Surface Frictional Properties Using the British Pendulum Tester

This test method covers the procedure for measuring surface frictional properties using the British Pendulum Skid Resistance Tester. The British Pendulum is a dynamic pendulum impact-type tester used to measure the energy loss when a rubber slider edge is propelled over a test surface.
The test surface is cleaned and thoroughly wetted prior to testing. The pendulum slider is positioned to barely come in contact with the test surface prior to conducting the test. The pendulum is raised to a locked position and then released, thus allowing the slider to make contact with the test surface. A drag pointer indicates the British Pendulum Number. The greater the friction between the slider and the test surface, the more the swing is retarded, and the larger the BPN reading.

Determining Asphalt Content of Hot-Mix Asphalt by Ignition Method
ASTM D6307

This test method covers the determination of asphalt content of asphalt mixtures by removing the asphalt cement in an ignition furnace. This test method can be used for quantitative determination of asphalt content in HMA mixtures for quality control and specification acceptance. This test does not require the use of solvents. Aggregate obtained by this test method may be used for gradation analysis. For testing, the asphalt cement in the mixture is ignited using the furnace equipment and its content is calculated by difference from the mass of the residual aggregate.

Determining Toughness and Tenacity of Bituminous Materials
ASTM D5801

This test method covers a procedure for measuring the toughness and tenacity of bituminous materials. This test is useful in confirming that asphalt cement has been modified with a material that provides a significant elastomeric component. Elastomer modified asphalts can be characterized by their ability to be stretched to a large elongation while at the same time resisting further stretching. Toughness and tenacity are two parameters for measuring this ability. A tension head is pulled from asphalt sample at a rate of 50 cm/min. A continuous record of the force versus elongation curve is made and used to calculate the toughness and the tenacity of the sample at 25°C.

Preparation of Asphalt Mix Specimens by Means of the
Superpave Gyratory Compactor

This test method covers the compaction of asphalt mix into cylindrical specimens using the Superpave Gyratory Compactor (SGC). It is used to prepare specimens for determining the volumetric and physical properties of compacted asphalt mix. It also refers to the determination of the relative density of the compacted specimens at any point in the compaction process. Compacted specimens are suitable for volumetric, physical property, and mechanical testing.

Determining the Fatigue Life of Compacted Asphalt Mixtures
Subjected to Repeated Flexural Bending

This standard covers the procedure for determining the fatigue life and fatigue energy of asphalt mixture beam specimens sawed from laboratory compacted or field compacted asphalt mixtures and subjected to repeated flexural bending until failure. The fatigue life and failure energy determined by this test can be used to estimate the fatigue life of asphalt mixture pavement layers under repeated traffic loading.

Indirect Tension Test Method for Resilient Modulus of Asphalt Mixtures
ASTM D4123

This test method covers the procedures for preparing and testing of laboratory compacted asphalt mixtures or field recovered pavement cores to determine resilient modulus using the repeated load indirect tension test. The test is conducted by applying compressive loads with a haversine or other suitable waveform. The load is applied vertically in the vertical diametral plane of a cylindrical specimen. The resulting horizontal deformation of specimen is measured, and with an assumed Poisson’s ratio, is used to calculate the resilient modulus.
The values of resilient modulus can be used to evaluate the relative quality of material as well as to generate input data for pavement design. The test can also be used to study effects of temperature, loading rates, rest period and loading waveform.

Determining Resistance to Permanent Deformation of Asphalt Mixtures
Subject to Cyclic Compression Test
EN12697-25a, BS DD226

These test methods determine the resistance to permanent deformation of a cylindrical specimen of asphalt mixtures at temperatures and loads similar to those experienced in roads. These tests can be used to rank asphalt mixtures on the basis of resistance to permanent deformation, as a guide to relative performance in the pavement.
The unconfined repeated loading dynamic creep test is performed according to BS DD226 standard method and Uniaxial cyclic compression dynamic creep test with confinement is done according to EN 12697-25a standard method. A cylindrical test specimen, maintained at elevated conditioning temperature, is placed between two loading platens. Test specimens may be either prepared in the laboratory or be cored from a pavement. The specimen is subjected to cyclic axial block-pulse pressure. During the test the change in height of the specimen is measured at specified numbers of load applications and the cumulative axial strain of specimen is determined as a function of the number of load applications.

Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt

This method covers a procedure for testing the rutting and moisture susceptibility of hot mix asphalt samples in the Hamburg Wheel Tracking device. The test is used to determine the premature failure susceptibility of HMA due to weakness in the aggregate structure, inadequate binder stiffness, or moisture damage. This test measures the potential for moisture damage effects because the specimens can be submerged in temperature controlled water during loading.
The method includes the testing of submerged, compacted HMA in a reciprocating rolling-wheel device. Test specimen is repetitively loaded using a reciprocating steel wheel. The deformation of specimen, caused by the wheel loading, is measured. The impression is plotted as a function of the number of wheel passes. Test specimens can be either slab specimens prepared by a roller compactor, or cylindrical specimens by superpave gyratory compactor. Alternatively, field cores having a diameter of 150 mm, 250 mm, or 300 mm, or saw-cut slab specimens may be tested.

Laboratory-Scale Foamed Bitumen Production
Testing for Determining Cold Recycled Mixtures quality

Foamed bitumen is produced by injecting small quantities of water and compressed air in to hot bitumen. The water evaporates, causing the bitumen to foam abruptly and expand 10 to 20 times of its original volume.
Laboratory-scale foamed bitumen plant is used to prepare foamed bitumen and mix design test specimens for preliminary testing. It permits the final pavement design to be determined in advance. Also the optimum foamed bitumen quality can be determined.