Low Strain Integrity Test, also known as Pile Integrity Test (PIT) is a non-destructive testing method for integrity assessments of concrete piles (augured cast-in-place piles, drilled shafts or driven piles). If major defects exist, test results may be interpreted to estimate the magnitude and location of defect.
Because of the simplicity, speed of execution and relatively low cost, PIT may be performed on 100% of the piles on a given job site.
The methodology involves a small impact by hand-held hammer on the pile top that generates a compressive stress wave in the pile. The stress wave propagates down the pile shaft and is reflected when it encounters either the toe or a non-uniformity of the shaft. These reflections cause a change in the acceleration signal measured on the pile top, which is picked up and processed by the Pile Integrity Tester (PIT) equipment and interpreted using PIT-Software.
CIMEC is equipped with pile integrity testers from Pile Dynamics, USA to perform low strain pile integrity test on pile.
Cross Hole Sonic Logging Test (CHSL) is a non-destructive test method whichinvolves measuring of propagation time of ultrasonic signals between two probes in vertical tube /ducts casted in pile shaft. Shafts are prepared for testing during their construction by installation of access tubes. The total number of access tubes typically depends on the diameter of the shaft. These tubes are usually attached to the reinforcement cage along the full length of the shafts.
The test can be used to collect precise information on the quality and integrity of concrete at different depths. Combination of profilescan be assessed for evaluation of the location.
The CHSL Analyzer System lowers the probes to the bottom of the shaft and moves the transceivers upward in unison, until the entire shaft length is scanned. As probes are pulled up, the first arrival time (FAT) of signal is measured and recorded versus the elevation. This provides a vertical profile scan of signal transit time. The scan is repeated for each pair of tubes. The data is interpreted for delayed pulse arrivals (or low signal strength) which indicate potential defects, and later reprocessed using CHSL-software. Poor concrete between the tubes also delays or disrupt the signal.
CIMEC is equipped with Cross Hole Analyzer Systems (CHAMP-Q) from Pile Dynamics, USA to perform Cross Hole Sonic Logging Test on piles.
Dynamic Load Testing is a fast, reliable, and cost-effective method of evaluating foundation load bearing capacity. CIMEC can perform Dynamic Load Testing on driven piles, drilled shafts, auger-cast piles, micro piles, and other cast in place foundations. Due to less execution time, several dynamic load tests can be conducted in a single day. In addition to bearing capacity, Dynamic Load Testing provides information on resistance distribution (shaft resistance and end bearing) and evaluates the shape and integrity of the foundation element.
A Pile Driving Analyzer (PDA) with pile top force and velocity transducers are used to conduct the pile test. Two strain transducers and two accelerometers are attached to the pile head, on opposite sides of the pile to cancel bending effects during hammer impact. The signals of strain and acceleration are conditioned and processed by the PDA. Signals of pile top force and velocity are measured and analysed during each hammerimpact. At the time of testing, PDA compute static pile capacity from pile top force and velocity data. This is subsequently checked with the more rigorous signal matching technique by a computer program ‘CAPWAP’ (Case Pile Wave Analysis Program) to estimate the static load capacity of pile and distribution of soil resistance along pile length.
CIMEC is equipped withPile Driving Analyzers (PDA-8G) from Pile Dynamics, USA to perform dynamic load test on piles.
Static load tests are used to measure the way in which a pile behaves under an applied load. The load is applied at a low strain and pile displacement is measured. Due to the slower and more precise process, the static load tests are considered to provide the most accurate results when measuring pile load carrying capacities and settlement/uplift of the pile.
Static load tests can be performed to validate foundation design assumptions regarding the axial compression or axial tension resistance provided by a pile, or its deflected shape under a lateral load. Another benefit of a static load test is that it can be carried out in all soil conditions and on all pile types.
Readings of the applied load determined from the jack pressure gage or load cell, and pile head movement determined by LVDTs, digital dial gages, or mechanical dial gages, are used to determine the safe load capacity of pile under axial loads or under lateral loads.
After processing the collected load test data, the results are analysed for load-movement results and pile movement analysis.
CIMEC is equipped with multiple jack system with total load capacity of 8000MT.
UPV method is an effective way for estimating the depth of surface cracks. The methodology involves detecting the travel time of stress waves of ultrasonic energy transmitted through concrete sections. Longer travel times through the same cross-sectional areas indicate discontinuities and potential cracking. Crack depth is estimated by varying the transducer spacing. The difference in travel time with varying distance between transducers is used to calculate crack depth.
CIMEC is equipped with PROCEQ PUNDIT LAB+ for crack depth measurements in concrete. Longitudinal stress wave pulses are generated by an electro-acoustical transducer that is held in contact with one surface of the concrete under test. After traversing through the concrete, the pulses are received and converted into electrical energy by a second transducer located at a distance from the transmitting transducer. The transit time is measured electronically. The pulse velocity and crack depthare calculated automatically by instrument.
Rebound Hammer test is a Non-destructive testing method of concrete which provide a convenient and rapid indication of the compressive strength of the concrete. The method, thus, also be used to assess the uniformity and quality of concrete. It is based on the principle that the rebound of an elastic mass depends on the hardness of the concrete surface against which the mass strikes.
Rebound Hammer test assess the likely compressive strength of concrete with the help of suitable correlations between rebound index and compressive strength. When the plunger of rebound hammer is pressed against the surface of the concrete, the spring- controlled mass rebounds and the extent of such rebound depends upon the surface hardness of concrete. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete.A concrete with low strength and low stiffness will absorb more energy to yield in a lower rebound value.
CIMEC is equipped with rebound hammers from Controls(Italy) & Proceq(Switzerland).
When compressive strength tests of laboratory-cured specimens fail to meet the specified acceptance criteria, core tests are commonly used to verify the strength and to obtain acceptance of the in-place concrete.
When the concrete is doubted or the structure is intended to be used for higher stress conditions, in-situ strength of concrete is determined to assess the current strength of a structure and to determine whether the strength and durability are adequate for its future use. From general perspective, the core test is required when the result of concrete cubes are not giving satisfactory result. In addition, concrete core test is also used for safety assessment of the existing concrete structure.
Concrete in the member represented by a core test is considered acceptable, if the average equivalent cube strength of the cores is equal to at least 85 percent of the cube strength of the grade of concrete specified for the corresponding age and no individual core has a strength less than 75 percent.
Ensuring sufficient concrete cover is critical for the durability of concrete structures subject to poor environment during their service life. The identification of embedded steel rebar, cover depth and size are the important parameters in the inspection of reinforced concrete structures. Usually, the information of interest includes the location of steel reinforcement, the concrete cover depth, the bar size/diameter, and the likelihood/extent of rebar corrosion. The Profometer test is a perfect on-site solution where the location, depth and size of rebar needs to be known. This may include Corrosion investigation, Quality Control and Assurance of new concrete structures, Location of rebar for penetrations or coring.
CIMEC is equipped with Proceq Profometer650 AI (Profometer analyser and rebar scanner) for concrete cover measurements and rebar scanning. This is an advanced cover meter that enable the precise and non-destructive measurement of concrete cover, estimation of rebar diameter and the detection of rebar locations using eddy current pulse induction as the measuring method. Multiple coil arrangements in the probe are periodically charged by current pulses and thus generate a magnetic field. When a reinforcing bar lies within this field, the lines of force become distorted. The disturbance caused by the presence of the metal in turn produces a local change in field strength as detected and indicated by the instrument. The resulting change in voltage can be utilized for the measurement. Advanced signal processing allows localization of a rebar, determination of the cover and estimation of the rebar diameter.
Corrosion of reinforcing steel is an electro-chemical process, and the behaviour of the steel can be characterised by measuring its half-cell potential. The greater the potential the higher the risk that corrosion is taking place. This technique is used for assessment of the durability of reinforced concrete members where reinforcement corrosion is suspected, and to evaluate the corrosion state of the rebars after repair work and thus evaluate the efficiency and durability of repair work. The measurement can be applied regardless of the depth of concrete cover and the rebar size. Half-cell potential measurements indicates corroding rebars not only in the most external layers of reinforcement facing the reference electrode but also in greater depth.
CIMEC is equipped with Proceq Profometer 650 AI (Corrosion meter) for half-cell potential measurements. The methodology involves measuring the potential of an embedded reinforcing bar relative to a reference half-cell placed on the concrete surface. The concrete functions as an electrolyte and the risk of corrosion of the reinforcement in the immediate region of the test location can be related empirically to the measured potential difference. The procedure is firstly to locate the steel and determine the bar spacing using a cover meter. The concrete cover is removed locally over a suitable bar and an electrical connection is made to the steel for half-cell potential measurements.
Load test on concrete structures is conducted to evaluate their flexural capacity.The testing is required to determine the serviceability of the structure when the presence / effect of the strength deficiency and its remedial measures are not fully known or when the required dimensions and material properties for analysis are not available.The goal of this type of testing is to compare field response of the structure under test loads with its theoretical response. Load testing on structures can be further categorized into diagnostic testing and proof testing. Diagnostic testing methods provide the measurements necessary to analyze differential loading effects (i.e., moment, shear, axial force, deflection, etc.) present in various structural members due to applied loads. Proof-load testing aims at determining the magnitude and configuration of loads that cause critical structural components to approach their elastic limit.
Methodology of load testing typically include the determination of testing objectives and load configuration, the selection and placement of instrumentation, the adoption of appropriate analysis techniques, and the evaluation and comparison of test results and analytical results. In case of bridges, the load effect on a span can be produced either by building up pre-weigh units on loading imprints as per codal provision or by any other configuration that produces the load effect. Any of the appropriate method of load distribution between the girders can be adopted in aiming at the test load and its configuration on the span.
The test load is applied in increments and the response of the structural element recorded using appropriate instruments. The type of response may be strains, rotations, deflections, and vibrations.
Soil electrical resistivity is a key factor when determining the design of the grounding system for new installations and is strongly affected by the content of electrolytes in the soil, its moisture content, and its temperature.Appropriate soil surveys and models are the basis of all earthing designs, and they are accomplished from an accurate soil resistivity testing.
The test method involves placing four equally spaced and in-line electrodes into the ground. The two outer electrodes (current electrodes) inject current into the soil. The two inner electrodes(potential electrodes) measure voltage, which is then used to calculate soil resistance.
Soil resistivity influences the plan of an earthing system absolutely and is the major factor that decides the resistance to earth of a grounding system. Thus, before designing and installing a new grounding system, the determined location should be tested to find out the soil’s resistivity.
The plate load test is used to determine the bearing capacity of Soil and the likely settlement under a given load.This test is very popular for selection and design of shallow foundation. The results of the plate load test are also applied in the design oftemporary working platforms for piling rigs or pads for crane outriggers.
The test involves loading a steel plate of known Size and recording the settlements corresponding to each load increment. The test load is gradually increased until the plate begins settling at a rapid rate. The total value of the load on the steel plate divided by the area of the plate gives the value of the ultimate bearing capacity of the soil. A factor of safety is applied to provide the safe bearing capacity.
The plate bearing test is typically carried out at foundation level, either on the surface or in a shallow pit. Plates of varying sizes up to 1000mm are available. The loading plate is placed on the ground and connected via a load cell to a reaction load.
Block vibration test is used for evaluation of in situ dynamic and damping properties of soils. The test can be conducted on the foundation element to analyze of the response of the structure if the dynamic load is applied. The block vibration test is of two types: Vertical vibration test and Horizontal vibration test.
A mechanical oscillator is used as a source of the vibration. The acceleration pickup and the associated vibration meter is attached on top of the block. The block is subjected to vibrations and amplitudes were measured at different frequencies for each eccentric setting.Amplitude verses frequency curves are plotted and analysed for the given eccentricity to determine the natural frequency of the foundation soil system and damping. The eccentricity of the oscillator mass is modified to record the natural frequency of soil at different eccentricity.