Explain in detail the non-destructive testing of concrete using Rebound hammer.

Explain in detail the non-destructive testing of concrete using Rebound hammer.
Non-destructive testing of concrete using Rebound hammer Rebound hammer test is used for estimation of concrete strength and for comparative investigations. It also used to measure elastic reboundery concrete.
The Rebound hammer consists of a spring control hammer which slides on, a plunger within ,a tubuler housing.
Working process: When the plunger is pressed against the surface of the concrete, the mass rebound from the plunger. It retracts against the force of the spring. The hammer influence against the concrete and the spring control mass rebounds, taking the rider with it along the guide scale. By pushing a button, the rider can be held in position to allow the reading to be taken. The distance travelled by the mass, is called the rebound number. The number is indicated by the rider moving along a graduated scale.
Each hammer differs considerably in performance and needs calibration f. The test can be conducted horizontally, onwards or at vertically- upwards or any intermediate angle. At each angle, the rebound number will be different for the same concrete and will require separate calibration of correction.

What is ferrocement ? List the properties of ferrocement.

 What is ferrocement ? List the properties of ferrocement.
Ferrocement is a comparatively new material. It consists wire meshes and cement mortar. It consists of closely spaced wire meshes also which are impregnated with rich cement mortar mix. The wire mesh is usually of 0.5 to 1 mm dia wire at 5 mm to 10 mm spacing and cement mortar is of cement sand ratio of 1 2 or 1 3 with water/cement ratio of 0.4 to 0.45. These elements are usually of the order of 2 or 3m in thickness with 2 to 3 mm external cover to the reinforcement.
Behind this material the basic ‘idea is that concrete can undergo large strains in the neighbourhood of the reinforcement and magnitude of strains depends on the distribution and subdivision of reinforcement throughout of the mass of concrete.
Advantages
(1) Less crack width
(2) Simplicity in construction
(3) Easier moundability
(4) Lesser dead weight
(5) Non-correcsive nature
(6) High tensile, strength
(7) Easy repairability

Civil Engineering Question :Describe the procedure to list the soundness of cement. Name the constituents causing soundness.

Civil Engineering Question :Describe the procedure to list the soundness of cement. Name the constituents causing soundness.

It is most needed that cement after setting should not sustain any appreciable change in volume. Some cement have been found to undergo a large expansion after setting causing disruption of the set and hardened mass.
The presence of excess of lime than that could be combined with acidic-oxide at the kiln is the main cause of of unsoundness in cement. Too high a proportion of Magnesium content or Calcium sulphate content may cause unsoundness of cement.
Unsoundness in cement does not come to surface for a considerable period of time..
The Le-chatellier test finds out unsoundness due to free lime only. Cement having a Magnesia content of more than 3% shall be tested for soundness by• autoclave test. Test process:—A heat cement specimen is placed in a standard autoclave and a steam pressure, inside the autoclave is raised in such a rate as to bring the gauge pressure bof the steam 21 kg/cm2 in l—1.25 m . fromthe time the heat is turned-on.
The autoclave is cooled and length measured again. A cement having calcium. sulphate can be easily tested by chemical analysis.

Instrumental Conditioning

Instrumental Conditioning
In Pavlovian conditioning the learning organism plays a purely passive role insofar as the delivery of the conditional and unconditional stimulus is concerned. In instrumental conditioning the organism plays a morbr less active role as far as the obtaining of reward or the avoidance of punishment i concerned. In a true sense the organism literally operates upon its environment hence also the name operant conditioning as coined by B.F.Skinner (1938).


Basic procedures in instrumental conditioning

Three basic features that characterize most instrumental conditioning experiments can be identified. First of all, the typical experimental plan uses procedures that involve, reward or punishment they being termed as reinforcers or reinforcing stimuli and the process being called reinforcement. The second, experimental plan can lead an organism to either produce or withhold some specified response. Thir4, a discriminative cue is ‘used in some experimental plan but not in others. A discriminative cue is a stimulus of some sort that tells the organism, in effect, when reinforcement can be obtained and when it cannot be obtained. It sets the appropriate occasion for the behavior that leads to reinforcement.
(1) Reward training
In this experiment a hungry white rat is placed in a twelve inches square box. This is a sound proof box known as Skinners box. It is also at times referred to as “experimental box”. In essence, the general procedures associated is that of simple reward training. The course of learning is marked much by trial and error. In the Skinner box experiment the rat at first accidentally presses the lever but when he discovers the reward associated with the pressing of the lever his lever pressing becomes intentional, directed towards the attainment of positive reinforcement.

(2) Discrimination training
The apparatus set up is the same as that in reward training with the addition of a small white light located in the wall of the box. This is referred to as the discriminative cue. In essence, the discriminative cue sets the occasion for the obtaining of reward and withholding the same. The process of experimental extension and that of spontaneous recovery can also be experimentally demonstrated via discriminative training.

(3) Escape training
In this type of training a dog is placed in one compartment of a two-compartment box. The two compartments are separated by a door, which can slide up and down. The door is arranged such that it can be dropped part way through a slot in the floor, creating a hurdle over which the dog can jump from the first compartment into the second. Both compartments are equipped with floors made of stainless steel bars through which an electric current is passed. The bars are wired in such a way that when current is passed through them a shock of moderate intensity is delivered to the dog through the dogs feet. At some time determined by the experimenter, the door drops and, at the same instance, current is turned on in the compartment the dog isin. The shock continues until the dog jumps over tl hurdle and reaches the ‘safe’ compartment, in which the shock is not present. The door closes and the dog ‘rests’ until the experimenter again drops the door and turns on the shock in the second compartment. The dog must then jump the hurdle once again, moving back to the original compartment, which is now safe. This process continues for as many trials as the experimenter may call for.
It might seen reasonable to think of escape training as a rather special case of reward training, on the assumption that escaping a noxious stimulus like shock is,warding.
(4) Avoidance learning
The same appatus used in the escape training paradigm is used with a few modifications. An easily visible overhead light is put in each compartment. This light act as a discriminative cue signaling the onset of electric shock within a specified period of ten seconds The dog can, on the signalling jump to the safe.compartment to avoid the punishing stimuli. Thus, this discriminative cue sets the occasion for the dog’s response.
An analogue can be drawn with discrimination training. The dog slowly begins to understand the cue provided by the light and comes to learn the appropriate occasion for escaping a punishing stimuli.
This procedure can also be labelled as a “two way active avoidance training” since the dog must not only actively produces a response to avoid punishment, but also, at the same time jumps across the hurdle separating the two compartments, each of which is “dangerous” at specified times. If only one compartment is permanently unsafe and the other permanently safe then we can label this procedure as “one-way active avoidance training’
(5) Punishment training
This training requires an organism to either withhold or omit a response in order to obtain reward or avoid punishment. In this type of training we continue beyond the point where reward training is accomplished with a few modifications in the Skinner box. The lever is to be connected to an electricity regulating device so that mild current can be passed on to the lever when required. Beyond the junction of reward training lever pressing is associated with reward as well as punishment in the form of mild electric shocks. The organism will now have to learn to withhold a rewarding response to avoid shock. This is an approach-avoidance conflict. It chooses the avoidance side and becomes passive to lever pressing activity. This passiveness as a result of punishment training can be also called “passive avoidance learning”

(6) Omission training
This is more or less similar to punishment training other than the basis of obtaining reinforcement. Reinforcement is based on a positive reward rather than avoidance due to a punishing stimulus. Here also we continue beyond the point where reward training was accomplished. Thereafter we reverse the procedure in the sense that lever pressings are no longer reinforced but failure to do so is. This can be done without any rules binding the process. The outcome is that the rat will learn to withhold or omit the lever pressing response in order to assure a continued flow of food pellets.

(8) Free Vs Controlled Responding
Instrumental conditioning can involve either of these two procedures. These at times are also referred to as free-operant and discrete-trial procedures respectively. The difference between the two is based on the controls of the opportunity to make the instrumental behavior in question. It is termed free-operant when the subject controls the opportunity to make the instrumental behavior and when the experimenter controls the same it is’ termed as discrete-trial or controlled responding.

Three basic laws of Pavlovian conditioning

Three basic laws of Pavlovian conditioning
1. Law of Excitation : It says that if a previously neutral CS is paired with a UCS, the CS’ acquires excitatory properties, that is, it acquires the properly of eliciting the CR.

2. Law of internal inhibition : Internal inhibition develops w’en the conditioned stimulus is not attended by he unconditioned, whether this be once or always, but in the latter event, only under certain circumstances. Thus come about extinction, retardation, conditioned inhibition, and differential inhibition. If a CS is not applied repeatedly, the CR gradually ceases to occur. This phenomena is termed as experimental extinction. In another case one of two similar stimuli, but not the other, is applied repeatedly, the second stimulus is inhibited as a special case of extinctive inhibition. This is referred to as differential inhibition.
Thus, this law characterizes a group inhibition phenomena which are caused by changes in the conditioned association itself and, unlike the various forms of unconditional inhibition, are acquired in learning processes
3. Law of external inhibition : In essence this law states that excitatory or inhibitory processes in conditioning can each be disrupted by novel distracting stimuli, This is called the law of external inhibition since the inhibition is not being acquired in the learning process but from outside.

Conditioning in PSYCHOLOGY

Conditioning in  PSYCHOLOGY 

Conditioning is a form of associative learning which results in changes in an organism’s behavior as a consequence of exposure to certain temporal relations between events. Conditioning has two forms. Classical or Pavlovian conditioning and instrumental or operant conditioning. In experimental studies of both varieties, the experimenter presents, an event of biological or motivational significance usually termed as reinforcer it may be food, water, or access to a sexual partner; or it may be a painful or distressing event such as a brief electric shock or the administration of a drug which causes nausea. Classical and instrumental conditioning differ in the other event with which this reinforcer is associated


Classical Conditioning
This type of conditioning was originally given by Ivan P. Pavlov (1927). In his classical experiment Pavlov designed an apparatus that could measure how much a dog’s mouth watered in response to food or other things in the environment. The dog, was strapped comfortably in a harness, standing on the experimental table in a sound proof roon. A tube was connected from the duct of the dog’s slivary gland to a dish to accumulate saliva for measurement purpose. Pavlov then sounded a tuningiork and noted that other than looking around the dog did not do any other response. After some time a plate of meat powder was placed before the dog. On getting the smell and eating the same the dog salivated. After the dog had eaten the plate was removed. Some time after the tuning fork was sounded again and the same procedure repeated and observations made. It was noted that after repeating this procedure a few more times, the dog on hearing the sound of the tuning fork started to salivate
Components of Pavlovian conditioning.

The following constitute the fundamental components and procedures of Pavlovian conditioning:

The unconditional stimulus (UCS) : Pavlov referred to the meat powder in his salivary conditioning experiment as a UCS. The word unconditioned means that the stimulus in question need not require prior training to produce the desired response. Thus, the essential feature of a UCS is that it should reliably elicit a response without prior training.

The unconditional response (UCR) : The UCR is that response that is elicited by the UCS. Here again unconditional means that no prior association of stimulus-response is essential for producing the required response. Since the primary feature of the UCS-UCR relationship is that the UCS reliably elicits the UCR, the UCR is often referred to as a highly reflexive response, one which happens quickly and quite automatically when the UCS occurs.


The conditioned stimulus (CS) : The CS is that stimulus which comes to elicit a response by being paired properly in time with the UCS. In a very real sense, the appearance of the newly emerging response comes to be conditional’ upon the presentation of the CS, hence its name. The important feature of a CS is that it must be some stimulus which is within the sensory range of the organism and previously must be having a neutral effect with respect. to the reflex under study.
The conditioned response (CR): The CR is that learned reflex which arises when the CS is paired properly in time’ with tãe UCS. Sometimes, incidentally, the CR is referred to as a ‘conditional reflex’ for it becomes conditional upon the presentation of the CS.

Learning

Learning can be defined as any relatively permanent change in behavior which occurs as a result of practice or experience. This definition has three important components :
(a) Learning is a change in behavior, for the better or worse.
(b) It is a change that takes place through practice or experience; changes due to growth or maturation are not learning. This part of the definition distinguishes learning from innately controlled species specific behavior.
(c) Before, it can be called learning, the change must be relatively permanent, it must last for a fairly long period.’