M-30 CONCRETE MIX DESIGN

As per IS 10262-2009

A1 Stipulations for Proportioning

Grade Designation M30

Type of Cement OPC 53 grade (confirming to IS-12269-1987)

Type of mineral admixture Fly Ash (confirming to Table 1 IS-12269-2009)

Size of aggregate 20mm

Minimum cement content 320kg/m3 (confirming to Table 5 IS- 456 : 2000)

Maximum water cement ratio 0.45 (confirming to Table 5 IS-456: 2000)

Workability 100mm (slump)

Exposure Severe

Method of placing Pump

Degree of supervision Good

Type of aggregate Crushed angular aggregate

Chemical admixture Super plasticizer (IS – 9103)

A 2 Test Data For Material

Cement used OPC 53 grade (confirming to IS-12269-1987)

Specific gravity of cement 3.15

Fly ash (confirming to IS 3812 part-1)

Specific gravity of fly ash 2.2

Chemical admixture Superplasticizer (confirming to IS 9103)

Specific gravity :

Coarse aggregate 2.74

Fine aggregate 2.74

Water absorption :

Coarse aggregate 0.5 %

Fine aggregate 1.0 %

Free (surface) moisture :

Coarse aggregate Nill

Fine aggregate Nill

Sieve analysis :

Coarse agg. IS Analysis of Percentage of Remark

Sieve size coarse aggregate different fraction

mm fraction

20 100 100 40 60 100

10 0.0 71.20 0.0 28.5 28.5

4.75 9.40 3.7 3.7

2.36 0.0

A-3 Target Strength For Mix Proportioning:

f'ck = fck + 1.65 swheref'ck = target average compressive strength at 28 days,

fck = characteristic compressive strength at 28 days, and

s = standard deviation.

standard deviation, s =5 N/mm2• (From Table 1 IS 10262)

Therefore, target strength =30 + 1.65 x 5 =38.25 N/mm2•

A·4 Selection of water cement ratio maximum water-cement ratio = 0.45 .( From Table 5 of IS 456)

A-5 Selection water content :

maximum water content =186 litre (for 25 to 50 mm slump range confirming to Table 2 IS 10262 for 20 mm aggregate)

Estimated water content for 100mm slump = 186+186 X 6 / 100

197 litre

As superplasticizer is used, the water content can be reduced up 20 percent and above.

= 197 X 0.8

157.60 litre

A-6 Calculation of cement content :

Water-cement ratio = 0.45

Cement content = 157.6 / 0.45 =350kg/m3

From Table 5 of IS 456, minimum cement content for 'severe' exposure condition = 320 kg/m3

350 kg/m3 > 320 kg/m3 hence O.K.

Now, to proportion a mix containing fly ash the following steps are suggested:a) Decide the percentage fly ash to be used based on project requirement and quality of material

b) In certain situations increase in cementitious material content may be warranted, The deci sion on increasing cementitious material content and its percentage may be based on experience and trial.

NOTE - This illustrative example is with increase of 10 percent cementitious material content.

Cementitious material content = 350 X 1.10 = 385 kg/m3 Water content = 157.6 kg/m3 W/C= 157.6/385 = 0.41

Fly ash @ 30% of total cementitious material content= 385 x 30% =115 kg/m3

Cement (OPC) = 385 - 115 =270 kg/m3

Saving of cement while using fly ash = 350-270 = 80kg/m3

A7 Proportion of volume of coarse aggregate and fine aggregate:

For w/c = 0.50

Ratio of coarse agg. To total agg. = 0.64 (As IS 10262, there is increase and decrease of .01 for every decrease and increase of .05 change in water cement ratio)

So for w/c =0.45

Volume of coarse aggregate = 0.64+0.01 0.65

For pumpable concrete these values should be reduced by 10 percent.

= 0.65 X 0.9

= 0.585

Volume of Fine aggregate = 0.415

A8 Mix calculation :

The mix calculations per unit volume of concrete shall be as follows:

a) Volume of concrete = 1 m3

b) Volume of cement = Mass of cement / specific gravity of cement X 1000

= 270 / 3.15 X 1000= 0.086 m3

c) Volume of fly ash = 115 / 2.2 X 1000 = 0.052 m3

d) Volume of water = 157.6 / 1 X 1000 = .1576 m3

e) Volume of chemical admixture = Mass of admixture / sp. gravity of admixture*1000( 2% by mass of cementitious material) = 7 / 1.145 X 1000 = .007 m3

f) Volume of all in aggregate = 1- (0.086 + 0.052 + 0.1576 + 0.007)

= 0.6974 m3

g) Masss of coarse aggregate =f x volume of coarse agg. x sp. Gravity of coarse agg. x 1000

= .6974 x 0.415 x 2.74 x 1000

= 1117.86 kg

h) mass of fine aggregate = 0.6974 x 0.415 x 2.74 x 1000

= 793 kg

NOMINAL MIX M30 CONCRETE

B-1 Stipulations for Proportioning

Cement : sand : aggregate = 1 : 1 : 2

Water cement ratio = .6

Volume of cement = (1 / 4.6) x 1

= .217 m3

Voume of coarse aggregate = 2.74 x 1000 x .435

= 1191.9 kg

ECONOMY FACTORS

CEMENT-

Cement use in design mix = 0.086 m3

Cement use in nominal mix = 0.217 m3

Difference of volume use = 0.217 - .086 = 0.131 m3

Rate of .035 m3 cement = 297 rs

Value of .131 m3 cement use = 1111 rs

Thus For 15000 m3 concrete we can save = 1111 x 15000

= 1.67 crore

Cement and steel are two expensive material use in construction, by saving cement we can achieve economy thus in above case by desiging design mix concrete we can save .131 m3 of cement per m3 of concrete thus saving 1.67 crore.

Fly ash-

Fly ash is a byproduct from burning pulverized coal in electric power generating plants. During combustion, mineral impurities in the coal (clay, feldspar, quartz, and shale) fuse in suspension and float out of the combustion chamber with the exhaust gases. As the fused material rises, it cools and solidifies into spherical glassy particles called fly ash. Fly ash is collected from the exhaust gases by electrostatic precipitators or bag filters. The fine powder does resemble portland cement but it is chemically different. Fly ash chemically reacts with the byproduct calcium hydroxide released by the chemical reaction between cement and water to form additional cementitious products that improve many desirable properties of concrete. All fly ashes exhibit cementitious properties to varying degrees depending on the chemical and physical properties of both the fly ash and cement. Compared to cement and water, the chemical reaction between fly ash and calcium hydroxide typically is slower resulting in delayed hardening of the concrete. Delayed concrete hardening coupled with the variability of fly ash properties can create significant challenges for the concrete producer and finisher when placing steel-troweled floors.

Thus by using fly ash we can reduce the cement quantity and achieve the economy.

Coarse aggregates

Coarse aggregates are particles greater than 4.75mm, but generally range between 9.5mm to 37.5mm in diameter. They can either be from Primary, Secondary or Recycled sources. Primary, or 'virgin', aggregates are either Land- or Marine-Won. Gravel is a coarse marine-won aggregate; land-won coarse aggregates include gravel and crushed rock. Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder.

Secondary aggregates are materials which are the by-products of extractive operations and are derived from a very wide range of materials

Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular subbases, soil-cement, and in new concrete. Recycled aggregates are classified in one of two ways, as:

1. Recycled Concrete Aggregate (RCA).2. Recycled Aggregate (RA)

In mix design coarse aggregate use = 1117 kg

In nominal mix coarse aggragate = 1191kg

So there is less amount of aggragate use in mix design, thus we can achieve economy.

QALITIES OF MIX DESIGN CONCRETE

Inspectors should familiarize themselves with the most important properties of concrete:• workability • durability • strength • volume change • air entrainment • density

All of these affect the finished product and knowledge of these properties is essential to produce a quality final product. Each property is explained below.

IMPOTANCE OF CONCRETE TESTING Concrete is tested to ensure that the material that was specified and bought is the same material delivered to the job site. There are a dozen different test methods for freshly mixed concrete and at least another dozen tests for hardened concrete, not including test methods unique to organizations like the Army Corps of Engineers, the Federal Highway Administration, and state departments of transportation.

There are many tests which are conducted to check the quality of concrete. These tests are basically divided into two categories

WORKABILITYAccording to Granville “it is that property of the concrete which determines the amount of useful internal work necessary to produce full compaction.”

Powers defined it as “that property of plastic concrete mixture which determines the ease with which it can be placed and the degree to which it resists segregation”

ACI (American Concrete Institute) defines it as ‘that property of freshly mixed concrete or mortar which determines the ease and homogeneity with which it can be mixed, placed, consolidated and finished’.

ASTM (American Society for Testing and Materials) defines it as “that property determining the effort

required to manipulate a freshly mixed quantity of concrete with minimum loss of homogeneity”.

TEST FOR WORKABILITY

The concrete slump test is an empirical test that measures the workability of fresh concrete.More

specifically, it measures the consistency of the concrete in that specific batch. This test is performed to

check the consistency of freshly made concrete. Consistency is a term very closely related to

workability. It is a term which describes the state of fresh concrete. It refers to the ease with which the

concrete flows. It is used to indicate the degree of wetness. Workability of concrete is mainly affected

by consistency i.e. wetter mixes will be more workable than drier mixes, but concrete of the same

consistency may vary in workability. It is also used to determine consistency between individual

batches.

The test is popular due to the simplicity of apparatus used and simple procedure. Unfortunately, the

simplicity of the test often allows a wide variability in the manner that the test is performed. The slump

test is used to ensure uniformity for different batches of similar concrete under field conditions  and to

ascertain the effects of plasticizers on their introduction.In India this test is conducted as per IS

specification.

DURABILITYDurability of concrete may be defined as the ability of concrete to resist weathering action, chemical attack, and abrasion while maintaining its desired engineering properties.

Durability is defined as the capability of concrete to resist weathering action, chemical attack and abrasion while maintaining its desired engineering properties. It normally refers to the duration or life span of trouble-free performance. Different concretes require different degrees of durability depending on the exposure environment and properties desired. For example, concrete exposed to tidal seawater will have different requirements than indoor concrete

There are many types but the major Concrete Durability types are:

1. Physical durability2. Chemical durability

Physical durability is against the following actions

1. Freezing and thawing action2. Percolation / Permeability of water3. Temperature stresses i.e. high heat of hydration

Chemical durability is against the following actions

1. Alkali Aggregate Reaction2. Sulphate Attack3. Chloride Ingress4. Delay Ettringite Formation5. Corrosion of reinforcement

Test for durability

An ultrasonic pulse velocity test is an in-situ, nondestructive test to check the quality of concrete and natural rocks. In this test, the strength and quality of concrete or rock is assessed by measuring the velocity of an ultrasonic pulse passing through a concrete structure or natural rock formation. This test is conducted by passing a pulse of ultrasonic wave through concrete to be tested and measuring the time taken by pulse to get through the structure. Higher velocities indicate good quality and continuity of the material, while slower velocities may indicate concrete with many cracks or voids.

STRENGTH

In the study of strength of materials, the compressive strength is the capacity of a material or structure

to withstand loads tending to reduce size. It can be measured by plotting applied force against

deformation in a testing machine. Some materials fracture at their compressive strength limit; others

deform irreversibly, so 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; these range from very small

table-top systems to ones with over 53 MN capacity.[1] 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.

HIGH-EARLY STRENGTH

There are three methods Mn/DOT makes adjustments to obtain high-early strength.

1.Adding 30% more cement by weight to the normal cement content (the fine aggregate is reduced) while the water and air contents remain unchanged.

2.Adding chemical admixtures to the standard mix. 3.A combination of 1 and 2.

The additional 30% cement or addition of a water reducer increases the cement-voids ratio of the mix and thereby strength is increased. Accelerating admixtures added to a standard mix, without changing the cement or water content, increase the rate of hydration thereby

increasing the early strength but reducing the ultimate strength. Use of chloride based admixtures for reinforced concrete is not recommended.

Increasing the cement content 30% produces high -early strength concrete. Do not increase the water content more than 5% over that used with the normal cement content. There is a tendency to increase the water content to the extent that the same slump is obtained. The addition of excess water will nullify the benefits of the increased cement content and produce a lower early and lower ultimate strength than anticipated. The actual slump value is less in a higher cement content mix due to the increased workability of the mixture that is a result of the high cement content. The lower slump concrete with the additional cement is just as workable as the normal concrete.

action tends to induce internal stresses in the concrete structure if the change in volume is restrained to any degree. For example, a concrete pavement resting on a wet subgrade and exposed to drying surface conditions will tend to curl or warp upward around the outside edges. This warp is resisted by the weight of the slab and also by interlocking features of the joints in the pavement and results in tensile stresses in the lower portion of the pavement.

DENSITY

The value of high density was addressed indirectly in connection with other related properties in concrete.

The factors that contribute to high density for all types of concrete are:• Use of well-graded aggregate of the largest possible maximum size. • Minimum water content consistent with good workability. • Minimum air content consistent with adequate durability. • Thorough consolidation during placement.

MIX DESIGNATION

Each mix is designed for a specific type of work, method of placement, and finishing. Varying the amount of sand, rock, or water in a mix will produce different placing and finishing characteristics and may also affect the quality of the finished product. Cement and air contents will affect the strength and durability of the concrete.

SAFETY Construction and building renovation sites are dynamic, ever changing work areas that offer unique safety challenges. Construction and renovation activities at the University may be performed by either outside contractors or University employees. The work may be done exclusively by one group or the other, or a project may be a collaborative effort. Because of these differing arrangements, it often is

unclear who has the responsibility and authority to ensure that safety and health regulations are followed.

General Contractors may have additional safety or training requirements that would apply for sites under their management and be considered mandatory for University employees as well. Questions about General Contractor safety or training requirements should be directed the University project manager and/or EHS.

Work Clothing & Personal Protective Equipment

1. Required personal protection equipment (PPE) will be worn at all times. At a minimum, each employee is required to wear a hard hat and safety glasses.

2. High visibility safety vests with reflective striping are required when employees are exposed to vehicular traffic. In the absences of vehicular traffic, high visibility shirts should be worn at all times.

3. Depending on circumstances, additional PPE may be required. This determination will be made by your supervisor, in consultation with EHS, and may include:

a. Protective glovesb. Hearing protectionc. Full face shields when cutting, grinding, or chippingd. Chemical splash gogglese. Respiratory protectionf. Other equipment such as protective clothing, fall protection when working above 6 feet,

or safety-toed shoes 4. All workers must wear shirts with sleeves, long work pants, and sturdy work shoes or boots. 5. Sleeveless or tank top shirts, short pants, sweat pants, sneakers, sandals, and high-heeled or

open-toed shoes are not permitted.

Reporting Emergencies, Injuries & Unsafe Conditions

6. Report all emergencies immediately to Public Safety at 911 from a campus phone or 609-258-3333 from a cell phone.

7. Follow the site emergency action plan in the event of a site evacuation or other emergency.8. Report unsafe practices or conditions to your supervisor immediately. If not corrected within a

reasonable time, report to EHS at 609-258-5294.9. Report all injuries, no matter how minor, to your supervisor as soon as possible, but no later

than the end of the work shift.

Site Protection and Security

10. Barricades, signs, or guardrails must be used wherever necessary for the physical protection of people or property. Barricades or guardrails should act as physical barriers, preventing contact by passers-by with the hazards created by construction or renovation activities.

11. Signs should be used to direct traffic, both vehicular and pedestrian, safely through or around the work site.

12. Floor openings or open sides higher than 4 feet must be protected with guardrails.13. Secure worksites by locking doors, fencing, or barricades after work hours and whenever the

site is unoccupied. 14. Whenever required, follow check in/out procedures when entering or leaving the work site.

Tools & Equipment

15. All power and extension cords must be equipped with ground-fault protection. If not built-in, a portable GFCI must be used between the receptacle and cord.

16. The use of all tools and equipment, including ladders, scaffolding, powder-actuated tools, forklifts, etc., shall be performed by skilled, properly trained workers.

17. Tools and equipment must be inspected before use and removed from service if found defective. 18. Safety guards, devices, or features must be maintained in full operating condition.

Fire Safety & Housekeeping

19. Follow hot work permit procedures for cutting, welding, or burning. Erect arc shields for the protection of co-workers or passers-by.

20. Follow good housekeeping practices. Keep work areas orderly and clean-up worksite debris at the end of each work shift.

21. Smoking is not permitted in any University building, including those under renovation or construction, or on construction sites except in designated areas.

Chemical Use & Storage

22. Material Safety Data Sheets (MSDS) must accompany any chemical brought to the site and be readily accessible at all times.

23. Chemical containers must be properly labeled.24. Storage and disposal of chemicals and other hazardous materials must be done in full

compliance with all applicable local, state, and federal regulations. Contact EHS at 609-258-5294 with any questions or concerns.

Other Requirements

25. The use of radios, disc players, IPODS, or other devices with ear phones is prohibited.26. Horseplay, fighting, scuffling, or creating a disturbance is strictly prohibited.

Disciplinary Procedure

27. General Contractors may have established disciplinary procedures for worksites under their control that may result in dismissal from the project for violations of safety rules and procedures.

Hand and Arm Protection

Potential hazards to hands and arms include skin absorption of harmful substances, chemical or thermal burns, electrical dangers, bruises, abrasions, cuts, punctures, fractures or amputations.  Protective equipment includes gloves, finger guards and arm coverings.

Types of Protective Gloves

There are many types of gloves available today to protect against a wide variety of hazards.  The nature of the hazard and the operation involved will affect the selection of gloves.  The variety of potential occupational hand injuries makes selecting the right pair of gloves challenging.  In general, gloves fall into the following four categories:

1. Leather, Canvas or Metal Mesh Gloves: These types of gloves protect against cuts, burns and punctures. 

2. Fabric and Coated Fabric Gloves: These types of gloves are made of cotton or other fabric.  They generally protect against dirt, chafing and abrasions.

3. Insulating rubber gloves: These gloves are used for protection against electrical hazards.  For more information on insulating rubber gloves for electrical work, see Electrical Safety Protective Methods

4. Chemical and liquid resistant gloves: When working with chemicals with a high acute toxicity, working with corrosive materials in high concentrations, handling chemicals for extended periods of time or immersing all or part of a hand into a chemical, the appropriate glove material should be selected, based on chemical compatibility.  The following table includes major glove types and their general uses.  This list is not exhaustive.  For more information on chemical resistant glove selection, see PPE for Chemical Hazards or the Safety Data Sheet for a particular substance.

Other Considerations

There are several factors besides glove material to consider when selecting the appropriate glove.  The amount of dexterity needed to perform a particular manipulation must be weighed against the glove material recommended for maximum chemical resistance.  In some cases, particularly when working with delicate objects where fine dexterity is crucial, a bulky glove may actually be more of a hazard.

Dexterity: Where fine dexterity is needed, consider double gloving with a less compatible material, immediately removing and replacing the outer glove if there are any signs of contamination.  In some cases, such as when wearing Silver Shield gloves, it may be possible to wear a tight-fitting glove over the loose glove to increase the overall dexterity.

Glove thickness, usually measured in mils or gauge, is another consideration.  A 10-gauge glove is equivalent to 10 mils or 0.01 inches.  Thinner, lighter gloves offer better touch sensitivity and flexibility, but may provide shorter breakthrough times.  Generally, doubling the thickness of the glove quadruples the breakthrough time.

Glove length should be chosen based on the depth to which the arm will be immersed or where chemical splash is likely.  Gloves longer than 14 inches provide extra protection against splash or immersion. 

Glove size may also be important.  One size does not fit all.  Gloves which are too tight tend to cause fatigue, while gloves which are too loose will have loose finger ends which make work more difficult. The circumference of the hand, measured in inches, is roughly equivalent to the reported glove size.  Glove color, cuff design, and lining should also be considered for some tasks.

Glove Inspection, Use and Care

All gloves should be inspected for signs of degradation or puncture before use.  Test for pinholes by blowing or trapping air inside and rolling them out.  Do not fill them with water, as this makes the gloves uncomfortable and may make it more difficult to detect a leak when wearing the glove.

Disposable gloves should be changed when there is any sign of contamination.  Reusable gloves should be washed frequently if used for an extended period of time.

While wearing gloves, be careful not to handle anything but the materials involved in the procedure.  Touching equipment, phones, wastebaskets or other surfaces may cause contamination.  Be aware of touching the face, hair, and clothing as well.

Before removing them, wash the outside of the glove.  To avoid accidental skin exposure, remove the first glove by grasping the cuff and peeling the glove off the hand so that the glove is inside out.  Repeat this process with the second hand, touching the inside of the glove cuff, rather than the outside.  Wash hands immediately with soap and water.

Foot Protection

Potential hazards which may lead to foot and leg injuries include falling or rolling objects, crushing or penetrating materials, hot, corrosive or poisonous substances, electrical hazards, static electricity, or slippery surfaces.

Different footwear protects in different ways.  Check the product's labeling or consult the manufacturer to make sure the footwear will protect the user from the hazards they face.

Foot and leg protection choices include the following:

Safety-toed shoes or boots protect against falling, crushing or rolling hazards. Safety-toed footwear must meet the minimum compression and impact performance standards in ANSI Z41-1999 or provide equivalent protection.

Some safety shoes may be designed to be electrically conductive to prevent the buildup of static electricity in areas with the potential for explosive atmospheres or nonconductive to protect workers from workplace electrical hazards.

Metatarsal guards protect the instep area from impact and compression.  Made of aluminum, steel, fiber or plastic, these guards may be strapped to the outside of regular work shoes.

Toe guards fit over the toes of regular shoes to protect the toes from impact and compression hazards.  They may be made of steel, aluminum, or plastic.

Rubber overshoes are used for concrete work and areas where flooding is a concern Shoes with slip-resistant soles are required for certain departments and should be used in areas where

slips and falls on wet floors are most likely. Studded treads and overshoes should be used when employees must work on ice or snow-covered

walking surfaces. Leggings protect the lower legs and feet from heat hazards such as molten metal or welding sparks. 

Safety snaps allow leggings to be removed quickly.

EYE AND FACE PROTECTION

Selecting the most suitable eye and face protection should take into consideration the following elements:

Ability to protect against specific workplace hazards Should fit properly and be reasonably comfortable to wear Should provide unrestricted vision and movement Should be durable and cleanable Should allow unrestricted functioning of any other required PPE

Protective eye and face wear must comply with the American National Standards Institute (ANSI) standard  Z87.1-1989 or later.

Types of Eye and Face Protection Are

Some of the most common types of eye and face protection include:

Safety Glasses

Safety glasses have safety frames constructed of metal or plastic and impact-resistant lenses.  Side protection is required.Must comply with ANSI standard Z87.1

Chemical Splash Goggles

Tight fitting eye protection that completely covers the eyes, eye sockets and facial area surrounding the eyes.  Provides protection from impact, dust and splashes.  Must comply with ANSI standard Z87.1

Dust Goggles

Dust goggles, sometimes called direct ventilated goggles, are tight fitting eye protection designed to resist the passage of large particles into the goggles. 

Must comply with ANSI standard Z87.1

Fluid Resistant Shields

These shields are fluid resistant or impervious and provide splash protection from biological material, such as human or non-human primate body fluids.These shields do not provide protection against chemicals or impact hazards and do not comply with ANSI Z87.1

Face Shields

These shields extend from the eyebrows to below the chin and across the width of the employee’s head.  Face shields protect against potential splashes or sprays of hazardous liquids.  When worn for protection against UV, must be specifically designed to protect the face and eyes from hazardous radiation.When used for chemical protection or UV protection, must comply with ANSI standard Z87.1.

Laser Eyewear

Protective eyewear is required for Class 3 and 4 laser use where irradiation of the eye is possible. Such eyewear should be used only at the wavelength and energy/power for which it is intended.  Contact the Laser Safety Officer at x6271 for information.

Welding Shields

Constructed of vulcanized fiber or fiberglass and fitted with a filtered lens, welding shields protect eyes from burns caused by infrared or intense radiant light; they also protect both the eyes and the face from flying sparks, metal splatter and slag chips produced during welding, brazing, soldering and cutting operations.

HEAD PROTECTION

Hard Hats

Hard hats can protect employees from impact and penetration hazards as well as from electrical shock and burn hazards.  Protective headgear must meet ANSI standard Z89.1-2009 or later. 

Hard hats are divided into two types and three industrial classes:

Type I hard hats are intended to reduce the force of impact resulting from a blow only to the top of the head. This form of impact, for example, may result from a hammer or nail gun falling from above.

Type II hard hats are intended to reduce the force of lateral impact resulting from a blow which may be received off-center, from the side, or to the top of the head. This form of impact, for example, may result from contact with the sharp corner of a side beam.

Class G (formerly known as Class A) – These hard hats are considered for general use and offer protection against low-voltage electrical conductors up to 2,200 volts (phase to ground).

Class E (formerly known as Class B) – These helmets are intended for electrical work and offer protection against exposed high-voltage electrical conductors up to 20,000 volts (phase to ground).

Class C – These helmets do not offer any electrical protection and are often electrically conductive.

Each hard hat should bear a label inside the shell that lists the manufacturer, the ANSI designation and the class of the hat.

Bump Caps

Unlike hard hats, bump caps do not offer protection against falling or flying objects. However, bump caps provide excellent protection against accidental impact with fixed objects, such as exposed pipes or beams. They should be worn when working in areas with low overhead hazards. Bump caps do not have an ANSI designation.

Care and Storage

Periodic cleaning and inspection will extend the useful life of protective headgear.  A daily inspection of the hard hat shell, suspension system and other accessories for holes, cracks, tears or other damage that might compromise the protective value of the hat is essential.  Paints, paint thinners and some cleaning agents can weaken the shells of hard hats and may eliminate electrical resistance.  Do not store protective headgear in direct sunlight, as UV light and extreme heat can cause damage.

Always replace a hard hat if it sustains an impact, even if damage is not noticeable.  Suspension systems can be replaced when damaged or when excessive wear is noted.

PROTECTIVE CLOTHING

There are many varieties of protective clothing available for specific hazards.  Examples of the body/skin protection include laboratory coats, coveralls, vests, jackets, aprons, surgical gowns and full body suits.  Uniforms, caps, or other clothing worn solely to identify a person as an employee would not be considered PPE.

Hats, long sleeves, long pants or sunscreen, while not defined as PPE, should be considered for protection against heat, cold, sun or insect exposure.  Also included in this category may be the use of a personal fall arrest system or body positioning system when working on elevated surfaces.

Hearing Protection

When an employee’s noise exposure cannot be reduced to safe levels, then hearing protection must be worn. There are several options for hearing protection available that include ear plugs, ear muffs, and hearing bands, which are also known as canal caps. Each should be carefully considered for the noise reduction they will provide, as well as for comfort and fit. EHS assists departments with hearing protection selection to ensure that these variables are properly addressed.  

Typical Hearing Protection Devices

Pre-molded Ear Plugs - Come in different sizes and shapes to fit different sized ear canals. They have virtually no expansion or contraction, so obtaining a good seal with the ear canal may be challenging. 

Formable or Foam Ear Plugs - When placed in the ear correctly, this type of ear plug, will expand to fill the ear canal and seal against the walls. This expansion allows foam ear plugs to fit ear canals of different sizes. 

Ear Muffs - These devices fit against the head and enclose the entire perimeter of the external ear. The inside of the muff cup is lined with acoustic foam, which reduces noise. Their effectiveness depends on how tight the seal is between the foam cushion and the head. 

Hearing Bands or Canal Caps - These devices cover the ear canal at its opening. They do not provide as much of a seal inside the ear canal and generally provide less protection than ear muffs or plugs, so they are typically not recommended.

Payment for PPE

Departments must pay for almost all PPE required by OSHA standards.  However, there are a few exceptions to this rule:

Departments are not required to pay for uniforms, items worn to keep clean, or everyday clothes, even when such clothing could serve as PPE or used solely for the protection from weather.

Departments are not required to pay for safety-toe shoes or prescription safety eyewear, so long as the employee is allowed to wear them off the job-site, are not used in a manner that renders them unsafe for use off the job-site, and are not designed for special use on the job.  (Please not that provisions in union contracts and University policies address reimbursement for safety-toe shoes)

If an employee voluntarily chooses to provide their own PPE, the department is not required to reimburse the employee.  The department must ensure that employee-owned PPE is adequate for hazards at the workplace.

The department must pay for replacement PPE, unless the employee has lost or intentionally damaged it.  Consideration must be given to the useful lifetime of PPE when assessing charges for lost or damaged PPE.