Concrete Engineering

By
KAUSHAL KISHORE
Materials Engineer, Roorkee

Concrete mix design is the process of choosing suitable ingredient of concrete and determining their relative quantities with the object of producing as economically as possible concrete of certain minimum properties, notable workability, strength and durability. It should be explained that an exact determination of mix proportions by means of table or computer data is generally not possible. The materials used are essentially variable and many of their properties cannot be assessed truly quantitatively. A Laboratory trial mix does not provide the final answer even when the moisture condition of aggregates are taken into account. Only a mix made and used on the site can guarantee that all properties of the concrete are satisfactory in every detail for the particular job in hand. In fact mix selection requires a knowledge of the properties of concrete and experimental data, and above all the experience of the expert who conduct the mix design. The selection of mix proportions is an art as much as a science. It is not enough to select a suitable concrete mix; it is also necessary to ensure a proper execution of all the operation involved in concreting. It cannot be stated too strongly that, competently used, concrete is a very successful construction material but, in the literal service of the word, concrete is not fool proof. The mix proportions once chosen, cannot expected to remain entirely immutable because the properties of the ingredients (cement, sand, aggregate, water and admixture) may vary from time to time.
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By
KAUSHAL KISHORE
Materials Engineer, Roorkee

Fly ash or pulverished fuel ash (pfa) is a finely divided powder thrown out as a waste material at the thermal power plants using pulverized coal for raising steam in the boilers. In the building industry, the use of fly ash a part replacement of cement in mortar and concrete at the construction site has been made all over the world including India and is well known. The important building materials which can be produced from fly ash are:

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By
KAUSHAL KISHORE
Materials Engineer, Roorkee

The problem of Alkali-silica reaction was believed to be non-existent in India till 1983, when its occurrence was diagnosed in two concrete dams. This paper describes this problem with respect to Indian aggregates and cement. A rapid method of test for alkali-aggregate reaction is investigated and described in the paper.

INTRODUCTION
The most common causes of deterioration in structural concrete with steel reinforcement in it are

• carbonation and chloride penetration leading to corrosion of steel resulting cracking and spelling of the concrete cover.
• inadequate cover to reinforcing steel Less common causes of deterioration in clude,
• freezing and thawing
• sulphate attack
• alkali-aggregate reaction.

There are three types of alkali-aggregate reactions, namely the alkali-silica, alkali-silicate and akali-carbonate reactions. Deterioration due to the alkali-silica reaction is more common and this paper refers to this aspect.
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By
Er. KAUSHAL KISHORE
Materials Engineer, Roorkee

NEED FOR CURING

The necessity for curing arises from the fact that hydration of cement can take place only in water-filled capillaries. That is why a loss of water by evaporation from the capillaries must be prevented. Evaporation of water from concrete, soon after placing depends on the temperature and relatively humidity of the surrounding air and on the velocity of wind over the surface of the concrete. Curing is essential in the production of concrete to have the desired properties. The strength and durability of concrete will be fully developed only if it is properly cured. The amount of mixing water in the concrete at the time of placement is normally more than required for hydration & that must be retained for curing. However, excessive loss of water by evaporation may reduce the amount of retained water below what necessary for development of desired properties. The potentially harmful effects of evaporation shall be prevented either by applying water or preventing excessive evaporation.
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By
Kaushal Kishore
Materials Engineer, Roorkee

A mix of M-80 Grade suitable for pumped concrete is to be designed with the following materials and detail.

1. OPC 53 Grade, 7-day strength 52.5 N/mm², Spgr 3.15

2. Silica Fume Specific Gravity 2.20

3. Standard deviation for the mix 5.0 N/mm²

4. Grading and properties of river sand and 12.5 mm crushed aggregate are given in Table-1

5. Superplasticizer based on modified Polycarboxylate, specific gravity 1.06, liquid pH 6.0. With the given set of materials, it was found that at a dosages of 2.5 % bwc it gives a reduction of 30% of water for the required slump of 100 mm after one hour at the average day site temperature of 37 degree C.
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Submitted by :BILAL RIAZ CHUGHTAI.
Group members:BILAL RIAZ CHUGHTAI, MUDASSAR MEHMOOD GHUMMAN, MUHAMMAD SOHAIL SALEH and AOON MUHAMMAD HANIF.
Supervised by: Dr. ATTAULLAH SHAH.

INTRODUCTION
1.1 GENERAL
In the world of construction, concrete like other materials is playing an important role in development. concrete is a composite material which is a mixture of cement, fine aggregate , coarse aggregate and water .The major constituents of which is natural aggregate such as gravel, sand, Alternatively, artificial aggregates such manufactured sand furnace slag, fly ash, expanded clay, broken bricks and steel may be used where appropriate. It possesses many advantages including low cost, general availability of raw material, adaptability, low energy requirement and utilization under different environmental conditions.

The goal of sustainable construction is to reduce the environmental impact of a constructed facility over its lifetime. Concrete is the main material used in construction in the world. Due to increase in Construction and Demolition activities worldwide, the waste concrete after the destruction of any infrastructure is not used for any purpose which is totally loss in the economy of the country because natural resource are depleting day by day. The debris is also a major problem for municipal authorities to dispose of at particular location. It is most common practice in all over the world that most of the materials (paper, plastic, rubber, wood, concrete, etc) are being recycled to save the natural resources and environment. Concrete is such a costly material but Now a day’s waste concrete is only being used as a landfill material instead of recycling the concrete as a recycled concrete aggregate (RCA) to use for the construction purposes.

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ABSTRACT
plain concrete possess very low tensile strength, limited ductility and little resistance to cracking .Internal micro cracks are inherently present in concrete and its poor tensile strength is due to propagation of such micro cracks. Fibres when added in certain percentage in the concrete improve the strain properties well as crack resistance, ductility, as flexure strength and toughness. Mainly the studies and research in fiber reinforced concrete has been devoted to steel fibers. In recent times, glass fibres have also become available, which are free from corrosion problem associated with steel fibres. The present paper outlines the experimental investigation conducts on the use of glass fibres with structural concrete. CEM-FILL anti crack, high dispersion, alkali resistance glass fibre of diameter 14 micron, having an aspect ratio 857 was employed in percentages , varying from 0.33 to1 percentage by weight in concrete and the properties of this FRC (fibre reinforced concrete) like compressive strength, flexure strength, toughness, modulus of elasticity were studied.
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By
Prof. B. E. Gite, Mr. Yogesh S. Nagare
Amrutvahini College of Engineering, Sangamner

Abstract
“Continuously reinforced concrete pavement” as the title suggests this type of pavement is reinforced throughout in longitudinal direction. This type of pavement has no transverse joints unless and until there is end of pavement or the pavement comes in contact with some other pavement or bridge. A longitudinal joint exists only if the road is wider than 14 feet. Due to reduction of joints smooth and continuous riding is possible resulting in fuel saving. Also CRCP roads are maintenance free if properly constructed and care is taken while placement of steel. Once CRCP roads are constructed they need not to be taken care of for the next 50-60 years. The principal behind this roads is that “Let the road crack”, exactly opposite as in case of other type of roads where we avoid crack formation at any cost. CRCP is allowed to crack due to which stresses in the pavement are released. The cracks formed are held tightly by the reinforcement, due to which widening and deepening of cracks is restricted. Hence we can conclude that in CRCP controlled cracking is permitted. The initial cost of CRCP is high, but as it is maintenance free, and lasts for decades, overall cost of CRCP is less as compared to other type of reinforced concrete pavements. Study and observations have shown that this type of roads are alarmingly successful, hence CRCP is widely used in USA, GERMANY, BRITAN, and several other developed and developing nations. Use of CRCP will enhance the cement, and steel industries; it will reduce the fuel consumption by vehicles, and will save lots of money required for frequent construction and repairs of other type of pavements.
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By
Kaushal Kishore
Materials Engineer, Roorkee

INTRODUCTION:
For the last 20 years, the use of by products of various origins in the production of concrete has become an increasingly widespread practice in the world. The main advantages are all the elimination of scraps and a reduction in the over exploitation of quarries.

Blast furnace slag is used in blended cement. Although many studies have been conducted on the evaluation of the electric arc furnace slag to be use in concrete as aggregates replacing natural aggregates, no studies have been performed regarding the use of induction furnace slag in concrete as aggregates replacing natural aggregates.

In making mild steel ingot scrap to sponge iron is fed into the induction furnace which produces large quantity of slag. For example Kotdwar a small town of Uttarakhand Steel Mills induction furnances alone generates 15,000 tonnes of slag per year and about 1,50,000 tonnes of slag is lying as dump around this city posing an environmental problem. If about 20 steel factories of Kotdwar generate such quantity of slag it can be calculated how much slag is being generated by about 600 induction furnace units of India.
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By
Kaushal Kishore, Materials Engineer, Roorkee

ABSTRACT:
The stresses induced in concrete pavements are mainly flexural. Therefore flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. A simple method of concrete mix design based on flexural strength for normal weight concrete mixes is described in the paper.

INTRODUCTION:
Usual criterion for the strength of concrete in the building industry is the compressive strength, which is considered as a measure of quality concrete. However, in pavement constructions, such as highway and airport runway, the flexural strength of concrete is considered more important, as the stresses induced in concrete pavements are mainly flexural. Therefore, flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. It is not perfectly reliable to predict flexural strength from compressive strength. Further, various codes of the world specified that the paving concrete mixes should preferably be designed in the laboratory and controlled in the field on the basis of its flexural strength. Therefore, there is a need to design concrete mixes based on flexural strength.
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