New materials have been introduced due to advances in technology and advancements in industry. Logical changes have been made in Chapter 5 on cement, Chapter 10 on concrete and Chapter 20 on special cements and cement concrete.
Concrete Mix Design 307
P RINCIPAL P ROPERTIES OF B UILDING M ATERIALS
- INTRODUCTION
- PHYSICAL PROPERTIES
- MECHANICAL PROPERTIES
- CHARACTERISTIC BEHAVIOUR UNDER STRESS
It is expressed as a ratio of the volume of the pores to that of the sample. Strength is the ability of the material to resist failure under the influence of stresses caused by loads, of which compression, tension, bending and impact are the most common.
E XERCISES
Ductile materials can be pulled up without stretching down, examples are copper and wrought iron. Flexible materials on the other hand have low modulus of elasticity and bend considerably without breaking.
S TRUCTURAL C LAY P RODUCTS
INTRODUCTION
Clay bricks have a pleasant appearance, strength and durability, and clay tiles used for lightweight partitions and floors have high strength and fire resistance.
CLAY AND ITS CLASSIFICATIONS
PHYSICAL PROPERTIES OF CLAYS
The temperature at which clay melts is determined by the proportion of liquids, texture, homogeneity of the material, character of the flame and its mineral composition. A determination of the fusibility of a clay is of great importance, both in assessing the cost of firing it and in estimating its refractoriness.
BRICKS
Because of disparity in composition, parts of the clay body melt at different rates so that the softening period spans a considerable range both of time and temperature. The uniformity of the clay mass determines very largely the influence of various elements; the carbonate of lime in large lumps may cause cracking when present in small percentages, but when finely ground 15 per cent of it may be allowed to make brick or tile.
CLASSIFICATION OF BRICKS On Field Practice
Bricks of the fourth class are burnt and greatly distorted in shape and size and are brittle in nature. Arch Bricks are fired, also known as clinker bricks, obtained from the inner part of the kiln.
CHARACTERISTICS OF GOOD BRICK
Cavity: The total number of holes, which should not be small, may exceed 25 percent of the brick volume.
INGREDIENTS OF GOOD BRICK EARTH
Silica: Enables the brick to retain its shape and gives it stability, prevents shrinkage and deformation. It burns red when excess oxygen is available and dark brown or even black when available oxygen is insufficient, however, excess iron oxide makes the brick dark blue.
HARMFUL SUBSTANCES IN BRICK EARTH
Magnesium rarely exceeds 1 percent, affects the color and makes the brick yellow, on burning; causes the clay to soften at a slower rate than in most cases lime and reduces deformation. As it dries, the moisture evaporates, leaving behind gray or white powdery deposits on the brick that spoil the look.
MANUFACTURING OF BRICKS Additives in the Manufacture of Bricks
A gap of about 1.0 m is left in the adjacent layers of piles in order to allow free movement for the workers. VitrificationTo convert the mass into a glass-like substance — the temperature ranges from 900–1100°C for low-fusing clay and 1000–1250°C for high-fusing clay.
DIFFERENT FORMS OF BRICKS
TESTING OF BRICKS
Minor — When efflorescence deposits do not exceed 10 percent of the stone's exposed surface. Moderate - When efflorescence deposition is more than 10 percent but less than 50% of the stone's exposed surface.
DEFECTS OF BRICKS
Heavy — When the efflorescence deposit is more than 50 percent, but the deposits do not powder or flake away the brick surface. The specifications limit efflorescence to be no more than moderate (10-50%) up to grade 12.5 and no more than slight (< 10 percent) for higher grades.
HEAVY DUTY BURNT CLAY BRICKS (IS: 2180)
BURNT CLAY PERFORATED BRICKS (IS : 2222)
Such bricks are weak in structure. i) The dimension of the hole parallel to the short side should not be more than 20 mm in the case of rectangular projection and 25 mm in the case of circular projection. ii) The surface area of each hole shall not exceed 500 mm2.
BURNT CLAY PAVING BRICKS (IS : 3583)
BURNT CLAY SOLING BRICKS (IS : 5779)
Water absorption should not exceed 20 percent by weight after immersion in cold water for approximately 24 hours.
BURNT CLAY HOLLOW BLOCKS (IS : 3952)
BURNT CLAY JALLIS (IS: 7556)
CLAY TILES
The burnt clay roof tiles must pass two tests: the transverse strength test and the water absorption test. Six tiles are tested and the average breaking load must not be less than specified in the code.
FIRE-CLAY OR REFRACTORY CLAY
FIRE-CLAY BRICKS OR REFRACTORY BRICKS
Neutral refractory bricks consist of chromite brick (50 percent chromium and iron ore containing 30 percent iron oxide and bauxite containing 15 percent aluminum and 5 percent silica), chrome magnesite brick (Cr2O3 18 percent, MgO 30 percent), spinel, and forsterite brick. The neutral refractory bricks are suitable in places where acid and alkaline liners must be separated, e.g.
TERRACOTTA
They are made from refractory clays with the addition of quartz sand and melting agents such as chalk. Polished terracotta is also called double fired terracotta.
PORCELAIN
STONEWARE
EARTHENWARE
MAJOLICA
GLAZING
The heat from the furnace volatilizes the salt, which enters the pores of the burning object and combines with the silica in clay to make sodium silicate. The frit is then ground with the remaining materials and water and is made of the consistency of cream known as slip.
APPLICATION OF CLAY PRODUCTS
Creamiste (manufactured from low-heat clay), a light porous material forms excellent aggregate for lightweight concrete. a) What are the requirements of soil that is suitable for burning bricks. What are the factors to be considered while choosing a site for manufacturing bricks. a) What components make brick clay unsuitable for the manufacture of bricks.
O BJECTIVE T YPE Q UESTIONS
How does an excess of each of the components of brick clay affect the quality of bricks. Which of the following procedures is used to determine the soundness of bricks? a) Immerse the stones in water for 16 hours and determine how much water the stone will absorb.
Answers Table
R OCKS AND S TONES
INTRODUCTION
ROCK-FORMING MINERALS
Quartz Silicon dioxide Colorless, vitreous No cracks Soluble in. SiO2) white to gray, (Perfect) hydrofluor. Aluminum silicates 2.803.10 in gray Brown in vitreous to undivided No. with hydrogen black pearl weather.
CLASSIFICATION OF ROCKS
Examples of rocks that result from the decay of massive igneous or sedimentary rocks (fragmental rocks) are sandstone, sand, gravel, carbonate conglomerate, and breccia. Examples of transformation of some rocks into metamorphic rocks are given in Table 3.3.
QUARRYING OF STONES
During the process, water is regularly poured into the well to soften the rock and facilitate drilling. Filling The holes are completely dried and the necessary amount of charge is introduced into the holes.
NATURAL BED OF STONE
The number of charges fired, the number of charges exploded and misfires must be recorded. Storage of explosives: The explosives must be stored in a warehouse (a special type of building) away from residential areas, petrol depots, etc.
SEASONING OF STONE
Quantity of explosives required: The quantity of explosives required depends on several factors such as the strength of explosives; method of blasting; number of boreholes—their size, position, etc. It is very difficult to include all the factors in an expression and obtain the exact amount of explosive required.
DRESSING OF STONE
USES OF STONES
For walls, piers, abutments, etc., sawn and separated stones from limestone, sandstone, dolomite and volcanic tuff are used. Granite, gabbro, basalt, marble, breccia, limestone, sandstone and volcanic tuff slabs are generally used.
CHARACTERISTICS OF GOOD BUILDING STONE
Weathering: The stone's resistance to wear due to natural influences should be high. Workability: Stone must be workable so that it is not uneconomical to cut, process and bring it out into the desired shape and size.
TESTING OF STONES
Cp = compressive strength of the specimen having a height greater than the diameter or lateral dimension. Wi = initial load (N) required to bring the track into contact with the surface of the sample D = diameter (mm) of the track.
DETERIORATION OF STONES
The water in the larger cylinder is drained and the sample is carefully taken out and dried in an oven at 100 to 110°C for not less than 24 hours. In cold places, the frost pierces the pores of the stones where it freezes, expands and creates cracks.
DURABILITY OF STONES
PRESERVATION OF STONES
The treatments, if used carefully under favorable circumstances, can result in an apparent slowing of the rate of decay. However, the rate of stone decay is so slow that a short period of experience is of very little value in determining the effectiveness of the treatment.
SELECTION OF STONES
The question of whether or not stone preservatives should be used on old and damaged stones is a difficult one. In fact, the value of preservatives has not yet been proven, and they may be harmful if tried over a long period.
COMMON BUILDING STONES
Building facing the sea Granite, fine-grained sandstone These are not affected by the weathering of sand particles blown by the wind 3. Facade of the building, sculpted (a) Marble, dense-grained sandstone These are lightweight, soft. works, ornamental works and easy to work and have. and statutes pleasant color and appearance.
ARTIFICIAL STONES
APPLICATIONS OF STONES
Which of the following stones has maximum % water absorption by volume. a) rocky rock (b) siliceous rock (c) calcareous rock (d) layered rock. Which of the following tests is used to determine the wear rate of stone.
Answer Table
Wood and Wood Products
INTRODUCTION
CLASSIFICATION OF TREES
GROWTH OF TREES
The wood is said to have a straight grain if the wood elements are straight and parallel to the pith and cross grain if the elements are not parallel to the axis. Cross-grain has a pronounced weakening effect on the strength of beams when the slope of the grains is 1:15 or greater.
CLASSIFICATION OF TIMBER (IS: 399)
Grade C: This classification is based on qualitative assessment of defects and rough estimate of the yield of usable material. Group B: Modulus of elasticity in bending above 9.8 kN/mm2 and below 12.5 kN/mm2 Group C: Modulus of elasticity in bending above 5.6 kN/mm2 and below 9.8 kN/mm2 on the basis of availability.
STRUCTURE OF TIMBER
In the cross-sectional direction, nutrients pass from the stem to the heart through groups of cells that run at right angles to the layers of the cambium and are called medullary rays.
CHARACTERISTICS OF GOOD TIMBER
SEASONING OF TIMBER
This is a fast process, but the elastic properties and strength of the wood are reduced. The wood is also dried more thoroughly and evenly, which reduces the hygroscopicity of the wood.
DEFECTS IN TIMBER
Knots are bases of twigs or branches buried by the cambial activity of the parent branch. Knots reduce the strength of the timber and affect workability and splitting ability as the grain becomes curved.
DISEASES OF TIMBER Dry Rot
DECAY OF TIMBER
Fungal and bacterial attack control: One of the main requirements in controlling fungal attack is the dryness of the wood. They usually do not attack seasoned wood and thrive primarily on wood in the forest yard.
PRESERVATION OF TIMBER (IS: 401)
At the end of the vacuum period, the preservative is introduced into the cylinder while the vacuum pump is working. The pressure is released when a certain part of the preservative injected into the wood is expelled due to the expansion of the trapped air in the cells.
FIRE RESISTANCE OF TIMBER
TESTING OF TIMBER (IS: 1708)
The failure of the sample is recorded according to its appearance and development as shown in Fig. The static deflection x due to the weight of the hammer is measured at the center of the sample.
SUITABILITY OF TIMBER FOR SPECIFIC USES
It is also used for wood impregnated with volatile or non-volatile chemicals that may interfere with the correct determination of moisture content by kiln drying or electric moisture meters. Sufficient time is taken for a clear separation of water and solvent (xylene or toluene) in the trap.
PROPERTIES OF WOOD Physical Properties
In general, the radial shrinkage of wood is 60 percent of the tangential, and the longitudinal shrinkage is negligible. Changes in the moisture content of the cell walls are associated with large changes in the strength and stiffness of the wood.
WOOD PRODUCTS
Therefore, the type of plywood should be determined by the type of panel surfaces. If the face and back are of the same quality, they are indistinguishable.
APPLICATIONS OF WOOD AND WOOD-PRODUCTS
Which of the following is not an objective of wood spices. a) Reduction of shrinkage and deformation (b) Reduction of weight. By reducing the moisture content of the wood above the fiber saturation points, which one of the following is not correct. a).
Materials for Making Concrete-I Cement
INTRODUCTION
The latter does not set and hardens in water like non-hydraulic lime or that are unstable in water, e.g. Examples of natural cement are Roman cement, Puzzolana cement and Medina cement and those of artificial cement are Portland cement and special cement.
PORTLAND CEMENT
Today, cement is widely used in all types of construction; in constructions where high strength is required, e.g. Cement mortar, concrete, reinforced masonry, artificial stone, plaster, pointing and partitions are routinely used in buildings.
CHEMICAL COMPOSITION OF RAW MATERIALS
When iron oxide combines with lime and alumina to form C4AF, it neutralizes some of the undesirable properties contributed by alumina in combination with lime alone. The oxides in fusion interact to form a series of more complex products to form cement clinker.
COMPOSITION OF CEMENT CLINKER
Therefore, each percentage of this available aluminum × 1.65 is the percentage of CaO required for C3A, and is entered opposite CaO as c3 in column 6. By subtracting this value of C3S from c + s, the true percentage of C2S is found and entered in column 8.
HYDRATION OF CEMENT
When the cement comes into contact with water, the hydration products begin to deposit on the outer periphery of the hydrated cement core. The calcium hydroxide crystals, also called portlandite, comprise 20-25% of the solids in the hydrated paste.
RATE OF HYDRATION
WATER REQUIREMENT FOR HYDRATION
The common belief that a water/cement ratio of less than 0.38 should not be used in concrete, because the hydration process requires the gel pores to be saturated, is not valid. In fact, a water/cement ratio of less than 0.38 is very common for high strength concretes.
MANUFACTURE OF CEMENT
The purpose of adding gypsum is to coat the cement particles by interfering with the hydration process of the cement particles. Crushed raw materials are fed into the ball mill (Figure 5.6) and a little water is added.
TESTING OF CEMENT
The autoclave is then opened and the test samples are placed in water at a temperature of 90°C. The temperature is gradually brought down to 27±2°C in 15 minutes. The compressive strength is calculated from the compressive load divided by the average surface area over which the load is applied. The result is expressed in N/mm2.
TYPES OF CEMENT
Sulfate-resistant Portland cement (IS: 12330): In this cement, the amount of tricalcium aluminate is limited to an acceptably low value (< 5). The compressive and transverse strength of this cement is 90 percent that of grade 33 ordinary Portland cement.
STORAGE OF CEMENT
How it differs from ordinary Portland cement. a) What are the initial and final hardening time of cement. Increasing the fineness of cement. a) reduces the rate of force development and leads to greater contraction.
Materials for Making Concrete-II Aggregates
INTRODUCTION
CLASSIFICATION OF AGGREGATES On the Basis of Geological Origin
Synthetic aggregates are made from thermally processed materials, such as expanded clay and clay, used to make lightweight concrete. According to size, aggregates are classified as coarse aggregate, fine aggregate and whole aggregate.
CHARACTERISTICS OF AGGREGATE
