Stones

Stones played important roles in construction fields. Stones are often used due to their properties; hard, durable, and naturally good looking. You can even find stones in your house, like roof, floor or kitchen! Stones are mostly used for road base, paving, garden walls, paths, roof tile in form of slates and so on.
Stones can be classified into 2 categories: Artificial and Natural stones.


ARTIFICIAL STONES (ENGINEERED STONES)

Artificial stones floor

Kitchen table

The combination of crushed natural stones and very low water/cement ratio of Portland cement. Pigment is added during the combination process to match the colours of the stones.




#Manufacturing process
Natural stones used :
 -Calcareous stone (marble,limestones or dolomite) 
 -Siliceous stone (granite, quartzite, sand, porphyry)

Process of manufacture artificial stones  

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NATURAL STONES
Natural stones are found and quarried throughout the world. Each natural stone is unique, different types of natural stones have their own properties.
Natural stones can be classified into 3 types:

• IGNEOUS STONES
• SEDIMENTARY STONES
• METAMORPHIC STONES

IGNEOUS STONES

Granite

Granite
Magmatic rocks which can found from the deep of the earth's crust are consisted in granite.
Properties:
-high compressive strength
-hard and durable
-less porosity
-high thermal stability 
#Applications
-can be used as external wall claddings
-floorings
-internal wall tiles 

Granite flooring

Granite wall

By using these stones, it made interior or exterior of the building attractive.

SEDIMENTARY STONES

Sedimentary stones formed by the solidification of material transported and deposited, primarily by water and ice.

How it make from?

(75% land surface) Igneous rocks + physically/chemically or biochemically weathered (wind) + >1000/ 10,000 years = Sedimentary Stones

Example: Such as sandstone, limestone, dolomite and shale.

Process of how sedimentary stones were formed

Limestone

Limestone

Limestone may be composed that contain either carbonate of lime (calcite), or carbonate of lime-magnesium (calcium magnesium carbonate, dolomite)

It comes with many different colors, structures and textures. Common types of limestone which have in gray or buff (structures), brown, yellow, red (iron oxide) , blue, black or gray (carbon impurities).

Properties:

#Porous

#Vary widely and hardness

#Soluble in water containing carbon dioxide

Limestone

-        #Attacked by acids ( rapid decay to softer limestone)

Application:

#Used as raw material in manufacture of cement

#Quicklime (CaO)

Do You Believe?

Sphinx of Giza & the pyramids behind it were mostly built with limestones

METAMORPHIC STONES

Metamorphic Stones formed by the gradual changes in structure and character of

Igneous/Sedimentary stones+ heat, water, pressure = Metamorphic Stones

Example: slate, marble, serpentine, quartzite, etc.

Properties of Metamorphic stones: Coarser, Denser, Less porous.

Different types of marble floor tiles

Marble

Commonly applied to any limestone or dolomite that can get good polishing, that have been exposed to metamorphic action and become partly crystalline.

Properties:

# varying colours and veins

# very hard, dense and scratch proof

# excellent self-polish that improve its appearance

# vulnerable to acid attacks and surface is not lasting if used externally in a polluted atmosphere

Marble floor tiles

# colour of marbles may be fade due to the sugaring that exposed on surfaces

# impermeable, but in dampness condition may staining

Do you believe?

Taj Mahal is built by using marble as building material.

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Different Stones, Different use - Construction Industry

*Fieldstone – rough stones obtained from river beds and fields.

*Rubble – irregular quarried fragments that have at least one good face.

*Dimension stone- quarried and cut into rectangle form.

*Cut stone - quarried and cut into large slabs.

*Ashlar – small rectangular blocks.

*Flagstone –used for flooring and paving, regular or irregular shape, thin slabs of stone

*Crushed stone – used for freely draining fill material, pavings, surfacing materials and aggregates.

Blocks

BLOCKS
Blocks are larger than bricks and usually requires both hands to life it for laying. Since they are larger, they can be laid faster compared with bricks. But the larger size also means less versatility in laying especially when building up ends or corners and also laying to curves. There are two types of blocks which is clay blocks and concrete blocks.


CLAY BLOCKS

Poroton Thermoplan Clay Block

Clay block is a light-blue/gray recolor of the sand texture. Clay can be found on the surface in groups of varying number usually surrounded by sand. It is usually below water but sometimes are found around or under the sand. Clay block construction is an efficient way to build because of its excellent energy saving characteristics combined with the quality and speed of building. Clay block construction projects are highly eco-friendly. The block does not affect the environment during their manufacture comparing with other building materials and the finished building offers high insulation values.

Fire Clay Blocks

The minimum average compressive strengths for clay blocks are;

Non-loadbearing walls/partitions              1.4 N/mm²

Facing and common blocks                    2.8 N/mm²

Blocks for loadbearing internal walls        2.8 N/mm²

CONCRETE BLOCKS

Concrete blocks are either dense or lightweight. Lightweight concrete blocks can be 1/3 the weight of dense blocks. Lightweight blocks have the following advantages ; 

-easier to handle and quicker to lay.

-the air in lightweight block provide better sound and thermal insulation.

-the lighter weight results in lighter foundations and structural members.

Types of concrete blocks

Solid blocks - no formed holes or slots.

Cellular blocks - with cavities (holes) which do not pass pass through.

Hollow blocks - with cavities which pass through.

	Concrete density1 kg/mm3	Strength N/mm2
Dense aggregate	1500-2000	2.8-3.5
Lightweight aggregate	700-1500	2.8-10.5
Autoclaved aerated	400-900	2.8-7.0

Features of concrete blocks

Shrinkage cracks can be avoided by the use of blocks with low drying (reversible) shrinkage, and by taking the necessary precautions described for calcium silicate brickwork. Lightweight concrete blocks have better thermal insulation compared to denser blocks and is a good fire resistance. The durability of factory-made blocks is good because they have a compressive strength of at least 7 N/mm²  can be used for external walls and below ground level as damp proof courses. 

Concrete density¹

kg/mm³

Strength

N/mm²

Dense aggregate

1500-2000

2.8-3.5

Lightweight aggregate

700-1500

2.8-10.5

Autoclaved aerated

400-900

2.8-7.0

Concrete Blocks

Bricks

BRICKS

Bricks is usually used in masonry construction and it is made primarily from baked clay. It used to construct the structures such as walls, chimneys and foundations. It comes in all shapes and sizes. It also made from many different types of materials in various ways of manufacture. In different type of bricks, it contains its own benefits and disadvantages. Mostly or commonly types of bricks today are made from clay and they can be manufactured in many ways. All form of bricks were originally handmade, dating back as far as 7,500 B.C. When the process turned to mechanization, handmade brick building materials were common up until the Industrial Revolution.

VARIOUS TYPES OF BRICKS

Brick Pavers are also used to
create patios and walkways.

1. Face Brick – The most expensive type of brick but it offer smoothest and highest quality of appearance if compared with other type of bricks.

2. Building Brick – Lower grade material designed for structural use and is generally not exposed.

3. Brick Veneer – Low cost and it is thin and lightweight brick material.

4. Brick Pavers – Thin , flat stones used in outdoor application such as hardscapes and patios. It is much harder and denser than other type of bricks.

Different Types of Bricks Show different appearance and colours

Different types of bricks got itself unique functions

FEATURES

Brick is available in a wide variety of colors and textures and may be made from concrete or fired clay. The color of a brick depends on the source of the materials used in its fabrication. A standard-size brick measures three and five-eighths inches by two and one-quarter inches by eight inches, though sizes may vary internationally. Building brick is equipped with holes to reduce weight and to allow for faster installation. Most other brick varieties are solid. Face brick is categorized as Indoor Use Only, Severe Weathering (SW) or Moderate Weathering (MW). Severe Weathering brick can withstand extreme temperatures without cracking, while Moderate Weathering brick can withstand common temperature variations in most climate zones.

BENEFITS

Bricks Structures are very durable and long-lasting. It only require little to no maintenance. It tends to have a desirable appearance without the need for paints, seals or other finishes. It is also a fairly classic material that can adapt to change the trends and decors. In addition, it is highly resistant to flames and helps prevent the spread of fire in the home.

Related Video Posted To Help You In Understanding Of BRICKS.

Aggregates

Different sizes and types of aggregates.

Aggregates are granular material such as sand, gravel, crushed stone, blast-furnace slag, and lightweight aggregates. These are added to cement with water to form concrete. The objective is to use as much aggregate as possible, binding the particles together with the hardened cement paste. Normally. the aggregates occupies approximately 65% to 80% of the volume of concrete.
The advantages to use aggregates in concrete are :
# Reduce the cost.
# Reduce heat output and therefore reduce thermal stress.
# Reduce shrinkage of concrete.
# Help to produce a fresh concrete to flow more easily.Provide dimensional stability.


Types of Aggregates
1. Lightweight Aggregates
These types of aggregates are used to produce lower density concretes, which are very good in reducing the weight of structures and also have better thermal insulation than normal weight concrete. Nowadays, artificial lightweight aggregates are commonly used in concrete because they are widely available . They can be divided into three main types:
# Sintered pulverised fuel ash
# Expanded clay or shale
# Foamed slag 
Lightweight aggregates are not as rigid as normal density aggregates, and therefore produce a lower elastic modulus and higher creep and shrinkage concrete. For the strength of concrete, the properties is depend on the lightweight aggregate type and source.

2. Normal Density Aggregates

The natural materials including gravels, igneous rocks (basalt & granite) and sedimentary rocks (limestone & sandstone)  are used to make concrete. All of the rocks have densities between the range of 2.55 to 2.75 and the produced concretes have densities between the range of 2250 to 2450 kg per meter cube. As a conclusion, the densities are depending on the mix proportions.

3. Heavyweight Aggregates

For the structures such as radiation shielding that required the concretes of high density, heavyweight aggregates can be used. The concretes that produce by barytes have densities between the range of 3500 to 4500 kg per meter cube while the concretes that produce by using steel shot have densities about 7000kg per meter cube.

Properties of Aggregates

1. Strength

Normal weight aggregates are generally considerably stronger than those of the hardened cement paste, and therefore do not have a major influence on the strength of most concretes. 

2. Porosity and Absorption of Water

Lightweight aggregates contain high porosity and normal aggregates also contain pores which can absorb and hold water. 

Before concrete mix, aggregates can be in one of the 4 moisture conditions such as:-

• Completely dry
• Air dry, pores partially filled with water
• Saturated with water and surface dry
• Wet with excess water on surface

3. Surface Characteristics

Surface texture developed the bond between an aggregate particle and a cementing material. A rough texture is producing a stronger bond and create a stronger portland cement concrete. A stronger bond also affected by the cleanliness of the surface which must not be contaminated by mud, clay or other materials.

Admixtures

ADMIXTURES  are the chemical that added into the concrete before or during mixing.
The admixtures can considered as 2 types, which are chemical admixtures and mineral admixtures.
There are 5 types of admixtures:
Plasticisers, Superplasticisers, Accelerators, Retarders, Air Entraining Agents


Chemical Admixtures:

Plasticiser

Plasticisers (it also known as water-reducers.)


Plasticisers are ploymers, they can absorbed onto the surface of cement grains with an ionic group pointing outwards. Beside that, it increased the workability of concrete without increasing water content.
Example: Carbohydrates and organic acids was material used of water-reducing.
With the lower of water/cement ratio which will increases the strength of the concrete with the same amount of cement.
There are few effects of Plasticisers which is:
- delaying (retarding) the set, make the concrete mixture difficult to mix and less workable
- decreasing the early strength gain of the concrete
- entrain air in the form of air bubble
- contain impurities affecting strength of hardened concrete
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Superplasticisers  (it also known as high-range water reducers.)


Superplasticisers was added into concrete mixtures which to improve the
fluidity and workability. The effect of Superplasticisers is greater than
obtainable with Plasticisers.
Normally only 1 or 2% of Superplasticisers was used of cement which is sufficient enough.
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Accelerators are mostly used in
 winter season countries.

Accelerators which is used to increase rate of setting to get the high speed of the heat revolution and it was suggested to be used in cold weather.
Example: Calcium Chloride (CaCl2) was the commonly thing which used in the cement to accelerators both the initial and final setting stage due to it was effective and readily available.
CaCl2 not recommended to be used in reinforced concrete (rc) due to it lead to corrosion of embedded steel reinforcement.
Beside, there are few number of alternative chloride-free accelerators which now are used based on to calcium formate, sodium aluminate or triethanolamine.
There are used to increase the hardening of cement paste, thereby it also:
- enhancing the early stage of strength gain
- reducing the curing time which the concrete was placed in cold weather
- reducing the setting time
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Retarders is used to delay the time of cement mix.

Retarders was uses to :
- counteracting the accelerating effect of hot weather
- controlling the set in large pours which the concreting may take few several hours
- when the concrete has to be transported over long distance it used to delaying the set
To retard the setting of cement admixture based on sugars (sucrose), starches, citric acid, zinc oxide or boric oxide.
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Air in the cement

Air Entraining Agents (AEAs) is used to entrain a controlled quantity of air in the form of microscopic, discontinuous and uniformly distributed bubbles in the cement paste.
The primary effect of entrain air causes disruption of the continuity of capillary pores and reduce the internal stress caused by expansion of pore water during freezing of the cement.
There are 2 effects of Air Entrainment :
- improvement in workability of mix.
- increase in porosity result in drop in strength, improvement in workabiltiy means the loss can be partially offset by reducing the water/cement ratio.
Example: Vinsol Resins, Alkysulfonates and Alkylsufates can be achieved as Air Entrainment.
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Damp-proofing Admixtures is use to prevent water movement by capillary action.

These are some videos about Admixture:

Retarders

Air Entraining Agents

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Mineral Admixtures:

Admixtures that having cementitious properties, which react mainly with the calcium hydroxide liberated by the hydration process.

Fly Ash (pozzoloans)

This admixture is to reduce the permeability, voids, expansion, heat of hydration, bleeding and segregation.

Besides, it increases compressive strength, workability, durability, flexual strength of concrete, protect the steel reinforcement from corrosion, lower the water requirement.

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Silica Fume (also known as mircosilica)

It is added to the concrete mixing to improve concrete properties, reduces the permeability of concrete to the chloride ions to protect the steel reinforcement from corrosion which usually located in the chloride-rich areas (sea).

Types of Portland Cement

Portland cement (or simply call as cement) is the material most commonly used in construction nowadays. There are several types of Portland cement:

Ordinary Portland cement

1. Ordinary Portland Cement (OPC)

This is the most widely used and cheaper than others. It is a general purpose Portland cement suitable for all uses. It is used in general construction projects such as buildings, bridges and floors.

2. Moderate Sulfate Resisting Portland Cement

It is designed to be resistant to sulfate attack and generates less heat at a slower rates. This cement is used in general construction projects that are exposed to soil or water containing sulfate ions. 

3. High Early Strength/Rapid-hardening Portland Cement

This cement is similar to Portland cement, but the cement clinkers  are ground to extremely fine particles. It is designed to develop early strength more quickly than ordinary Portland cement. This is used for maintaining a rapid pace of construction because it allows the concrete to bear loads sooner. This cement also suitable used in cold weather, which reduces the rate of hydration of cement. The concrete made with this cement achieves the 3 days strength of rapid hardening cement in 16 hours and 7 days strength in 24 hours.

4. Low Heat Portland Cement

This cment is designed to release heat more slowly than OPC, which means that it gains strength more slower. This cement is usually used for large concrete structures such as dams, which have a low surface to volume ratio.

5. Sulfate Resisting Portland Cement
This type of cement will be used where the concrete structures is exposed to  severe sulfate action, or the concrete is exposed to soil and groundwater with a high content of sulfate.

White Portland cement

6. White Portland Cement

This cement is similar to OPC, it is identical to gray Portland cement except for its high degree of whiteness. White Portland cement is more expensive than OPC due to higher raw materials cost and the greater care during manufacturing.

7. Portland Blast-furnace Cement

This is a special blended cement with low heat of hydration characteristics for mass concreting. The concrete that used this cement have chloride and sulfate resistance properties. This cement is not suitable for use at low curing temperatures but it can be used for construction in sea water.

Left to right: fly ash, metakaolin, silica fume,
 fly ash, slag and calcines shale

8. Pozzolanic Cement

Pozzolanic Cement consists of pozzolanic materials such as fly ash, volcanic ash, pumicites and so on. This cement are cheaper, they have improved plasticity and they have higher resistance to sea water and 
sulfate attack.

Cement

Cement, one of the material used in forming concrete. The cement powder mixes with water to form paste and acts like glue, holds the aggregates together. Also, provide strength, durability and water-tightness to the concrete. Different types of cement will produce different properties of concrete. There are various type of cement, for example, ordinary portland cement (OPC) is commonly use in construction,white portland cement, high alumina cement and others.

Manufacture of cement

Important components to manufacture cement:

- Calcium Oxide (CaO)

 usually occurs naturally in form of calcareous calcium carbonate (CaCO3) [chalk & limestone]

- Silicon Dioxide (SiO2)/silica

[clay & shale]
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There are 2 ways to produce cement, dry & wet processes.

DRY PROCESS

1. Chalk & clay reduced sizes to about 75μm (less than) and mixed in the desired proportion.

2. The mixture is then dried as powder.

3. The dried powder is preheated and calcining in heat exchanges.

4. The powder is then poured into inclined rotary kiln and the temperature is increasing as the powder goes down the kiln and undergoes 2 chemical changes (calcining and clinkering).

Dry Process

WET PROCESS
Compared to the dry process, wet process has more procedures to follow. There are differences between dry and wet processes.
1. Chalk & clay reduced sizes to about 75μm (less than) and mixed in the desired proportion.

2. The mixture is mixed with water to form slurry. 

3. The slurry is poured into the inclined rotary kiln. (No preheat and calcining)

4. The powder is then poured into inclined rotary kiln and the temperature is increasing as the powder goes down the kiln and undergoes 4 chemical changes (Drying > Preheating > Calcining > Clinkering)

*Sentences underlined indicated the differences between dry and wet processes. 

Manufacturing cement

Gypsum (calcium sulfate dehydrate, CaSO4.2H2O) is added into clinker, it's function is to slow down the curing process and prevent the cement paste from hardening too fast.

Gypsum


video  below that might help you understand more about the difference between cement and concrete.