Stone Stories 2

Now that we're familiar with the classes of stones, let's delve even further!

Properties of stones:

Stones	Classification	Suitability
Granite	Igneous	Most suitable for engineering works such as bridge abutments, piers, sea walls, dams
Serpentine	Igneous	Ornamental works and quality building works
Sandstone	Sedimentary	For pavements, roof tiles, ornamental works and heavy engineering works
Limestone	Sedimentary	For pavements, roofing and in the manufacture of cement.
Laterite	Metamorphic	For rough stone masonry work and stone pitching
Marble	Metamorphic	Flooring and decorative ornamental works

Other general purposes of stones as building materials are:

• Foundations and Walls

          - sawn stones for substructure
          - limestones and sandstones for walls, piers and abutments

                         

          

• Facing and Architectural Items

         - Granites and sandstones are sawn from slabs or split from semi-finished product blocks to make
           facing slabs and stones, stairs and landings, parapets, etc.

        

• Road Construction

- curb stones that separate roadways from sidewalks

         

 - paving blocks for pavements

- cobblestones as reinforcement for slopes of earthworks and banks of water   basins

• Underground Structures and Bridges

Formwork to make slabs

Stone finishes

          - Granite and limestone in slab and stone forms are used for these; in other words, igneous and

            sedimentary rocks.

          - Tunnels and above-water elements of bridges are built of granite, diorite, gabbro and basalt. 

          - Face stones and facing slabs for tunnels and bridges are given rock face, grooved or fluted finishes.

• Heat- and Chemically-Resistant Items

          These are manufactured from non-weathered rocks, which are rocks that have not been exposed to

          the elements that cause wear, such as frost and chemicals.Most of them are made from chromite, 

          basalt, andesite and tuffs for high temperature working conditions.

Now that you know, you need not stay stoned when it comes to stones! (Yes, the pun is intended.)

Bricked!

Bricks are pretty much a staple building material in Malaysia and several parts of the world. Once constructed into walls and the like, they can be covered with plaster then tiles or coated with paint, or some other type of finishing...or they can be left as is for a natural aesthetic look.

That said, there are different types of bricks in the industry. Different types of bricks are best suited for different situations, so what may work for one situation may not work for another. What makes it so confusing is the fact that they are categorised in several ways, so when you hear "types of bricks" it might mean clay bricks, or it might mean facing bricks...or for all you know, it might be its grade. So how are bricks categorised?

Here are several possibilities:

1. Main Ingredient
Bricks can be grouped by the main ingredient used to manufacture them. This is one categorisation that is widely used, and is also more easily understood by the average person outside of the construction industry - their physical characteristics can sometimes be enough to give it away. Some of the commonly used bricks are clay bricks, concrete bricks and silica bricks.

• Clay Bricks

                                     

Clay bricks are perhaps more recognisable, due to their rustic, reddish-brown hue. They are extremely water absorbent, which can be proven by a water absorption test. The natural composition of clay makes clay bricks extremely fire resistant. Malaysia has an abundance of clay...but unfortunately, clay bricks can be rather costly and thus they are not the first choice that comes to mind, especially for more economical constructions.

• Concrete Bricks

Concrete bricks can either maintain their natural colour or be tinted with some other colour during the manufacturing process. They possess lower fire resistance than clay bricks. They absorb a lot of water, but they also release the water fast (a fact which can be proven, once again, by the water absorption test). Other than that, they have pretty much the same characteristics as normal concrete.

• Silica Bricks

Silica bricks have a smoother finish than concrete bricks. As their name implies, their main ingredient is sand. Like concrete bricks, the fire resistance of sand bricks is inferior to clay bricks. Sand bricks are great for a subtly textured effect on a structure.

2. Function

Bricks are manufactured according to their purpose, and as such can be classified according to their function. There are three types of bricks if you look at it from this angle, namely facing bricks, engineering bricks and common bricks.

• Facing Bricks

Facing bricks are meant to enhance the aesthetics of a structure. Hence, the surfaces of facing bricks are usually smooth or tastefully textured depending on the effect one wishes to achieve. As facing bricks are meant to be presentable, they are manufactured to fit as neatly as possible.

• Engineering Bricks

Engineering bricks are the bricks that do the brunt of the work in a structure. They are designed to carry heavy loads and to withstand more trying conditions than common bricks. As they are manufactured purely to do hard work, they do not carry the aesthetic value of facing bricks. 

• Common Bricks

As their name implies, common bricks are, well, common. They are relatively roughly hewn in comparison to both facing bricks and engineering bricks, and they lack the strength of engineering bricks. Their colour is also not regulated. It might seem as though common bricks are the worst of the three, and to an extent they are - but if used right, common bricks are the most economical option.

There are others too, such as categorisation by grade (quality), et cetera. But that topic is too wide and too varied to be discussed in a short post, so we shall leave it be.

Until next time, then!

Concrete Chronicles 2

The characteristics of set concrete and its further maintenance depend on:

• Its strength.

How can you know its strength? Simple! Just use this formula to calculate the maximum load resistance for one square unit of your concrete:

STRENGTH =   Pmax  N/mm2

                             A

Concrete is said to have achieved maximum strength upon 28 days of setting it.

• The compaction process.

Compaction is the process of removing entrapped air to form a homogenous dense mass. The compaction of concrete can be achieved in four ways:

Hand rodding

This is the crudest method to compact concrete. A steel rod is used to    compact the concrete to release trapped air at equal intervals. A predetermined number of strokes is used every time.

Mechanical vibration

Mechanical vibration compacts concrete equally and steadily, unlike hand rodding which is done manually. The picture on the left shows a mechanical vibrator.

Centrifugation (machine)

Centrifugation is usually used to produce concrete forms that are circular in cross-section, such as lamp posts.

Steps:

1) Concrete is fed into horizontal mould, which is spinning slowly.

2) Once adequate concrete has been fed, the speed is upped.

3) Water is forced out of the mix and flows out of the mould.

4) A small amount of dry cement is sprinkled to prevent upsetting the water:cement ratio.

5) Two round rods are held against each end-ring to finish the surface.

  - High pressure and shock

• The curing process.

The process of creating an environment favourable for the setting and hardening of concrete in a relatively short period of time is termed 'curing'. This takes place directly after the concrete has been placed and compacted.

The curing process controls the loss of water on the surface of the concrete.

• Its durability.

Its durability refers to the span of time concrete can withstand the ravages of time with minimum maintenance.

Stone Stories

(Hate walls of text? Then here's a way to cheat: watch these videos to get the gist of our topic today!)

Igneous rock:

Sedimentary rock, and how it evolves into metamorphic rock: 

The origin of this geological matter seems as though it is more of a contradiction rather than a fact of life.  People have long believed that stones - or rather rocks - are created from scratch but in actual geological context, the rock formation process is actually a cycle whereby the rocks are created, eroded and reformed once again.  The oldest rock was formed approximately 4.6 billion years ago.  Thus, one can only imagine how that rock was formed.

The diagram below shows the formation process of stones/rocks:

Different types of rocks reside in different strata, as illustrated below:

Volcanic activity plays a vital role in the formation of rocks.  As magma cools in the magma chambers, intrusive igneous rocks and minerals such as granite are formed.  Once the volcano erupts, the lava drools down causing it to eventually cool down.  This will create - or rather, form - extrusive igneous rocks.  In the long run, these rocks will be eroded by wind and rain. The eroded materials then find its way into the ground and waterways.  What next?  The sedimentary materials that rest at the bottom of oceans, lakes and rivers will accumulate.  Over a long period, the new layers will cover and compress the older layers. The older layers will become harder due to extreme pressure and in turn form sedimentary rocks.

Natural stone has been used in most constructional applications namely, green design. Energy price has increased and the need for energy conservation when heating or cooling buildings have recently brought it to the fore. Dimension rock is an example of a sustainable natural rock which is created by the separation of natural bedrock underlying all land on every continent.

Rock formation actually involves the formation of igneous rocks, sedimentary rocks and metamorphosis rocks.  Once the sedimentary rocks are formed, it metamorphoses into metamorphic rocks.  This depends on the temperature and pressure exerted on the layers of rock. These rocks actually undergo a process of stretching and compression.

The demand for beautifully cut, perfectly formed rocks and stones has birthed an industry for artificial stones, which are synthetically manufactured stones. These stones are gaining footage and popularity for the level of control afforded by synthetic production.  Artificial stones are made from crushed natural stones bonded together using Portland cement with a minimum water/cement ratio. Not all artificial stones become part of a structure; sometimes they can stand solo as a decorative piece in a home. Luxury home are particularly partial to these decorative stones. In short, artificial stones are manufactured for the ease of meeting the increasingly stringent demands of clients.

Blocks 101

Blocks are widely used in the construction industry. Blocks happen to be larger than bricks, enabling them to be laid more quickly as compared to bricks. This material provides convenience to the user as they fasten the construction process.

General process of laying blocks:

Clay Blocks

Clay blocks are versatile and efficient materials used in the construction industry. The ability of clay blocks to save energy combined with the build quality and speed overpowers other traditional blocks. The benefits are such that buildings with clay blocks have become the foremost method of construction in many European countries. Clay blocks are suitable for single- and multi-storey applications as they are used both commercially and domestically. Modern clay blocks are precision-engineered walling units designed to be thermally and acoustically efficient. During the manufacturing process, clay is prepared with sand, straw or recycled materials; extruded, dried and fired. The addition of these materials helps enhance their properties as they are burned off during firing leaving behind miniscule small holes and connecting pores. The air trapped within these pores help retain heat and reduce sound transmission.

Here's a video on an innovation on clay bricks; he is using vetiver grass, which is termite-proof, instead of straw:

And if you're up for some explosive action, come watch this:

Benefits of clay blocks

·         a pleasant room temperature all year round

·         ideal humidity levels

·         dry walls without any trapped vapour

·         healthy indoor air which can be circulated very easily

Ecological aspect

·         The façade built as a monolithic wall without any artificial insulation and thus it is free of harmful biocides. This is due to the fact that biocidal treatment of fungal and algae growth poses problems with artificial insulation systems.

·         Compound thermal insulation systems are more susceptible than a rendered monolithic wall and they have a limited lifespan (max. 30-40 years). After that the façade has to be disposed of as hazardous waste. This is not only absurd from an ecological aspect, but also very expensive. This insulation mania will cause considerable ecological problems in the future.

·         Clay can even be used as healing clay.

      

      The picture below depicts the construction of a boundary wall with blocks:

Concrete Blocks

Concrete blocks are dense yet lightweight blocks. Lightweight concrete blocks are mostly used for internal wall partitions. Their light weight contributes to several advantages. Among them are:      

•             Easy to handle

•             Quick to lay

•             The air inside the blocks provides better sound and thermal insulation

•             Lighter foundation and structural members

•             Can be cut and chased with hand tools

•             Holds nails and screws without plugs

Types of concrete blocks:

•             Hollow blocks

•             Cellular blocks

•             Solid blocks

Hollow block

Hollow Blocks 

Hollow blocks are made of cement, stone chips, stone dust and sand. Hollow blocks reduce the cost of construction and as such, it is widely used.  These are not only cheaper than bricks, but also rich with other features such as:

• High tensile strength
• Act as thermal insulators due to their hollowness

Features

• Natural thermal insulation
• Superior compression strength
• Light weight (up to 40% reduction in dead load).
•  Environmental friendly

Benefits

• Up to 60% reduction in cement mortar consumption
• 30% reduction in plastering cost
• Almost 500% improvement in labour productivity -> substantial reduction in labour cost
• Saves cement in masonry work & reduces cost of construction
• High value > high quality and low price

Are you wondering how the blocks are made hollow? Wonder no more once you watch this video: 

And here's a closer look at the machinery used to produce them:

Cellular block

Cellular Blocks

Each cellular concrete block offers the right balance of improved compression strength and lightness, traits which are essential for its perfection. They are engineered to facilitate easy chasing and groove-cutting for unhindered usage of electrical conduits and water pipes. Cellular blocks have cavities - or rather, holes - which do not punch right through them.

Cellular blocks are innovatively-designed pre-cast blocks with cavities which facilitate easy, neat and precise conduiting work for electrical wires, water and soil pipes for plumbing, telephone wires and television cables, ensuring concealed workmanship They also preserve the smooth surface of the wall.

Features

• Specially-designed blocks with cavities (with the option of 12, 8 and 4 cavities), for conduiting              superior compression strength.
• Lightweight (up to 40% reduction in dead load).
• Complies with ISI standards.
• Natural thermal insulation.
• With low setting time during monsoons, construction is easier than with conventional bricks.
• Environmental-friendly
• Available in various sizes/specifications suitable for load-bearing and non-load bearing applications.
• Load bearing blocks can bear a load of up to 200 kgs/cms, and supplied based on customer requirement.

Benefits

•  More economical than burnt bricks
• Reduces plastering costs and cement mortar consumption
• Improves labour productivity while reducing labour costs
• Saves cement in masonry work & reduces cost of construction
• High quality for relatively low price

This is a video on how such blocks are made the conventional way: by hand.

Solid blocks

Solid blocks are blocks that do not have slots or any formed holes. Solid concrete block units are of a consistent and superior quality to meet the requirements of all relevant standards.

Features

• Superior compression strength.
• Lightweight
• Environmental–friendly

      Benefits

           ·         Reduces cement mortar consumption by 60 %

           ·         Improves labour productivity by 500%, reducing labour costs

           ·         Saves cement in masonry work & reduces cost of construction

           ·         High value: high quality and low price

      Here's a short clip on how solid concrete blocks are made:

Hopefully, you are now more familiar with the types of concrete blocks available in the industry. Until next time, then!

Cemented Confusion

It is not unusual for those who are unfamiliar with the construction industry to confuse concrete with mortar and grout. Some might even mistakenly think that they are the same thing, albeit used for different purposes.

Well, that's wrong.

The difference lies in their ingredients. Let's see.

1. Concrete  is made up of:

       concrete                        water                        fine aggregate (sand)          coarse aggregate (gravel)


2. Mortar does not have coarse aggregates:

       concrete                        water                        fine aggregate (sand)          

3. Grout has neither fine nor coarse aggregates:

       concrete                        water 


So to sum it up...

	CEMENT	WATER	FINE AGGR.	COARSE AGGR.
CONCRETE	X	X	X	X
MORTAR	X	X	X
GROUT	X	X

Now you know that they are not the same!

Concrete Chronicles

Concrete is one of the most commonly used building material in the construction industry today, although it is a relatively new material. Concrete's make-up is a mixture of several ingredients - cement, sand (fine aggregate), coarse aggregate and water - in varying ratios depending on the desired aim: strength or economy.

Cement acts as the bonding agent. In fact, hardened concrete is formed because of a chemical reaction between water and cement in a concrete mixture. A wet construction site will thus be advantageous because then the setting concrete need not be covered with a wet cloth to preserve moisture.

Here are some illustrations on how concrete is used in floor construction:

Ground floor construction.

Upper floor construction.

Concrete can be moulded into practically any form, as it mimics the shape of its formwork; it can even be pumped and laid in various different, difficult positions.

Advantages:

• Durable
• Fire resistant
• High compressive strength
• Low maintenance
• Not affected by corrosion
• Not susceptible to insect attacks
• Easy to handle when batching and mixing
• Reasonable price (economical)
• Widely available 

Disadvantages:

• Low tensile strength, cracks easily
• Fresh concrete shrinks upon drying (water evaporates), while hardened concrete expands upon contact with moisture
• Concrete expands and contracts with changes in temperature
• Concrete will disintegrate under alkali and sulphate attacks
• Lack of ductility - unsuitable for earthquake-resistant designs

The quality of concrete depends on:

• The quality of its ingredients
• The batching and mixing ratios
• The grades of aggregate used
• The amount of water used
• The quality of the compaction process
• The curing process

There are several types of concrete available for use. Some of them are:

• In-situ Concrete

The concrete is mixed and tested on site. This is how it s made:

• Pre-cast Concrete

The concrete is readily mixed, and pre-cast panels are made at a factory off-site then shipped to the construction site. This has the advantage of quickening the construction process (as we do not need to wait for the concrete to set and cure) and also reducing the cost of formwork.

• Pre-tensioned Concrete

Sometimes we require the concrete structures to withstand more force than what normal concrete structures can afford. In that case, we can pre-stress or pre-tension the concrete to increase its resistance to stress.  Illustrated below is the method to create pre-tensioned concrete:

Step 1: Stretch the steel pre-stressing strands tightly across the casting bed. 

Step 2: Cast the concrete around the strands and left to cure, during which the concrete will bond to the strands.

Step 3: After the concrete has adequately cured, cut the strands. The concrete will go into both compression and tension simultaneously. This will increase its strength.