8 CAUSES OF CRACKS IN CONCRETE YOU SHOULD KNOW

Cracking is one of the most common problems in concrete and it should be avoided seriously. Different causes of cracks in concrete are described below:

1. SHRINKAGE:

Shrinkage is one of the major causes of cracking in hardened concrete. In drying shrinkage, the volume of concrete is gradually decreased and if the component is restrained against free movement, tensile stresses are developed which causes cracks.

2. TEMPERATURE CHANGES:

The temperature variation in concrete results in the differential volume change. When the tensile strain capacity of concrete exceeds due to the differential volume change, it will crack.

3. CHEMICAL REACTION:

Due to the alkaline nature of cement, it reacts with the carbon dioxide (CO2) present in the atmosphere resulting in an appreciable increase in the volume of the materials which finally leads to cracking.

4. POOR CONSTRUCTION PRACTICES:

Poor construction practices such as adding excessive water to the mix, lack of curing, poor compaction, using low-grade materials, unreasonable placements of construction joints etc. are also responsible for cracking in concrete.

5. ERRORS IN DESIGN & DETAILING:

Errors in design and detailing such as an inadequate amount of reinforcement, improper design of foundation, precast members and slabs, improper selection of materials, lack of sufficient contraction joints etc may result in excessive cracking.

6. CONSTRUCTION OVERLOADS & EARLY FORMWORK REMOVAL:

The load induced in the structure during construction can also lead to cracking especially at the younger stage when the formwork is removed earlier.

7. ELASTIC DEFORMATION AND CREEP:

The different components of the building such as wall, column, beam. slab etc undergo elastic deformation when loaded. The deformation of concrete depends on the type of building materials used in the construction such as bricks, cement concrete blocks etc. This unusual deformation of concrete results in cracking.

8. CORROSION OF CONCRETE:

The corrosion of steel develops a huge amount of iron oxides and hydroxide that have a much greater volume than the volume of metallic iron. Hence the volume is increased and

WHY STEEL RODS ARE USED IN CONCRETE REINFORCEMENT?

The fact which makes it possible to combine steel and concrete is that concrete contracts on setting in the air and if a steel rod is embedded in a mass of wet concrete, it will be found that considerable force is necessary to pull out when the concrete is set. If the steel section is in the form of a plate, although it will resist removal when the concrete is set, yet it can be knocked off by sharp blows.

In the first case, the concrete grips the still, while in the second it only adheres. The grip depends upon the strength of concrete used in the work as well as the perfection with which the concrete has been mixed, placed in position, compacted and cured. Besides this, the grip also depends upon the condition of the surface of the rod (whether it is smooth or rough). Specially shaped bars (ribbed bars etc.) have therefore been introduced from time to time with the object of increasing the grip.

It is on account of the similar coefficient of expansion of the two materials, the superior bond value of high tensile strength and less cost of steel that’s why steel rods are used in reinforcement in R.C.C work

8 IMPORTANT TESTS ON BRICKS YOU SHOULD KNOW

Bricks are the most common and useful building materials used for masonry construction works. To build a long lasting structure we should always use good quality bricks and other building materials. In our previous article, we have already discussed the types of bricks used in construction. Today we will discuss some important brick tests to determine the quality of bricks. The common brick tests performed on the field as well as in the laboratory are described below.

1. COMPRESSIVE STRENGTH TEST:

This test is performed to determine the compressive strength of bricks. It is additionally known as crushing strength test of bricks. Normally, 5 samples of bricks are selected and transported to the laboratory for testing. A brick sample is kept on the crushing machine and then the pressure is thoroughly applied axially until it breaks. The maximum pressure at which the brick starts to crack is noted. The test is repeated with all 5 brick samples one by one and the average result is considered as the compressive strength or crushing strength of bricks.

2. WATER ABSORPTION TEST:

In this test, bricks are weighed first in dry condition (W1) and then they are fully submerged in water for 24 hours. After immersion of 24 hours, the bricks are collected and weighed again in wet condition (W2). The difference of weight between dry and wet condition is considered as the water absorbed by the bricks. Then the amount of water absorption is determined in percentage.

Water absorption (%) = [(W2-W1)/W1] * 100

The less water consumption by the bricks indicates their greater quality. A brick will be considered as good quality if it does not consume more than 20% water of its own weight.

3. EFFLORESCENCE TEST:

This test is carried out to obtain the presence of alkaline substances in bricks. First, bricks are fully submerged in fresh water for 24 hours. After 24 hours they are collected from water and left them to dry. After completely dried the bricks are closely observed to find the presence of alkali. If a white or gray layer is formed on the brick surface, it means alkali is present in the brick.

Observation Efflorescence

No Deposition Nil

10% of the brick surface. Slight (Ok)

10% – 25 % of the brick surface. Moderate

25% – 50% of the brick surface. Heavy

>50% of the brick surface. Extreme (Serious)

4. IMPACT TEST:

In this test few bricks are dropped from 1-meter height. If bricks are broken it indicates low impact value and not acceptable for construction work. Good quality bricks do not break at all.

5. DIMENSION TOLERANCE TEST:

20 bricks are randomly collected and arranged in a straight line. This is done to see the variation of shape, size, and color with the standard bricks.

6. SOUNDNESS TEST:

In this test, two randomly selected bricks are hardly punched with each other. If they produce a clear metallic sound and remain unbroken then they are good quality bricks.

7. HARDNESS TEST:

This test is done to know the hardness of bricks. In this test, scratches are made on the surface of the brick by a hard thing. If it does not leave any impression on the brick surface then it will be considered as good quality bricks.

8. STRUCTURE TEST:

In this test, a brick is fractured and firmly investigated. If any flaws, holes or cracks are seen inside the broken brick, then it is considered as poor quality brick.

Neufert Architects' Data, Third Edition 3rd Edition

Neufert Architects' Data, Third Edition 3rd Edition

Architects' Data provides an essential reference for the initial design and planning of a building project. Organized largely by building type, and with over 6000 diagrams, it provides a mass of data on spatial requirements and also covers planning criteria and considerations of function and siting.

22 Haganim st. Ramat Ha’sharon / Bar Orian Architects

 

 

From the architect. The thirteen-story building at 22 Haganim Street in Ramat Hasharon is situated on a large parcel of land (3500 sq. meters). “22 Haganim st. is a unique landmark in the development of an architectural language we have been exploring and developing for the past several years – building ‘Villas in the Air’.” This new language marks a breakthrough of the traditional typology of a building with a ground floor, topped by story after story of identical floors, and a penthouse. The Villas in the Air mark a departure from repetitive, typical floors, and replace them with a variety of types of floors on top of each other, creating large rooftop terraces along the entire height of the building.

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Foam concrete

also known as foamedconcrete, foamcrete, cellular lightweight concrete or reduced density concrete, is defined as a cement based slurry, with a minimum of 20% (per volume) foam entrained into the plastic mortar.As mostly no coarse aggregate is used for production of foam concrete the correct term would be called mortar instead of concrete.