Concrete and Steel: Properties and Types

Posted on Oct 14, 2024 in Technology

Consistency of Fresh Concrete

Many trials have been designed to estimate the workability of fresh concrete mixtures to be placed and compacted on site. This is called the consistency property of fresh concrete. Without a doubt, the most used test is the Abrams’ slump test (IRAM 1536).

Slump Test

The test uses a metal mold, cone-shaped with a 20 cm higher base, 10 cm lower base, and 30 cm in height, and a smooth round steel rod 16 mm in diameter and 60 cm long with a rounded tip. The procedure is as follows:

  1. Take a sample of fresh concrete.
  2. Separate fresh concrete in a bucket, slightly in excess of the amount necessary to fill the cone.
  3. Mix the sample with a trowel.
  4. Place the cone on a smooth, flat, non-absorbent surface.
  5. Hold the cone firmly against the floor during the test.
  6. Fill the cone with fresh concrete in three layers of equal thickness. Compact each layer with 25 strong blows of the rod, evenly distributed (Figure 1).
  7. During compaction of each layer, avoid penetrating the compacted layers above.
  8. Make up and smooth the concrete surface using the trowel.
  9. Remove the mold vertically, as soon as possible at a constant speed, i.e., without a strong pull up and avoid stopping before completion.
  10. Measure the settlement of the concrete based on the height of the mold.
  11. Record the value of the settlement to the nearest ½ cm.

Settlement and Compaction

Overall, we can say that the lower the measured value of the settlement, the greater the effort needed to compact the concrete. The CIRSOC 201 regulation establishes settlement and compaction guidelines.

Steel

Steel is an alloy of iron with small amounts of other elements, i.e., iron combined with about 1% carbon. When heated to ember and submerged in cold water (quenching), it acquires great hardness and elasticity.

Types of Steel

  • Alloy Steel and Special Steel: Elements not present in carbon steels are added.
  • Autotemplado Steel: Steel that acquires hardening by simple cooling in the air, without oil or water immersion.
  • Calm or Quiet Steel: Steel that has been completely deoxidized before straining through the addition of manganese, silicon, or aluminum.
  • Carbon Steel: Steel with low carbon content and additions of chromium, nickel, molybdenum, and vanadium.
  • Steel Bearings: Obtained from alloys of 1% carbon and 2% chromium, which undergoes a process of quenching and tempering. Used in ball bearing construction.
  • Mild Steel: General name for all non-alloy steels, obtained in the molten state.
  • Hard Steel: It is presented once tempered martensite 90%.
  • Effervescent Steel: Steel that has not been completely deoxidized before pouring it into molds.
  • Sintered Steel: Obtained from a mixture of powdered iron and graphite, or complete carburization of a mass of sintered iron.
  • Cast Steel or Tools: A special type of steel obtained by melting in a crucible.
  • Steel Indeformable: Steel that largely resists geometric distortion when hot (hot working materials) and during tempering heat treatment (parts that cannot be machined after hardening).
  • Magnetic Steel: Steel manufactured with permanent magnets.
  • Stainless Steel: Corrosion-resistant steel with a variety of compositions, but always contains a high percentage of chromium (8-25%). It is used when it is essential to prevent corrosion. Mainly used for surgical instruments and equipment subject to chemicals or seawater.
  • Nonmagnetic Steel: Type of steel that contains approximately 12% manganese and has no magnetic properties.
  • Cast Steel: Steel of any kind formed by filling a mold when the metal is still liquid.
  • Spring Steel: Steel with high elasticity and high resistance to breakage. Although current applications can use hard steel, when it comes to docks that have to support heavy loads and fatigue stresses, frequently used are silicon-toughened steels in water or oil and tempered.

Other Types of Steel:

Steel puddling, High-speed steel, heat-resistant steel, mild steel, special steels, forged steel, ordinary steel.

Classification of Steel

Steels are classified into five major groups: carbon steel, alloy steel, low alloy ultra-resistant steel, stainless steel, and tool steels.

  • Carbon Steels: 90% of steels are carbon steels. These steels contain varying amounts of carbon, less than 1.65% manganese, 0.6% silicon, and 0.6% copper. This type of steel is used to manufacture machines, car bodies, building structures, hair barrettes, among others.
  • Alloy Steels: These steels are composed of a certain proportion of vanadium, molybdenum, and other elements in addition to larger amounts of manganese, silicon, and copper than carbon steels. These steels are used to make gears, axes, knives, etc.
  • Low Alloy Ultra-Resistant Steel: This is the latest family of the five. These steels are cheaper than conventional steels because they contain fewer expensive alloy materials. However, they are given special treatment that makes their resistance much greater than that of carbon steel.