Lecture 2: Course Introduction - Reinforced Concrete

**LECTURE 2: COURSE INTRODUCTION** **REINFORCED CONCRETE** is a material composed of Portland cement or any other hydraulic cement, fine aggregates, coarse aggregates, water, with or without admixture, and reinforcement, prestressed or non-prestressed and designed on the assumption that the two mat...

**LECTURE 2: COURSE INTRODUCTION** **REINFORCED CONCRETE** is a material composed of Portland cement or any other hydraulic cement, fine aggregates, coarse aggregates, water, with or without admixture, and reinforcement, prestressed or non-prestressed and designed on the assumption that the two materials act together in resisting forces. **Portland cement** is the most common type of *cement* in general use around the world as a basic ingredient of *concrete*, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th century by Joseph Aspdin, and usually originates from limestone. **Portland cement** is not a brand name, but the generic term for the type of **cement** used in virtually all concrete, just as stainless is a type of steel and sterling a type of silver. Therefore, there is no such thing as a **cement** sidewalk, or a **cement** mixer; the proper terms are concrete sidewalk and concrete mixer.  **Fine aggregates** are essentially any natural sand particles won from the land through the mining process. **Fine aggregates** consist of natural sand or any crushed stone particles that are ¼" or smaller. This product is often referred to as 1/4\'" minus as it refers to the size, or grading, of this particular **aggregate**. River sand is sand used in construction. A picture containing ground, outdoor, building material, brick Description automatically generated **Coarse aggregates** are any particles greater than 0.19 inch, but generally range between 3/8 and 1.5 inches in diameter. Gravels constitute the majority of **coarse aggregate** used in concrete with crushed stone making up most of the remainder. In construction the size of gravel ranges from ¾ inch to 1 inch in diameter and it is called as ¾ or G1.  A close-up of a faucet Description automatically generated with medium confidence **Admixtures** are natural or manufactured chemicals which are added to the concrete before or during mixing. **Admixtures** are classed according to function. There are five distinct **classes** of chemical **admixtures**: air-entraining, water-reducing, retarding, accelerating, and plasticizers (superplasticizers). Functions of admixtures to modify hardened concrete properties: a) To retard or reduce heat generation during early hardening. b) To accelerate the **rate** of strength development. c) To increase the strength of concrete or mortar (Compressive, tensile, or flexural).  **Prestressed concrete** is a form of **concrete** used in construction. This compression is produced by the tensioning of high-strength \"tendons\" located within or adjacent to the **concrete** and is done to improve the performance of the **concrete** in service. Prestressed concrete will be discussed to you thoroughly in the last chapter. A picture containing text Description automatically generated **MATERIAL PROPERTIES** **A) CONCRETE** 1\) Unit Weight of concrete = 23.60 kN/m^3^ page 2-13 NSCP 2015 2\) Tensile strength = poor 3\) Compressive strength = good fc' = compressive stress = 17, 21, 25, 28, 32, 35 MPa specified values of fc' fc = allowable compressive stress = 0.85 fc' for Strength Design Method (SDM) sect 422.2.2.4.1 p. 4-142 NSCP 2015 = 0.45 fc' for Alternate Design Method (ADM) sect 429.4.1 p. 4-194 NSCP 2015  4\) Modulus of Elasticity E~c~ = 4700 [\$\\sqrt{fc\'}\$]{.math.inline} for normal weight concrete section 419.2.2.1b p. 4-129 NSCP 2015 **B. REINFORCED STEEL BARS (rebars)** A picture containing stone Description automatically generated 1\) Rebar Designation ASTM STD. DES. PHIL. STD. DES. \# 3 10 mm ϕ \# 4 12 mm ϕ \# 5 16 mm ϕ \# 6 20 mm ϕ \# 8 25 mm ϕ \# 9 28 mm ϕ \# 10 32 mm ϕ \# 11 36 mm ϕ **NOTE:** a. ASTM is American Society of Testing and Materials b. ASTM Standard Designation is used in USA c. To find the diameter in inches for ASTM bars divide it by 8, e.g. for \#4 the diameter is 4/8 or ½ inch, d. \#7 or 22 mm ϕ bar is not available commercially in the Philippines but available commercially internationally 2\) Compressive Strength = good 3\) Tensile Strength = good fy = yield stress = 230 MPa - structural grade - white = 280 MPa and 345 MPa - intermediate grade - yellow = 420 MPa - high grade - green 4\) Modulus of Elasticity Es = 200 000 MPa sect 420.2.2.2 p. 4-132 NSCP 2015 1