Concrete Construction Book

CONTENTS

1. Concrete: The Man-Made Stone, 5
Types of Portland Cement, 7
Selecting Cement Materials, 9
Admixtures, 14
Coloring Concrete, 21
High-Strength Concrete, 23
Other Specialty Concretes, 24

2. Planning and Site Work, 27
Building Codes, 27
Zoning Laws, 29
Site Survey, 31
Soil Survey, 32
Setting Grades Stakes, 36
Staking Out a Building, 44
Electronic Automatic Levels, 47

3. Footing Forms, 51
Building Footing Forms, 51
Stepped and Tapered Footings, 54
Form-A-Drain Footing Forms, 57
Waterstops, 62

4. Prefabricated Forms, 65
Plywood Form Panels, 66
Time Saving Forming Products, 74
Steel-Ply Forms, 75
Assembling the Forms, 76
Steel-Ply Fillers, 80
Connectors, 83
Special Purpose Ties, 89
Stacking Forms, 92
Pilaster Forms, 98
Column Forms, 99
Curved Walls, 100
Culvert Forms, 104
Form Stripping, 104

5. Insulated Polystyrene Concrete Forms, 105
Constructing the Forms, 106
Placing the Concrete, 109
ARXX Forming Systems, 110
Covering the Forms, 111
The Outsulation System, 111

6. Reinforcing, 115
Counteracting Stress, 115
Corrosion in Rebar, 117
Estimating Reinforcing, 118
Other Concrete Reinforcement, 120

7. Planning for the Concrete Pour, 123
Check for Route and Site Delivery Problems, 124
Pre-Pour Inspections, 125
Concrete Delivery, 129
Checklist for Concrete Pouring, 130

8. Testing Concrete, 131
Slump Testing, 131
Compression Testing, 133

9. Pumping Concrete, 135
Pumped Concrete, 135
Shotcrete and Gunite, 137
Using Shotcrete, 140

10. Concrete Slabs, 143
Slab Foundations, 143
Forming Up a Slab Foundation, 146
Using Screed Joint Forms, 147
Pouring Concrete Slabs, 150
Small Concrete Pours, 151
Large Concrete Pours, 152
Finishing Lightweight Concrete, 154

15. Formwork for Steps, 197
Stair Layout, 197
Forming Up Steps, 202
Reinforcement for Concrete Steps, 210

16. Small Projects, 211
Planning, 211
Mixing Small Concrete Batches, 213

17. Estimating Concrete Quantities, 217
Footings and Walls, 217
Flatwork and Slabs, 218
Basic Geometry Formulas, 220
Estimating Aids, 228

18. OSHA, 233
Changes to the Standard, 234
General Requirements of the Standard, 235
Equipment and Tools, 236
Requirements for Cast-In-Place Concrete, 236
Precast Concrete, 239
Lift-Slab Operations, 239
Masonry Construction, 240
What Other Help Can OSHA Provide?, 240
OSHA Sections 1926.700 - 1926.705, 244

Glossary, 257

Conversion Tables, 275

Index, 279

1 CONCRETE: THE MAN-MADE STONE

Concrete is a remarkable material that can be cast into almost any shape. If properly reinforced, it supports tremendous loads and stresses. Quality concrete work produces long-lasting structures that are pleasing in appearance and require very little maintenance. It's one of the most versatile, economical and commonly-used construction materials.

Concrete is used in buildings, bridges, sewers, culverts, foundations, footings, piers, abutments, retaining walls and pavements. No matter what its final use, concrete's makeup is basically the same worldwide: a mix of portland cement, aggregates, and water. Its strength is determined by the amount of portland cement in the mix, the size of the aggregate used, and the amount of water added.

People sometimes call a concrete floor a cement floor, but the terms aren't really interchangeable. Cement alone is just dust. Add water and it becomes a paste. Add in the aggregates and it becomes concrete. The aggregates, usually sand and gravel or crushed rock, are the inert ingredients of the concrete mix. The portland cement and water are the active ingredients.

The first requirement for good concrete is high-quality cement. (We'll discuss the various types of cement later, along with how to handle them.) Next is a reliable supply of clean sand and coarse aggregate. Finally, you need clean water. Mix the cement and aggregates together. When water is added to the mix, it starts a chemical reaction with the portland cement called hydration. It's this chemical reaction that hardens the mixture into concrete. The process of hydration doesn't mean that the concrete is "drying out." On the contrary, you must keep concrete moist during the initial setting period. Concrete will even harden under water, which is one reason it's an ideal foundation material.

The principal factor in controlling the strength of concrete is the water-to-cement ratio — but consistency is also important. To build a uniform concrete structure, you need to create mixes with the same proportions of ingredients each time.

"Hardened concrete can be strong, watertight, and resistant to the elements — or weak and unreliable. Everything depends on the quality of workmanship."

The compressive strength of concrete, measured by the pounds per square inch (psi) of pressure that cured concrete can withstand, is very high. However, its tensile strength — the ability to resist stretching, bending, or twisting — is very low. That's why concrete must be reinforced with steel or some other product. Building codes throughout the country regulate the design of reinforcing in concrete structures. In earthquake zones or tornado-prone areas, they need additional engineered reinforcement. It's a wise contractor who works with the code office and checks out the correct reinforcement requirements before starting construction.

Freezing and thawing are concrete's worst enemies, especially when it's in the curing stage. We'll discuss preventative measures to use in freezing temperatures later. Concrete can withstand a tremendous amount of heat. Because of its resistance to fire, it's the material of choice in fire-hazard areas.

Concrete is fairly predictable. Knowledgeable contractors can usually control the setting time with additives or placing and curing methods. Any contractor using concrete has to understand its variables. After all, once water is added to cement, it will harden. You can speed up or slow down this process, but the bottom line is that the concrete will get hard. Hardened concrete can be strong, watertight, and resistant to the elements — or weak and unreliable. Everything depends on the quality of workmanship.

Storing Portland Cement
An important point to remember is that portland cement is moisture-sensitive. You must be careful how you store it. If kept dry, it will retain its quality indefinitely. But if stored in contact with damp air or moisture, portland cement will set more slowly and have less than optimum strength. Whenever possible, store bagged cement in a warehouse. Cover any cracks and openings in storehouses. If you have to store it outdoors, pick a shaded area, stack the bags on pallets and cover them with a waterproof covering.

Types of Portland Cement
The American Society of Testing Materials (ASTM) Designation C150 discusses types of cement and their characteristics. Portland cement is the most active component of concrete, and usually the most expensive. Type II is a hydraulic cement that forms a water-resistant product as it hardens. Selecting and using the proper cement is important in achieving the best mix at the most economical price. Fortunately, the widespread availability of limestone, shale, and other naturally-occurring materials used in its production helps keep portland cement affordable.

Different types of portland cement are manufactured to meet different physical and chemical requirements for specific purposes. Type I and II portland cements, which provide adequate levels of strength and durability for most applications, are the cements used most often for concrete. However, specialized applications may require other cements that provide higher levels of certain properties. Using high-early-strength cements for pavement repairs and blended cements with aggregates susceptible to alkali-aggregate reactions are examples of such applications.

Although IA, IIA, and IIIA (air-entrained cements) are available as options, concrete producers prefer to use an air-entraining admixture during concrete manufacture. This gives them better control over the desired air content. But air-entrained cements can be useful under conditions where there's no way to measure the air content of fresh concrete.

The availability of portland cements will be affected for years to come by energy and pollution requirements. In fact, increased attention to pollution abatement and energy conservation has already greatly influenced the cement industry, especially in the production of low-alkali cements. Using high-alkali raw materials in the manufacture of low-alkali cement requires bypass systems to avoid concentrating alkali in the clinkers, which consumes more energy. If the type of cement you need isn't available, you can get comparable results by modifying available types. High-early-strength concrete, for example, can be made by using a higher content of portland cement or by using admixtures such as chemical accelerators or high-range water reducers (HRWR).

Blended Portland Cements
Blended cement, as defined in ASTM C595. is a mixture of portland cement and blast furnace slag (BFS) or a mixture of portland cement and a pozzolan (most commonly fly ash). Blast furnace slag mixtures are classified as IS, I(SM) and S.

There are several benefits to using blended cements in concrete.
These include:

• reduced amount of mixing water needed


• reduced bleeding


• improved workability and finishability


• enhanced sulfate resistance


• inhibited alkali-aggregation reaction


• reduced heat generated during hydration, which reduces the chance of thermal cracking on cooling

Concrete mix plants can provide specialty concrete mixes to s
your specifications by adding admixtures at the plant.

Modified Portland Cement (Expansive Cement)
Expansive cement increases in volume significantly more than plain portland cement during the early hydrating period. Concrete placed in an environment where it loses moisture will begin to shrink. The amount of shrinkage depends on the characteristics of the materials, mixture proportions, and the placing methods. When subgrade friction, reinforcement, or other parts of the structure restrain concrete slabs, drying shrinkage will induce tensile stresses. These stresses usually exceed the concrete's tensile strengths, causing cracking. Using expansive cements can compensate for the drying shrinkage stresses. This minimize cracking in concrete slabs, pavements and structures. That's why expansive cement is also called shrinkage-compensating concrete.

There are three types of expansive cements defined in ASTM C845, although only Type K is used in any significant amount in the United States:

Type K: Contains anhydrous calcium aluminate
Type M: Contains calcium aluminate and calcium sulfate
Type F: Contains tricalcium aluminate and calcium sulfate

White Portland Cement
White portland cement is a true portland cement. The only significant difference is its color. White portland cement is made to conform to the specifications of ASTM C150, although no specification provides for white portland cement specifically. The controlled manufacturing process yields a finished product that's white because it contains little or no iron and manganese oxide, the substances that give cement its gray color. Use it wherever you need white or colored concrete or mortar.

White portland cement is used primarily for architectural purposes, such as:

• precast curtain walls and facing panels


• terrazzo surfaces


• stucco


• finish coat plaster


• cement paint


• grout


• decorative concrete

Selecting Cement Materials
To select the best cementitious materials for a concrete structure, you'll have to consider the exposure conditions, type of structure, the characteristics of the aggregates, availability of the material, and the method of construction.

The type of structure must be classified as either mass or structural:

• Mass concrete is any extremely large volume of concrete, such as in a dam, where special measures have to be taken to minimize cracking from the heat generated by hydration and the attendant volume change.
• Structural concrete is concrete that will normally be placed into reinforced structural elements such as beams, columns, walls, and slabs small enough that heat generation isn't a problem.

Of course, all concrete is considered structural, since it's at the core of most construction projects. However, many features of a structure fall into the two extremes — either strictly massive or flexural. The designer needs to determine if measures should be taken to limit the heat generation. Flexural concrete has reinforcing metal or fiber-reinforced polymers (FRP) embedded in the concrete, and is designed by engineers to resist bending forces.

One of the most important factors in the quality and economy of concrete is the quality and quantity of the aggregates.

You need to use quality aggregates to get good concrete. It's cheaper to use good aggregates when you build than to go back and repair a finished project later. Most concrete ready-mix companies buy government-approved aggregates. The aggregates have to pass tests for specific gravity, absorption rates, and organic impurities.

Absorption (ASTM C127; ASTM C128)
Determining the absorption rate of the aggregate helps the labor and field workers know how much mixing water to use with that gate when making concrete. The aggregate's absorption capability is also a gauge of the durability of the concrete when subjected to critical saturation during freezing and thawing. Modern concrete batch plants use computer-controlled tests of their aggregates when loadings readymix trucks. The aggregate has to measure up to the demands of the pour where the batch will be placed.

If you need aggregates for concrete with strengths of 6,000 greater, be sure and choose your aggregates wisely. Run tests of concrete strength specimens made from concrete using the aggregates being evaluated, with the required slump and air content. Use various cement factors and water content, and include any required chemical admixtures. If the needed strength can't be reached with a reasonable slump, air content, cement factor, and chemical admixture(s), the aggregate isn't acceptable for high-strength concrete.

In general, it's best to use the largest aggregate compatible with the structure being built. On projects that don't involve large quantities of concrete, make a careful study of the economy of using large aggregates. Using large aggregates reduces the cement content, but increases the labor cost involved in the handling of aggregates. Most concrete suppliers will help you determine the correct aggregate size for your needs. But keep in mind that they may charge a considerable amount more for a mixture using larger aggregates, depending on the availability of those aggregates.

(We're going to stop here. The remaining portion of Chapter 1 goes on to talk about mixing water, water-to-cement ratio, admixtures, pozzolans, corrosion inhibitors, air entrainment, coloring concrete and more.)

Concrete Construction

This comprehensive concrete manual has the information you need, both the tried-and-tested methods and materials, and more recent innovations. It covers styrofoam forming systems, fiber reinforcing adjuncts, and some architectural innovations, like architectural foam elements, that can help you offer more in the jobs you bid on.

Forming, one of the most important elements of concrete work, gets special attention. Innovative forming systems offer significant benefits, but many contractors steer clear because they're unfamiliar. This book gives you the know-how, so you can take advantage of everything that's out there.

Every chapter provides detailed, step-by-step instructions for each task, with hundreds of photographs and drawings that show exactly how the work is done.

• How to select the right concrete material for the job


• Laying out foundations and footings


• Footing forms, including Form-A-Drain and stepped footings


• Prefabricated building forms — plywood, corrugated-paper, and Steel-Ply forming systems
• Insulated polystyrene concrete forms (ICFs), including ARXX and Outsulation systems


• Planning the pour and pre-pour inspections I Concrete reinforcement


• Pouring, testing, installing joints, finishing and curing the concrete


• Hot and cold weather pours


• Constructing and pouring foundation walls, slabs, sidewalks, driveways, curbs and steps
• Shotcrete and gunite


• Special concrete finishes and textures


• Estimating concrete quantities for large and small projects


• OSHA requirements for working with concrete

To keep your jobs organized, there are checklists for each stage of the concrete work, from planning, to finishing and protecting your pours.

Whether you're doing residential or commercial work, this manual has the instructions, illustrations, charts, estimating data, rules of thumb and examples every savvy contractor can use on their concrete jobs.

The Author
Ken Nolan completed his apprenticeship with Local 57 of the Bricklayers & Allied Craftsmen, then worked in heavy construction and highway projects until starting his own contracting company. Holding a degree in vocational education, he taught construction at occupational centers in New York, and wrote the curriculum for the trade and technical education programs for the New York State Department of Education. He has written four highly-successful construction manuals, and holds patents
for several construction tools he developed on the jobsite.