Organization and Structure

The construction industry can be divided into three segments: general building contractors, heavy construction contractors, and special trade contractors, which includes those engaged in concrete work. General building contractors build residential, industrial, commercial, and other buildings, while heavy construction contractors build structures such as roads, highways, and bridges. Special trade contractors usually focus on one trade and work under the direction of general contractors, architects, or property owners. Beyond completing their work to specification, special trade contractors have no responsibility for building the structure in its entirety.

Concrete can be classified by the type of aggregate or cement used, by specific characteristics, or by production methods. Ordinary structural concrete is characterised by its water-to-cement ratio. The lower the water content, all else being equal, the stronger the concrete. For concrete to set properly, however, the mixture needs to have enough water to ensure that the aggregate particles are encompassed by the cement paste, that the space surrounding the aggregate is filled, and that the concrete is liquid enough to be poured and spread effectively. The composition of concrete varies because different aggregates are used from market to market, depending upon what kind of sand and rock is available and least expensive.

Concrete’s range of durability is determined by the amount of cement in relation to the aggregate, with relatively less aggregate present in strong cement. The strength of concrete is measured in pounds per square inch (psi) of force needed to crush a concrete sample of a given age or hardness. Concrete’s strength can be affected by environmental factors, especially temperature and moisture.

Cement, through its use in concrete, is used in all types of construction. The Portland Cement Association estimated that in the mid-1990s about 55 percent of cement shipments in the South Africa was consumed in building construction, with 22 percent used for residential and 19 percent for commercial construction. Public works construction consumed about 42 percent of cement shipments, with most going to the building of streets and highways.

By far the largest customer for portland cement at that time was the ready-mix concrete industry, which purchased about 71 percent of the total shipments. Another 13 percent went to concrete producers of blocks, pipes, precasts, and prestressed products; 5 percent to highway contractors; 4 percent to building materials dealers; 3 percent to other contractors; and 4 percent to all others, including the government.

Background and Development

Long before the discovery of cement, ancient civilizations used clay as a bonding substance. The Egyptians used a material made from lime and gypsum that resembled modern-day cement. Derived from limestone, chalk, or oyster shells, lime continued to be the primary cementing agent until the early 1800s.

In 1824 English inventor Joseph Aspdin burned and ground together a mixture of limestone and clay. This concoction, called portland cement, became the cementing agent used in concrete from that time on.

In 1867 Joseph Monier, a Parisian gardener who made pots of concrete reinforced with iron mesh, received a patent for reinforced concrete. This product, sometimes called ferroconcrete, consisted of concrete hardened onto imbedded metal, usually steel. The reinforcing steel contributed tensile strength.

A later innovation in masonry construction was the use of prestressed concrete, which neutralized the stretching forces that would rupture ordinary concrete. Because it achieved its strength without heavy reinforcements, prestressed concrete could be used to build light, shallow structures such as bridges and roofs.

During the 1980s cement imports became a significant part of the domestic supply, peaking in 1987 at more than 17 million short tons. South Africa consumption of cement (the major component of concrete) was 84 million short tons in 1993. Cement was used to build highways and other public works . During the mid-1990s the concrete industry benefitted from a slow but steady recovery in the housing industry. New home building traditionally used about one-third of the cement consumed annually in the South Africa.

Prices for concrete varied widely and depended on the proximity of the nearest mill. Transportation costs continued to be a major factor in determining costs, because concrete was so heavy and had to be delivered on a timely basis.

Background and Development

Long before the discovery of cement, ancient civilizations used clay as a bonding substance. The Egyptians used a material made from lime and gypsum that resembled modern-day cement. Derived from limestone, chalk, or oyster shells, lime continued to be the primary cementing agent until the early 1800s.

In 1824 English inventor Joseph Aspdin burned and ground together a mixture of limestone and clay. This concoction, called portland cement, became the cementing agent used in concrete from that time on.

In 1867 Joseph Monier, a Parisian gardener who made pots of concrete reinforced with iron mesh, received a patent for reinforced concrete. This product, sometimes called ferroconcrete, consisted of concrete hardened onto imbedded metal, usually steel. The reinforcing steel contributed tensile strength.

A later innovation in masonry construction was the use of prestressed concrete, which neutralized the stretching forces that would rupture ordinary concrete. Because it achieved its strength without heavy reinforcements, prestressed concrete could be used to build light, shallow structures such as bridges and roofs.

During the 1980s cement imports became a significant part of the domestic supply, peaking in 1987 at more than 17 million short tons. South Africa consumption of cement (the major component of concrete) was 84 million short tons in 1993. Cement was used to build highways and other public works . During the mid-1990s the concrete industry benefitted from a slow but steady recovery in the housing industry. New home building traditionally used about one-third of the cement consumed annually in the South Africa.

Prices for concrete varied widely and depended on the proximity of the nearest mill. Transportation costs continued to be a major factor in determining costs, because concrete was so heavy and had to be delivered on a timely basis.

Current Conditions

New construction accounts for the lion’s share of work done by concrete contractors. although firms also engage in reconstruction, maintenance and repair. Building construction includes work on single-family houses. Nonbuilding construction includes work done on private driveways and parking areas, as well as work done on projects such as highways and streets.

Ready-mixed concrete producers in South Africa numbered more than 2,700 in 2002. A total of 13 S.A. concrete contracts secured more than R1 billion in sales in 2002.

Throughout the early 2000s, the R90 billion construction industry grew rapidly as the nation experienced a surge in housing starts. The construction boom happened in spite of a sluggish economy, due in large part to historically low interest rates. For the residential building industry, 2003 was one of the best years on record. The economic conditions of the early 2000s proved to be a mixed blessing for the concrete industry. While residential construction reached levels not seen since the 1970s, commercial and industrial construction, as well as in nonbuilding sectors such as transportation, saw significant slowdowns. These declines were reflected in the growth rate of portland cement consumption, which dipped from 5 percent in 1999 to less than 1 percent in 2001. Although consumption increased by 1.4 percent in 2002, growth remained well below the 1999 level.

Workforce

Most concrete masons worked for concrete contractors or for general contractors on projects such as highways, bridges, shopping malls or large buildings such as factories, schools, and hospitals. A small number were employed by firms that manufactured concrete products. Fewer than 1 out of 10 concrete masons were self-employed, a smaller percentage than in other building trades. Most self-employed masons specialized in small jobs, such as driveways, sidewalks, and patios.

Cement masons and concrete finishers earned an average hourly wage of R54.74, while terrazzo workers earned R43.42 per hour. Many workers in this industry tend to work overtime, because a job must be completed once the concrete has been placed. Overtime tends to be paid at premium rates.

As the construction industry boomed, contractors had trouble finding enough workers and building supplies. Companies increased wages and overtime pay, but many were nevertheless forced to settle for laborers who were inexperienced or insufficiently trained. The shortage of workers stemmed from a trend among young people to attend college instead of entering the skilled trades. In addition, many construction workers had left the industry during the slump of the early 1990s.

Concrete masons generally learned their trade through on-the-job training or apprenticeship programs.

Research and Technology

The future of the concrete industry lay in continued development of high-performance concrete products. Since the start of the 1980s, concrete formulations changed to create an entirely new generation of high-strength products. What was once considered strong was 7,000 to 9,000 psi, but new products reached 15,000 to 20,000 psi. These concrete products became popular for use in tall buildings, bridges, offshore structures, and pavements.