Concrete is an extremely strong and flexible building material used in projects from driveways and homes to skyscrapers. Concret is composed of cement, aggregates and water.
Cement is produced by heating raw materials in a kiln and then grinding them into powder, acting as an adhesive material to join together other construction materials.
Cement
Concrete house slabs Melbourne is one of the most versatile building materials, being utilized everywhere from driveways and sidewalks to homes and skyscrapers. Concrete consists of water mixed with coarse and fine aggregate stone (known as aggregate) as well as cement which forms a paste when mixed with water and holds together all other ingredients.
Ordinary Portland cement (OPC) production involves heating raw materials such as limestone and clay to 1,500degC in long rotating kilns before grinding into a fine powder. A small amount of gypsum is then added to control hydration rate and make the concrete workable for longer.
Once combined with the correct proportions of water and aggregates, concrete is poured into molds for curing in controlled environments of temperature and moisture. Once set, its final outcome is an incredibly strong building material capable of withstanding immense compression while resisting tensional stresses while remaining cost-effective and readily available worldwide.
Aggregates
Aggregates are hard, durable construction materials that comprise most of a concrete mix. Their properties include strength, thermal and elastic properties as well as dimensional stability and water resistance – with specific types chosen based on design requirements for individual projects.
Most aggregate is extracted from natural sand and gravel pits, hard-rock quarries or by dredging submerged sediments. Some can also be produced through crushing and screening recycled concrete for reuse; it may even be mined from underground deposits or recycled industrial byproducts like slag.
When selecting aggregates for concrete mixture, its size, weight and moisture content of each particle must be taken into account. Low quality aggregates can negatively impact the end product; for instance chert aggregates have limited resistance to weathering which causes surface defects known as popouts in concrete. Furthermore, friable or brittle aggregates often split under stress reducing strength significantly reducing strength in finished concrete products.
Water
Water is essential in creating concrete because it stimulates a chemical reaction between aggregate and cement that bonds it together, as well as helping lubricate its mix to make it manageable for production purposes. Therefore, producers of concrete should closely monitor how much water is being consumed by their production methods.
The amount of water necessary depends on your mix design and water-to-cement ratio (w/c ratio). According to American researcher Duff Abrams, concrete’s strength inversely proportional with its w/c ratio; lower ratios allow for greater compaction but may compromise strength of final product.
Many ready-mix producers rely on reclaimed or wash water to reduce freshwater use in their plants, but it often needs treatment before being discharged into the environment, which can be costly for producers and prevents their full utilization of this source of reclaimed water in all of their mixes. Therefore, concrete producers must closely monitor how process water moves through pumps, pipes, swales, curbs and berms to maintain a continuous supply.
Mixing
The mixing process involves the blending or mixing of solid and liquid constituents of concrete to form a workable product, an essential step in creating quality concrete products. It may involve on-site mixing by hand and shovel or factory production using trucks with rotating drums; no matter which process is used, proper mixing ensures quality for every project at hand.
Ready-mixed concrete comes in four main varieties, which include conventional, lightweight, precast and fiber-reinforced mixes. Most ready-mixed mixes are produced at local plants before being delivered by trucks with rotating drums directly to construction sites.
Homogeneity of concrete is an integral component of its strength. Measurements of macroscopic properties in various parts of a mixer and at different points during its discharge cycle can help determine this factor. Johansson conducted an analysis examining aggregate distribution vs mixing duration, finding that increasing mixing duration increased homogeneity up to a certain limit determined by maximum coarse aggregate size and type of mixer used (figure 5).