From the time it was discovered to be first used almost 6,500 years ago [1] by stone traders in Jordan and Syria, to the modern era, concrete has pervaded our lives, becoming one of mankind’s better inventions. We have use for it in buildings, structures, roads, airports and what have you. So incredibly strong are its characteristics, that it is often used in the English language to portray traits of strength, resolve and solidity in living creatures.

Yet for all its fame and wide utility, there still exists confusion in most people’s minds as to what it is. It is often confused with cement. Cement is not concrete. Cement is a binding and cohesive agent comprising clay, limestone and calcium. As a standalone, cement has no strength and can be easily broken. However, when blended with ‘aggregates’ like water, rocks, sand/silica it solidifies into concrete.  

How your concrete is made

Your concrete is made by a process of using a layer of rocks and sand/silica and covering it with a ‘paste’ of cement mixed with water in the right proportion. Most applications create concrete by mixing cement with water and sand, which constitutes the additive. When applied over a layer of rocks or used with the additive in the mixture stage, a chemical reaction called ‘hydration’ starts, wherein the paste binds with the additives and starts to solidify, forming concrete.

A fine mix of cement and water is then used to give the wet layer a smooth finish.

In short, the following steps need be followed when creating concrete :

• Mixing of the materials in their right proportions and at the right temperature
• Evaluation of the mixture to be worked with and corrective measures to remediate inconsistencies in the mixture
• If being mixed on-site, or if being transported for utilization at another place, due regard to be paid to the period of mixing and the revolutions per minute
• Transportation of the mix in a viable manner. Special vehicles with mixing tanks to ensure continuous revolutions is always recommended  
• Pouring in pre-fabricated / laid out formwork for casting, with due care for pouring/dropping of the mix from the specified height
• Vibrating for proper compaction, and testing thereafter
• Finishing the concrete as desired
• Covering of the concrete immediately on hardening with hessian
• Removal of formwork after concrete is set
• Curing of the hardened concrete for a suitable period with water. The recommended period is 4 weeks for complete curing

It is to be noted that cement for all its versatility as a binding agent, is sometimes less preferred to other binding agents like lime for lime concrete in buildings and bitumen for asphalt concrete found in roads [2].

In its wet stage, your concrete mixture can be used in any shape or form, by pouring the wet mix into or onto the form or surface. Concrete is used in columns, pillars, foundations, slabs and just about any structure needing its solid properties.

The strength of Concrete

The strength [2] of Concrete varies and depends on the mixture of cement, sand and aggregates. Commonly called ‘the grade of concrete’, its strength is denoted by ‘M’ which stands for Mix followed by a number which denotes its strength. The mix comprises the ratio of cement to sand to other aggregates. Accordingly, we have M5, M10, M15, M20 and so on, with a higher number denoting a higher concrete grade strength.

The strength required is determined by the nature of the load-bearing and the strength that the concrete is required to sustain. M15 and M20 are commonly used for plain cement concrete works and reinforced concrete works respectively.

The types of Concrete

The embellishments of the concrete in question or the requirement are reflected in the concrete finish. Accordingly, there is :

• Plain / Smooth-finished concrete
• Reinforced concrete or Reinforced Cement Concrete (RCC) is concrete fortified with steel bars and additives with higher tensile strengths than concrete to compensate for the low tensile strength in the concrete 
• Aggregate concrete – which comprises a number of additives set in cement, which are then exposed by stripping off the final layer of wet cement paste
• Stamped concrete – where artistic impressions are set in the wet concrete, so the finished concrete has a design look
• Stained or Acid-stained concrete – where a mixture of water, hydrochloric acid, acid stain color and acidic metal salts are added to old or new concrete floors, patio or other areas with the intention of creating a colorful design or pattern

Caring for your Concrete

Rock-solid as it seems, concrete also needs attention due to some of its properties. The following steps [3] are recommended considering its innate properties, the weather it can be exposed to, the loads it is required to take, wear and tear, ingress of water, staining possibilities and other issues arising from its installation location.

• Sealing joints and cracks that arise in concrete is at the forefront of concrete care measures. Despite its solid state, concrete absorbs water and ingress of water will ruin concrete. Silicon sealant is strongly recommended
• Keeping it clean with a power pressure washing solution will remove low lying dirt, dust and stains and transform your concrete into a fresh-looking installation. Scrubbing of accumulated slush or stagnating water is recommended 
• Removal of weeds and grass sprouting through cracks is also something that must be done periodically and followed up by cleaning and sealing of the crack
• Avoiding de-icing chemicals, though helpful for snow falls, ultimately proves detrimental for concrete due to the repeated thaw and freeze cycles that cause water overlays on the cement and frequently-changing temperatures
• Loading weights beyond the load-bearing capacity of the concrete or subjecting it to loads it was not intended for, can lead to cracking and fracturing of the concrete necessitating considerable remedial measures
• Epoxy coating finishes are known to confer long lasting benefits on concrete as it offers all-weather and all-wear protection to the surface along with aesthetic looks

Conclusion

Like all construction materials, your concrete needs care at regular intervals, if your investment is going to look attractive, last long and pay back. Well-maintained concrete stands out and proves the perfect foil for a well-laid out property or construction.

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[1] Concrete questions : The Invention of Concrete: A Complete History (concretequestions.com)

[2] The Constructor.org : https://theconstructor.org/concrete/ 

[3] Concrete Network : https://www.concretenetwork.com/concrete/maintaining/