Monday 24 August 2015

Selecting the Right Aggregates for Concrete

All categories of concrete are prone to shrink. Shrinkage potential of a concrete mixture is perhaps one of the most crucial topics to consider while executing a construction project. Concrete shrinkage results in loss in volume, which in turn may facilitate cracking. The feature of concrete may also result in developing curling or warping issue. These problems diminish the load-carrying capacity of a structure and even lead to the problem of joint stability such as spalling. These unwanted factors usher in a potential health and safety issue. In order to overcome all these potential hazards, it is crucial to understand concrete shrinkage.

Cement Aggregate Concrete Testing

Concrete aggregates experience a change of volume because of factors like loss of moisture or decrease in temperature. Similar to most substances on earth, concrete has the tendency to expand and contract with change of temperature. If the surface of a concrete slab is cooler than the bottom, the concrete structure contracts resulting the slab edges to curl upward. Likewise, if the surface is allowed to dry and the bottom is kept moist, then the concrete slab warps upward.

However, to avoid this discrepancy, cement aggregate concrete test proves to be helpful. As such, the necessity of using the right type and quality of aggregates in construction projects is paramount. The fine and coarse aggregates usually occupy 60 to 75 per cent of the concrete volume. Moreover, these ingredients strongly influence the concrete’s hardened properties. Fine aggregates usually consist of naturally found sand or crushed stone.


Some natural aggregate deposits also consist of gravel and sand that can be readily used in concrete after conducting a minimal processing. This variety of aggregate deposits is known as pit-run gravel. Natural gravel and sand is scoured from river or seabed. Chips of stone are produced by crushing quarry rock, boulders, cobbles or even large-size gravels. There is no second opinion about maintaining certain standards for aggregates. Apart from being clean, these must be hard and strong and should not contain any absorbed chemical. Moreover, these particles should contain adequate amount of clay or other fine material to facilitate hydration and bond of the cement paste.

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