Structural Lightweight Concrete

Structural lightweight concrete is a concrete aggregate obtained replacing in whole or in part the ordinary aggregate with an artificial lightweight aggregate formed by expanded clay. The possibility of creating lighter structures such as beams, piles and floors, cast on site or prefabricated, is feasible by replacing the larger parts of the traditional “natural” aggregate (gravel or stones) with an “artificial” aggregate, made up of expanded clay aggregates or ECA or Lightweight Expanded Clay Aggregate (LECA).

Structural lightweight concrete made with rotary kiln produced Expanded Clay Aggregates solves weight and durability problems in buildings and exposed structures. Structural lightweight concrete has strengths comparable to normal weight concrete, yet is typically 25% to 35% lighter. Structural lightweight concrete offers design flexibility and substantial cost savings by providing less dead load, improved seismic structural response, longer spans, better fire ratings, thinner sections, decreased story height, smaller size structural members, less reinforcing steel, and lower foundations costs. Structural lightweight concrete precast elements have reduced trucking and placement costs. The excellent durability performance of structural lightweight concrete made with Expanded Clay Aggregate or expanded shale, clay or slate structural lightweight aggregate is a result of the ceramic nature of the aggregate, and its exceptional bond to and elastic compatibility with the cementitious matrix.

The closed structure of the aggregate is obtained by integrating the fine part of the material with traditional aggregate and natural sand. Furthermore, by changing the density of expanded clay and the replacement percentage of the ordinary aggregate, it is possible to obtain concrete with variable densities between the limits indicated, with strength levels starting from 15 N/mm2 up to 70 N/mm2.

This concrete can be made directly on site, mixed in concrete mixing plants or at the prefabrication plant. Pre-mixed concrete in bags are also available and are mostly used for smaller interventions, generally in restoration work.

Structural lightweight aggregate’s cellular structure provides internal curing through water entrainment which is especially beneficial for high-performance concrete, (HPC) Internal curing improves the contact zone which mitigates micro cracking.

Being among one of the lightest in the range (with a density of 1.400 ÷ 1.600 kg/m3) they are practical and safe for building reinforcement toppings in the restoration of floors and in all those applications that call for a structural casting without over-loading the existing structures.

Concrete using Expanded Clay Aggregate (EC) has better thermal properties, better fire ratings, reduced autogenous shrinkage, excellent freezing and thawing durability, improved contact zone between aggregate and cement matrix, less micro-cracking as a result of better elastic compatibility, more blast resistant, and has better shock and sound absorption, High-Performance lightweight aggregate concrete also has less cracking, improved skid resistance and is readily placed by the concrete pumping method.

Construction of Marine Structures

High performance lightweight concrete is substantially suitable construction materials to be used in the construction of marine structures. This is because offshore platforms are frequently constructed at shipyards and then floated and towed to the construction site and finally installed at specified location.

This construction process could be improved if the weights of marine structural elements are decreased. This reduction can be achieved by using high performance lightweight concrete.