- story by MaterialDistrict
Please note that this Engineered Cement Composites are currently in an experimental phase, although very near to production. This new concrete looks like regular concrete, but is 500 times more resistant to cracking and 40 percent lighter in weight. Tiny fibers that comprise about 2 percent of the mixture’s volume partly account for its performance. Also, the materials in the concrete itself are designed for maximum flexibility. Because of its long life, the Engineered Cement Composites (ECC) are expected to cost less in the long run, as well. The ductile, or bendable, concrete is made mainly of the same ingredients in regular concrete minus the coarse aggregate. It looks exactly like regular concrete, but under excessive strain, the ECC concrete gives because the specially coated network of fibers veining the cement is allowed to slide within the cement, thus avoiding the inflexibility that causes brittleness and breakage.
Lightweight ECC Technology
Lightweight concrete with densities between 900 and 1600 Kg/m3 has been used in various structural and non-structural applications, offering considerable weight saving. By adding ductility, lightweight ECC can further broaden the applicability. Four approaches to achieving lightweightedness for a Polyvinyl Alcohol (PVA) fiber ECC are explored in this project, including uses of air-entrainment admixture, polymeric micro-hollow-bubble, natural lightweight aggregates perlite and glass micro-bubbles. Density, uniaxial tensile behavior, and compressive strength of 15 mix designs are examined. The experimental results show that multiple cracking and strain hardening can be achieved by all these approaches; however, tensile and compressive strengths and robustness of strain capacity significantly vary with content and type of lightweight “filler” used. Mixes by adding glass micro-bubbles with controlled size distribution exhibit more superior mechanical performances than other approaches. For example, tensile strength of 4 MPa with strain capacity above 4% is achieved in a lightweight PVA-ECC with 2% fiber volume fraction at a density of 1450 Kg/m3, along with a compressive strength of 41 MPa.