Ice, snow and cold temperatures – any of these makes construction in the winter time challenging, especially for ready-mix concrete producers and users. Often, projects have to be delayed due to adverse weather conditions. With concrete admixtures from Master Builders Solutions® concrete producers can be flexible and adjust to the needs of winter concreting; the jobsites can keep production going.
Hardening of concrete is a chemical reaction of cement with water. As any chemical reaction, hardening slows down with lower temperatures and nearly stops when the temperature is 5°C and below. As a consequence, construction activity is greatly reduced during winter months. Generally, to produce and place concrete in these temperatures the concrete must first be heated at the concrete plant, then precautions need to take place at the job site such as the addition of accelerators, heating blankets and freeze protection. However, those measures are expensive and inconvenient. Accelerators and freeze protection agents bring about diminished workability control of fresh concrete and are limited in their usage in some markets and applications.
Accelerated hardening thanks to crystal seeds
The accelerating admixture Master X-Seed enhances early age strength development of concrete by increasing the intrinsic reactivity of the cement. Master X-Seed is able to do this through its unique chemistry, which consists of very small crystal seeds. During the hydration of concrete these seeds provide the crystallisation surface for the hardening cement past. This accelerates the hardening process, the heat development of the cement hydration kicks in earlier and ensures that the concrete core temperature and its hardening processes proceeds normally even at freezing temperatures outside.
Finally, the hardened concrete reaches the same mechanical properties as non-accelerated concrete under normal temperature conditions. This acceleration process takes place at all temperatures and provides ideal reactivity for cement, even at temperatures below freezing.
Master X-Seed has been used successfully to help concrete producers and contractors on key projects, for example for the winter construction of the Quality Hotel Friends and the Mall of Scandinavia in Stockholm, Sweden, and the rehabilitation of the “Fallender Bach” (Falling Creek) highway tunnel at Inn-Valley, Austria, which was under tremendous time pressure.
“A decisive advantage of using Master X-Seed is that – different to conventional accelerators – the rheology properties of the fresh concrete is not altered,” says Jan Kluegge, Head of European Marketing Ready Mix for BASF. “All required workability classes including SCC can safely be achieved; even under high dosages the concrete does not get harsh or heavy to trowel as with conventional accelerators.” Furthermore extended workability retention can be achieved leading to consistently high quality concrete installations.
Overall concrete works can be performed faster and with fewer efforts. The process of the construction project becomes largely independent of weather conditions and can safely and predictably be carried out under winter conditions.
Adapted from press release by Katherine Guenioui
Read the article online at: https://www.worldcement.com/product-news/12122014/basf-tackles-the-effects-of-winter-weather-on-ready-mix-concrete-6/