![\"\"](\"https:\/\/www.coralynne.co.za\/blog\/wp-content\/uploads\/2024\/06\/CONCRETE-CURING-PIC-01-scaled.jpg\")
<\/a><\/figure>\n<\/div>\n\n\nWith the country\u2019s generally temperate climate, it is easy to forget that many provinces and neighbouring Lesotho regularly experience sub-zero temperatures, points out Hannes Engelbrecht, Concrete Business Unit Director for Domestic and Sub Saharan Africa (SSA) at CHRYSO Southern Africa. Temperatures do not even need to reach freezing point; the concrete hydration process slows down steadily as temperature drops and actually stops when it goes below about 5 degrees Celsius.<\/p>\n\n\n\n
A significant amount of current concrete construction \u2013 especially for wind turbine bases and foundations for solar photovoltaic infrastructure \u2013 is, in fact, taking place in provinces like the Northern Cape and Eastern Cape where temperatures fluctuate widely. Efficient stripping time of formwork is crucial in allowing these projects to meet their stringent deadlines to complete construction and start delivering renewable energy.<\/p>\n\n\n
<\/a><\/figure>\n<\/div>\n\n\n\u201cLow temperatures create a range of problems for contractors and concrete product manufacturers,\u201d says Engelbrecht. \u201cMost projects in today\u2019s world need to be delivered on a fast track basis, so there is no room for slow concrete curing to hold up the schedule. Similar constraints apply in the manufacture of precast products, where production must simply keep up with customer orders and delivery deadlines.\u201d<\/p>\n\n\n\n
He highlights that precast product manufacturers can use a combination of super plasticisers and accelerators to speed up their stripping times and reduce the storage space needed for products to cure. Accelerators work during the first 18 hours of the concrete\u2019s curing time to ensure efficient hydration required to depalletize. Should temperatures be lower than freezing point, this makes the concrete strong enough to resist the expansion of water as it freezes \u2013 so that the concrete will not crack.<\/p>\n\n\n
<\/a><\/figure>\n<\/div>\n\n\nPatrick Flannigan, Technical Manager of the Concrete Business Unit at CHRYSO Southern Africa, explains that there are two categories of accelerator \u2013 chloride and non-chloride. While chloride-based accelerators are usually the first choice, they cannot be used if there is steel in the structure or where steel reinforcing is present due to the risk of rust, corrosion and degradation.<\/p>\n\n\n\n
\u201cIf there is steel reinforcing in the concrete, then a non-chloride accelerator must be selected,\u201d says Flannigan.<\/p>\n\n\n\n
Regarding the use of accelerators in readymix concrete that must travel varying distances to site, he points out the accelerator is best applied once the readymix has arrived on the customer\u2019s site. After it is added to the concrete in the mixing truck, it needs to be thoroughly mixed for 5 to 10 minutes before being poured. The admixture gives operators a good 30 to 40 minutes of workability before the accelerated hydration begins, depending on the type of concrete mix.<\/p>\n\n\n\n Another growing benefit of accelerators has emerged as a result of the global sustainability drive, he says, as cement producers, contractors and other customers aim to reduce their carbon footprint. This trend has seen the increased use of extenders such as fly ash and granulated slag in cement.<\/p>\n\n\n\n \u201cThe fly ash and slag only start working once there is an initial hydration of cement,\u201d he says. \u201cThis means that the early strength of a concrete mix will be delayed when there are extenders added.\u201d<\/p>\n\n\n\n The accelerating admixture overcomes this initial delay in the early setting, allowing users to achieve their sustainability goals without compromising on speed of the curing process.<\/p>\n","protected":false},"excerpt":{"rendered":" South Africa\u2019s colder months can bring headaches for contractors \u2013 as well as concrete product manufacturers \u2013 if low temperatures slow down the curing of their concrete and disrupt production programmes. CHRYSO explains how its accelerators can help keep workflow on track. <\/p>\n","protected":false},"author":2,"featured_media":8715,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[31],"tags":[74],"class_list":["post-8714","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-client-focus","tag-chryso-southern-africa"],"_links":{"self":[{"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/posts\/8714","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/comments?post=8714"}],"version-history":[{"count":0,"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/posts\/8714\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/media\/8715"}],"wp:attachment":[{"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/media?parent=8714"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/categories?post=8714"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.coralynne.co.za\/blog\/wp-json\/wp\/v2\/tags?post=8714"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/a><\/figure>\n\n\n\n<\/a><\/figure>\n<\/figure>\n\n\n\n