How builders can get the most out of mortar

How builders can get the most out of mortar

Simon Chudley from Tarmac Cement and Lime, outlines how builders can get the most out of mortar in the winter months.

It goes without saying that good organisation is key to the smooth-running of any project but, when the cold weather rolls in, outdoor construction projects can suddenly get a little more challenging for builders. Without careful pre-planning, the change in weather can affect product performance and productivity on site.

Beating the frost

The cold weather can affect a lot of things when it comes to outdoor construction but, for mortar, temperature can have a significant impact on its usability and strength. At temperatures below 3°C, for instance, cement will not hydrate sufficiently which can lead to frost damage, slow setting and poor strength. Additional care must be taken, therefore, when working with a mortar mix.

This can be managed, in the first instance, by simply avoiding either mixing or laying the mortar when the air temperature falls below 5°C. It’s also important that, once placed, the mix is kept above 5°C for 48 hours. Freezing temperatures can have a huge impact on the compressive strength and the bond strength – that’s aside from the detrimental affect it has on the water penetration resistance of masonry. If newly placed mortar does fall below freezing before it has chance to develop, it can lead to cracking, scaling and crumbling of the product.

While the best advice is always to hold off until temperatures are above 5°C before carrying out tasks involving mortar, this is, of course, easier said than done and the formation of cracks and spalls can still be annoyingly unpredictable. When time is of the essence, and frost threatens to hinder the project, an insulation quilt sandwiched between two sheets of polythene sheeting will provide the mortar with some protection.

Resisting the elements

It’s not just the cold that can affect mortar. Extreme wind conditions can lead to increased evaporation and cause the product to dry prematurely. It’s important to pre-plan here simply by putting up wind barriers and securing the area with plastic sheeting.

Another uncontrollable and troublesome factor to consider is rainfall. If the mortar mix has not had sufficient time to cure and is left uncovered, a heavy downpour of rain can easily wash some cement out of the mortar.

Without the necessary protection from wet weather, you can be left with a weakened surface which may lead to problems later down the line. This might include dusting of the surface, resulting in a porous surface that will allow far more water to be absorbed and, therefore, less resistance to freeze-thaw cycles. The most serious consequence, however, could be surface scaling – particularly in more torrential rain.

To ensure a strong bond, and overcome slow curing, it is crucial to protect new mortar from the elements with a water-resistant tarp or similar plastic sheeting. Any covering should be adequately secured to prevent it from being dislodged, as well as facing away from masonry facework to avoid sweating and consequent staining. It’s important to ensure that any pallets of bricks and blocks on site are also sufficiently covered to protect from the rain frost and snow. Any bricks that do get saturated should not be laid.

The product performance

As those in the trade know, in colder months the quality of the mortar mix itself is as important as the working conditions and opting for a high-quality manufacturer ensures that the product is air-entrained. Mixes, such as Blue Circle Quality Assured Mortar, contain billions of microscopic air pockets that relieve internal pressure on the mortar by providing small chambers for water to expand into when it freezes. This gives the concrete increased resistance to freeze-thaw attack.

The cold winter months can easily see cement spoil when left open outside, so choosing product with the right packaging is also important to consider. To keep cement dry and prevent any wastage, go for products that are available in weather-proof packaging and tubs. This is often overlooked but, nevertheless, can save time and money associated with replacing cement spoiled by exposure to the elements.

Tool maintenance

Tools, too, need extra attention in the winter months to prolong their life. Keeping your tools clean and well-oiled throughout colder periods can prevent the tedious job of chipping away at hardened mortar or dirt and removing rust in the spring. After all, good tools are quite an investment!

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