Mortar being used on bricks

We answer the top questions house builders have surrounding mortar

Marshalls plc ammonite logo
Wednesday 17th April, 2019

Here we share our answers to the top 6 questions that many house builders are asking today.

1. What can affect the quality of a mortar mix?
Using unsuitable aggregates, adopting incorrect mixing procedures and adding too much water to the mix can all lead to inconsistent quality in mortar. Clearly these factors are a concern if you’re mixing mortar on site, but it’s also worth bearing in mind if you’re sourcing factory made mortar. The best way to ensure your mortar is consistently high quality is by using quality assured ready-made mortars that are produced to BS EN regulations and used using the official guidance like we do across all our sites.

2. How important is sand in a mortar mix?
Sand is crucial to a good ready to use mortar. Not all sands produce a good quality mortar. A reputable manufacturer will lab test many different sands to find the best locally available sands to go with the cement and Admixture that have been chosen. Marshalls also ensure all materials are tested to meet the British Standard requirements before there use in our RTU mortar.

3. What impact does an Admixture have on a mortar mix?
We use admixtures for two main reasons. The first is to ensure the mix has a stable air content. This is crucial for workability and long term freeze thaw performance of the mortar within the structure. Mortar without an air entrainer could stress under the ingress of water, which may freeze in the winter time, expand, and then cause cracks in not only the mortar but the surrounding brick too. The second admixture we use is a retarder that allows the product to be usable for a number of days. In the case of Marshall’s factory made mortars, we have two set product types. We have our standard 36 hour package for Monday to Friday use, then a 72hour use for weekends. It’s important to mention that whilst the chemical delays the hardening whilst it is in the plastic tub, once it is laid on a dry brick or block, the cement set begins as normal.

4. Why choose a factory produced mortar?
Whilst your construction workers may have years of experience in mixing mortars on site; human error in quantities and different views on how best to mix can lead to a low quality finish. Good mortar plants, like the one we run at Marshalls, use a computerised process control unit which stores all the approved and tested designs and stores all the approved and tested designs. This means that the quantity of each raw material is consistently accurate so that every mortar mix is the same high quality, every time.

5. How long can you use a ready to use mortar on site?
A factory made, ready to use mortar contains a chemical retarding agent which delays the cement set for a period of time. In the case of Marshalls factory made mortars, that is typically 2 days or more. It’s important to mention that whilst the chemical delays the hardening whilst it is in the plastic tub, once it is laid on a dry brick or block, the cement set begins as normal.

6. How is the quality of factory made mortar checked before it’s delivered to site?
At Marshalls we do a manual cone test on the mortar before it leaves the depot, and again when it arrives on site. This checks the workability of the mortar so we can give customers confidence in the product. But over and above that, a good quality mortar supplier needs to be doing regular spot checks of products in a lab. All our testing is done is line with BS EN 998-2 & BS EN 1015-18 and we ensure that testing is done regular across each production facility in the group. Compressive test results are then available for our customers on demand allowing visibility on performance.

Marshalls Mortars and Screeds is part a part of the Marshalls group that offer a range of ready to use mortars that conforms to the British Standard.

You can find out more about this in the Ready to Use Mortar section of our website.

If you have found this article useful, the video below contains more in depth detail so please view the video now:

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