Killed A Lot Of Americans. (4)
Crosswords1 min ago
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For more on marking an answer as the "Best Answer", please visit our FAQ.The reason the old concrete has crumbled is almost certaily due to lack of cement in the mix. The minimum cement in poportion to sand and stone is 1 part cement, 2 parts gritty sand and 4 parts 1/2" limestone chippings. Cement is expensive but don't be tempted to cut down on the quantity. This is known as 6 to 1 mix.
The job is simple enough but quite hard work. You need to allow 3 to 4" of bedding under the blocks. Having dug out your trench lay in a good bed of semi dry concrete and lay in your blocks directly onto this, tapping them down to get them level. Don't get the concrete too wet. Then back up the blocks with a good wedge of concrete. This is to prevent them moving backwards if caught with the car tyres. Depending on how many blocks you need to replace, you could get a few bags of ready mixed material from B&Q. Do not use smooth building sand. Hope this is of help to you. Peter