Don't let your concrete spoil
Concrete is the most popular artificial material on earth by weight or volume. It is made of stone and Portland cement, typically. Portland cement is a mixture of primarily sand and quicklime (calcium oxide). When water is added, the quicklime reacts with the water creating calcium hydroxide and heat. The calcium hydroxide molecules bind together to create a hard material.
If too much water is added to the mixture, there is excess water in the concrete with nothing to bind it and the result is weak concrete.
Pre-mix vendors make sure the water to quicklime ratio is correct
concrete slump test
To make sure the consistency of the concrete is proper, a slump test is performed. A slump test is done by filling a slump cone full of concrete in three stages. After each stage the concrete is tamped 25 times. Once the cone is filled the slump cone is removed. The concrete should slump a specified amount. If the cone collapses or shears it is not usable as a slump test. If the concrete is too wet is will slump too much. If the concrete has begun to set it will slump too little.
Concrete that has started to set will slump too little
ASTM C-94, Specification for Ready-Mixed Concrete state that pre-mix concrete should be poured within 1.5 hours of having been mixed. This makes certain the concrete is fresh and will set up properly. Once the concrete has spoiled by sitting too long it will not mold or finish properly. If you are having pre-mix concrete poured for your driveway, walkways, street, parking lot, foundation, or street make certain your contractors are following American Society of Concrete Contractors specifications.
Concrete older than 1.5 hours cannot be used
Ismaels Construction partners with the best pre-mix providers in the Seattle area to deliver and pour fresh concrete that sets well and lasts long. If you need a concrete contractor partner, call Ismael today.