Masons and DIY homeowners generally have three choices to obtain the concrete needed to complete a job; hand mixing with bags of dry cement, ready mix delivery or metered delivery.
A simple 10x10 foot patio requires 73.9 bags of 60lb bags or if an 80lb bag, 55.4 bags are needed for hand mixing. For ready mix or metered concrete, a delivery of 1.23 yards is required. The ready-mix order should include an additional half yard or more (greater cost) to ensure there is enough concrete to complete the job. Skilled masons can accurately measure but a difference of an inch depth unaccounted for could mean a second order is needed to complete the job.
The metered truck will deliver the dry ingredients, add water, and pour exactly what is needed to complete the job. Hand mixing is best for far smaller jobs. For this and similar projects, ready mix concrete or metered concrete would be the preferred method.
Ready mix refers to concrete that has been mixed at a concrete batch plant and delivered to the jobsite via a concrete drum truck. Trucks often deliver more than one load per trip from the plant. To avoid premature hardening during the trip, the drum rotates to keep the concrete at the right consistency.
Once onsite, the concrete is remixed to ensure proper slump. Remixed concrete tends to set more rapidly. A variety of admixtures and water are often added at the jobsite to ensure the correct properties are attained before concrete is placed. Cement manufacturers suggest delivering concrete within 90 minutes of mixing. It is best to get to the site in less than an hour for optimal results.
Metered concrete is produced by a volumetric truck and has the advantage of being mixed, fresh onsite within 15 minutes of the truck arrival. The volumetric truck carries Portland cement, sand, gravel and water in separate bins and tanks. The driver enters the requested PSI and any admixture data into the control panel. The proportioned materials are brought into the auger hopper to begin mixing. The mixer auger blends and mixes into the final product and poured through the chute to precisely place the product.
Per Zimmerman Industries, a leading manufacturer of volumetric trucks, “A volumetric mixer can produce concrete meeting any standard or specification. In independent testing conducted by the Volumetric Mixer Manufacturers Bureau, concrete produced from a volumetric mixer gained a higher PSI than the same concrete delivered from a drum truck using the same materials.”
Drum trucks can produce high-quality concrete but concrete poured fresh from a volumetric truck will generally result in a higher quality product every time.