Editing Concrete (section)

===Sample analysis—workability===
{{Main|Concrete slump test}}
[[File:Cannon Renewal Project - October 2016 (30662609012).jpg|thumb|Concrete floor of a [[parking garage]] being placed]]
[[File:Concreteathruz.jpg|thumb|Pouring and smoothing out concrete at Palisades Park in Washington, DC]]

Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (pouring, pumping, spreading, tamping, vibration) and without reducing the concrete's quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of [[hydration reaction|hydration]]) and can be modified by adding chemical admixtures, like superplasticizer. Raising the water content or adding chemical admixtures increases concrete workability. Excessive water leads to increased bleeding or [[Segregation in concrete|segregation of aggregates]] (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. Changes in gradation can also affect workability of the concrete, although a wide range of gradation can be used for various applications.<ref>{{cite book |last1=Sarviel |first1=Ed |title=Construction Estimating Reference Data |date=1993 |publisher=Craftsman Book Company |isbn=978-0-934041-84-3 |url={{google books|plainurl=y|id=TopgKO4x_2kC}}|page=74 |language=en}}</ref><ref>{{cite journal |last1=Cook |first1=Marllon Daniel |last2=Ghaeezadah |first2=Ashkan |last3=Ley |first3=M. Tyler |title=Impacts of Coarse-Aggregate Gradation on the Workability of Slip-Formed Concrete |journal=Journal of Materials in Civil Engineering |date=1 February 2018 |volume=30 |issue=2 |doi=10.1061/(ASCE)MT.1943-5533.0002126 }}</ref> An undesirable gradation can mean using a large aggregate that is too large for the size of the formwork, or which has too few smaller aggregate grades to serve to fill the gaps between the larger grades, or using too little or too much sand for the same reason, or using too little water, or too much cement, or even using jagged crushed stone instead of smoother round aggregate such as pebbles. Any combination of these factors and others may result in a mix which is too harsh, i.e., which does not flow or spread out smoothly, is difficult to get into the formwork, and which is difficult to surface finish.<ref>{{cite web |url=https://www.concretenetwork.com/aggregate/ |title=Aggregate in Concrete – the Concrete Network |access-date=15 January 2017 |url-status=live |archive-url=https://web.archive.org/web/20170202232307/https://www.concretenetwork.com/aggregate/ |archive-date=2 February 2017  }}</ref>

Workability can be measured by the [[concrete slump test]], a simple measure of the plasticity of a fresh batch of concrete following the [[ASTM]] C 143 or EN 12350-2 test standards. Slump is normally measured by filling an "[[Duff Abrams|Abrams cone]]" with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive surface. It is then filled in three layers of equal volume, with each layer being tamped with a steel rod to consolidate the layer. When the cone is carefully lifted off, the enclosed material slumps a certain amount, owing to gravity. A relatively dry sample slumps very little, having a slump value of one or two inches (25 or 50&nbsp;mm) out of {{convert|1|ft|mm|spell=in}}. A relatively wet concrete sample may slump as much as eight inches. Workability can also be measured by the [[flow table test]].

Slump can be increased by addition of chemical admixtures such as plasticizer or [[superplasticizer]] without changing the [[water-cement ratio]].<ref>{{cite journal |last1=Ferrari |first1=L. |last2=Kaufmann |first2=J. |last3=Winnefeld |first3=F. |last4=Plank |first4=J. |title=Multi-method approach to study influence of superplasticizers on cement suspensions |journal=Cement and Concrete Research |date=October 2011 |volume=41 |issue=10 |pages=1058–1066 |doi=10.1016/j.cemconres.2011.06.010 }}</ref> Some other admixtures, especially air-entraining admixture, can increase the slump of a mix.

High-flow concrete, like [[self-consolidating concrete]], is tested by other flow-measuring methods. One of these methods includes placing the cone on the narrow end and observing how the mix flows through the cone while it is gradually lifted.

After mixing, concrete is a fluid and can be pumped to the location where needed.