freshconcrete

Fresh concrete, also known as plastic concrete, is concrete in the state immediately after mixing and before hardening. It is a workable slurry of cement, water, aggregates, and admixtures, designed for placement, compaction, and finishing. The mix proportions determine workability, pumpability, and resistance to segregation and bleeding. Temperature of the constituents and ambient conditions influence plastic properties and early strength development.

Workability is often described by slump. Higher slump indicates a more flowable mix but can risk segregation and excessive bleed; too low slump hampers placement. Admixtures such as plasticizers, superplasticizers, air-entraining agents, retarders, and accelerators modify rheology, setting time, and frost resistance. The grading of aggregates affects packing density, strength, and economy.

Handling and placement require timely transport, placement into forms, consolidation with vibration, and protection from rapid moisture loss and temperature changes. Early-age curing maintains moisture and appropriate temperatures to support hydration and strength gain. Curing duration depends on climate, mix, and structural requirements.

Quality control includes verifying batch accuracy, conducting slump tests, measuring in-situ temperature and air content, and monitoring for segregation or bleeding. Potential issues in the fresh state include plastic shrinkage cracking, laitance, and premature loss of workability due to overheating or water loss. Safety considerations focus on cement causticity, dust, and operation of heavy equipment.

Applications span cast-in-place and precast elements, where the fresh concrete properties must meet specific project specifications and curing regimes.