Factor Affecting Work Ability and Strenth of Concrete

FACTOR AFFECTING WORKABILITY AND STRENGTH OF CONCRETE GONZALES, MEL HARVEY A. COLLEGE OF ENGINEERING DLSU

WORKABILITY A general term to describe the properties of fresh concrete. • Consistency (or fluidity) --describes the ease of concrete flow • Cohesiveness --describes the ability to keep concrete uniformity (no concentration of a single component) • Homogeneity refers to stable distribution of cement, aggregate, and water and resistance to segregation

Workability -Factors Affecting Workability: Water Content • Extra water can lubricate the particles in mixture: the more the water, the easier the flowing. However, too much water will cause segregation • W/C increase • Fluidity increase

Workability -Factors Affecting Workability: Aggregate • • • •

Aggregate/cement ratio �Fine aggregate/Coarse aggregate �Maximum aggregate size �Aggregate shape and texture

Workability -Factors Affecting Workability: Cement • Fineness Fluidity decrease With fineness increase • �Cement Content: Lubrication effect of paste

Workability -Factors Affecting Workability: Admixtures • Air entraining agent • -Pozzolanic admixtures • Superplasticizers • --release water; retarding, air entraining effect

Workability -Factors Affecting Workability: Temperature

• Can influence the hydration rate and water loosing rate • Temperature increase • Workability decrease

SLUMP TEST

Measures workability

RHEOMETER

measures yield stress and plastic viscosity

FACTOR AFFECTING STRENGTH • CONCRETE POROSITY • WATER CEMENT RATIO • SOUNDNESS OF THE AGGREGATE • AGGREGATE – PASTE BOND

DUCTAL • is an innovative technology which covers a family of ultra-high performance concretes with exceptional characteristics in terms of mechanical resistance (compressive strengths up to 200 MPa, flexural tensile strength beyond 40 MPa), durability, abrasion resistance, and resistance against chemical and environmental attack (freeze and thaw, salt water, etc.). •      This new technology permits the development of innovative solutions which are competitive, offer faster construction, require less maintenance, and have a reduced impact on the environment.

DUCTAL • it is significantly stronger than normal concrete. Compressive strengths range between 20,000 to 30,000 psi (150 to 200 MPa) compared to 3,000 to 7,000 psi (20 to 50 MPa) for normal concrete and flexural strengths range between 3,000 to 7,000 psi compared to 500 to 1,000 psi (3 to 7 MPa) for normal concrete.

REFERENCES: • WORKABILITY AND QUALITY CONTROL OF CONCRETE BY : G. H. TATTERSALL • M. Lepech and V.C. Li, "Bridge Decks in Michigan Go Jointless" in Civil & Environmental Engineering Newsletter for Alumni and Friends, University of Michigan, Ann Arbor,