Current Research Topics

A substantial amount of research is being carried at the NSF Center for Science and Technology of Advanced Cement-Based Materials at Northwestern University [32]. A survey of the literature is kept by The American Ceramic Society [33, 34]. Four gen­eral critical areas, necessary to maintain technological leadership, have been identified by the US industry [35]: (1) design and structural systems, (2) constituent materials, (3) concrete production, delivery, and placement, and (4) repair and rehabilitation (Table 3). Topics of current scientific research include characterization of microstruc­tural features (e. g., C-S-H gel, pore shape, heterogeneity), mechanical properties (model prediction, measurement, performance improvement), chemical behavior (e. g., in corrosive environments, hydration process, CaCO3 efflorescence), characteris­tics of concrete at elevated temperatures. Other specific areas include test methods to determine properties (i. e., fatigue, creep, and chemical properties) of FRP, which are reproducible and reliable. Repair of structures is a relevant area that has several world­wide organizations involved. In addition to the American Concrete Institute (ACI), groups providing information include the International Concrete Repair Institute, Concrete Repair Association (U. K.), Building Research Establishment (U. K.), American Concrete Pavement Association, American Association of State Highway Transportation Officials, The Concrete Society (U. K.), The Cathodic Protection Association (U. K.), and US Army Corps of Engineers.

Table 4 summarizes recent developments regarding cement and concrete materials. Improved materials and advanced sensors are needed for very demanding applications

Table 3 Main research needs in the concrete industry [adapted from 35]

Design and Structural Systems

Structural concrete

System survivability

Reinforced concrete Modeling and measurement High-performance concrete Technology Transfer

Design methodologies for reinforcement and fibrous concrete Interaction prediction, monitoring Improved technologies and advanced testing methods Accelerating technology transfer from 15 to 12 years Appraisal services by standard and code bodies

Fire-, blast-, and

earthquake-resistant materials and systems Crosscutting innovations Constituent materials New materials

Smart systems for design of fire-, blast-, and heat-resistant alternative reinforced structures Survivability reserach Concrete as part of multimaterials systems

Noncorroding steel reinforcement Concrete with predictable performance Materials with reduced shrinkage and cracking Reduction of alkali-silica reactions in concrete

Measurement and prediction

Prediction methods and models for permeability, cracking, durability, and performance Quantifying benefits of using alternative materials

Recycling

Reuse of high-alkali wastewater

Aggregate recycling

Reuse of cementitious materials

Concrete production,

delivery, and placement Information and control

Intelligent, integrated knowledge systems Improved control over nonspecified concrete On-line batching control

Production

Test methods and sensors

Increased applications for robotics and automation Improved sensing technologies and portability Technologies to insure performance requirements Nondestructive test methods

Energy and environment

Reuse and recycling issues Reduction of transportation energy use Increased use of waste from crosscutting technologies Life-cycle model for CO2 impact

Repair and rehabilitation New repair methods

New repair materials and applications technologies Self-repairing concrete

Assessment tools and modeling

Nondestructive testing for stress Long-term monitoring of structures

Repair field

Mitigation of alkali-silica reactivity Corrosion-canceling technologies

Low-maintenance, long-life repair of concrete for corrosion protection of embedded steel

such as concrete in offshore oil platforms [36] and in the nuclear industry where con­crete structures have performed well [37]. However, as these structures age, degradation due to environmental effects threaten their durability. Items of note are corrosion of steel reinforcement following carbonation of the concrete or ingress of chloride ions, exces­sive loss of posttensioning force, leaching of concrete, and leakage of posttensioning system corrosion inhibitor through cracks in the concrete.

Table 4 Recent US patents on cement-related materials development Assignee Number Short title

Подпись: MBT Schweiz 6,489,032 Aso Cement 6,464,776 Sumitomo Osaka 6,419,741 Sika AG 6,387,176 Daicel-Huels 6,376,580 Taiheiyo Cement 6,358,311 RoadTechs Europe 6,315,492 Polymer Group 6,258,159 Takemoto Yushi 6,176,921 Daicel-Huels 6,114,033 U. of Michigan 6,060,163 Arco Chemical 6,034,208 FMC Corporation 6,022,408 Toho Corporation 5,997,631 W. R. Grace & Co 5,938,835 DPD, Inc. 5,935,317 Lafarge Canada 5,928,420 W. R. Grace & Co 5,840,114 College of Judea 5,772,751 Elkem ASA 5,769,939 MBT Holding 5,728,209 Dipsol Chemicals 5,653,796 Union Oil of California 5,599,857 Dow Chemical 5,576,378 C F P I 5,567,236 Louisiana State US 5,565,028 ENCI Nederland 5,482,549 Takenaka Corporation 5,466,289 Cement structure containing a waterproofing layer Dusting-inhibited cement with improved strength Cement clinker and cement containing the same Polymers for high-flow and high-strength concrete Cement retarder and cement retardative sheet Additives for cement materials and cement materials Road repair material comprising cement and resin Synthetic polymer fibers into cement mixtures Cement dispersants

Cement retarder and cement retardative sheet

Fiber reinforcement of cement composites

Copolymers as cement additives

Compositions for controlling alkali-silica reaction

Hardener for waste-containing cement articles

Cement composition inhibit drying shrinkage

Accelerated curing of cement-based materials

Alkali-reactive aggregate and sulphate resistance

Early-strength-enhancing admixture for precast cement

Light-weight insulating concrete

Cement-based injection grout

Unitized cement admixture

(Phosphorous acid) Admixture for cement

(Waterless) Polymer concrete composition

High Tg polymer for portland cement mortar

Improved rheology of cement-products

Alkali-activated class C fly ash cement

Cement and products using such cement

Ultra high-strength hydraulic cement compositions