Technical Committee 225-SAP
Deputy Chair: Prof. Dr.-Ing. Hans W. REINHARDT
Activity ending in: 2014
Super Absorbent Polymers (SAP) are a new component for the production of building materials. They have a considerable potential with regard to application in construction.
The state-of-the-art report of the RILEM TC 'Internal Curing of Concrete' gave an account of the positive effects of the use of SAP in High-Strength Concrete (HSC) as an efficient internal curing agent. Through the use of SAP, self-dessication and correspondingly autogenous shrinkage of HSC could be reduced or even avoided, by providing internal water reservoirs. Because of their very high water absorption capacity, the polymers have a theoretically higher effectiveness than other materials (e.g. lightweight aggregates). The work of TC ICC triggered and intensified the research on SAP. A number of researchers investigated the effects of adding SAP to concrete on its rheological behaviour and shrinkage as well as on the strength development. The findings of these investigations are partly controversial, which can to some extent be ascribed to the sensitivity of the results on the type of SAP, the amount of additional mix water and other variations in the examined concrete compositions. SAP particles are known to significantly expand as a result of their water absorption. This influences the workability of the fresh concrete. The creation of bigger pores on one hand and the continuing hydration of cement due to additional water supply on the other hand, are expected to influence the overall mechanical behaviour of concrete and its durability. A careful laboratory analysis of these phenomena should be performed, before recommending SAP-based industrial applications on a large scale.
Besides the utilization as an internal curing agent, some other prospective applications of SAP in concrete appear promising (e.g. regulating the viscosity of the mixture during spraying process, increasing of frost resistance etc.). Furthermore, there are research activities on the use of SAP as water regulating agent in other building materials with inorganic hydraulic and non-hydraulic binders. However, very little is known on the results of this work.
Terms of reference
Researchers in different countries around the world are presently investigating possibilities and limits of using SAP for solving various problems encountered by practitioners in the field.
The main objectives of the committee are (1) to coordinate research efforts and compile the results of studies into mechanisms of internal curing using SAP and effects of SAP addition on HSC properties in the fresh and hardened state, (2) to collect and analyze information on applications of SAP for other purposes in concrete und other building materials on the basis of inorganic binders, and (3) to develop practical recommendations for utilizing SAP in construction. These recommendations will mainly address technological procedures (e.g. storing of SAP, mixing procedure, curing), the material mix design (e.g. optimization of the type, dosage and properties of SAP, the amount of additional water) and testing methods for specific material properties which may be affected by the use of SAP, as well as the specification of SAP for practical applications. In doing so, numerous interacting phenomena such as shrinkage, creep, thermal effects, cracking, and interface quality should be investigated and taken into account.
In summary, the aim is to collect all available information and knowledge as well as to coordinate on-going research efforts, and to ultimately produce a state-of-the-art report, which will include recommendations on the use of SAP and should serve as a general guide to assist researchers and material technologists. The conclusions of the TC are expected within 3 to 4 working years.
The members to be recruited for the TC will be recognized experts in the domain. In order to take into account the different practices and standards in Europe, Japan and North America as well as their respective spheres of influence, including ISO, EN and ASTM standards, the TC will include representatives from the aforementioned world regions.
Since one of the goals of the TC is the elaboration/generation of recommendations for engineers and practitioners, their participation is necessary. Actions are expected in the different geographical areas covered by the members of the TC to initiate local (national or multi-national) groups involving practitioners.
These groups will work complimentarily to the TC. They will provide the TC with information about practitioners’ needs and expectations and carry the results of the TC through the standard making process until its achievement.
Detailed working programme
The work of the TC will initially focus on bringing together the expertise and knowledge of all participating members. The first synthesis of expertise will be done at the inaugural TC meeting.
On this base, the TC will simultaneously address the following items:
- Properties of SAP for building applications
- Utilization of SAP for reducing / preventing autogenous shrinkage of HSC/HPC
- Application of SAP in concrete for other purposes than internal curing
- Use of SAP as water regulating agent in various building materials with inorganic hydraulic and non-hydraulic binders.
Activities of the committee will include performing a series of round-robin tests and organizing an international RILEM workshop on Application of Super Absorbent Polymers in Construction.
The outcome of this committee work will be a state-of-the-art report including recommendations for the practitioner
The proposed TC is a follow-up of TC 196-ICC 'Internal Curing of Concrete' lead by Prof. K. Kovler, and, among other subjects, it will develop further the methodology of internal curing formulated in the TC 196-ICC state-of-the-art report, which will be published soon by RILEM.
The experimental investigations of the proposed TC will be coordinated with TC SFC 'Sonic methods for quality control of fresh cementitious materials' lead by Prof. H.-W. Reinhardt. The work will provide input to relevant standardization work within ACI, ISO and NIST.
The TC fits into the RILEM's technical program, in particular the items 'Performance, maintenance and repair of building materials and structures during the service life' and 'Updating of test methods'.
The work will be carried out in connection with national or multi-national local groups involving practitioners as mentioned in Section 3.
- State-of-the-art report
- Recommendations for the practitioner
- International RILEM conference (workshop).
- During the tenure of the TC: publication, by their respective authors, of the ongoing results (in scientific journals and conferences)
- Regular reports in 'Materials and Structures'
- At the end of the TC tenure: publication of a final report summarizing the main results and the general conclusions in a dedicated conference or workshop.
Group of users
The targeted users are researchers, practitioners and standardization bodies in the field of concrete technology as well as technology of other building materials based on inorganic binders.
Specific use of the results
Reliable rules and recommendations for the utilization of SAP in concrete and other building materials should enable the introduction of this new additive into the practice of construction. The use of SAP offers new possibilities with regard to enhancing the durability of building materials as well as the confident steering of other relevant properties in fresh and hardened state. A considerable economic impact can be expected due to the benefits connected with the utilization of SAP.
Through the local national or multi-national groups specified in Section 3, the practitioners are envisaged to implement the TC’s recommendations in their respective countries until the adoption of national or international standards.