Study on long-term leaching behavior of low alkaline cement

Hitomi, Takashi*; Iriya, Keishiro*; Nakayama, Masashi; Sato, Haruo

Proceedings of 3rd International Conference on Sustainable Construction Materials & Technologies (SCMT-3) (Internet), p.e0179_1 - e0179_9, 2013/08

http://www.claisse.info/2013%20papers/data/e179.pdf

Leaching procedure is studied on Low alkaline cement in which pozzolanic reaction is used for decreasing pH of pore water of cement hydrate to avoid influence on rock and other materials. Leached depth of Low alkaline cement (HFSC) by the immersion examination with Horonobe simulated ground was smaller than depth of ion-exchanged water. Water exchanging is smaller than that of Ordinary Poltland Cement (OPC) with the same water binder ratio, since soluble Portlandite was not produced and dissoluble Calcium Silicate components were mainly produced. Although simulated groundwater in Horonobe URL was used for immersion examination, the low alkaline cement hydrates is more durable for leaching degradation than OPC. For all cements, groundwater showed tendency of accelerate leaching compared to ion exchanged water. This study shows that HFSC has higher durability for leaching degradation to groundwater than OPC.

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project, 3 (Contract research)

Nakayama, Masashi; Kobayashi, Yasushi; Noguchi, Akira; Miura, Norihiko*; Noda, Masaru*; Iriya, Keishiro*; Hitomi, Takashi*

JAEA-Research 2009-036, 49 Pages, 2009/11

JAEA-Research-2009-036.pdf:20.34MB

In Horonobe Underground Research Laboratory (Horonobe URL) Project, construction practicality test with HFSC (Highly Fly-ash contained Silica-fume Cement) is planned in a part of the gallery. It is necessary to validate that HFSC has performance under the actual construction, before HFSC is placed in the gallery. The main tasks in 2008 are follows; (1) suggestion of mix design for liner concrete of shaft in Horonobe URL, (2) investigation of long term pH changes in order to use for modeling, and (3) an experiment for interaction between HFSC and ground water around Horonobe URL. (1) 4 types of mix proportion are designed for ordinary concrete and high strength concrete which contains polypropylene fiber or not. As early age strength, 5N/mm is required because of concrete formwork. HFSC424 with low water binder ratio can fulfill this requirement in combination with super plasticizer. (2) pH and components of solid and liquid phase which were made in 2003, and stored in water were analyzed. And cement paste of shotcrete which are made in 2006 were also analyzed. In this pH of shotcrete is lower than other in situ concrete since accelerating agent may act as decreasing factor of pH. (3) An experiment which investigates dissolution of HFSC cement hydrates to ground water around Horonobe URL. According to the experiment, dissolving depth of HFSC is 4 times small comparing to Ordinary Portland Cement hydrates after 30th water exchange.

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project (Contract research)

Matsuda, Takeshi*; Noda, Masaru*; Iriya, Keishiro*; Konishi, Kazuhiro*; Nakayama, Masashi; Kobayashi, Yasushi

JAEA-Research 2007-089, 139 Pages, 2008/05

JAEA-Research-2007-089.pdf:13.57MB

In Horonobe Underground Research Center construction of underground facility began in 2005 and construction practicality test with HFSC (Highly Fly-ash contained Silica-fume Cement) is planned in a part of the gallery. Before the HFSC will be contracted in the gallery it is necessary to check that the HFSC has performance under the actual construction. The main work of this Japanese fiscal year is making a detailed test plan for the HSFC construction practicality, that is scheduled after 2007 and laboratory tests on lowering behavior of pH in the HFSC concrete were conducted. On the construction practicality test with low alkaline concrete, HFSC in-situ experiment plan was studied in case using HSFC424N as shotcrete. The aims of the in-situ test are the validation in applicability of low alkaline concrete as a support member for underground opening in the realistic geological environment and building the method to evaluate influence to the surrounding geological environment. The location of the in-situ test is in the connection tunnel of a depth of 140m and the geology is the Koetoi formation. The period of the test is approximately 10 years. The test plan was designed to be able to make a comparison with Ordinary Portland Cement. As it is necessary to confirm the strength property of the HFSC concrete with materials procured at construction site, strength of the base concrete using local procured fine aggregate and coarse aggregate based on the result of the selection of mix proportion in 2005 research was checked. On laboratory tests on lowering behavior of pH in HFSC concrete, the pH of immersion fluid was measured and components of the immersion fluid and the solid phase were analyzed using test specimens in a long-term immersion test which had been continued since 2005.

Development of low-alkaline cement using pozzolans for geological disposal of long-lived radioactive waste

Mihara, Morihiro; Iriya, Keishiro*; Torii, Kazuyuki*

Doboku Gakkai Rombunshu, F, 64(1), p.92 - 103, 2008/02

https://doi.org/10.2208/jscejf.64.92

To reduce uncertainties in the safety assessment of a disposal system for long-lived radioactive waste, cement was developed which generates leachates with a lower pH than that of ordinary cement paste. This cement was termed "low-alkaline cement". Large amounts of pozzolans were used to produce the low-alkaline cement from ordinary Portland cement. To reduce the pH values, silica fume was found to be efficient, however large amounts of silica fume reduced the workability of fresh concrete. Therefore, we also used fly ash with silica fume, high-volume fly ash silica fume cement (HFSC). The low pH value and self-compacting HFSC was developed. Two types of HFSC showed high compressive strength, smaller drying shrinkage and lower temperature rise than those of ordinary cement concrete. They can therefore be applied to the structure and filling concrete in the disposal system.

New type of shotcrete containing much pozzolanic additives

Miura, Norihiko*; Konishi, Kazuhiro*; Iriya, Keishiro*; Nakayama, Masashi; Matsui, Hiroya

Semento, Konkurito, (728), p.63 - 67, 2007/10

High level radioactive waste(HLW) repository is to be constructed at depth of over 300m below the surface. Shotcrete and lining will be used for safety under construction and operational period. Concrete is a kind of composite material which is constituted by aggregate, cement and additives. Low alkaline cement has been developed from the viewpoint of long term stability of the barrier systems which would be influenced by high alkaline arising from cement material. Japan Atomic Energy Agency(JAEA) has been developed HFSC(Highly Fly-ash contained Silica-fume Cement) which is one of a low alkaline cement contained silica-fume and fly-ash. JAEA is now implementing the construction of the underground research laboratory(URL) at Horonobe for the purpose of research in deep geological science and repository engineering technology. This report shows the properties of HFSC using as shotcrete.

Study on applicability of low alkaline shotcrete in Horonobe URL project

Konishi, Kazuhiro; Nakayama, Masashi; Mihara, Morihiro; Yoshida, Yasushi*; Iriya, Keishiro*; Akiyoshi, Kenji*; Noda, Masaru*

JAEA-Research 2006-040, 53 Pages, 2006/06

JAEA-Research-2006-040.pdf:12.6MB

no abstracts in English

Development of low alkaline cement considering pozzolanic reaction for support system in HLW repository construction

Nakayama, Masashi; Iriya, Keishiro*; Fujishima, Atsushi; Mihara, Morihiro; Hatanaka, Koichiro; Kurihara, Yuji*; Yui, Mikazu

Materials Research Society Symposium Proceedings, Vol.932, p.159 - 166, 2006/00

Cementitious material is one of candidates of engineered barriers in TRU and HLW repositories. However, since ordinary Portland cement may rises pH of pore water due to its high alkalinity, bentnite and rock which contact with cementitious barriers as a mulch barrier system may deteriorate for a long term by its high pH. Low alkalinity cement with high pozzolanic material content are developed in order to reduce such hyper alkaline deterioration. This paper shows that pH of pore water of this cement is about 11, and that it can be applied for actual structures as self compacting concrete and shotcrete.

Evaluation of Hydraulic Conductivities of Bentonite and Rock under Hyper Alkaline and Nitrate Conditions (III) (Summary)

Iriya, Keishiro*; Kubo, Hiroshi*

JNC TJ8400 2005-003, 90 Pages, 2004/02

JNC-TJ8400-2005-003.pdf:2.97MB

Circumstance of TRU waste repository shows alkaline condition due to leaching of cementitious materials. The waste containing significant soluble nitrate may changes ground water chemistry to high ion strength. Consolidation test and permeability test are carried out in order to assess quantitatively permeability of bentonite altered by hyper alkaline and nitrate. Modeling is progressed based on experimental results. The following results are obtained. 1)Consolidation test was carried out in 3 types of bentonite and 30% sand mixture in which kation exchanged with nitrate. It is noted that permeability of bentonite increased at from 40 to 200 times by kation exchange. 2)Permeability of hyper alkaline solution is almost same to water. Permeability of hyper alkaline solution with nitrates increased corresponding to rising ion strength.3)The results of batch of column test were simulated. The model can explain clearly the results in short period. This can estimate leaching ratio and secondary minerals. The model can simulate the experimental results by two types of velocity theory on altering bentonite.

Study on construction method of concrete in the underground research laboratory (IV)

Iriya, Keishiro*; Tajima, Takatoshi*; Noda, Masaru*

JNC TJ5400 2003-008, 150 Pages, 2004/02

JNC-TJ5400-2003-008.pdf:21.54MB

In situ experiment on the low alkalinity cement is planned in construction of Horonobe Underground Research Center. This will be carried out in a part of the vertical shafts and horizontal experimental tunnels. The problems for actual using should be solved and improved until starting construction. This study has been carried out in order to improve the HFSC taking the Horonobe environment into account. Model analysis and preliminary laboratory experiment on hyper alkaline alteration of bentonite and rock have been carried out. And long term permeability experiment on this alteration was planed. pH decreasing ratio of HFSC is predicted by pH measuring for 1.5 year and geo-chemical code. Open data and undefined reaction were pointed out in order to accomplish the model on low alkalinity cement with high pozollanic content. The effects on fresh concrete properties and harden concrete due to changing properties of fly ash were investigated. Experimental basic planning on Horonobe low alkalinity in situ test are proposed. And finnaly, procedure of improvement HFSC in Horonobe construction are investigated and proposed.

Evaluation of Hydraulic Conductivities of Bentonite and Rock under Hyper Alkaline and Nitrate Conditions (II)

Iriya, Keishiro*; Fujii, Kensuke*; Kubo, Hiroshi*

JNC TJ8400 2003-067, 285 Pages, 2003/02

JNC-TJ8400-2003-067.pdf:18.35MB

Hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions were investigated.