Conference Tour on April 15, 2021
North Breakwater at Otaru Port
Construction of the north breakwater began in 1897 as one of the large national projects. Dr. Isami Hiroi, a civil engineer, was appointed head of the Otaru Port Construction Office to supervise the project. The work was carried out in two phases; that is, a 1,289m long section from 1897 to 1908 and a subsequent 419m section from 1908 to 1921. After completion of the breakwater, construction work began on the south breakwater and the coal shipping wharf, forming the port as it is known now. Dr. Hiroi began developing innovative civil engineering techniques and theories including the mixing of volcanic ash for strengthening concrete. The long-term durability tests of concrete that he initiated are worthy of special mention.
Domestic cement production had recently begun in Japan in 1875; accordingly Dr. Hiroi had concerns about quality and the amount of cement production. To evaluate the durability of concrete, he decided to initiate long-term durability tests in the actual environment. Dr. Hiroi started producing gourd-shape test pieces (the mortar briquettes) for use in strength tests. Production of the mortar specimens started in 1896, a year before the project began, and continued for 40 years until 1937, when Mr Chouemon Ito, 2nd Head of the Office, took over the work. The following test parameters were implemented: 13 kinds of cement produced by different manufacturers; 19 kinds of volcanic ash (different kinds and locations); 10 kinds of fine aggregate (different locations); and 4 kinds of mixing water (seawater, salted water, and two fresh water). The total number of test pieces reached approximately 60,000 of 491 varieties, of which about 4000 still remain for future tests. It can be inferred that Dr. Hirai originally intended to carry on testing for 50 years. However, another series of tests was started during Taisho Period (1912-26), so the test became called the "100-year durability test" some-where down the line.
During the conference tour on April 15, you may visit near the breakwater by small boat and a museum displaying the construction of the breakwater and the 100-year durability test.
(Reference) Japan Society of Civil Engineers: Japan’s Concrete Technology, 2014.
North breakwater at Otaru Port