Alkali-Aggregate Reaction, Where Are You? - The Issues and Discussion of Modern Concrete Science - page 48

According to testing results of rapid mortar stick method, expansion rate at 14
day of mortar specimens numbered 1# cial sand

made from crushing gravel all exceed 0.2 % except for 3# specimen. So these
aggregates can evaluated comprehensively as reactive aggregate possessing
potentially harmful reaction, and crushed limestone aggregate numbered 8# can be
evaluated as non-reactive aggregate possessing no potentially harmful reaction as
the expansion rate is less than 0.1 %.
The above contents are cited from

6# which are molded by arti

*

Experimental Report on Durability of

Pavement Concrete at Yushu Airport written by Yang Wen-ke and Cen Guo-ping.

The author had communicated with technicians from local construction
department and asked whether there had discovered alkali-aggregate reaction or
not. Their answer is they had built many projects along with Yangtze River, Yellow
River, and Lancang River (Yushu locates at the source of three rivers) and found no
alkali-aggregate reaction even though they adopted this kind of aggregate and high
alkali cement.
The author had also made several experimental board for observing alkali-
aggregate reaction, and the mix proportion is shown in Table 4.3 .
Sand is alkali-active and obtained from Baqu River Quarry in Batang of Yushu.
Coarse aggregate are divided into two categories of 2 - 4 and 0.5 - 2 cm. They are

alkali-reactive and produced by crushing gravel in Baqu River
Additive is AJF-6 high effective air-entraining agent. The dosage is 1 % of
cement mass (liquid), and the manufacturer is Beijing Anjian century science
developing limited company.
The test section is located at second row of south side of air force parking place
at Yushu Airport in Qinghai. There are 4 boards in all.
A stele is set and carved with words for memory after the test section is

finished.

The tablet inscription written by author himself is as follows.
Alkali-aggregate reaction is one of the most cutting-edge issues among the
current concrete research field. Debate about alkali-aggregate reaction is more

enough, while the practical example is relatively less within the world. Meanwhile,
project cost increased greatly in order to prevent this problem.
The owner and main project technicians from design, supervising, and con-
struction units, who had joined in the construction of Yushu Airport, are full of
scienti c and truth-seeking spirits. Taking advantages of local natural conditions of

anoxic plateau, rainy and windy, frost and cold, etc., and employing the unique
local coarse and

fine aggregate possessing alkali activity and cement with high

Table 4.3 Concrete mix proportion of test section
Cement Sand Water Air-entrain-

ing agent
330 752 615 639 142 3.3
Note Cement is 42.5-grade Ordinary Portland Cement with a brand of Kunlun Mountain produced
by Datong Cement Factory in Qinghai Province

Larger crushed
stone (2 - 4 cm)

Smaller crushed stone
(0.5 - 2 cm)