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Hydration Heat Test

Hydration heat test refers too internal temperature of the concrete.

The outline of the examination is to test to the internal temperature when the concrete is curing,Plan for the blend of concrete that uses Silica cement admixture. The objective of the examination is conducted by creating the basic plan for the blend and measuring compressive strength when Silica cement admixture is used as a replacement material for ordinary cement and blast furnace cement, and measuring the internal temperature when the concrete is curing by measuring the temperature change in the center of the cube after pouring concrete inside the wooden 1.0m×1.0m×1.0m panel frame.

Test conducted by:
Department of Research and Development, Product Giken, Inc. Japan.
Measured from July 5 to July 15, 2007

Test site:
Examination building at Product Giken, Inc.

Using ordinary Portland cement and based on the blend (designed strength: 24 N/mm2, slump: 15cm), the cement is replaced with Silica White. The same procedure is performed on blast furnace cement, as well. An air-entraining and high-range water-reducing agent is used in order to make concrete properties constant. Blend, compressive strength, and other properties of the fresh concrete are shown below.
W= water
N= ordinary cement
B= blast furnace cement
SW= Silica White
G= Coarse aggregate
S= Coarse aggregate
AE= water reducing agent.

Table of Blends:

Unit: Kg

Name of the Blends

W

N

B

SW

G

S

AE

24-15-25 N

153

283

--

--

1078

762

2.26

24-15-25 N-SW

181

268

--

67

1026

686

3.02

24-15-25 B-SW

181

--

268

67

1021

683

3.02


Compressive strength and properties of fresh concrete:

Name of the Blends

Measured on:

Compressive strength

Mixing temperature

Air volume

Slump

(age of the material: 28 days)

24-15-25 N

7/9 PM14:00

27.2

27

4.5

15

24-15-25 N-SW

7/5PM14:00

29.5

25

4.4

15.5

24-15-25 B-SW

7/12PM14:00

28.9

--

4.3

15.5

Unit:
compressive strength= mm2
temperature= 0C  
air volume= %
slump= cm

Temperature Change Result :

Using the three types of blended concrete specified in the preceding clause measurement of the internal temperature change was done when the concrete is curing after pouring each type of concrete inside the wooden 1.0m×1.0m×1.0m panel frame in the laboratory where the temperature is kept constant.

After measuring the internal temperature, changes that occurred in the three types of blended concrete (see the graph below and attached measurement data), it was revealed that it was possible to lower the curing temperature by replacing cement blended with Silica Cement Admixture. Moreover, during the curing process, the temperature gradient decreased when BB cement and Silica cement admixture were blended in. It can be assumed that this happened because the curing temperature lowered the amount of mixed cement per 1m3 , which was reduced by the cement replacement with the blast furnace slab and Silica Cement Admixture.
   However, the compressive strength did not decrease even when the amount of cement per square meter decreased.  Although the cause cannot be determined unless more detailed tests are conducted in the future, it seems that this was probably due to the close-packed structure resulting in the closest packing possible (by micro-filler effect, etc.) and because the strength was enhanced due to the secondary curing reaction (by pozzloanic action, etc.)