چكيده به لاتين
Human activities in the last 40 years have led to an increase of about 20% in the
concentration of carbon dioxide (CO2) in the air. In the 1970s, the idea of absorbing and
storing carbon dioxide was proposed through concrete curing, which means that carbon
dioxide can be stored for a very long time due to the stability and insolubility of the products
produced during carbonation processing. After that, research was started to identify the
advantages and disadvantages of carbon dioxide storage in cement-based materials. The use
of biopolymer materials and its effect on carbonation and mechanical characteristics and
durability of concrete is an issue that has been less discussed in the research on concrete
curing with carbon dioxide.
The use of biopolymer materials, which are known as environmentally friendly materials,
in addition to storing carbon dioxide, have properties such as increasing long-term
compressive strength and reducing the negative effect of increasing the water-cement ratio. In
the current research, the effect of slags and one of the types of biopolymer materials known
as guar gum powders has been investigated. For this purpose, first by conducting several
tests, the best conditions for curing with carbon dioxide were determined, after that, different
amounts of slag and guar gum were added to it, and by conducting compressive and bending
strength tests, as well as the depth of carbonation penetration, the best amounts of additives
were determined.
Based on the preliminary results of the tests for curing with carbon dioxide, the best type of
curing is 12 hours in the mold, 12 hours outside the mold and 1 day in the carbonation room
with a concentration of 99.9% carbon dioxide, a relative humidity of 90% and a temperature of
30 degrees Celsius. After determining the best curing conditions, experiments were
conducted to determine the effect of changing the ratio of water to cement on the samples
cured with carbon dioxide. It was observed that the rate of change of compressive strength in
water-cement ratio of 0.55 is higher than 0.35. The reason for this is the production of more
calcium hydroxide gel, because the porosity is lower in the water-cement ratio of 0.55
compared to 0.35.
For the sample without slag and the sample with 0.25% of slag, two types of curing were
tested, the first mode for the condition that the sample is exposed to carbon dioxide for 24
hours and the second mode for the condition that the sample is exposed to carbon dioxide
until the age of 28 days. The resistance diagrams in the presence of slag has a decreasing
trend in the short term, but for 10% slag, we have a better situation in the long term, for curing
with water or carbon dioxide curing. Of course, in 7 days, the maximum strength is around
25% slag, and even in 10% slag, the bending strength graph of the sample curing with water is
higher than the sample curing with carbon dioxide. It was observed that basically carbon
dioxide curing does not have a special effect on the bending strength and sometimes even has
a negative effect (such as the sample with 10% slag). The main effect of carbon dioxide
curing is on compressive strength and permeability, which in the long term had the best
resistance effect on the sample with 10% slag.
At the end, the effect of guar gum powder on concrete performance was investigated and it
was observed that the optimal percentage of guar gum in these charts is clearly 0.2 percent.
Guar gum does not have the effect of recording resistance in cement samples curing with
carbon dioxide, but the absorption of carbon dioxide increases with the increase of guar
percentage. Therefore, biopolymer materials should be used along with another material so
that we can use the positive effect of guargam in absorbing carbon dioxide and cover the
negative effect of guargam in resistance with other materials.
