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Apakah julat kadar pH air yang dianggap bersesuian dalam bancuhan konkrit?
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Following conclusion are drawn from a journal of Quality of Water for Making Concrete: A Review of Literature by Kucche, K. J. et al. (2015):

  1. Degree and rate of attack of corrosion of steel is increases as pH value of water decreases. It was found that, the rate of corrosion is more below 3.0 pH value of water. Chlorine ions present in water form hydrochloric acid (HCl), can act as a catalyst for oxidation of steel in concrete. This results formation of Fe(OH)2 which allows to easier penetration of chloride ions and hence formation of corrosion.
  2. There is reduction of compressive strength and split tensile strength of concrete with reduction in pH value of water.
  3. There is reduction of bond strength and freeze-thawing action of fiber reinforced concrete with increase in pH value of water.
  4. Presences of high alkali about 1% to 1.25% of Na2O3 shows, minimum shrinkage of concrete and high freeze-thawing resistance.
  5. Compressive strength of concrete is increase when temperature is in between 200oC - 250oC because of accelerated curing of concrete. It was observed that, there is reduction in strength more rapidly at temperature ranges 700oC – 900oC.

Dipetik daripada: http://www.ijsrp.org/research-paper-0115/ijsrp-p3720.pdf

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The 5 to 6 pH may have harmful effects, but this seems to be a borderline case. The U.S. Army Corps of Engineers Handbook for Concrete and Cement states that water with a pH between 6 and 8 may be regarded as safe for use in mixing concrete, so your water is outside those limits. However, limits published in the Seventh (revised) Edition of Fulton's Concrete Technology (South Africa) range from 4 to 8.5. The book further notes that high alkalinity of the pore water should neutralize any acidity in the mix water during hydration. Concrete stability may be affected if the low pH is caused by organic acids in the mixing water, according to a Danish concrete manual. ASTM C 94, Standard Specification for Ready-Mixed Concrete, doesn't include pH limits for mixing water but does require testing questionable-quality water to assess harmful effects on compressive strength and setting time.

Dipetik daripada: http://www.theconcreteproducer.com/how-to/concrete-production/acidic-mix-water_o

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The water used for mixing and curing should be clean and free from injurious quantities of alkalis, acid, oils, salt, sugar, organic materials, vegetable growth and other substances that may be deleterious to bricks, stone, concrete or steel. Potable water is generally considered satisfactory for mixing. The pH value of water should be not less than 6.

Dipetik daripada: http://www.gharexpert.com/tips/articles/Construction/1837/Water-1837-Water-Construction_0

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