Influence of Internal Sulfate Attack on Some Properties of High Strength Concrete

Abstract

One of the most important problems that faces the concrete industry in Iraq is the deterioration due to internal sulfate attack , since it reduces the compressive strength and increases the expansion of concrete. Consequently, the concrete structure may be damage .The effects of total and total effective sulfate contents on high strength concrete (HSC) have been studied in the present study.
 The research studied the effect of sulfate content in cement , sand and gravel , as well as comparing the total sulfate content with the total effective SO3 content. Materials used were divided into two groups of SO3 in cement ,three groups of SO3 in sand ,and two groups of SO3 in gravel.
 The results show that considering the total effective sulfate content is better than the total content of sulfates since the effect of sulfate in each constituent of concrete, depends on it's granular size .The smaller the particle size of the material the more effective is the sulfate in it. Therefore, it is recommended to follow the Iraqi specification for total effective sulfate content, because it gives more flexibility to the use of sand and gravel with higher sulfate content.
 The results of compressive strength at 90-days show that the effect of total effective SO3 content of ( 2.647% , 2.992% , 3.424% ) that correspond to total sulfate of ( 3.778%, 3.294%, 4.528%) decrease the compressive strength by (7.53%, 11.44%, 14.59%) respectively.
 

Impact of Sulfate in the Sand on the Compressive Strength of Metakaolin-Based Geopolymer Mortar

“…the loss in compressive strength of mix G3, which contained (1.532) % of SO3 in the sand, was (28.9 and 30.94) at 7 and 28 days, respectively, compared to the reference mix. Likewise, for the rest of the other mixtures, as given in Tables 6 and 7, it is concluded that the reduction in compressive strength of concrete is affected by the increase in the total effective sulfate content more than the total sulfate within the mixture this is consistent with the findings of (Mas et al, 2012;Fawzi et al, 2015). For example, when total sulfates in the mix (12) increase by (30.55%), the short and final ages of mortar strength are decreased by (61.91and 62.23) %, respectively, when compared to the reference mortar with a total effective sulfate of (0.51%).…”

“…Sodium silicate (Na2SiO3), NaOH, and potassium hydroxide are commonly employed in alkaline solutions for geo-polymer production (Al-Jaberi et al, 2021). Because it is challenging to find well-graded sand with an acceptable sulfate concentration that may be utilized in mortar, sulfate-contaminated sand is a local issue in Iraq (Fawzi et al, 2015). Sulfate is known to offense away at concrete and mortar, causing them to expand, weaken, and decay.…”