Development of hydrophobic concrete by adding dual‐crystalline admixture at mixing stage

Abstract

A novel approach has been presented to add a dual-crystalline hydrophobic admixture in fresh concrete for improving hydrophobicity against chloride and harmful chemicals. Dual-crystalline material can utilize water of the fresh concrete to form crystals, but the challenge is to maintain adequate hydration and strength while improving hydrophobicity. This study presents the results from a comprehensive laboratory investigation on the application of 1, 2 and 8% of crystallizing aqueous and cementitious hydrophobic mineral in fresh concrete. Despite the high slump in the fresh mixture, no segregation was observed in the matured concrete. There was a marginal reduction of strength when a high percentage of admixture was used. Despite this, significant reduction of water absorption was observed indicating greater hydrophobicity. The optimum performance was found in mixtures with 2% admixture. Mixture with 2% aqueous hydrophobic admixture revealed marginal strength gain compared to 2% crystalline cementitious hydrophobic admixture, although water protection appears to be better in cementitious mixture.admixture, compressive strength, crystal structure, fresh concrete, hydrophobic treatment, permeability, water absorptionAlthough concrete is known for its long serviceability, its performance could be greatly compromised when exposed to a harsh environment like bridges, concrete pavements, and coastal defenses. The deterioration is mainly caused by excessive water, chloride penetration and attack by other harmful substance like chemicals, fuel spillage, etc. In the United Kingdom, for example, there are about 61,000 highways and bridges, most of them are reinforced concrete pavements with reinforced steel, their maintenance expenses reached more than £4 billion in the period 2012-2013. 1,2They are subjected to rainfall of 1,420 mm as recorded in the year 2012, and about 1,120 mm in 2014. 3,4 The easy entrance of water into concrete can produce many disadvantages affecting its desired performance and durability and could bring many problems into being; including corrosion of the embedded steel, and leakage. Also, some waterassociated issues like freezing and thawing could drag concrete to a series of deterioration stages. 5 Reflecting the need to protect concrete from moisture damages and to decrease its permeability without compromising its strength, the research presented in this study jumps from the improper performance and benefits of in situ protection. Also, it is worth mentioning that there is a need to get over the fact of insufficient penetration of protection materials in concrete and try to develop a way of application on concrete so that it will cover the whole mass of concrete. 3 The purpose of this study is to investigate the performance of a crystallizing material mixed at mixing stage, in different percentages, within the concrete mixture.Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, i...

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