Recycled Aggregate Concrete (RAC) mixes (1.15: 2.3: 4.6) cement: fine aggregate (sand): coarse aggregate (demolition concrete waste), water / cement (0.5), and 50 % demolition aggregates were prepared according to standard procedure. The resistance of the recycled aggregate concretes towards chemicals was investigated throughout the attack of (Acid: acetic Acid HAC, and salt: Sodium Chloride NaCl) solutions. The test was carried out based on adopted experiments designed using Response Surface Methodology (RSM). A 2-operating parameter central composite design was adopted to study the impact of concentration of the HAC and NaCl solutions (0.1-0.45) Molar, and immersion period (0.57-6.9) day of the (RACs) specimens on weight loss, compressive strength and density. The results obtained confirmed that weight loss increases, but both compressive strength and density decreases after the aggressive solutions attack, however HAC seemed more aggressive. The decrease in compressive strength was (2.8-42) % and (3.2-10.8) %, while the decrease in density was (0.72-2.05) % and (0.6-1.8) % for the samples immersed in HAC and NaCl solutions respectively. The mathematical models presenting the effect of concentration of the aggressive media and immersion duration on weight loss, compressive strength and density were estimated, and the effects were optimized and modeled. The Analysis of Variance (ANOVA) revealed that an optimum compressive strength (37.8 and 34.8) MPa is obtained for the RACs immersed for 0.56 day at 0.1 Molar HAC and NaCl respectively.

In previous work, concrete mixes incorporated with different types of acetates (inorganic and organic) were formulated, cured for 28 days in water, and then tested for compressive strength. The effect of the water-to-cement ratio and the acetate content was optimized using a central composited design based on the response surface methodology approach. The results confirmed that the optimum compressive strength was achieved for the mixes incorporated with calcium acetate (CaA) using of 0.48 water-to-cement ratio. In the current work, the effect of curing age on compressive strength and density was studied for the optimum mixes. Also, the water absorption of the mixes carried out by immersion test was assessed at different temperatures (25-55 °C). Microscopic observations were also noted. The results obtained confirmed that the compressive strength and density of the CaA-concrete mix increase with increasing the curing age. The thermodynamic study of water absorption assured the dependence of water absorption on temperature. The activation energies depicted from the Arrhenius relation and the decrease in the water absorption rate for the concrete incorporated with CaA are considered as an indicator of decreasing the porosity of the concrete mixes compared to the control mixes without CaA. The findings assured that the modified mixes with CaA are promising construction materials owing to their outstanding strength and lower water absorption rates compared to conventional concrete.

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Nowadays, admixtures are used with the aim to provide strength and durability to concrete with less water use. New and low-cost admixtures gained a large amount of consideration to mitigate the problems associated with concrete’s durability and service life without upsetting its strength properties. The current work investigates the effect of three types of acetates on the workability, density, and compressive strength of concrete, which is used in structures of the Iraqi ports that suffer from corrosion damages and deterioration owing to the aggressive marine environments. Potassium acetate (KA), calcium acetate (CaA), and ethyl acetate (EA) are incorporated with different doses (1.38–5.6 wt.% of cement) in concrete mixtures using different water/cement ratios (0.48–0.54) based on an espoused central composite experimental design. The experimental results confirmed that the average workability increased with increasing the acetate dose, particularly with CaA. The density and compressive strength of 28 days of water-cured mixtures increased with increasing acetate dose following the order: Ca > K > Ethyl acetate and decreased with increasing w/c ratio. The high rise in compressive strength and workability linked to control mixtures was 30.8% and 77.3% as well as 15.7% and 64.3% for the mixtures incorporated with 5.6 wt.% CaA and KA, respectively. While it was 14.2% and 58.3% for the mixtures incorporated with 3.5 wt.% EA. RSM was employed to optimize and model the design and hardened properties of concrete mixtures. ANOVA results predicted the same trend, which was obtained from the experimental results. The mathematical models were valued with high-regression coefficients. The highest compressive strength of 42.68 MPa has been achieved for a concrete mixture of 0.48 w/c ratio by the incorporation of 5.1 wt.% CaA through a model with R2 96.97%. The relatively low-cost acetate admixtures, particularly CaA, seemed promising for the fabrication of concrete with outstanding properties.