Influence of Mix Water Quality on Compressive Strength of Making Concrete

The influence of concrete mixing water quality on the compressive strength of concretes was investigated in this study. During the study, the compressive strength (CS) of the concretes was determined at 7, 14, and 28 days age. This study used 8 types of water of varying qualities as concrete mixing water (water with 71 UTN impurity level, water with 250 UTN impurity level, water with 1000 UTN impurity level, well-sourced water, acidified water, and alkaline water). Potable water was used as reference water. The results indicated that the lowest CS has been obtained by using alkaline water at a concrete age of 7 days while the usage of water with 250 UTN impurity level as a concrete mixing water yielded the highest CS. in addition, the lowest CS has been obtained when using a mixing water of alkaline at a concrete age of 14 days while the highest CS resulted from using water with 71 and 250 UTN impurities levels. Furthermore, the usage of water with 71 UTN impurities level and an acidic water as a concrete water mixing gave the lowest CS at twenty eight days concrete age, while using magnetic water and water with 250 UTN impurities as concrete mixing water resulted in the highest CS. The use of water with 250 UTN impurities as concrete mixing water favored CS development at all concrete ages. These obtained results have shown a various effects of different impurities which significantly indicate that only a few water impurities affect the concrete’s CS seriously..


Introduction
Water is a major constituent of concrete that has a significant effect on its workability. Water is also important for efficient cement hydration. Therefore, the quality and quantity of water during concrete making must be carefully considered. Several researchers have investigated the influence of several types of water on concretes, including seawater, alkali water, mineral water, sewage water, industrial wastewater, water containing several chemical impurities, and black water from oil wells (Mujahed F.S. (1989), ( Olugbenga ATA (2014) ). The influence of the usage of microbes in concrete mixing water on the quality of the concretes has been studied by Ghosh & Chattopadhyay (2006). The outcome of the study pointed towards increasing CS and tensile strength of concretes produced with such water (Ghosh P. Mandal, et.al. (2006)). (2012) examined the chemicals effect on high-performance concretes by using various hydrochloric acid (HCI) concentrations in mixing and curing. The investigation's results showed that higher chemical contents decreased the CS and splitting tensile strengths of the concretes as compared with those cured and mixed in normal water (Arunakanthi E., et.al. (2012) ). The effect of sodium bicarbonate (NaHCO3)-containing water and sodium carbonate (Na2CO3) based on CS and the setting time of concrete were investigated by Venkateswara & Vangala (2013). The study found the existence of Na2CO3 in mixing water substantially increase the concrete's initial and final setting time. In addition, the results showed that the CS and the concretes tensile strength were notably (Venkateswara Reddy. and Vangala (2013)) .A study investigation on the influence of the magnetic water use as a mixing water replacing the normal water, has shown a positive effect as reported by (Reddy, et.al. (2014)) and (Ubale Pradnya, et.al (2016).

Experimental Work
This study used Type I Ordinary Portland Cement (OPC) which met the Iraqi specifications No.5/ 1984(Iraqi Specification No. 5 ,1984. The fine aggregates used was a natural sand which met the necessities of an Iraqi Number 45/1984 specification. For the rough collective, there were crushed stones of 12.5 mm maximum size which met the Iraqi No. 45/1984 specification (Iraqi Specification No. 45 ,1984). For all the mixes, a mixing cement: a fine aggregates: the coarse aggregate ratio of 1:1.5:3 was used. The water samples (8) for the mixing purpose were sought from different sources as follows: i. Magnetic water: Normal tap water was passed through an electromagnetic field in the physics lab. ii.
Water with UTN impurity level of 71, 250 and 1000: different levels of water impurities were prepared to achieve the desired turbidity level by dissolving metakaolin into tap water. iii.
Well water: This water was drawn from a well from the Ramadi region and used as mixing water. iv.
Acidic water: This was prepared by introducing a certain amount of HCl into tap water. v.
Alkaline water: This was prepared by introducing a certain amount of NaCl into tap water. vi.
Potable water: This water served as the reference water. It is normal tap water sourced from the Ramadi region.
These water samples served as the concrete mixing water in different experimental setups. The effect of impurities on the concrete mixtures after using these water sources as mixing water was investigated. The parameters measured include , total dissolved solids (TDS), pH, conductivity, turbidity and salinity, and as illustrated in Table 1. Testing the CS test has been conducted according to BS 1881: Part 116 on the concretes at the 7th, 14th, and 28 days post-curing.

Setting time:
the results indicate the effectiveness of the magnetic water which remarkably increased both the initial and final concrete setting times. The observed differences in the initial concrete setting time compared to tap water were approximately +8 min in the case of water at a turbidity level of 71 UTN, +15 min for water with turbidity of 250 UTN, +18 min for water with turbidity of 1000 UTN, magnetic water at-32 min, -5 min for well water, +40 min for acidic water, and -10 min alkaline water. The use of acidic water as mixing water produced the utmost initial concrete time set. The observed change in the final concrete time setting , compared to tap water, was about -38 min magnetic water, +14 min for water with turbidity 71 UTN, +20 min for water with turbidity 250 UTN, +18 min for water with turbidity 1000 UTN, -8 min for well water, +36 min for acidic water, and -10 min for alkaline water. Furthermore, it can be seen that the acidic water usage provided the utmost initial concrete setting time as shown in Figure 1 and Figure 2 . Based on various mixing water types, alkaline water achieved the highest CS while concrete with the least CS has been achieved using water with 250 UTN turbidity. Besides, alkaline water produced as well concretes with the least CS at concrete age of 14 days, while the concrete with the highest CS has been obtained using water with 71 and 250 UTN turbidity as depicted in Figure 4. While using water with a turbidity of 71 and 250 UTN as concrete mixing water produced concretes with the highest CS as depicted in Figure 5.
The concretes with the lowest CS at 28 days concrete age have been obtained using magnetic water as concrete mixing water. Acidic water and water with a turbidity of 71 UTN produced concretes with the lowest CS as well at 28-days concrete age . the using of magnetic water as mixing water gave the highest compressive strength compared with using of normal tap water. This may be due to form of a stronger hydrogen bonds due to the broken hydrogen bonds after magnetization. The smaller size of magnetized water molecules led to thinner water layer surrounding the cement than normal water molecules, therefore less water demand has a positive effect of

Conclusions
The results of this study showed various effects of different impurities levels in which some have a notable positive influence on the concrete's CS while other impurities have a negative impact. This study has proved the efficiency of using a magnetic water as a concrete mixing water which could produce concretes having the highest CS rather than using tap water. However, using acidic and alkaline water as concrete mixing water has detrimental effects on the strength of concrete.