1 Introduction

For any project to be done a complete soil investigations must be carried out, these investigations are very hard, expensive and time-consuming work. That’s why, a need appear to reduce them as much as possible. The corrosion of steel reinforcement is one of the most important aspects in the durability of reinforced structural elements (Oh and Jang 2005) in addition to the failure of the concrete itself.

Chloride attack is the main cause of structural damage in reinforced structural elements which is triggered by the propagation of the chloride ions through the pore solution to the reinforcement level (Mallick et al. 2018). The chloride ions may be redounded by the ingredients of concrete mixture, such as aggregates, mixing water, cement, and Additives for concrete mixtures. Alternatively, they may spread into the sclerotic concrete from the surrounding environment (Karthick et al. 2016). The diffusion of chloride ions from the external environment through concrete to the reinforcement steel’s surface, leads to the erosion of the precautionary layer and finally to reinforcement corrosion (Hirao et al. 2005). One such case is the spread of chloride ions from the surrounding soil into the hardened concrete in foundations or substructures (Maslehuddin et al. 2007). There are no guidelines or threshold limits for the chloride concentration in the soil and its influence on reinforcement corrosion (Maslehuddin et al. 2007). That is because chloride effect is dependent upon many factors such as type of cement used in the concrete mixed. Chloride does not affect the concrete or the reinforcement in direct way but it does make deterioration of concrete from cyclic freezing even worse if the concrete was so exposed (Niville 1995). The existence of chloride ions in concrete has the potential to boost erosion of reinforcement (Al-Amoudi et al. 2015). The major concern when dealing with reinforced structural elements exposed to soils containing chlorides is erosion of reinforcement bars. Concrete permeability will have a “time” effect, where if chlorides are founded in any but the smallest amounts and there is even a little moisture in the soil, then erosion of reinforcement steel will eventually occur (Ali 2017). With comparatively impermeable concrete, the start of erosion will only be belated, and that is all. When the ground water rose above the concrete foundations they will be affected by chemical effects associated with consecutive cycles of drying and moistening. At high water table the concrete saturate with water, and when it drops, part of the water evaporates from concrete causing salts crystallizing. A following water rise causes the concrete saturation again with water that contain higher salts concentration. The repetition of this process by time causes salts crystallization inside the concrete pores, if it is permeable, resulting in a swelling leading to develop cracks in concrete. There is an allowable size limit for these cracks for various types of exposure; these limits range from 0.1 mm for very extreme environment to 0.4 mm for moderate environment (Mallick et al. 2018).

Carbonation is another chemical process which leads to concrete degradation. This process is the interaction of calcium hydroxide Ca(OH)2, with carbon dioxide CO2 existing in the air. At first, carbonic acid is engender by carbon dioxide dissolving in the pore water, and it in turn reacts with calcium hydroxide to form calcium carbonate (CaCO3) (Bonic et al. 2015). The greater permeability and porosity of concrete, the easier it is gets corroded (Glasser et al. 2008). However, the main result for concrete carbonation is the reduction of alkaline nature of concrete, which is a very important precondition for reinforcement corrosion (Bonic et al. 2015). Total soluble salts TSS is defined as all soluble soil salts, where the solubility of these salts varies by its nature. The degree of solubility is affected by the temperature, the pH value and the quantity of the dissolved carbon dioxide CO2, as well as evaporation and moisture (Atyah and Muir 2013). The importance of this test is to estimate the proportions of salts that cause the erosion of concrete and pipes and reinforcing steel. When their solubility is free in water, it has a significant impact on the degree of damage to the concrete (Emmanuel et al. 2012).

This study included collect, sort and analyze the data of (464) boreholes in the study area and for depths from 0 to 35 m. The data were obtained from the National Center for Construction Laboratories & Researches (NCCLR 2016)/Babylon laboratory reports (NCCLR).

2 Methodology

The methodology of this work include the steps listed in the flow chart shown in Fig. 1.

Fig. 1
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The work flow chart

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2.1 The Study Area

An-Najaf governorate is located at the southwest of Iraq away from the capital Baghdad of about 161 km southwest (Fig. 1). It has an area of about 29,000 km2 and comprise about 7.1% of the country total area (Mallick et al. 2018). It is located at the intersection of longitude 44°21′0″ eastern and latitude 32°2′0″ northern. This study involve parts of An-Najaf and Kufa cities that located between the coordinates 44°17′00″ and 44°25′0″ Eastwards and 32°7′0″ and 31° [the researcher]. Figure 1 shows the location of An-Najaf province. Figure 2 show the of study area and locations of boreholes (Fig. 3).

Fig. 2
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Location of An-Najaf province

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Fig. 3
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Location of study area

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2.1.1 An-Najaf City Soil Description

Generally, An-Najaf City Soil consist of sand about 50–85.1% of the soil components, with some layers of clay and silty clay soil at various depths. SPT test values that dominated on most of the region are high and exceeds 50 blows. the most existing soil conditions are dense to very dense sand, and cemented sand. Angle of Internal friction Ø range between 26.3° and 41.2° in most of the region (Ali and Fakhraldin 2016). The bearing capacity form SPT values ranged between 5 and 20 Ton/m2 in the studied region (Al-Maliki et al. 2018).Sulfate content in soil varies between 0.36 and 14% while in groundwater was between 84 and 239% (Al-Mamoori et al. 2017). Gypsum content is very high, it rang between 10 and 25% (Al-Mamoori 2017).

2.1.2 An-Najaf City Climate Description

The study area is characterized by desert climate, that is a hot dry summer and cold winter (Iraqi Ministry of Planning, Central Statistical Organization). Summer temperatures in the study area range between 41 in June, 44 in July and 43.4 in August, while the temperatures diminish in winter to 5 in December, 4 in January, and 5.6 in February. Rainfall is limited from October to May and unevenly distributed. The total annual rainfall is 101, 112, 121 ml/cm2 (Environmental Statistics Report, Iraqi Ministry of Planning). The climate is an important factor affecting the quality of soil, water and air. The increase in the amount of rain precipitation leads to the filtration of water through the soil layers, washing salts and then the rise of groundwater levels, in addition to the reduction of some elements in soil and groundwater. On the contrary the lack of rainfall and increase the temperature, especially in the summer, lead to water evaporation, soil dryness, lower ground water levels and increased crystallization of salts (Mahmoud and Jaafar 2017).

2.2 Research Method

In order to achieve the objective of the study, the following steps were taken

  1. 1.

    The used data were obtained from the National Center for Construction Laboratories & Researches (NCCLR)/Babylon laboratory reports. Babylon laboratory is a department that attached to the National Center for Construction Laboratories & Research (NCCLR), that is part of the Ministry of Construction and Housing authority. The laboratory is effective since its emergence in 1977. Therefore; information about the province of An-Najaf and all areas are available in this center.

  2. 2.

    After collecting the data, the exact locations for each borehole were obtained using GPS (see “Appendix”).

  3. 3.

    The data obtained was arranged in tabular format within the Excel program including the borehole location and concentrations for each depth.

  4. 4.

    Position the boreholes sites on the latest administrative map of the study area.

  5. 5.

    In order to e facilitate and simplify the produced maps each Neighborhood was replaced by a certain number. Neighborhood’s names and numbers are listed in Table 1.

    Table 1 Neighborhoods numbering
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This research data were obtained from 464 boreholes spread in An-Najaf and Al-Kufa cities and for depths from 0 to 35 m.

2.3 Software Program

The Geographic Information System (GIS) is an integrated geographic information system published by the Environmental Systems Research Institute (ESRI). Arc Map is the central part of the program that has many tasks, such as mapping, editing, displaying, present digital data, working with layers, add elements to the maps such as scale and map legend. This research included sorting and categorizing the collected date in Excel program, the sorted data include the names of the sites and the sites’ features, as well as tables containing the data that we will use in the analysis process. Then the Excel file imported to the GIS program to analyze and produce maps using Inverse Distance Weighted (IDW) tool for this aspect. IDW is an interpolation method that use points with known values or sample points to estimate values at other unknown points. In GIS program there are eight interpolation methods. Inverse Distance Weighting IDW is one of these methods which assumes that each input point has a local influence that diminishes with distance. The reason of using this method is because it can estimate extreme changes in terrain such as: Cliffs, Fault Lines, dense evenly space points are well interpolated (flat areas with cliffs) and can increase or decrease amount of sample points to influence cell values. Finally geotechnical maps were prepared for each soil property. In this paper the version GIS (10.2.1) of the program was used.

The Geographic Information System (GIS) have tools that can help make, manage, analyze, and visualize any data specially these related to civil and urban infrastructures. It helps engineers and decision maker to transform the geotechnical data into practicable information that are useful for the reliable and safe working with infrastructures during their lifecycle (Shahrour et al. 2007).

3 Results and Discussion

Figures 4, 5, 6, 7, 8, 9, 10, 11 and 12 show the produced maps for chloride concentrations.

Fig. 4
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Chloride concentration at depths 0–2 m

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Fig. 5
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Chloride concentration at depths 2–4 m

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Fig. 6
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Chloride concentration at depths 4–6 m

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Fig. 7
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Chloride concentration at depths 6–8 m

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Fig. 8
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Chloride concentration at depths 8–10 m

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Fig. 9
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Chloride concentration at depths 10–12 m

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Fig. 10
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Chloride concentration at depths 12–14 m

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Fig. 11
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Chloride concentration at depths 14–16 m

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Fig. 12
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Chloride concentration at depth 35 ms

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From these maps it’s found that chloride content in the soil of the study area range from − 0.01 to 0.99% and with an average of 0.5. The maximum value found in at depth 4–6 m while the minimum value found in location at depth 4–6, 8–10 and 14–16 m. The maximum, minimum and average values for chloride content ranges in addition to the dangerous zone for each depth are listed in Table 2.

Table 2 Chloride content ranges for all depths
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The high values of chloride salts content can be attributed to the rise in the groundwater levels in the region, As well as evaporation and drought factors. It is noted that the chloride content in most locations exceed the permissible value that effect on the soil engineering behavior which is 0.1%, and that poses a danger to the foundations and reinforcing steel. Increasing chloride content leads to a decrease in Atterberg limits and an increase in the value of the maximum dry density. And affect the properties of compression resistance of concrete as the resistance decreases with increasing the chloride content, especially in the early age of concrete.

The produced maps for calcium carbonate content are listed in Figs. 13, 14, 15, 16, 17, 18, 19, 20 and 21.

Fig. 13
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Calcium carbonate content at depths 0–2 m

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Fig. 14
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Calcium carbonate content at depths 2–4 m

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Fig. 15
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Calcium carbonate content at depths 4–6 m

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Fig. 16
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Calcium carbonate content at depths 6–8 m

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Fig. 17
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Calcium carbonate content at depths 8–10 m

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Fig. 18
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Calcium carbonate content at depths 10–12 m

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Fig. 19
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Calcium carbonate content at depths 12–14 m

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Fig. 20
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Calcium carbonate content at depths 14–16 m

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Fig. 21
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Calcium carbonate content at depth 35 m

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From these maps it’s found that calcium carbonate content in the soil of the study area range from − 53 to 0.18 and with an average of 26.6. The maximum and the minimum values found at depth 4–6 m. The maximum, minimum and average values for calcium carbonate content ranges in addition to the dangerous zone for each depth are listed in Table 3.

Table 3 Calcium carbonate content ranges for all depths
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It is noted that the soil of the study area contains a high percentage of calcium carbonate in some locations. This may be due to the geological nature of Najaf, which contains large quantities of limestone, the dry climate contributes to the deposition of carbon materials from groundwater (Allen 2005) and its union with the calcium ion form calcium carbonate. In general, calcium carbonate content in most locations and for all depths has exceeded the permissible limit that affect the soil engineering behavior which is 30%. So this pose a risk and lead to engineering problems such as cracks, buildings differential settlement and soil weakening. As for total soluble salts (TSS) the produced maps included in Figs. 22, 23, 24, 25, 26, 27, 28 and 29.

Fig. 22
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TSS content at depths 0–2 m

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Fig. 23
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TSS content at depths 2–4 m

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Fig. 24
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TSS content at depths 4–6 m

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Fig. 25
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TSS content at depths 6–8 m

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Fig. 26
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TSS content at depths 8–10 m

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Fig. 27
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TSS content at depths 10–12 m

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Fig. 28
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TSS content at depths 12–14 m

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Fig. 29
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TSS content at depths 12–36 m

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4 Conclusions

  1. 1.

    Geographic Information System a helpful way to predict soil properties in non-Spatial data locations.

  2. 2.

    Geotechnical maps created by this work illustrate a powerful database and visual display of the data.

  3. 3.

    Using such maps help saving time, expenses and potentials.

  4. 4.

    Eventual maps created by this research will be used as a guidance for engineers and decisions makers to decide the safety of the site soil to build any project and type of suitable treatment needed.

  5. 5.

    The chloride content in the soil of the study area range from − 0.01 to 0.99% and with an average of 0.5. The maximum value found in at depth 4–6 m while the minimum value found in location at depth 4–6, 8–10 and 14–16 m.

  6. 6.

    The chloride content in most of An-Najaf province has exceeded the permissible limit in most locations and for all and this required taking percussions to protect foundations.

  7. 7.

    Calcium Carbonate content in the soil of the study area range from − 0.18 to 53 and with an average of 26.6. The maximum and the minimum values found at depth 4–6 m.

  8. 8.

    Calcium Carbonate content is within the permissible limits in most locations except in some locations.

  9. 9.

    The results show that the salinity of soil in the governorate is true but not absolute because salinity is unequal for all locations and depths. This salinity is liable to increase and decrease over time according to the geological and environmental factors affecting it.