Performance of concrete at sea



The solution in seawater is made up of several distinct components in varying amounts. Seawater mostly comprises ions of calcium, magnesium, potassium, and chloride among other chemicals.

The chemical makeup of most seawater is rather homogeneous, with soluble salts making up around 3.5 percent of the total weight. The Atlantic Ocean has the greatest ionic content of Na+ and Cl-, which are normally 11000 and 20000 mg/litre, respectively. The concentration of the principal ions found in the Arabian Gulf Sea is displayed in Table 1.

Table 1

Shows the main ions levels in Arabian gulf sea

Major Ions	Concentration (mg/I)
Sodium	20.700
Magnesium	2.300
Chloride	36.900
Sulfate	5.120
TDS	66.650
TDS Ratio	1.00

Figure 1. appearance diagram illustrates the chemical process that many constructions made of concrete in seawater throughout the US, Canada, Cuba, and Parama are subjected to. Concrete cylinders placed in seawater are said to be susceptible to spalling and cracking in the sections of the concrete that consistently keep above high-tide contours.

Fig. 1. Concrete Cylinder Held Up Against the Sea

Previous studies:

Significant new information on the behavior of concrete in seawater has been obtained from additional research conducted by the Portland Cements Association (PCA) on the long-term investigation into cement behavior in concrete (LTS) program. No matter how cementitious the concrete specimens were, their 37-year study's findings showed that saltwater had no negative effects on them.

Additionally, when a single side of a slab or wall made of a permeability solid is in touch with a solution of salt and the other sides are exposed to moisture loss through evaporation, concrete can deteriorate due to points out resulting from crystallizing of saltwater in the pores, as noted by Kumar Mehta and Monteiro (2006) show that in Akinkurolere et al. (2007). [1]

Filed investigation:

Portland cement was utilized. It was stored dry, lump-free, and in accordance with BS 12. Table 2 describes in clearly the characteristics of cement. Freshwater and seawater are pure and without oil.

Fine aggregate is a clean-sand accumulation that is devoid of organic materials.

The samples underwent a few preliminary testings. The chemical elements of fresh and sea water were determined using physicochemical investigations, as illustrated in the cement setting time and sieve analysis of the aggregate were used to estimate the fineness of the materials employed.

Processing and the casting process of the mixture Cubes:

A manually operated Weighing Balance was used to weigh the ingredients

for the concrete sample during batching.

The concrete mix ratio was 1:2:4 by weight, with a water-cement ratio of 0.6.

Mixing was performed hand on an immaculate concrete floor, with the components properly blended in the dry condition twice before gradually adding water and fully mixing the concrete.

The concrete specimen was further mixed by rotating the cement, water, and aggregate mixture until the end result was homogeneous in color and consistency.

The specimen cubes were cast within a steel mould of 150x150x150mm, with the mold and base fastened together. The interior of the mold was smeared with oil to facilitate removing of the firm concrete.

The new concrete mixing for every batch was properly compacted using tamping rods to eliminate air trapped inside, which can impair concrete strength.

Measuring Compressible Strengths:

The compressive capacity of the concrete cubes was evaluated at 7, 14, 21, 28, and 90 days after curing using compressed testing equipment. The cube was put between compression plates straight to the surface and crushed at a steady pace (without shock) until collapse occurred. The maximum load at breakdown and strength of compression were read through the machine's top screen. The strength at compression was determined by dividing the greatest load in Newtons of force (N) by the specimen's average cross-sectional area in square millimeters (mm2).

Table 2

Pure The concrete's Structural Properties

Test	Concrete mixed with fresh water	Concrete mixed with salt water
Slack(mm)	75	80
Initial time (min)	35	35
Final time (min)	280	280

Table 3 indicates a longer setting time, suggesting that flashing and incorrect set issues are not a concern for concrete mixed with sea water. Additionally, the slump number indicates that it is within the typical range for concrete.

Table 3

Test	Fresh water	Sea water
PH	7	7.8
Electrical Conductivity	1053 micro s/cm	57.9 Micro s/cm
Total dissolve solid	1490 mg/l	31200 mg/l
Chloride	220 mg/l	6000 mg/l
Nitrate	-	-
Hardness	246 mg/l	-
Calcium	62 mg/l	210.6 mg/l
Magnesium	28 mg/l	1644 mg/l
Acidity	-	-
Alkalinity	-	0.8 mg/l
Iron	-	0.14 mg/l
Sulphate	110 mg/l	1400 mg/l
Potassium	-	475 mg/l
Chromium	-	0.03 mg/l
Phosphate	-	1.10 mg/l
Salinity	-	32. 6 g/l
Total suspended solid	-	-
Total solid	-	-
Odour	Unobjectionable	Unobjectionable
Colour	-	Blue
Temperature	20 OC	32.6 OC

Table 4

Fine Aggregate

Size (mm)	Passing (%)
10	100
3.35	96
2.36	95
1.70	81
0.212	2.5
0.125	0.8
0.063	0.2
Receiver	-

Table 5

Rough aggregate

Size (mm)	Passing (%)
30	100
26.5	78
25	47
20	16
14	2.9
10	0.2
3.35	0
Receiver	-

Table 6

Compressive Strength

Concrete designation	Curing days	Average weigth of cube (Kg)	Average crushing load (kN)	Strength (N/mm2)
FF	7	8.45	275.5	12.24
	14	8.53	335	14.89
	21	8.80	355.5	15.80
	28	9.05	449.5	19.98
	90	9.04	475	21.11
FS	7	8.433	290	12.89
	14	8.70	330	14.66
	21	8.75	300	13.33
	28	8.87	422	18.75
	90	9.02	450.5	20.22
SF	7	8.50	22	14.31
	14	8.77	370	16.44
	21	8.60	385.5	17.13
	28	8.84	453.5	20.16
	90	9.20	491.6	21.85
SS	7	8.55	310	13.78
	14	8.80	405	18
	21	9.08	445	9.91
	28	9.35	493.5	21.93
	90	9.40	520.7	23.14

Perform & Result:

Discovered that, throughout the course of all curing days, the strength of concrete that has been saltwater cured increases consistently and surpasses that of the control cast (FF). At 28 days, the 1:2:4 mix's compressive strength, or around 20N/mm2, is comparable to the concrete batches FF's compression strength.

Furthermore, it was observed that even after 28 and 90 days, respectively, the strength of the concrete samples that were cast in salt water (SF) and cured in fresh water (SF) had increased.

Actually, fresh-fresh water conditions apply to structures constructed on main and interlards. Most fresh-salt water habitats are located in structures or buildings that are next to lagoons or the ocean. Although situations involving salt and fresh water are rare, they are evident when there is a shortage of fresh water or when the surface water that is available is salinized. Facilities built close to an ocean or sea are the main places where salt-salt water situations arise. The last option is to paint or coat the steel with a fresh water-prepared cement slurry to prevent corrosion of steel buried in prestressed or reinforced components. It is also feasible to design the member with a larger concrete cover.

References:

1. Joseph, A. (1824) «Properties of Concrete», Concrete Technology, No.2, pp. 74–102. Ken Hover (2005) «Strategies for Reducing Shrinkage Cracking in Flatwork».