EFFECT OF SUPHURIC ACID ON HIGH PERFORMANCE MORTAR

GUIDED BY:MR. S. Nachimuthu

Presented BY:J. Uma BharathiP. KanageswariSonam Choden

ABSTRACT Durability is the property required for fulfilling all the service

requirements of a mortar structure such as an RCC framed building, during its intended life, with normal expected maintenance.

The majority of masonry structures exhibit excellent long-term performance with comparatively low maintenance cost. Durability of a masonry structure is influenced by many factors including the durability of both the masonry units and mortar, as well as proper installation of a damp proof course; the durability of the mortar contributes significantly to the overall durability. Mortars used in masonry structures exposed to aggressive environments are designed to resist a range of possible physical and chemical degradations. The physical forms of degradation may be caused by abrasion from wind action, salt crystallization and freeze-thaw action; the chemical form of deterioration is usually caused by reactions with soluble salts.

The sulphuric acid solution can harm the structure which may be present in the ground water, polluted building materials, sea water, etc. The ordinary mortars have been ineffective over this environmental condition, hence letting us to adapt high performance mortar.

1. INTRODUCTION

I. Mortar:Cement mortar is a building compound created by mixing sand and a selection of aggregates with a specified amount of water. The mortar can be used for a number of applications, such as plastering over bricks or other forms of masonry. Sometimes referred to as sand cement, mortar blends today often incorporate different grades of plastics to create various types of polymer cement mortars.

II. HIGH PERFORMANCE MORTARHigh performance mortar is a mortar mixture, which possess high durability and high strength when compared to conventional mortar. According to ASTM-C270, if the 28 days compressive strength of mortar is above 17.5 N/mm2 it is called as high performance mortar.

 

3. CAUSES OF MORTAR DETERIORATION• DETERIORATION BY SURFACE WEAR

• CRACKING BY CRYSTALIZATION OF SALTS IN PORES:

• DETERIORATION BY FROST ACTION

• CHEMICAL CAUSES DETERIORATION

o SULPHATE ATTACKo ACID ATTACK

CHEMICAL ATTACKS

• Carbonation

• Acid attack

• Sulfate attack

• Chloride attack

• Sea water attack

CARBONATION

Ca(OH) 2+Co 2 CaCo 3

Leads to Carbonation shrinkage.

Reduce the PH of the pore water and leads to corrosion.

Lab test-Phenolphthalein test

ACID ATTACK

It Converts Calcium compounds into calcium

salts

2HCL+Ca(OH) 2 CaCl 2+2H 2O

H 2So 4+Ca(OH) 2 CaSo 4+2H 2O

SULFATE ATTACK

• Sulfuric acid is very corrosive which initiate the sulfate attack

which leads to corrosion.

• Corrosion of mortar consist of two stages

• H 2So 4+Ca(OH) 2 CaSo 4.2H 2O(Gypsum)

• Gypsum+C 3A Expansion cracking of mortar

PROCEDURE:

1. The mortar cube of 1:2 with water content of 0.2, 0.3 and 0.4 were casted .

2. After curing the mortars, it is submerged in Sulfuric acid bath having different normality's such as 0.3, 0.5, 1.0.

3. The normality of sulphuric acid may get alter in time, therefore the normality is checked time to time by titration.

4. By using the following formula :

V1N1=V2N2

V1=

For 0.3N add 8.5ml of sulfuric acid in 1000ml of water

1000 X 0.336

5. Taking the mortar weight each week after submerging in sulphuric acid.

6. The load carrying capacity is found by using compression testing machine.

Erosion on mortar

RESULTS

FOR 0.3N SULPHURIC ACIDSL.NO SAMPLE WEIGHT

KGWEIGHT LOSS IN 7 DAYSKG

WEIGHT LOSS IN 14 DAYSKG

1 0.2 792 773 753

2 0.2 749 729 707

3 0.2 782 762 740

4 0.3 766 751 727

5 0.3 745 732 705

6 0.3 751 737 711

7 0.4 810 803 795

8 0.4 790 874 778

9 0.4 803 796 787

FOR 0.5N SULPHURIC ACIDSL.NO SAMPLE WEIGHT

KGWEIGHT LOSS IN 7 DAYSKG

WEIGHT LOSS IN 14 DAYSKG

1 0.2 679 655 628

2 0.2 674 653 627

3 0.2 652 630 601

4 0.3 733 713 688

5 0.3 746 726 699

6 0.3 781 762 738

7 0.4 835 827 814

8 0.4 843 833 821

9 0.4 852 842 832

FOR 1N SULPHURIC ACIDSL.NO SAMPLE WEIGHT

KGWEIGHT LOSS IN 7 DAYSKG

WEIGHT LOSS IN 14 DAYSKG

1 0.2 774 748 710

2 0.2 792 777 742

3 0.2 794 767 730

4 0.3 806 783 752

5 0.3 777 754 723

6 0.3 781 759 724

7 0.4 827 811 790

8 0.4 807 791 771

9 0.4 829 817 795

FOR 0.5N SULPHURIC ACIDSL.NO SAMPLE WEIGHT

KG

WEIGHT LOSS IN 7 DAYSKG

WEIGHT LOSS IN 14 DAYSKG

1 0.2 730 690 635

2 0.2 715 671 614

3 0.2 691 655 598

4 0.3 794 760 716

5 0.3 767 734 690

6 0.3 789 751 708

7 0.4 796 773 733

8 0.4 821 799 762

9 0.4 814 792 750

FOR 0.3N SULPHURIC ACIDSL.NO SAMPLE WEIGHT

KG

WEIGHT LOSS IN 7 DAYSKG

WEIGHT LOSS IN 14 DAYSKG

1 0.2 679 655 628

2 0.2 674 653 627

3 0.2 652 630 601

4 0.3 733 713 688

5 0.3 746 726 699

6 0.3 781 762 738

7 0.4 835 827 814

8 0.4 843 833 821

9 0.4 852 842 832

FOR 1N SULPHURIC ACIDSL.NO SAMPLE WEIGHT

KGWEIGHT LOSS IN 7 DAYSKG

WEIGHT LOSS IN 14 DAYSKG

1 0.2 724 676 609

2 0.2 743 694 627

3 0.2 769 720 651

4 0.3 794 753 694

5 0.3 740 700 642

6 0.3 735 690 630

7 0.4 801 763 711

8 0.4 794 756 703

9 0.4 799 761 709

FOR 0.5N SULPHURIC ACIDSL.NO SAMPLE LOAD IN KG LOAD CARRYING

CAPACITY IN N/MM2

1 0.2 4750 9.7

2 0.2 4250 8.7

3 0.2 4500 9.2

4 0.3 4000 8.2

5 0.3 3500 7.1

6 0.3 4250 8.7

7 0.4 3750 7.7

8 0.4 3750 7.7

9 0.4 3500 7.1

FOR 0.3N SULPHURIC ACIDSL.NO SAMPLE LOAD IN KG LOAD CARRYING

CAPACITY IN N/MM2

1 0.2 6000 12.2

2 0.2 5500 11.2

3 0.2 4500 9.2

4 0.3 4750 9.7

5 0.3 4500 9.2

6 0.3 5500 11.2

7 0.4 4250 8.7

8 0.4 4750 9.7

9 0.4 4250 8.7

FOR 1N SULPHURIC ACIDSL.NO SAMPLE LOAD IN KG LOAD CARRYING

CAPACITY IN N/MM2

1 0.2 3000 6.1

2 0.2 3000 6.1

3 0.2 3750 7.7

4 0.3 3000 6.1

5 0.3 2500 5.1

6 0.3 3250 6.6

7 0.4 2750 5.6

8 0.4 3250 6.6

9 0.4 3000 6.1

CONCLUSION:Increase in water content leads to

decrease in weight loss due to sulphate attack.

Strength of mortar decreases due to sulphate attack.