Carbon reaction with mortar

The different types of admixtures, known to reduce alkali-aggregate reactions, can be divided into two groups those that are effective in reducing the expansion due to the alkali-silica reaction, and those that lower expansions resulting from the alkali-carbonate reaction. For the alkali-silica reaction, reductions in the expansion of mortar specimens have been obtained with soluble salts of lithium, barium and sodium, proteinaceous air-entraining agents, aluminum powder, CUSO4, sodium silicofluoride, alkyl alkoxy silane,... 

After the sintered substance has cooled, extract it from the crucible and triturate it in a porcelain mortar. Treat a small part of the triturated substance with water, filter the solution, and test its reaction with litmus. Pass a stream of carbon dioxide through the solution. Note the odour that appears. Explain what happens. Write the equations of the reactions. 

C) Preparation of Benzamide (Sm.). Perform the experiment in the hood. Place 5 g of ammonium carbonate in a mortar and pulverize well. Add 2 ml of benzoyl chloride and mix with the pestle for a few minutes. Add 2 ml of concentrated aqueous ammonia, and allow to stand for 10 minutes. Transfer the reaction mixture... 

In hardened cement-based composites the transportation of liquids and gases through pore and microcrack systems plays a very important role in many processes, such as hydration of Portland cement, pozzolane effects of microfillers, carbonation, corrosion of cement paste and reinforcement due to reaction with external agents, shrinkage and creep, etc. These processes are partly described in respective Sections 4.1, 4.3, 6.5 and 11.5. Only basic information is reiterated below concerning the flow of liquids and gases through concretes and mortars. 

Many studies have been carried out on old concretes to determine the reactions that could be responsible for deterioration. Sarkar, et al.,1 examined a seventy-five year old stone building containing mortar that had shown signs of distress. The presence of g5q)sum (endothermic effect at 133°C), quartz (endothermal peak 573°C), calcium carbonate (endother-mal effect at 900°C), and thamdite (endotherm at 880°C) could be identified. It was concluded that one of the main causes of deterioration was the interaction of SO2 from the atmosphere with mortar and sandstone. In another study,a fifty year old concrete was subjected to examination... 

Steel in cement mortar is in the passive state represented by field II in Fig. 2-2. In this state reinforcing steel can act as a foreign cathodic object whose intensity depends on aeration (see Section 4.3). The passivity can be lost by introduction of sufficient chloride ions or by reaction of the mortar with COj-forming carbonates, resulting in a considerable lowering of the pH. The coordinates then lie in field I. The concentration of OH ions can be raised by strong cathodic polarization and the potential lowered, resulting in possible corrosion in field IV (see Section 2.4). 

Reaction.—i. Grind up in a mortar i c.c. of sulphonic chloride with 5 grams powdered ammonium carbonate, and leare on the water-bath until the smell of the sulphomc chloiide has gone. Add water, filter, and wash, and crystallise the residue of benzene sulphonamicle from spirit, CqHjSO.CI -f 2NH4HCOJ = CoHr,SO,jNHo + 2H20- -2CO,-fNH,Cl. 

Preparation of Sodium Vanadate. Put a thoroughly triturated mixture of 0.5 g of vanadium(V) oxide and 1 g of sodium carbonate into a crucible and place it into a crucible furnace. Raise the furnace temperature to 800 °C and control the course of the process. Lower the hot crucible into a beaker with water to separate the melt easily from the crucible walls. Crush the melt in a mortar and treat it with water while heating. Evaporate the solution until crystallization begins. Examine the crystals under a microscope. Write the equation of the reaction. 

Transfer both compounds into a porcelain mortar with dry carbon tetrachloride (about 20 ml). Rinse the walls of the weighing bottle that contained the sodium peroxide with a small amount of carbon tetrachloride (2-3 ml) and add this solution to the reaction mixture. 

Preparation and Properties of Sodium Ferrite. Mix 2 g of an iron(III) oxide powder and 20 g of anhydrous sodium carbonate in an iron crucible. Fuse the mixture on the flame of a gas burner or in a muffle furnace at 800-900 °C. Pour out the hot melt onto a glazed tile. When it solidifies, grind pieces of the melt in a mortar and spill the powder into a beaker with water. What settles onto the bottom of the beaker Write the equations of the reactions. What type of oxides does iron(III) oxide belong to Which salts hydrolyze more strongly, iron(II) or iron(III) salts What does this depend on ... 

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