Tests were performed on several limestones. Indiana limestone is a gray oolitic carbonate rock, mainly composed of calcite (> 97.3 wt%), and a small amount of other components, such as Al2O3, SiO2 and MgCO3 . It consists mainly of calcite-cemented oolites, but a small amount of sparry calcite crystals may be also present. Cordova Cream limestone (also known as Austin chalk) contains calcareous microorganisms composed of clear calcite set in a structureless matrix of microcrystalline calcite, and it is a lightly bedded . Cadeby Stone is a light cream- colored stone classified as dolo-oomicrite with dolomite as major component and small amounts of other components, such as iron oxides, calcite and barium sulfates. The MIP data  of this stone show a pore size distribution between 0.1 and 10 μm, and a total porosity measured by vacuum impregnation ~21.5 vol%. The amount of pores smaller than 0.1 μm is negligible, while 89% of the porosity is formed by pores in the range from 0.1 to 5 μm. The sorptivity of this stone is 0.064 ± 0.02 cm/min1/2 and the capillary water uptake 15.7 vol%. Highmoor stone is a dolo- microsparite white magnesian limestone consisting of fine dolomite crystals in micritic cements. Patches of dark iron oxide can be observed in thin sections. This stone has spherical pores and a homogeneous structure. The MIP data  show a unimodal pore size distribution. The total porosity measured by vacuum impregnation is around 24.6 ± 1.4%, 47% of the pores being larger than 5 μm. The amount of pores smaller than 0.1 lm is negligible. The sorptivity of the stone is 0.055 ± 0.02 cm/min1/2 and the capillary water uptake 11.8 vol%.
Polyacrylic acid with a molecular weight of 5000 was obtained in the form of a 50 wt% aqueous solution (Polysciences Inc).
Thermogravimetric analysis (TGA) was used to assess the adsorption of PAA on calcite samples. Pure calcite powder and PAA solutions were run in a Perkin Elmer TGA 7 (using nitrogen purge gas) as controls. To determine the concentration of PAA (wt%) in the control solutions, samples were heated in the TGA to 110 °C to drive off water and held at that temperature until they reached constant weight. The percent of sample weight remaining at this point was then taken as the concentration by weight of PAA in the control solutions.
For determination of adsorbed PAA with different concentrations of bulk solution, samples of 250 mg of calcite powder were equilibrated with 10 ml of PAA solutions of varying concentrations by mixing with a magnetic stirrer for several hours. Solutions of both pH ~3.5 (pH of the PAA solutions) and of alkaline pH (obtained by addition of solid KOH) were used. The calcite was separated from the solution by vacuum filtration, so that both the filtrate and recovered powder could be analyzed via TGA. The stable weight at 110°C was taken as the initial weight for calcite samples, and the stable weight at ~325°C was taken as the weight after PAA had been decomposed . At higher temperatures, the pure calcite lost weight, but powdered calcite exposed to a KOH solution showed no significant weight lost at ≤ 350 ̊C, so that temperature was the highest used for these tests.
To evaluate how readily the PAA layer would be removed by the movement of water through the pores of a stone, washout experiments were performed. A 40 mg sample of the PAA- treated calcite samples from each PAA-calcite mixture was stirred with 5 ml of deionized water or calcite solution for 3 days, prior to thermogravimetric analysis.
It was observed that the pH of the PAA-calcite solutions changed over time, which could indicate a continuous change in the surface of the calcite and its zeta potential. To minimize this effect, we explored the effect of adjusting the pH of PAA solutions to different levels with KOH before mixing with calcite. One gram of calcite powder was continuously stirred with 40 ml deionized water or 0.2% PAA solutions adjusted to pH of 3.6 (no KOH added), 7.2, 8.2 and 9.2 using KOH, and the pH of each solution was checked over time. The 0.2% PAA solution was representative of the range of concentrations under investigation, within which a monolayer was expected.
Capillary rise tests were performed using the apparatus shown in Figure 2. The equipment is explained in more detail in ref. 18. The relevant properties of the stone are shown in Table 1.
Table 1. The last column is the concentration of PAA that would be expected to produce an adsorbed monolayer (~5 nm) or a fractional layer (1 nm) on the pore walls, as explained below. PAA solutions were prepared at concentrations 0.5, 0.75, 1.0, and 1.5 wt%, and the pH was adjusted to neutral using KOH. The solution was allowed to wick into samples of each stone with approximate dimensions of 5 x 5 x 25 cm. Once saturated, the samples were allowed to dry under ambient conditions, then placed into contact with a bath of 12 wt% sodium sulfate (as in Figure 2). The first test used two sets of stones: five samples of the Cadeby limestone and five of the Indiana limestone. Each set contained an untreated stone, as well as stones treated with neutralized PAA solutions at concentrations of 0.5, 0.75, 1.0, and 1.5 wt%. The test was run on ten samples of Cordova Cream limestone, using the treatment levels from the previous test.
To measure the density of the polymer solution as a function of its concentration, 15 solutions were made containing between 0.05 and 20 weight percent PAA. Each of these solutions was then analyzed using a Paar density meter with an accuracy of three decimal places.