Degradation of cement-based materials by various organic acids in agro-industrial waste-waters

Interactions between hydrated cement paste and organic acids: Thermodynamic data and speciation modeling

“…For the first group, alteration mechanisms appear similar to those observed with strong acids such as nitric or hydrochloric acids [3,16,17]. For the second group, the physical and chemical properties of the acid salts (solubility, molar volume, affinity of salt for the cement matrix) seemed to influence the intensity of alteration and a correlation was observed between the molar volumes of the salts and the intensity of alteration of the matrix [18].…”

“…This value is still high and representative the range of our previous studies [13,17,18,22], to examine the different chemical species present in solution and their respective concentrations. However, preliminary stability diagrams covered a wider range (from 10 -5 to 1 mol/L) to highlight the major species in solution according to pH and acid concentration.…”

“…Accordingly, several tests of cement paste leaching by carboxylic acid solutions have been performed with acid concentrations of 280 mmol/L [18,21,44] or 300 mmol/L [19] with respect to the maximum concentration of acids found in liquid manure [3]. Also, total carboxylic acid concentrations have been measured in the range 300 -400 mmol/L during experiments on the biodegradation of Portland cement paste by fungi [22].…”

“…The total concentrations of carboxylic acids found in agrofood effluents are commonly high and range between several tens of mmol per litre for wine vinasses and several hundred mmol per litre for agricultural effluents (sugarcane vinasses, silage juices and liquid manure) [3,18]. Accordingly, several tests of cement paste leaching by carboxylic acid solutions have been performed with acid concentrations of 280 mmol/L [18,21,44] or 300 mmol/L [19] with respect to the maximum concentration of acids found in liquid manure [3].…”

“…Also, even though it is suspected, no real evidence of the role of polyacidity (e.g. citric and succinic acids) on the aggressiveness of the acid has been found so far [3,15,18]. Calcium is generally considered when studying the acid-cement interactions but the stability of aluminium should also be better investigated since most binders renowned as more stable than Portland cement in acidic environments are aluminium-rich materials (cement with slag, metakaolin-bearing binders, calcium aluminate cements).…”