Abstract
The purpose of this work was to assess the technical feasibility to valorize sludges, generated and stored at the Los Berros drinking water facility (PPLB), as raw material to produce building products (mortar and concrete) for the construction industry. The experimental study was divided into three stages: 1) sampling and characterization of PPLB sludges to determine their potential as raw material (sand substitute and supplementary cementing materials) to produce mortar and concrete; 2) production and characterization of specimens, using sludge in different weight ratios of mixtures with cement, lime, commercial mortar and plaster to prepare mortars and concretes and 3) comparison of compressive strength and drying contraction values between each specimen and the Mexican criteria to build mortars and concretes. The characterization results of the PPLB sludges showed that these residues could be used as a sand substitute in mortar and concrete formulations, since they were mainly comprised of this material (46.83%). The specimens prepared with a) the binary formulations, sludge-cement and sludge-mortar (90-10%) and b) the ternary formulation, sludge-lime-cement (90-5-5%), gave the best results (ranging from 130 to 150 kg cm-2) of the compressive strength test. The compressive strength values of these formulations were higher than those of equivalent mortar (types I, II and III) and cement mixtures (125 kg cm-2) prepared according to the Mexican complementary technical criteria to design and build masonry. These cementing properties exhibited by the PPLB sludges might be associated to their high content of aluminum and silicon oxides, 31.98 and 33.23%, respectively. Thus, calcium silicate (the main carrier strength in hardened cement) can be produced from lime hydration of cement with the active silica present in the sludge. Considering all these results, the PPLB sludges present a high feasibility for being valorized as raw materials (supplementary cementing material and sand substitute) to produce building products for the construction industry.
Highlights
In Mexico, 2.8 109 m3 year 1 of raw water are treated in approximately 307 drinking water facilities[1]
The experimental study was divided into three stages: 1) sampling and characterization of PPLB sludges to determine their potential as raw material to produce mortar and concrete; 2) production and characterization of specimens, using sludge in different ratios of mixtures with cement, lime, commercial mortar and plaster to prepare mortars and concretes and 3) comparison between results obtained in compressive strength and drying contraction tests for each specimen and the Mexican criteria to build mortars and concretes
Sampling and characterization of drinking water sludges: Table 3 and 4 show the values of the physicochemical parameters determined in the mixed sample of the PPLB sludges
Summary
In Mexico, 2.8 109 m3 year 1 (average flow rate) of raw water are treated in approximately 307 drinking water facilities[1]. PPLB starts in 1985 and the sludges generated have been traditionally stored in protected sites located in the PPLB. Drinking water sludges have traditionally been classified as wastes They present chemical compounds, such as calcium, silicon, etc., similar to those reported in literature as raw materials used to elaborate ceramic products[2,3,4,5,6,7,8,9], for the preparation of adsorbents and catalysts[10] and as soil substitute for land application and elaboration of fire-breaks in woods[11-15]. Due to the residual content of aluminum, drinking water sludges can be used to clarify wastewaters These residues have shown similar physicochemical characteristics to the raw materials used to elaborate sun-dried bricks, despite that this use
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