Maria del Pilar Durante Ingunza

Use of Sludge Ash as a Stabilizing Additive in Soil-Cement Mixtures for Use in Road Pavements

AbstractThis paper presents a study evaluating the use of sludge ash as a stabilizing additive to soil-cement mixtures for use in base and subbase road pavements by investigating the mechanical behavior of these mixtures. The methodology consisted of materials testing, including the geotechnical characterization of the soil and the mechanics of the soil-cement and the soil-cement-sludge ash mixtures. An unconfined compression test evaluated the mechanical behavior of soil-cement mixtures with cement contents of 3, 6, and 9% compressed with normal, intermediate, and modified pressures. The sludge ash contents added were of 5, 10, 20, and 30%. The results indicate increasing strength for all ash levels studied. The largest gain in strength was for a mixture with 20% sludge ash, which increased the strength by 26% compared with the mixture without sludge ash.

Sewage Sludge as Raw-Material in Asphalt Mixtures

The aim of this study is to assess the volumetric and mechanical behavior of concrete asphalt mixtures, using natural sludge as a partial substitute for the tiny aggregate and calcined sludge as filler. This assessment was performed based on technical and environmental parameters, using laboratory tests obeying current Brazilian norms, according to international standards. The addition of natural sludge to the mixtures has increased stability, increased air voids contents of the mixtures. The addition has compromised mixture adhesiveness. With respect to the addition of calcined sludge to the mixtures, the mixtures with calcined sludge displayed the same behavior as those with cement. It was observed decrease in empty space volume of the mixtures and consequent increase in empty space-bitumen relation and increased stability. The mixture addition of natural sludge that has the best mechanical and volumetric performance is the one with 7.5% of natural sludge in the granulometric composition of the mixture. The mixture with 1% of calcined sludge had the best volumetric and mechanical performance.

Use of Septic Tank Sludge as Raw Material in the Manufacture of Bricks

The present paper analyzes the feasibility of using septic tank sludge subsequently treated in an anaerobic pond as raw material in the ceramic industry. An experiment was conducted involving the manufacture of 500 bricks using 6.5% (dry weight) of sludge at a ceramic plant in the Northeast of Brazil. To reproduce the methodologies, the same conditions and methods used by the local ceramic industry were adopted. To evaluate the bricks produced and environmental risk, compressive strength, water absorption and lixiviation tests were carried out, obeying current Brazilian norms, according to international standards. Results show the technical feasibility of using sludge as raw material in the red ceramic industry, highlighting the firing temperature of the bricks as a determinant variable. Moisture content of the sludge-clay mixture emerges as limiting factor in the manufacturing process. The moisture value determined as acceptable in the study was 22%.

Recycling of Kaolin Processing Waste as Aggregate in Asphalt Concrete

The aim of the present study is to assess the incorporation of kaolin processing waste as partial substitute for aggregates in asphalt concrete. Mixtures elaborated from the conventional mixture with the gradual incorporation of kaolin processing waste (5 to 40%) were evaluated by volumetric composition, mechanical behavior and susceptibility to moisture tests, obeying current Brazilian norms, according with international standards. The results show that the coarse kaolin waste displays grains with varying diameters, and, as such, can substitute part of the conventional aggregates and filler used in an asphalt mixture. Moreover, its mineralogical composition showed the same minerals in the composition of conventional aggregates used in paving. The assessment of the mechanical behavior of these mixtures indicate that the increased waste levels in the mixtures studied caused an increase in stability and a reduction in tensile strength. When susceptibility to moisture was considered, the results indicate that up to 25% of residue can be used as a substitute for conventional aggregates.

Petrographic Characterization of Waste Rocks: Applicability as Concrete Aggregates

Petrographic characterization showing mineralogical, textural and structural aspects of rocks is an essential technique in the study of the performance of concrete aggregates, specifically on the investigation of the alkali-aggregate reaction (AAR). The assessment of this deleterious reaction, considered as one of the most important pathologies, is a required test in the waste utilization programs. In this paper, waste rock samples of a feldspar mine were studied by optical microscopy, approaching aspects related to morphology, texture and alteration degree to determine the potential alkali reactivity for use as aggregates in cementitious mixtures. The rock studied shows characteristics that make it susceptible to be a reactive aggregate, due to, mainly, the strained quartz and the microcrystalline quartz. However, these results must be confirmed by standard mechanical test methods.