Search

A comprehensive large-scale laboratory testing program using direct shear (DS), triaxial (TX), and simple shear tests was performed on municipal solid waste (MSW) retrieved from a landfill in the San Francisco Bay area to develop insights about and a framework for interpretation of the shear strength of MSW. Stability analyses of MSW landfills require characterization of the shear strength of MSW. Although MSW is variable and a difficult material to test, its shear strength can be evaluated rationally to develop reasonable estimates. The effects of waste composition, fibrous particle orientation, confining stress, rate of loading, stress path, stress-strain compatibility, and unit weight on the shear strength of MSW were evaluated in the testing program described herein. The results of this testing program indicate that the DS test is appropriate to evaluate the shear strength of MSW along its weakest orientation (i.e., on a plane parallel to the preferred orientation of the larger fibrous particles within MSW). These laboratory results and the results of more than 100 large-scale laboratory tests from other studies indicate that the DS static shear strength of MSW is best characterized by a cohesion of 15 kPa and a friction angle of 36° at normal stress of 1 atm with the friction angle decreasing by 5° for every log cycle increase in normal stress. Other shearing modes that engage the fibrous materials within MSW (e.g., TX) produce higher friction angles. The dynamic shear strength of MSW can be estimated conservatively to be 20% greater than its static strength. These recommendations are based on tests of MSW with a moisture content below its field capacity; therefore, cyclic degradation due to pore pressure generation has not been considered in its development. [ABSTRACT FROM AUTHOR]

• Solid wastes were used as raw material to prepare green calcium sulphoaluminate cement. • The prepared standard green calcium sulphoaluminate mortar meets the current commercial standard for 52.5 N cement. • Blinds of ordinary Portland cement and green calcium sulphoaluminate cement are used produce foamed concrete for the use of road embankment. • Both fresh and hardened state properties measurements show that the proposed mixture design allows for the application of cast-in-situ foamed concrete for road embankment. This paper aims at using green calcium sulphoaluminate (GCSA) cement to prepare foamed concrete for the use of road embankment. Solid wastes were used as raw material to prepare the GCSA cement. X-ray diffractometer (XRD) analysis shows that ye'elimite, gehlenite and belite are the main mineral phases in the produced GCSA clinkers, which is in accordance with the sulphoalumiate cement (CSA). Afterwards, the GCSA cement was blended with ordinary Portland cement (OPC) as binder to make the foamed concrete. The dosage of GCSA cement in the blinds was first optimized by comparing the 3-d and 28-d compressive strengths of mixes having different amount of GCSA cement. The optimized blinds (with 25% GCSA cement) was used to design foamed concrete mixes with wet density of 700 kg/m3, 800 kg/m3 and 900 kg/m3 using different amount of foam. Stability and consistency measurements were conducted at the fresh state. Mechanical measurements including compressive strength, flexural strength, splitting strength, elastic modulus and California bearing ratio were conducted at the hardened state. The measurements show that the proposed mixes have good spread ability and stability and high strength, elastic modulus and bearing capacity, indicating that the proposed mixtures can be accepted in industry practice for the in-situ foam concrete road embankment. [ABSTRACT FROM AUTHOR]