Control Low Strength Material (CLSM) is a self-compacting, easy flow and low-strength material. CLSM is used primarily as backfill, void fill, and utility bedding in lieu of conventional compacted fill. Since CLSM needs no... [ view full abstract ]
Control Low Strength Material (CLSM) is a self-compacting, easy flow and low-strength material. CLSM is used primarily as backfill, void fill, and utility bedding in lieu of conventional compacted fill. Since CLSM needs no compaction, the trench width or excavation size required can be minimized, thus achieving cost reductions.
In this research work, low amounts of Portland Cement (PC) and high volumes of Class F fly ash (FA) as a supplementary cementing material were employed. Several amounts of fine steel slag (SL) aggregates were also used in the CLSM mix productions. Both the excavation and structural filler materials were designed with a maximum compressive strength at 28 days of 1.7 MPa and 8 MPa, respectively.
In this research study, three experimental phases were carried out: 45 kg of cement and 360 kg of FA were employed in the first two experimental phases and 90 kg of cement and 270 kg of FA were employed in phase 3. In phase 1, a water-binder ratio of 0.55 was defined and 0%, 20%, 50% and 100% of SL aggregates were employed to produce a structural filler material. However, due to the bleeding and segregation of the CLSM materials when employing 100% of SL aggregates, it was decided to employ quantities inferior and up to 50% SL aggregates replacement in the following 2 phases (phase 2 and phase 3). All the mixtures were validated by means of the flow test in fresh state and compressive strength at 28 days, as defined in the ACI –229R report recommendations.
The density, absorption capacity, splitting tensile strength, modulus elasticity and material weight loss after exposing the specimens to the wetting and drying test were determined for all the mixtures in the three experimental phases.
CLSM suitable for excavation (phase 2), can be achieved with up to 50% of SL the resulting material having similar fresh-state and hardened-state properties to that of the control mix with 45kg of cement and 360kg of fly ash and employing a water to binder ratio of 0.71. A lower water-cement ratio with a small amount of superplasticizer was required in order to produce materials to be applied to structural fills. It was determined that the results obtained from the employment of 50% of SL in phase 3, improved the physical and mechanical properties of the materials for structural fills when contrasted to those produced only employing natural aggregates.
The employment of high-volume FA mixes with up to 50% of SL aggregates guaranteed adequate properties to the CLSM material production, including both the environmental and the durability aspects evaluated by the leaching, wetting and drying test, respectively.
Proof of compliance - requirements and quality assurance , New products, applications and machinery
