Abstract
In some cases of emergency backfill engineering projects, traditional backfill materials cannot meet the requirements of fast construction due to their long curing time. This study presents a new kind of rapid hardening controlled low strength material, which utilizes both rapid hardening sulphoaluminate cement and recycled fine aggregate from urban red brick construction waste. Totally, sixteen mixtures were prepared for the experiment with different cement-to-sand ratios and water-to-solid ratios. The flowability and bleeding rate of fresh mixture were measured to evaluate its workability, and the compressive strength of hardened mixture was tested to evaluate its rapid hardening and mechanical properties. Test results indicate that rapid hardening controlled low strength material containing recycled fine aggregate from urban red brick construction waste can achieve the desirable flowability, but the bleeding rate increases with the increase of flowability. In addition, 2-hour compressive strength can reach 0.08 - 0.12 MPa, and 4-hour compressive strength is 0.32 - 1.54 MPa, which can meet the requirements of emergency backfill construction. At last, based on the derived compressive strength, a fitting model for predicting compressive strength evolution of this new rapid hardening backfill material is developed, which fits accurately with these experimental data.
Highlights
Chinese urban construction waste generally has a high content of waste concrete, waste mortar, waste red clay brick and tiles, waste soil, the dust and other impurities
This study presents a new kind of rapid hardening controlled low strength material, which utilizes both rapid hardening sulphoaluminate cement and recycled fine aggregate from urban red brick construction waste
Test results indicate that rapid hardening controlled low strength material containing recycled fine aggregate from urban red brick construction waste can achieve the desirable flowability, but the bleeding rate increases with the increase of flowability
Summary
Chinese urban construction waste generally has a high content of waste concrete, waste mortar, waste red clay brick and tiles, waste soil, the dust and other impurities. Over the past several decades, a significant research effort has begun aiming at the re-use of construction waste in civil engineering field, e.g. to produce recycled concrete [1], recycled mortar [2]. It is too difficult to use on road engineering due to its poor quality. In urban road construction and maintenance, the construction time limit is very urgent for reducing the effect on the surrounding residents' life. The present traditional backfill materials, such as cement stabilized soil, graded gravel and lime-fly ash stabilized aggregate etc., cannot meet the requirements of fast construction due to their long curing period. The traditional backfill materials cannot be compacted effectively due to the narrow backfill space or the limitation of pipeline and other structures, which often results in some engineering damages [5]
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