Design and application of controlled low strength materials as a structural fill Vahid Alizadeh ⇑ , Sam Helwany, Al Ghorbanpoor, Konstantin Sobolev University of Wisconsin-Milwaukee, Department of Civil Engineering and Mechanics, 3200 N. Cramer St., EMS Building, Milwaukee, WI 53211, United States highlights  CLSM mixtures were developed as structural fill for bridge abutments.  Performance criteria were compressive strength and flowability.  Higher temperatures promote early strength gain in CLSM mixtures.  Higher temperatures lower the rate of later-age strength gain in CLSM mixtures.  Bond strength performance of the CLSM to steel anchors was investigated. article info Article history: Received 6 July 2013 Received in revised form 3 December 2013 Accepted 5 December 2013 Keywords: Controlled low strength materials (CLSM) Mixture proportioning Bridge abutment Flowability Compressive strength Bond strength Pullout test abstract Controlled low strength materials (CLSM) are flowable and self-compacting construction materials that have been used in a wide variety of applications. This paper describes design of an optimized CLSM mixture that was used as a structural fill for construction of a bridge abutment. The main performance criteria for selection of a potential CLSM mixture were compressive strength to support the bridge loads, excavatability and flowability to fill the entire abutment in one continuous pour. Several CLSM mixtures were developed and tested in the laboratory for engineering properties including flowability, density, compressive strength and stress–strain behavior. Since it was a critical area of concern in design of the CLSM bridge abutment, the bond strength performance of the CLSM to steel anchors was also investigated. In pullout tests, a CLSM mixture with higher compressive strength resulted in higher bond strength and more brittle slippage. A numerical simulation of pullout tests indicated that the bond strength decreases with increase in bar size and embedment length. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Recently, the use of controlled low strength materials (CLSM) as a cost and time efficient substitute of compacted fills has grown considerably. CLSM is a mixture of soil or aggregate, cementitious materials, fly ash, water and sometimes chemical admixtures that hardens into a material with a higher strength than the soil. CLSM, also known as flowable fill, is defined by the ACI 229R-99 [1] as a flowable self-compacting cementitious material that has a speci- fied 28-day compressive strength of 8.3 MPa (1200 psi) or less. CLSM can be used as a replacement for compacted backfill and is defined as excavatable if the 28-day compressive strength is 2.1 MPa (300 psi) or less. Compared with conventional earthfill materials that require controlled compaction in layers, CLSM has several inherent advantages for use in construction, including: ease of mixing and placement, ability to flow into hard-to-reach places, self-leveling characteristics, rapid curing, incompressibility after curing, which reduce equipment needs, labor costs, and associated inspections. Moreover, environment-friendly utilization of by-product materi- als such as fly ash or foundry sand in CLSM translates into greater economy and the potential for a sustainable construction [2,3]. The challenge in the application of CLSM is that it behaves like a compacted soil. Therefore, much of the available knowledge and publications on its applications have fallen between concrete mate- rials engineering and geotechnical engineering, and it often does not receive the level of attention it deserves by either group [4]. CLSM is a multipurpose construction material that has been used in a wide variety of applications that are well documented in the literature. Among the many applications of CLSM, the following are the most important [1]: backfill for building excava- tions, utility trench, and retaining walls; structural fill for footings, road bases and utility bedding; and void-filling for underground 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2013.12.006 ⇑ Corresponding author. Tel.: +1 414 236 0244. E-mail addresses: alizadeh@uwm.edu (V. Alizadeh), helwany@uwm.edu (S. Helwany), algh@uwm.edu (A. Ghorbanpoor), sobolev@uwm.edu (K. Sobolev). Construction and Building Materials 53 (2014) 425–431 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat