This short work details the history of Type K shrinkage compensating cement.

Shrinkage compensating concrete is one of the most common products currently used to mitigate the influence of drying shrinkage cracking in slabs, beams and other structural components. Type K expansive concretes have proved effective for prevention of structural and aesthetic damage due to tensile cracking in many modern applications. However, the ACI 223R-10 technical guide still indicates that a shrinkage compensating slab cannot expand adequately if it is surrounded on all sides by mature reinforced concrete. The objective of this project was to investigate whether the presence of a stiff external restraint condition, which may be provided by adjoining concrete, prevents a Type K expansive concrete slab from compensating for shrinkage. To investigate this behavior, the field condition of a slab-to-slab interaction was simulated using a steel restraint system with varying degrees of stiffness and amounts of Type K expansive cement component. Test frames were instrumented to evaluate the force and displacement responses of the Type K expansive concrete to the different boundary conditions provided by varying the steel restraint system. The results of this investigation support a conclusion contrary to that currently found in the ACI 223R-10 guiding document. This study concludes that a Type K expansive cement concrete does not suffer a severe reduction in shrinkage compensation in the presence of a very stiff boundary condition.

Owners, engineers, and contractors have been forced to contend with drying shrinkage for as long as portland cement has been used in slabs-on-ground, containment structures, and other concrete elements. The resulting cracks and warping have long-lasting impacts on both the performance of the concrete and the lifetime maintenance cost. Various construction methods have historically been used to mitigate this issue including modified mix designs, curing compounds, joint detailing, and transfer devices to reduce warping (curling). With advances in type K shrinkage compensating cement technology, however, designers and contractors now have access to a concrete that can eliminate shrinkage cracks, extend joint spacing to extremes, vastly reduce costly joint construction, and shorten construction schedules. This solution reduces not only construction costs but also maintenance costs on the structure for years to come. Shrinkage compensating concrete (SCC) produced using ASTM C845 Type K cement has been used in floors, elevated building decks, bridge decks, post-tensioned concrete, and containment structures since the mid 1960’s. Today, Type K SCC cement technology is even better understood, making way for higher performing concrete elements.

Expansive component systems provide the possibility to control the effects of concrete drying shrinkage in civil engineering applications, promoting durability for new construction and repair alternatives. Drying shrinkage is a natural consequence of concrete upon water loss after hardening. When there are restrictions such as internal reinforcement, adjacent structural elements and subgrade friction, concrete drying shrinkage can lead to cracking if no provisions are considered on the mix design or on the construction procedure. Expansive component Type G reacts chemically with Portland cement and water in the concrete mix to produce calcium hydroxide platelet crystals, which after setting, produce a volume increase. Providing internal or external restrictions, a concrete, that contains an expansive component system, can induce compression stress in the concrete mass and tension stress in the reinforcement. Concrete cracking can be reduced because such induced compression stress counteracts the tensile stress in the concrete mass caused by drying shrinkage. This article comprises a variety of applications of concrete, including the expansive component Type G, in Mexico as a solution means of improved functionality and durability of modern construction.

Type K Shrinkage Compensating Concrete (SCC) concrete is uniquely suited for use in slabs and walls because it typically requires fewer expansion joints than a convention portland cement (PC) concrete. This allows for continuous placement of much larger slabs and walls and facilitates the construction of high performance smooth slabs with few interruptions. Typically shrinkage-compensating concrete construction practice is to pour adjoining wall sections a minimum of five days apart in order to allow for the initial expansion of the material. The need for unrestrained expansion is implied in the ACI 223R-10 Design Guide in Chapter 5 in a discussion on sequencing the placement of wall segments. This paper discusses testing that was performed at two different locations, spanning both two different times of year and two unique climates. The tests used vibrating wire strain gages (VWSG) to investigate the restrained behavior of a wall segment in a six million gallon clear well tank in Springfield, IL, as well as the unrestrained behavior of two slabs-on-grade in Los Angeles, CA. Measurements were taken for a minimum of 30 days and a maximum of 170 days. Testing results are then compared to similar scenarios using ordinary PC concrete.