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.

This paper reexamines the authors’ experimental results on the dimensional stability of concrete slab-on-ground under a variety of environmental conditions. The experiments considered the dimensional properties of concrete slab materials using both Demec targets and vibrating wire strain gages. Realistic slab-on-ground sections were investigated in this study in that the concrete slabs were exposed to a controlled environment on the top surface and to actual ground moisture on the bottom surface. The concrete materials tested were normal Portland cement concrete (PCC), high strength concrete (HSC), concrete with shrinkage reducing admixtures (SRA), and concrete with calcium sulfoaluminate cement (CSA). The compiled database contains: 1) standard concrete material test results; 2) joint movements in concrete slab-on-ground; and 3) internal relative humidity and temperature through the slab-on-ground depth. The experimental results revealed that CSA was quite stable with little long-term shrinkage/cracking or warping, whereas PCC and HSC had continuing crack growth during 600 days of curing. The SRA exhibited a modest reduction in shrinkage/crack at the early stage, and while this decrease extended for the length of the testing no further decrease in the shrinkage growth or sectional stability was noted when compared to PCC at the end of 2 years. Evaluation of the vibrating wire strain gage method of measuring long term concrete shrinkage was found to be less prone to user bias and more accurate than the Demec target method or the ASTM C157 method.

Samples of Type K shrinkage-compensating cement from all 17 mills producing that cement in 1974 were obtained and evaluated for compliance with the specification that was proposed at that time for these types of cements. The cements were also evaluated for specific gravity, fineness, heat of hydration, and expansion and drying shrinkage in mortars. An X-ray diffraction analysis was also made for each cement in an attempt to compare cements to note significant differences in composition or relative amounts of constituents. A standard concrete mixture was also made with all the cements and evaluated for air content, slump, compressive strength, expansion, and drying shrinkage. The results from these evaluations are revisited. The application of the 1974 proposed specification called attention to several short-comings in that specification.

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.