International Concrete Abstracts Portal

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.

Constructing large capacity, monolithically placed water storage tank slabs is a complex proposition. Previously, specifying low-shrinkage concrete mixes and monolithic placement of the slab within a specified time period was the prescribed method, yet shrinkage cracking still occurred. We felt more could be done to improve concrete placing and finishing, reducing shrinkage cracking and enhance durability. An investigation on the use of an Internally Cured Concrete mix on the floor and roof slabs of the Denver Water 10-Million Gallon [MG] (38-Million Liter [ML]) Lone Tree Tank No. 2 that Bates Engineering Inc. was designing was pursued. The tank floor and roof slab are each about 61,000 ft2 (5,700 m2) and would be monolithically placed. Laboratory trial batches performed determined plastic and hardened characteristics of the ICC as compared to traditionally proportioned mix designs. Tests performed in the laboratory included: compressive strength and drying shrinkage (ASTM C 157(1), modified 7-day saturation). An ICC mix was selected based on durability expectations. Results of the floor slab placement were successful and only two shrinkage cracks were observed, 7-day and 28-day compressive strength tests, workability and consistency surpassed expectations. As a result, it was decided to use ICC concrete on the remaining structural components.

Continual functioning of Liquid Containing Structures “LCS” is necessary for the well being of a society during and after an earthquake. While the seismic design criteria for buildings are primarily based on life safety and prevention of collapse, concrete storage tanks should be designed to meet the serviceability limits such as leakage. This study was aimed at evaluation of the leakage behavior of ground supported open top rectangular RC tanks under the effects of cyclic loading. Full-scale specimens representing a cantilever wall were designed and built to simulate leakage through the most critical region of the tank wall. A steel water pressure chamber was installed at the wall foundation connection region to simulate the effect of the water pressure on the induced cracks at the critical location of the tank wall. Cyclic loading was applied at top of the wall while the critical region of the wall was subjected to pressurized water. This study is limited to rectangular tanks in which the wall dimensions promote one-way behavior. It is concluded that in order for leakage to occur, the strain in the reinforcement at both faces of the wall need to be close to the yield level.

In Japan, a new super-workable concrete, which has higher flowability and filling capacity, has attracted attention as being effective in rationalization of concrete execution. It can be applied for simplifying placing work while securing high quality of reinforced concrete structures. Especially in case of heavily reinforced structures, it is highly applicable because of its excellent filling capacity or lower consolidation effort. For several years, the authors have studied improvements of workability of some special concretes, such as anti-washout underwater concrete, expansive grouting concrete for inverted placement, and ultra high-strength in-site concrete, and have consequently succeeded in developing super-workable concrete, suitable for rapid placing or perfect filling without consolidation. The authors also have established a new evaluating method for segregation resistance of mortar and aggregate, that is useful to design mix proportion, or keep high quality of super-workable concrete in site. Recently, opportunities to apply super-workable concrete to several actual structures with difficult construction conditions have arisen. One is the LNG (liquefied nitrogen gas) in-ground storage tank, which has much complicated reinforcement at the junction of base mat and side wall, another is a tall, thin reinforced concrete wall, which must be placed from upper point, 6 to 8 m in height. This paper describes the basic properties of super-workable concrete, the new method of quality control, and a summary of applications to reinforced concrete structures mentioned.

Presents a scheme to rescue a reinforced concrete building from the severe attack of sulfate water. Our practical solution to this problem included: replacement of spread footings, making the basement an inside-out water tank, protection of columns against sulfate attack, and stabilization of soil in the vicinity of the rectangular spread footings.