Describes the performance of a cement-based grout recommended for possible use to control brine inflows in potash mines. The grout consists of Type III high-early-strength cement, fly ash, and sodium saturated brine. Specimens were prepared and submerged in containers filled with brine to cure under confining pressures of 0, 3.40, and 6.9 MPa (0, 500, and 1000 psi). The isotropic confining pressures were designed to simulate different mining environments and to accelerate penetration of brine into the specimens so that long term performance could be evaluated. Tests were conducted at different ages to determine the compressive strength, splitting tensile strength, and static and dynamic modulus of elasticity. The performance of grout mixtures containing brine with zero and 40 percent fly ash over the three-year test program seems to be in an acceptable range. Confining pressure can adversely affect the physical properties results of grout over time. This investigation found that a reduction in the physical properties was occurring after two years, especially when the grout was subjected to a confining pressure. The grout with fly ash exhibited a more scattered data under different confining pressures than grout with no fly ash; however, it showed a better long term performance. Generally, fly ash grouts stored under zero confining pressures were found to perform better than those subjected to high confining pressures.

Three reactive aggregates from New Brunswick, Canada, a greywacke, a gneiss, and a meta-volcanic rock were evaluated for their potential alkali reactivity (AAR) in concrete mixtures incorporating 420 kg/m 3 of cementitious materials. The concrete mixtures consisted of the control made with CSA Type 10 low- and high-alkali cements and mixtures incorporating ASTM Class F fly ash at 20, 30, and 56 percent replacement levels of the high-alkali cement. The susceptibility of the concretes to AAR was evaluated by casting test prisms and subjecting these to various accelerated curing conditions in the laboratory. For comparison purposes, mortar bars were also made and tested according to the ASTM C 1260-94 Accelerated Mortar Bar Test procedure. The AAR concrete prism tests performed in this study have shown that none of the test prisms cast from concrete mixtures incorporating 20, 30, and 56 percent fly ash showed significant expansion after two years of testing at 38 C and relative humidity >95 percent. These results were in good accordance with those obtained in the accelerated mortar bar test. Some alkaline immersion tests results would indicate, however, that concrete incorporating 20 percent fly ash might not offer adequate protection against potential deleterious expansions with highly reactive aggregates.

Hgh Reactivity Metakaolin (HRM) is produced by controlled thermal activation of purified kaolinite, an aluminosilicate mineral, to a reactive, amorphous state. HRM, being pozzolanic, reacts with free lime (Ca(OH) 2), a byproduct of portland cement hydration. In this investigation, two high- performance concrete mixtures containing HRM were studied. In the first mixture proportion, HRM was formulated as an addition to the cement. In the second mixture, HRM was used as a cement replacement. The compressive strength and rapid chloride permeability of the HRM concretes was compared to nonpozzolanic concrete controls and concretes that contained equal amounts of silica fume. The results of this study show that the strength and impermeability of HRM concrete is significantly higher than nonpozzolanic concrete. The HRM concrete showed properties equivalent to similar silica fume (SF) concretes, while using significantly less superplasticizer to reach an equivalent consistency.

A rapid-hardening cement was made by blending mixtures of high- alumina cement (HAC) and ground granulated blast furnace slag (GGBS). The addition of slag alters the course of hydration reactions in HAC. A chemical compound 2CaO.Al 2O 3.SiO 2.8H 2O (gehlenite hydrate or stratlingite), only seen in plain HAC in small amounts, readily forms and becomes the main stable hydrate in the blended cement concretes in the temperature range of 5 to 38 C, replacing the metastable hydrates which lead to loss of strength in HAC through the conversion reaction. The properties of mortars and concretes made with this cement were assessed in a series of durability studies carried out by the Building Research Establishment. Mortars made with the blend have shown excellent sulfate resistance. Concrete specimens were compared with those from HAC concretes of similar proportions, following exposure for two years in aggressive sulfate, marine, and soft acid water environments. The findings, at this relatively early stage, are very encouraging. Longer term tests will be carried out at five and 10 years. Concretes made with the blend have shown a greater tolerance of high water-cement ratio mixtures in forming stable products with reduced temperature rises and enhanced durability in terms of their excellent sulfate, seawater, and soft acid water resistance.

The first two abrasion-erosion concrete repair projects in the United States that used silica fume (SF) concrete started in 1983. One was the stilling basin rehabilitation of the Kinzua Dam, in northwestern Pennsylvania. The other was the Los Angeles River low-flow channel rehabilitation project (completed in 1985). The first known application of SF concrete (SFC) addressing cavitation resistance occurred in 1985, also at the Kinzua Dam, but for a sluice repair. This paper largely summarizes long term performance information relating to the 1983 to 1985 SFC placements. Other, more recent, SFC projects in which abrasion-erosion or cavitation was a concern are mentioned. Also presented are two mixtures featuring portland cement with ground granulated blast furnace slag and SF that were recently used in a very severe environment. Overall, after up to 10-1/2 years in service, the various SFCs are performing very well. The 1983 Kinzua Dam stilling basin SFC wear after 10-1/2 years is only a small fraction of that seen in previously utilized concretes. For the Los Angeles River SFCs, all of the three different SFC mixtures that were employed are performing comparably as of March 1994. Overall erosion was uniform and to an estimated 4 to 12 mm depth. The 1985 Kinzua Dam sluice repair concrete showed no evidence of cavitation damage by 1994.