From Smokestacks to High Tech: Retraining Workers for a Technological Age

This comment will examine a jobs re-training program, The Employment Training Panel (ETP), an innovative piece of job training legislation enacted in California in 1982. Designed with the dual purpose of economic development and job training and employment, the bill seeks to (1) foster job creation and put the unemployed back to work, (2) meet employer needs for skilled workers, and (3) minimize employers\u27 unemployment insurance costs. ETP does so by working closely with the State\u27s Department of Economic and Business Development to entice new business to locate in California and to encourage existing business to expand their operations by offering to train whatever employees the company needs at virtually no cost to the employer. Workers who have lost jobs with companies which are closing down or laying off can thus be retrained for new jobs. By recycling employees back into the work force quickly, ETP can assist employers to reduce their unemployment insurance costs. Since more of the employers\u27 contributions stay in the unemployment insurance fund, it may remain solvent, thus avoiding higher contribution rates

Lightweight Aggregates as an Internal Curing Agent for Low-Cracking High-Performance Concrete

The use of lightweight aggregates to supply a source of internal curing for Low Cracking, High Performance Concrete (LC-HPC) is evaluated. Prior research is used as a basis to estimate the amount of with lightweight aggregate replacement needed to optimize the amount of moisture available in the mix for internal curing. An aggregate optimization program (KU Mix) is revised to include modifications for the addition of aggregate with different specific gravities, such as lightweight aggregate, for the purposes of internal curing. Fourteen concrete mixes are designed to evaluate the free shrinkage and strength properties of LC-HPC mixes with lightweight aggregate for the purposes of internal curing. Six mixes in Program I are used to evaluate different replacement levels of lightweight aggregate. Eight mixes in Program II are used to evaluate the use of lightweight aggregate with Grade 100 slag. All mixes have a water/cement ratio of 0.44, 24.7% paste content (equivalent to a cement content of 540 lb/yd3) and an air content of 8%. Both 7-day and 14-day curing periods are evaluated for the free shrinkage specimens. Cylinders are cast for every batch and tested for the 28-day strength. The effect of adding lightweight aggregate does not significantly decrease the strength of any one mix. The addition of the lightweight aggregate increases the amount of internal curing water available and reduces shrinkage. The recommended mixes to reduce free shrinkage from Programs I and II were the 14-day cured lightweight aggregate mix with the highest level of replacement and the 14-day cured lightweight aggregate mix with a 30% cement replacement of slag, respectively

Lightweight Aggregate as Internal Curing Agent to Limit Concrete Skrinkage

The effectiveness of prewetted, vacuum saturated (PVS) lightweight aggregate (LWA) as an internal curing agent to reduce concrete shrinkage is evaluated for curing periods of 7 and 14 days. Normalweight aggregate is replaced by LWA at volume replacement levels ranging from 8.9 to 13.8%. Some mixtures contain a partial replacement of portland cement with slag cement while maintaining the paste content at approximately 24.1% of concrete volume. Comparisons are made with mixtures containing low-absorption granite and high-absorption limestone normalweight coarse aggregates. At the replacement levels used in this study, PVS LWA results in a small reduction in concrete density, no appreciable effect on concrete compressive strength, and a substantial decrease in concrete shrinkage for drying periods up to 365 days. Increasing the curing period from 7 to 14 days reduces concrete shrinkage. Thirty and 60% volume replacements of portland cement by slag cement result in reduced shrinkage when used with a porous LWA or normalweight aggregate. After 30 and 365 days of drying, all mixtures with LWA exhibited less shrinkage than the mixtures with either low- or high-absorption normalweight aggregates

Lightweight Aggregate as Internal Curing Agent to Limit Concrete Shrinkage

The effectiveness of prewetted, vacuum-saturated (PVS) lightweight aggregate (LWA) as an internal curing agent to reduce concrete shrinkage is evaluated for curing periods of 7 and 14 days. Normalweight aggregate is replaced by LWA at volume replacement levels ranging from 8.9 to 13.8%. Some mixtures contain a partial replacement of portland cement with slag cement while maintaining the paste content at approximately 24.1% of concrete volume. Comparisons are made with mixtures containing low-absorption granite and high absorption limestone normalweight coarse aggregates. At the replacement levels used in this study, PVS LWA results in a small reduction in concrete density, no appreciable effect on concrete compressive strength, and a substantial decrease in concrete shrinkage for drying periods up to 365 days. Increasing the curing period from 7 to 14 days reduces concrete shrinkage. Thirty and 60% volume replacements of portland cement by slag cement result in reduced shrinkage when used with a porous LWA or normalweight aggregate. After 30 and 365 days of drying, all mixtures with LWA exhibited less shrinkage than the mixtures with either low- or high-absorption normalweight aggregates