[ti:Making Better Concrete With Rice?] [ar: Bob Doughty] [al:Agriculture Report] [by:www.51voa.com] [00:00.00]This is the VOA Special English [00:02.80]Agriculture Report. [00:04.73]Rice hulls, or husks, [00:07.77]are the protective coverings [00:09.91]on grains of rice. [00:11.50]Rice with just its hull removed [00:14.45]is brown rice. [00:16.24]Rice without its hull [00:18.23]or bran is white rice. [00:20.97]Once rice is harvested, [00:23.51]the hulls are out of a job. [00:25.80]They may be taken [00:27.39]to landfills or burned. [00:29.83]Sometimes they are used [00:32.46]to absorb waste [00:33.91]in chicken houses. [00:35.85]Other times they are [00:37.75]used to amend soil. [00:39.84]But a chemist in Texas [00:42.34]has another idea. [00:44.24]Rajan Vempati led a group [00:48.10]that developed a new process [00:49.74]to make rice hulls into ash. [00:52.94]The idea is to replace [00:55.04]some of the portland cement [00:56.98]traditionally used [00:58.07]in making concrete. [00:59.91]Portland cement is a material [01:02.01]that holds together the sand [01:04.35]and crushed stone in concrete. [01:07.64]Rajan Vempati thinks [01:10.67] rice hull ash could help [01:12.61]the concrete industry [01:13.81]produce less carbon dioxide. [01:16.35]Carbon dioxide is released [01:19.13]in cement manufacturing [01:20.83]when fuel is burned [01:23.21]and limestone is heated. [01:25.69]The Portland Cement Association says [01:28.53]the gas from the limestone [01:30.94]is reabsorbed as concrete ages. [01:34.17]But cement manufacturing [01:36.88] produces around five percent [01:39.27]of the carbon dioxide released [01:41.41]by human activity worldwide. [01:44.20] Carbon dioxide is one of the gases [01:47.63]that may affect the climate [01:49.72]by trapping heat. [01:51.46]The process for making [01:53.94]rice hull ash heats the hulls [01:56.68]to eight hundred degrees centigrade. [02:00.01]Carbon is driven out, [02:02.60]and fine particles of [02:04.84]almost pure silica remain. [02:08.13]The process releases [02:10.27]some carbon dioxide, [02:12.17]but Rajan Vempati says [02:14.26]it would be reabsorbed [02:16.26]into the soil naturally. [02:18.59]Another inventor, [02:20.79]Prasad Rangaraju, [02:22.78]is an engineer [02:24.28]at Clemson University [02:25.67]in South Carolina. [02:27.81]He tested the cement, [02:30.10]and says less could be used [02:32.24]because the rice hull ash makes it [02:35.33]a stronger building material. [02:37.48]Also, the inventors say [02:41.18]the light-colored material [02:42.78]better reflects sunlight, [02:44.89] so buildings would cost less to cool. [02:47.77]The National Ready [02:49.94]Mixed Concrete Association [02:51.84] points out that using ash [02:54.50]in cement is not a new idea. [02:57.76]The ancient Romans discovered [03:00.48]that volcanic ash made better cement. [03:03.75]But the modern inventors say [03:06.75]rice hull ash works better [03:09.30]than other materials. [03:11.00]They developed the process [03:13.13]with money from the [03:14.87]National Science Foundation. [03:16.70]They have not yet [03:18.67]brought it to market. [03:20.56]Rice hull ash is already available, [03:23.81]but the product is relatively costly. [03:27.14]Cost, including transportation, [03:30.38]may decide the success of the new technology. [03:34.85]Using it could make the most sense [03:37.50]in areas where farmers grow lots [03:40.49]of rice and the hulls might just go to waste. [03:44.62]And that's the VOA Special English [03:48.16]Agriculture Report, [03:49.95]written by Jerilyn Watson [03:51.89]with Steve Baragona. [03:54.00] I'm Bob Doughty.