活性稻壳灰对混凝土强度和耐久性能的影响

研究了高火山灰活性稻壳灰对混凝土强度和耐久性能的影响。结果表明：混凝土中掺加稻壳灰后强度提高，且高水胶比时强度提高率更大；同时，混凝土的抗盐酸溶液的侵蚀能力、抗碳化和抗渗性能也得到改善。其主要原因可归结为：稻壳灰的掺入降低了混凝土的实际水胶比，促进了水泥的水化，使混凝土中有更多的C—S—H凝胶生成，并减少了混凝土中羟钙石的数量，降低了混凝土细孔的平均尺寸，使得混凝土的结构更加密实。     

稻壳灰高性能混凝土力学性能试验研究

为减少水泥用量,降低成本,提高稻壳灰的利用率,发展绿色环保的高性能混凝土,以稻壳灰等质量取代水泥掺入混凝土中,复掺硅灰和粉煤灰,采用混凝土正交试验方法,研究稻壳灰、硅灰和粉煤灰的最佳掺量.通过分析在标准养护和干燥养护条件下混凝土的力学性能试验结果,确定了混凝土的最优配合比,并制备出工作性能较好,强度为C60的稻壳灰高性能混凝土.     

稻壳灰混凝土的力学性能试验及强度预测

为了降低混凝土成本,改善混凝土性能,将稻壳灰部分替代水泥,并与粉煤灰、硅灰复掺制备混凝土。通过正交试验考察水胶比、稻壳灰掺量、粉煤灰掺量及硅灰掺量对混凝土抗压强度的影响规律。结果表明,水胶比对混凝土强度影响最大,考虑混凝土性能兼顾经济性,混凝土最佳配比为:水胶比为0.3、稻壳灰掺量为20%、粉煤灰掺量为15%、硅灰掺量为5%。采用RBF神经网络的预测模型对混凝土128 d抗压强度进行预测,预测结果与实测结果具有很好的吻合度。     

掺稻壳灰碾压混凝土的初步研究

本文研究了在碾压混凝土中用稻壳灰取代部分水泥的可能性，得出不同稻壳灰掺量时最佳用水量及最佳水胶比，以及碾压工艺对上述混凝土强度的影响。     

稻壳灰改性铝酸盐水泥的试验研究

针对铝酸盐水泥中后期强度倒缩的问题,进行了稻壳灰作为外掺料改性铝酸盐水泥的试验研究。分别测试了稻壳灰对铝酸盐水泥抗压强度、抗折强度、泌水率及渗透率的影响,并通过XRD分析探讨了稻壳灰的作用机理。结果表明:适量的稻壳灰不仅可以提高铝酸盐水泥的早期强度,还可以有效改善其中后期强度,稻壳灰掺量以15%为佳;稻壳灰的比表面积巨大,其表面可有效吸附大量水分子,改善了铝酸盐水泥的泌水性;稻壳灰的填充效应使硬化浆体中的连通孔隙数量减少,进而改善了铝酸盐水泥的渗透性;稻壳灰活性被激发后可与水化产物发生反应,削弱了发生在水化反应中后期的晶相转变作用,避免了硬化浆体的中后期强度倒缩。     

稻壳灰对本地化高延性水泥基材料性能的影响

为了降低高延性水泥基复合材料的生产成本和提高废弃稻壳的建材资源化利用，首先利用国产涂油PVA纤维和天然河砂分别替代进口PVA和石英砂探究了本地化高延性水泥基复合材料的配制工艺，在此基础上试验研究了稻壳灰作为辅助胶凝材料替代部分水泥（10%、30%和50%，质量分数）对高延性水泥基复合材料流动度、抗压强度、拉伸性能和弯曲性能的影响规律。研究结果表明：采用国产涂油PVA纤维和天然河砂可成功配制强度等级可达C30且14 d的极限拉伸应变可达到1.44%的国产化高延性水泥基复合材料。水胶比和PVA纤维掺量分别是影响高延性水泥基复合材料抗压强度和拉伸强度的主要因素。相比对照组，随着稻壳灰替代率的增加，浆体流动度由于稻壳灰的吸水性逐渐下降，最大可降低10%；基体14 d抗压强度略有提高后大幅降低；试件抗拉强度呈略微下降趋势，而极限拉伸应变则显著提高可高达2.94%；基体弯曲强度呈先增加后逐渐降低的趋势，，且纯弯段裂纹数量明显增多，且裂纹宽度均低于100μm。可见，稻壳灰替代10%的水泥有利于高延性水泥基复合材料抗压强度、极限拉应变和弯曲强度的提高，同时对浆体流动度影响较小。微观分析可知，具有良好火山灰活性的稻壳灰可与水泥水化产物反应提高胶凝产物总量，同时降低Ca(OH)2数量，进而增强了高延性水泥基复合材料的强度。     

稻壳灰/硅藻土复合调湿材料研究

稻壳灰具有超大比表面积和微孔结构,且生态效应优于其它工业废弃物,对其高效利用意义重大.以稻壳灰和天然硅藻土为原材料,掺以适量无机改性掺合料,制备稻壳灰/硅藻土复合调湿材料.通过试验研究稻壳灰/硅藻土复合调湿材料的调湿、强度和耐水性.采用XRD分析探讨材料强度和耐水性的形成机理;通过扫描电镜分析和材料吸附/解吸理论研究材料的调湿机理.研究表明,稻壳灰复合量为9%～17%时,复合调湿材料吸、放湿速率分别达到0.058 0～0.066 0 kg/(kg·d)和0.042 6～0.047 5 kg/(kg·d);60 d抗压强度为6.01～6.50 MPa、软化系数达0.71～0.76.无机改性掺合料与稻壳灰、硅藻土中的SiO_2和Al_2O_3反应生成大量C-S-H凝胶和斜方钙沸石、菱沸石等新硅铝酸盐矿物,使材料产生强度和耐水性;复合调湿材料对空气中水分子的毛细孔道效应、表面化学及物理吸附作用,使其具有优异的调湿性能.     

稻壳灰固化红黏土的路用性能及微观机理

为响应建设节约的发展思路，向红黏土中掺入稻壳灰，并通过一系列实验探讨稻壳灰对红黏土力学性能的影响，分析稻壳灰对红黏土的微观作用机理。试验结果表明，掺入稻壳灰后红黏土液塑限变化较小；其最优含水率与渗透系数随稻壳灰掺量的增加而增高，最大干密度降低；掺入稻壳灰的红黏土抗压强度随掺量的增加呈先增后减的趋势，当稻壳灰掺入量为15%，养护时间为28 d时达到最大值。电镜扫描试验发现：稻壳灰表面覆盖大量的胶凝物质，红黏土结构密实性相应提升。用稻壳灰改良红黏土能节约路基的建设成本，同时也有利于保护环境，实现资源的可持续利用。     

高活性稻壳灰的制备及其对水泥性能的影响

通过研究煅烧制度对稻壳灰火山灰活性的影响 ,提出了一种有效制备高活性稻壳灰的方法。采用这种方法 ,可以稳定地实现半工业化生产 Si O2 含量大于 90 %且主要为非晶态的白色多孔状稻壳灰 ,其火山灰活性很高。在稻壳灰的粉磨过程中 ,必须加入助磨剂 ,否则细颗粒的二次团聚会使稻壳灰的活性降低。在水泥中掺入不同比例的稻壳灰 ,可以大幅度地提高水泥胶砂强度 ,而且水胶比越大 ,强度提高率越大。     

掺稻壳灰的活性粉末混凝土拌合物性能研究

在一定条件下焚烧稻壳形成的稻壳灰具有高火山灰活性并有望用于活性粉末混凝土中。将自制高活性稻壳灰采用内掺法加入活性粉末混凝土中代替部分优质水泥,研究稻壳灰替代量对不同钢纤维掺量的活性粉末混凝土工作性能、含气量及表观密度等的影响。结果表明:当稻壳灰等量替代水泥后,随替代量的增加,活性粉末混凝土拌合物流动性降低,含气量减小,表观密度先增大后减小;而随着钢纤维掺量的增加,拌合物的流动性降低,含气量稍有减小,表观密度增加幅度较明显。     

Concrete with Highly Active Rice Husk Ash

1　IntroductionForengineering ,economicandecologicalbenefits ,theuseofpozzolanicandcementitiousmaterials ,suchasgranulatedblast furnaceslag ,flyash ,silicafumeandnaturalpozzolan ,inthecementandconcreteindustryhasrisengreatlyfromthemiddleofthelastcenturyan…     

Concrete with Highly Active Rice Husk Ash

The overall aim was to investtgate the effect of highly active husk ash (RHA) produced by an industrial furnace on some properties of concrete. The strength, pore volume and pore distribution of concrete and the Ca(OH)2 content in concrete were investigated by JIS A 1108 ( Method of test for compressive strength of concrete), a mercury instrument porosimeter, and the thermogravimetric analysis, respectively. The results show that, with RHA replacement of cement , the compressive strength of concrete is increased evidently;the average pore radius of concrete is greatly decreased, especially the portion of the pores greater than 20nm in radius is decreased while the amount, of smaller pores is increased, and the more the RHA replacement, the less the amount of Ca(OH)2 in concrete. The latter two results are the main reasons for the strength enhancement of concrete.     

Effect of silica forms in rice husk ash on the properties of concrete

The strength and durability properties of concrete with or without three types of rice husk ash(RHA),namely,amorphous,partial crystalline,and crystalline RHA,were investigates.The three types of RHA were added into concrete at a 20% replacement level.Consequently,the pozzolanic reactivity of amorphous RHA was higher than that of partial crystalline and crystalline RHA.Concrete added with amorphous RHA showed excellent characteristics in its mechanical and durability properties.The results showed that the higher the amount of crystalline silica in RHA,the lower the concrete resistivity value became.When compared with each other,concretes with 20% of the cement replaced with these types of RHA achieved similar ultrasonic pulse velocity values,but all were lower than that of the control concrete.The incorporation of these kinds of RHA significantly reduced chloride penetration.The results not only encourage the use of amorphous materials,they also support the application of crystalline or partial crystalline RHA as mineral and pozzolanic admixtures for cement.     

Effectiveness of Surface Coatings Against Intensified Sewage Corrosion of Concrete

Three different kinds of coatings were coated on the concrete surface, and the changes in appearance, surface roughness, microstructure and components of coatings in artificial sewage were investigated. In addition, the strength, micrograph, mineral compositions and pore structure of concrete specimens after removing coatings were also studied. The results show that epoxy coal tar pitch coating(ECTPC) has the best effect of protecting concrete from the sewage corrosion. After being immersed in sewage for 90 days, the compressive strength of concrete coated with ECTPC is still as high as that of specimen immersed in water, and the cement paste has a high CH content and dense structure with low porosity, which mainly accounts for its excellent barrier property and certain antibacterial function. Cement-based bactericidal coating(CBC) also has good effectiveness to sewage corrosion of concrete. The strength and microstructure of concrete coated with CBC in sewage are still significantly superior to those of uncoated concrete. Although cement-based capillary crystalline waterproofing coating(CCCWC) is a good waterproof material, it is not suitable for the corrosion resistance of concrete in sewage. After 2 months corrosion, almost all of the CH crystals in coating reacted with the metabolic acid substance by microbes. Therefore, the strength and pore structure of concrete coated with CCCWC are only slightly superior to those of uncoated concrete. Overall, the protective effect of cement-based inorganic coatings is relatively poor.     

混凝土孔结构与强度关系模型研究

研究了混凝土孔隙对强度的影响规律。结合混凝土材料科学、断裂力学的相关研究理论，分析了混凝土孔隙对弹性模量和断裂表面能的影响，对Griffith断裂理论进行了修正，进而提出了混凝土孔结构复合体模型。该模型不仅考虑了孔隙率对混凝土强度的影响，还考虑了孔径分布的影响，并对模型的断裂过程进行了分析。程序计算结果表明，计算强度与试验强度有较高的相关性，通过在模型中引入水泥质量分数对基体强度的影响能够使强度模型应用于不同水灰质量比混凝土孔结构的研究。     

灰砂混凝土的强度及孔结构与蒸压制度的关系

通过测试两种配比的灰砂混凝土在八种蒸压制度下的强度、断裂能及孔结构、ＢＥＴ表面积,研究了蒸压制度对抗压强度、抗折强度、劈拉强度及断裂能的影响,力求用孔结构及ＢＥＴ表面积测试数据从微观上解释力学性能的变化规律。     

Pore Size Distribution of High Performance Metakaolin Concrete

The Compressive strength, porosity and pore size distribution of high performance metakaolin (MK) concrete were investigated. Concretes containing 0,5%,10% and 20% metakaolin were prepared at a water/cementitious material ratio (W/C) of 0.30.In parallel, concrete mixtures with the replacement of cement by 20% fly ash or 5 and 10% silica fume were prepared for comparison.The specimens were cured in water at 27℃ for 3 to 90 days .The results show that at the early age of curing(3 days and 7 days),metakaolin re-placements increase the compressine strength ,but silica fume replacement slightly reduces the compressine strength.At the age of and after 28 days ,the compressive strength of the concrete with metakaolin and silica fume replace-ment increases.A strong reduction in the total porosity and average pore diameter were observed in the conctete with MK 20% and 10% in the first 7 days.     

干燥大温差气候下混凝土孔结构研究

采用压汞法对比研究了标准养护条件下和干燥大温差气候下混凝土的孔结构。研究表明,干燥大温差气候下混凝土的孔隙率提高,平均孔径和临界孔径变大,孔体积分布曲线偏向于大孔径段,且孔隙中有害孔和多害孔所占的百分比显著提高。孔结构的劣化造成宏观性能的降低,表现为强度的损失。