Shrinkage and Expansive Strain of Concrete with Fly Ash and Expansive Agent

The effects of fly ash and MgO-type expansive agent on the shrinkage and expan-sive strain of concrete with high magnesia cement were investigated. The results show that high volumes of fly ash may reduce the shrinkage strain of concrete and inhibit the expansive strain of concrete with MgO-type expansive agent, but can not eliminate the shrinkage of concrete. MgO-type expansive agent may produce expansive strain and compensate the shrinkage strain of concrete, re-lieve the cracking risk, but the hydration product of magnesia tends to get together in paste and pro-duce expansive cracking of concrete with high magnesia content according to SEM observation.

Applied technique of the cemented fill with fly ash and fine-sands

Traditional stabilization of backfilling material is done by using Portland cement. However, the high price of cement forced mining engineer s to seek cheaper binding materials. Fly ash, which is the indus- trial wast e from thermal power plant, possess the potential activity of jellification, and can b e used in cemented fill as a partial substitute for cement to reduce the fill co s t. Tests were done during the past few years in Xinqiao Pyrite Mine and Phoenix Copper Mine to determine the technology parameters and the suitable content of f ly ash. Specimens with different cement/fly/ash tailings (sands) ratios were tes ted to obtain the strength values of the fill mass based on the analyses of both the chemical composition and physical and mechanical properties of fly ash . The compressive strength of specimens with a ratio of 1∶2∶8 (cement to fly ash to tailings ) can reach 2 MPa after 90 d curing, totally meeting the requiremen t of artificial pillar and reducing the fill cost by 20%-30%.

Cement-fly Ash Stabilization of Cold In-place Recycled (CIR) Asphalt Pavement Mixtures for Road Bases or Subbases

For lack of laboratory and field performance data on stabilization of reclaimed asphalt pavement （RAP） aggregate and stabilized soil （S） for road bases and subbases construction, the influences of RAP/S ratio, cement and fly ash content, modifying agent （MA） on the compact, unconfined compressive strength, indirect tensile strength and water stability of the CIR mixtures were investigated. The experimental results showed that the maximum dry density and the optimum moisture content of the mixture changed significantly with the RAP/S ratio and cement-fly ash content. Unconfined compressive strength, indirect tensile strength and water stability were improved significantly by the addition of MA, and the water stability was improved by nearly 20% on average. Scanning electron microscopy（SEM） images indicated that MA accelerated the hydration of cement-fly ash system. Needle-like AFt and fibrous C-S-H gel were observed in the mixtures, which resulted in the cementation effect among the CIR mixture particles and a more compact microstructure. All these could be the cause of high strength of the CIR mixtures with MA.

Effects of seeding nucleation agent on geopolymerization process of fly-ash geopolymer

Geopolymer, an inorganic aluminosilicate material activated by alkaline medium solution, can perform as an inorganic adhesive. The geopolymer technology has a viability to substitute traditional concrete made of portland cement （PC） because replacing PC with fly ash leads to reduced carbon dioxide emissions from cement productions and reduced materials cost. Although fly ash geopolymer stimulates sustainability, it is slow geopolymerization reaction poses a challenge for construction technology in term of practicality. The development of increasing geopolymerization reaction rate of the geopolymer is needed. The purpose of this study is to evaluate seeding nucleation agents （NA） of fly ash geopolymer that can accelerate polymerization reactions such that the geopolymer can be widely used in the construction industry. Results from the present study indicate that the use of NA （i.e., Ca（OH）2） can be potentially used to increase geopolymerization reaction rate and improve performance characteristics of the fly ash geopolymer product.

掺碱激发剂粉煤灰-水泥胶砂强度性能试验研究

在粉煤灰-水泥中掺入碱激发剂不但可以改善粉煤灰活性,提高粉煤灰-水泥胶凝材料的性能,而且还保护环境,可以带来显著的经济效益。制作掺入不同碱激发剂的粉煤灰-水泥试块,测定在不同碱掺量下的试块的胶砂强度,进而评价碱激发剂对粉煤灰活性的激发效果。通过试验可知,掺适量碱均可提高粉煤灰活性;不同龄期NaOH的最佳掺量不一致,3 d时NaOH最佳掺量为粉煤灰质量的5%,而28 d时为6%;不同龄期粉煤灰的最佳CaO掺量基本一致,均为粉煤灰质量的8%;NaOH早期强度发展较快,后期水玻璃发展较快;CaO比NaOH激发效果好。

大掺量粉煤灰水泥研究及其在工程中的应用

利用正交试验和作图方法,分析不同因素对大掺量粉煤灰水泥强度的影响,找出大掺量粉煤灰水泥的优化配合比.结果表明,在42.5普通硅酸盐水泥中掺入≥50%粉煤灰,化学外加剂和矿物掺合料分别为1%和5%时,水泥各项技术性能都达到GB1344-1999标准32.5强度等级的要求.本文还介绍了该水泥在土木工程中的应用情况.

大掺量粉煤灰水泥配制研究

本文通过对大掺量粉煤灰水泥配制技术影响因素的试验研究 ,表明通过采用适当的物料配比 ,合理的激发途径 ,可在粉煤灰掺量达到 6 0～ 70 %的情况下 ,配制相当于原国家标准中普通硅酸盐 42 5号、5 2 5号水泥 。

掺氢氧化钠激发剂粉煤灰-水泥强度性能试验研究

掺碱能激发粉煤灰的早期活性,在粉煤灰-水泥中掺氢氧化钠,通过室内试验测定3d、28d龄期的胶砂强度值。首先,分析胶砂实验的强度值可知,3d龄期时,胶砂强度达到最大的氢氧化钠最佳掺量为5%,28d时为6%;粉煤灰的掺量都为10%;相对于基准组,3d龄期时强度提高率最高的粉煤灰最佳掺量为20%,28d为30%;其次,将3d龄期的强度提高率和28d时比较,结果显示掺氢氧化钠的胶砂强度早期强度发展快,后期发展较缓慢。

掺入粉煤灰的碱激发胶凝材料路用性能研究

为了提高农村水泥路面修复的效果,提出一种掺入粉煤灰的碱激发胶凝材料用于路面修复。对碱激发胶凝材料的特性进行分析,试验研究碱当量、激发剂、胶凝材料体系的变化对粉煤灰碱激发胶凝材料路用性能的影响。结果表明:碱当量的增加可以加速激发粉煤灰;氢氧化钙+硫酸钠复合时激发的效果最优;矿粉活性可以明显改善碱激发胶凝材料的力学性能。说明采用粉煤灰掺量的碱激发胶凝材料具有可替代水泥作为混凝土路面修复材料的理论可行性。

生石灰消化性能对大掺量CFB固硫灰蒸压加气混凝土性能影响研究

以CFB固硫灰为主要原料制备蒸压加气混凝土砌块,通过改变生石灰消化性能,解决固硫灰因活性低、吸水量大、流动性差导致无法在加气混凝土砌块中大量使用的难题。实验结果表明,通过提高石灰煅烧程度减缓消化可改善加气混凝土料浆发气性能,但会降低加气混凝土砌块的抗压强度;通过添加0.05%蔗糖减缓消化既能改善料浆发气性能,降低砌块绝干密度,还可以使砌块符合GB/T 11968—2020《蒸压加气混凝土砌块》中B06、A3.5等级的要求。

三维数值模拟在掺碱粉煤灰-水泥胶砂强度试验的应用

粉煤灰-水泥中掺氢氧化钠能够增加水泥早期强度,本次试验通过测定3 d、28 d龄期的胶砂强度值;并分析得出氢氧化钠最佳掺量分别为5%和6%;粉煤灰的最佳为10%;相对与基准组强度提高率最高的粉煤灰掺量分别为20%和30%。其次,将3 d龄期的强度提高率和28 d比较,得出龄期对强度发展的影响;同时,利用有限元方法模拟混凝土试件单轴抗压的受压破坏过程;并将数值模拟结果与物理实验对照,精度基本满足要求,其方法为混凝土的研究提供新思路。

一种水泥混凝土化学激发剂的制备和性能研究

该文重点制备一种水泥混凝土化学激发剂并进行性能验证。通过单体滴加法自行制备XC添加剂,再按比例混合三乙醇胺、三异丙醇胺、自制XC添加剂、可再分散乳胶粉、纳米二氧化硅制得XCA-1型水泥混凝土化学激发剂。通过混凝土试验验证表明：添加该激发剂后不但可使C40混凝土配合比强度增大约6.5%的幅度,还可使混凝土配合比减少5%~10%的水泥用量,具有一定的经济效益,并从经济性和适用性方面综合考虑,XCA-1型水泥混凝土化学激发剂的较优掺量为0.03%。