Properties of cement mortars containing clinoptilolite as a supplementary cementitious material

This paper presents a study of the properties and behavior of cement mortar with clinoptilolite which is one of the most common zeolite minerals found in nature. Six mortar mixtures were prepared by replacing the Portland cement with 0%, 5%, 10%, 15%, 20% and 30% clinoptilolite by weight. Test results showed that water demand, soundness and setting times of the cement pastes increased with the increase of clinoptilolite content. Compressive and flexural strength of the mortars containing clinoptilolite were higher than the control mixture. Dry unit weight of the mortars with clinoptilolite was lower than the control mortar. Clinoptilolite replacement decreased water absorption and porosity of the mortars. The control mortar showed less durability to carbonation compared to the mortars made with clinoptilolite at the end of carbonation tests. Freeze–thaw resistance of the mortars containing 5% clinoptilolite was higher than control mortar. The effect of clinoptilolite incorporation on high-temperature resistance seemed to be dependent on amount of clinoptilolite, temperature level, and the cooling method.     

Effects of the usage of diatomite and waste marble powder as partial replacement of cement on the mechanical properties of concrete

Diatomite is a pozzolanic material containing amorphous silica, cristabolite and minor amounts of residual minerals. Waste marble powder (WMP) is an inert material which is obtained as an industrial by product during sawing, shaping, and polishing of marble and causes a serious environmental problem. This paper describes the procedures and results of a laboratory investigation of mechanical properties carried out on the concrete specimens containing diatomite and WMP as partial replacement of cement in concrete. The laboratory work essentially consists of characterization of the raw and waste materials, preparation of concrete specimens with diatomite and WPM in different ratios by weight as replacement for cement and a superplasticizing admixture to reduce water demand and compression and flexural tests of the specimens. Test results indicated that the concrete specimens containing 10% diatomite, 5% WPM and 5% WPM +10% diatomite replacement by weight for cement had the best compressive and flexural strength and the replacement of cement with diatomite and WMP separately and together using a superplasticizing admixture could be utilized to improve the mechanical properties of the conventional concrete mixtures.     

Effect of copper slag as a fine aggregate on the properties of cement mortars and concrete

An experimental investigation was conducted to study the effect of using copper slag as a fine aggregate on the properties of cement mortars and concrete. Various mortar and concrete mixtures were prepared with different proportions of copper slag ranging from 0% (for the control mixture) to 100% as fine aggregates replacement. Cement mortar mixtures were evaluated for compressive strength, whereas concrete mixtures were evaluated for workability, density, compressive strength, tensile strength, flexural strength and durability. The results obtained for cement mortars revealed that all mixtures with different copper slag proportions yielded comparable or higher compressive strength than that of the control mixture. Also, there was more than 70% improvement in the compressive strength of mortars with 50% copper slag substitution in comparison with the control mixture. The results obtained for concrete indicated that there is a slight increase in density of nearly 5% as copper slag content increases, whereas the workability increased significantly as copper slag percentage increased compared with the control mixture. A substitution of up to 40–50% copper slag as a sand replacement yielded comparable strength to that of the control mixture. However, addition of more copper slag resulted in strength reduction due to the increase in the free water content in the mix. Also, the results demonstrated that surface water absorption decreased as copper slag content increases up to 50% replacement. Beyond that, the absorption rate increased rapidly and the percentage volume of the permeable voids was comparable to the control mixture. Therefore, it is recommended that up to 40–50% (by weight of sand) of copper slag can be used as a replacement for fine aggregates in order to obtain a concrete with good strength and durability requirements.     

分散剂对纳米碳黑水泥砂浆性能的影响

制作9组、共81个无分散剂纳米碳黑砂浆(CBM)和有分散剂纳米碳黑砂浆(CBDM)试件,探讨分散剂以及纳米碳黑的掺量对水泥砂浆的力学性能、吸水率及压敏性能的影响。结果表明,与素砂浆相比CBM的吸水率明显降低,抗压和抗折强度明显提高;其中掺量为2%时,其抗压强度较素砂浆提高了8.94%,抗折强度提高了38.88%。而掺入分散剂的CBDM的力学性能普遍降低,吸水率普遍增大,压敏性能也随之降低。造成这些现象的原因可能是由于分散剂导致砂浆的孔隙率增大。     

Basic properties of epoxy cement mortars without hardener after outdoor exposure

The purpose of this study is to evaluate the properties of epoxy cement mortars without a hardener after outdoor exposure for a year. The epoxy cement mortars with and without a hardener were prepared for various polymer cement ratios, and tested for their weight change, flexural and compressive strengths, water absorption, carbonation depth and pore size distribution. Especially, the basic properties of the epoxy cement mortars without a hardener were compared with those of epoxy cement mortars with a hardener and those of ordinary cement mortar. The test results showed the successful production of the epoxy cement mortars without any hardener, which gave better strength and durability than ones with a hardener. Polymer–cement ratios of 5–10% for strengths and less than 20% for durability are recommended for optimum mix proportions of epoxy cement mortars without a hardener.     

矿物掺合料对硫铝酸盐水泥-普通硅酸盐水泥复合体系性能的影响

研究了矿粉、硅灰和粉煤灰3种矿物掺合料对硫铝酸盐水泥-普通硅酸盐水泥复合体系的标准稠度用水量、凝结时间、水化放热、胶砂抗折及抗压强度、砂浆干缩率、抗硫酸盐侵蚀性能和水化产物的影响。结果表明:随矿物掺合料掺量的增加,复合体系的标准稠度用水量增大,凝结时间延长;掺加矿物掺合料后水化放热峰出现时间延后,总水化放热量减少,其中掺加矿粉和硅灰的试件初期水化速率减慢程度较掺加粉煤灰试件更明显;3种矿物掺合料对复合体系强度的影响差别较大,掺加3%硅灰的试件3 d抗压强度增长较快;硅灰的掺加会使砂浆干缩率增大,矿粉、粉煤灰的掺加可以减小砂浆试件的干缩;矿物掺合料的掺加会提高胶砂试件抗硫酸盐侵蚀性能,掺粉煤灰的试件抗硫酸盐侵蚀性能最好。     

硫酸和硫酸钠混合溶液对砂浆的腐蚀作用

用普通硅酸盐水泥和硫铝酸盐水泥的混合水泥以及磨细高炉矿渣和聚合物乳液配制了4种水泥砂浆,研究了这些水泥砂浆试样在1%(质量分数,下同)硫酸加10%硫酸钠的混合溶液中浸泡不同时间后的质量变化和强度变化.结果发现,混合溶液对4种水泥砂浆都具有强烈的腐蚀作用.磨细高炉矿渣能显著提高砂浆的耐腐蚀性能;进一步添加聚合物乳液(聚胶比为10%),则砂浆的抗表面剥落性能有很大改善,其中尤以苯丙乳液与丁苯乳液的混合乳液改性砂浆效果更好,但添加聚合物乳液会导致砂浆的抗压强度大大降低.此外,水泥砂浆试样在混合溶液及清水中浸泡后,它们的抗压强度比值要比它们的抗折强度比值对硫酸/硫酸钠腐蚀介质更为敏感.     

不同粒径废玻璃粉对水泥胶砂力学性能的影响

采用3种粒径(20、200、2 000目)的废玻璃粉等体积取代水泥胶砂中的标准砂,体积取代率分别为5%、10%、15%、20%,研究玻璃粉粒径和掺量对水泥胶砂的抗压强度和抗折强度的影响,并对玻璃粉水泥胶砂强度随龄期的变化规律进行了分析讨论。结果表明:不同粒径玻璃粉水泥胶砂的强度随玻璃粉掺量的变化规律存在较大的差异;在玻璃粉掺量相同的情况下,掺入较大粒径玻璃粉的水泥胶砂强度明显降低,玻璃粉粒径越小,强度降低程度越小,当玻璃粉粒径达到微米级,水泥胶砂的抗压强度和抗折强度均显著提高;玻璃粉水泥胶砂的抗压强度随龄期增长,早期强度增加的较快,后期发育增速变缓,而抗折强度早期增长的幅度较大,后期发育比较平缓。     

Mixed cement containing fly ash for masonry and plastering work

A class-F fly ash was used in making masonry mortars suitable for brick joints and for plastering. The mortars were made of a locally produced mixed cement and fly ash at 20% and 40% cement replacement with and without the addition of an air entraining agent/plasticiser. The testing programme includes the determination of water demand, relations between water-to-binder ratio and flow, setting time, air content, water retention, compressive strength and flexural strength.The obtained results suggest that fairly coarse grade class-F fly ash can be incorporated into mortars as replacement of the mixed cement for joint and plastering. The main concern is the low water retention which would be minimized by using a better grade/finer fly ash or by incorporation of plasticiser. Mixed cement containing 20–40% fly ash can be used to make Type N or Type S mortars. Furthermore, relations between flow values and water to binder ratio (W/B) of the mixed cement containing fly ash are developed as a practical aid for selection and formulation of mortar for brick construction and rendering/plastering.     

石粉含量对水泥砂浆性能影响的试验研究

以机制砂石粉含量为变化因素,研究不同强度水泥砂浆的标准稠度用水量、保水率及力学性能随机制砂石粉含量提高的变化情况。结果表明,砂浆标准稠度用水量随石粉含量的提高而增加;适宜石粉含量可提高砂浆的保水率,不同石粉含量砂浆的保水率均高于88%;适宜石粉含量有利于提高砂浆的抗压强度和抗折强度,不同强度等级砂浆的最适宜石粉含量有一定差异。     

硅灰和偶联剂对PB-g-PS胶乳改性水泥砂浆的性能影响

质量比为50/50的聚丁二烯接枝聚苯乙烯(PB-g-PS)胶乳用于改性水泥砂浆。考察了硅灰和偶联剂含量对胶乳改性水泥砂浆的流动度、抗压和抗折强度以及吸水量的影响。研究表明:改性砂浆的流动度随偶联剂含量的增加而增加,随硅灰的含量增加而降低;适量偶联剂和硅灰能降低改性砂浆的毛细孔吸水量;胶乳的加入使抗压强度降低,部分改性砂浆的抗折强度有所提高,偶联剂和硅灰的加入极大地改善了砂浆的力学性能,改性砂浆的抗压、抗折强度最大值分别为31.25、8.18 MPa。利用SEM观察了改性砂浆的结构,改性砂浆结构更加致密,界面结构得到改善,并观察到了带状和树枝状的聚合物膜结构。综上所述,硅灰、偶联剂和胶乳三者可以复合改性水泥砂浆。     

Performance of high wokability slag-cement mortar for ferrocement

The performance of high workability mortar mix, applicable for the casting of thin ferrocement elements by using slag as cement replacement and superplasticizer as water reducing agent is investigated. Cement mortars (1:2. 1:2.5 and 1:3) incorporating various percentages of slag and superplasticizer were designed to have high workability (136±3% flow). Performance of the mortars is studied in terms of compressive strength, unit weight, strength development and water absorption. Effect of three different curing regimes on strength and strength development of the mortars is also the part of this study. The results showed that the high workability slag cement mortars of reasonably high strength, low water absorption and exhibiting early age strength comparable to that of the OPC mortars can be designed in order to cast thin ferrocement elements by the method of pouring.     

Effect of Granulated Blast Furnace Slag and fly ash addition on the strength properties of lightweight mortars containing waste PET aggregates

In this work, the effect of Granulated Blast Furnace Slag (GBFS) and fly ash (FA) addition on the strength properties of lightweight mortars containing waste Poly-ethylene Terephthalate (PET) bottle aggregates was investigated. Investigation was carried out on three groups of mortar specimens. One made with only Normal Portland cement (NPC) as binder, second made with NPC and GBFS together and, third made with NPC and FA together. The industrial wastes mentioned above were used as the replacement of cement on mass basis at the replacement ratio of 50%. The size of shredded PET granules used as aggregate for the preparation of mortar mixtures were between 0 and 4 mm. The waste lightweight PET aggregate (WPLA)–binder ratio (WPLA/b) was 0.60; the water–binder (w/b) ratios were determined as 0.45 and 0.50. The dry unit weight, compressive and flexural–tensile strengths, carbonation depths and drying shrinkage values were measured and presented. The results have shown that modifying GBFS had positive effects on the compressive strength and drying shrinkage values (after 90 days) of the WPLA mortars. However, FA substitution decreased compressive and flexural–tensile strengths and increased carbonation depths. Nevertheless a visible reduction occurred on the drying shrinkage values of FA modifying specimens more than cement specimens and GBFS modified specimens. The test results indicated that, GBFS has a potential of using as the replacement of cement on the WPLA mortars by taking into consideration the characteristics. But using FA as a binder at the replacement ratio of 50% did not improve the overall strength properties. Although it was thought that, using FA as binder at the replacement ratio of 50% for the aim of production WPLA concrete which has a specific strength, would provide advantages of economical and ecological aspects.     

PB-g-PS胶乳改性水泥砂浆的性能

利用氧化还原引发体系,采用半连续乳液接枝共聚的方法合成了聚丁二烯接枝聚苯乙烯(PB-g-PS)接枝共聚胶乳,其中聚丁二烯(PB)与聚苯乙烯(PS)的质量比为70/30,50/50和30/70.在固定流动度为(175±5)mm,且在20℃水中养护6 d,然后在20℃,相对湿度为65%的空气中养护21 d的混合养护条件下,考察了聚灰比、聚丁二烯与聚苯乙烯的质量比对PB-g-PS胶乳改性水泥砂浆的水灰比、流动度、保水率、抗压和抗折强度以及吸水量的影响,并与羧基丁苯胶乳改性水泥砂浆进行了性能对比试验.结果表明:在一定掺量范围内,胶乳都具有良好的减水作用,能有效提高砂浆的保水性能,显著降低聚合物改性砂浆的毛细孔吸水率;加入聚合物对砂浆力学性能有重要影响,使其抗压强度总体降低,抗折强度部分提高,因此,PB-g-PS胶乳可以作为水泥改性剂使用.     

HEMC改性水泥砂浆在硫酸盐侵蚀作用下的力学性能

研究了羟乙基甲基纤维素(HEMC)改性水泥砂浆在硫酸盐侵蚀作用下的力学性能演变规律及HEMC的作用机理.结果表明:HEMC会明显降低水泥砂浆在硫酸盐侵蚀作用下的抗压强度和抗折强度,但能显著提高黏结抗拉强度;硫酸盐短期侵蚀作用能提高HEMC改性水泥砂浆的力学性能,但长期侵蚀作用会显著降低力学性能;HEMC改性水泥砂浆在硫酸盐长期侵蚀作用下仍具有优良的力学性能,原因在于HEMC能优化水泥砂浆的孔结构及内部界面结构,显著降低水分和硫酸根离子的渗透和扩散;就硫酸盐长期侵蚀作用下的力学性能而言,HEMC在水泥砂浆中存在着较佳掺量范围.     

Effect of cement kiln dust (CKD) on mortar and concrete mixtures

The aim of this study was to investigate the use of cement kiln dust (CKD) as a cementitious material in concrete and mortar. CKD was added to concrete and mortar mixtures to study its effect on the strength and on the ability of the cover zone to absorb water, an important factor in the deterioration process. Experimental results on compressive strengths, flexural strength and toughness of concrete samples containing CKD are reported. The sorptivity and the initial surface absorption tests (ISAT) of mortars were used to measure the absorption characteristics for different mortar samples containing CKD. It was found that substitution of cement with CKD does not lead to strength gain for all samples studied and proper addition of CKD has no negative effects on strength properties. It is also shown that mortars prepared using suitable amounts of CKD have better absorption characteristics. However, above certain limits, the water absorption of the mortar increased with increasing CKD contents and decreasing mortar strengths.     

Mechanical properties and microstructure of multilayer graphene oxide cement mortar

This study reports on the effects of multilayer graphene oxide (MGO) on compressive strength, flexural strength, and microstructure of cement mortar. The cement mortar was prepared with type P. II. 52.5 Portland cement, standard sand, and MGO. Four mixes were prepared with inclusion of MGO (0%, 0.02%, 0.04%, and 0.06% by weight of cement). The testing result shows that the compressive of GO-cement mortar increased by 4.84%–13.42%, and the flexural strength increased by 4.37%–8.28% at 3 d. GO-cement mortar’s compressive strength and flexural strength at 7 d increased by 3.84%–12.08% and 2.54%–13.43%, respectively. MGO made little contribution to the increases of compressive strength and flexural strength of cement mortar at 28 d. The results of X-ray diffraction (XRD), scanning electron microscope (SEM), and nitrogen (N₂) adsorption/desorption tests show that the types of hydration products and crystal grain size did not change after adding MGO. Still, it can help to improve the microstructure of the cement mortar via regulating hydration products and can provide more condensed cores to accelerate hydration. Furthermore, the regulating action of MGO for the microstructure of cement mortar at an early age was better than that at 28 d.     

PTB乳液对水泥砂浆力学性能和抗侵蚀性能的影响

研究了PTB乳液改性水泥砂浆的力学性能、抗氯盐和抗硫酸盐侵蚀等性能.结果表明,掺入PTB乳液对水泥净浆有缓凝作用,大幅延长了水泥净浆的终凝时间;掺入PTB乳液降低了水泥砂浆的抗压强度,但是降低抗压/抗折强度比改善了水泥砂浆的延性,提高了水泥砂浆的综合力学性能.PTB乳液/水泥为0.22时的PTB乳液水泥砂浆在氯化钠、硫...     

Sulfate resistance of blended cements containing fly ash and rice husk ash

In this paper, the sulfate resistance of mortars made from ordinary Portland cement containing available pozzolans viz., fly ash and ground rice husk ash (RHA) was studied. Class F lignite fly ash and RHA were used at replacement dosages of 20 and 40% by weight of cement. Expansion of mortar prisms immersed in 5% sodium sulfate solution and the change in the pH values of the solution were monitored. The incorporation of fly ash and RHA reduced the expansion of the mortar bars and the pH values of the solutions. RHA was found to be more effective than fly ash. Examination of the fractured surface of mortar prisms, after a period of immersion, by scanning electron microscopy confirmed that sulfate attack of blended cement mortars was restricted owing to the reductions in calcium hydroxide and C/S ratio of the C–S–H gel in the blended cement mortar. In comparison to Portland cement mortar, less calcium sulfate and much less ettringite formations were found in the mortars made from blended cement containing RHA. The amounts of calcium sulfate and ettringite found in the blended cement mortar containing fly ash were also small but were slightly more than those of RHA mortar. Up to 40% of Portland cement could be replaced with these pozzolans in making blended cement with good sulfate resistance.     

掺矿渣粉和减水剂的HEMC水泥砂浆力学性能

研究了掺矿渣粉和高效减水剂的羟乙基甲基纤维素改性水泥砂浆的力学性能（包括抗压强度、抗折强度、弹性模量、粘结抗拉强度）及其与新拌砂浆体积密度和硬化砂浆孔隙率的关系。掺加减水剂、矿渣粉和羟乙基甲基纤维素后,砂浆的抗压强度与新拌砂浆体积密度和硬化砂浆孔隙率密切相关,抗折强度与之部分相关,粘结抗拉强度则与之无关。减水剂和矿渣粉可增加砂浆的密实度,减小孔隙率,从而使砂浆的抗压强度、抗折强度、粘结抗拉强度和弹性模量得到提高;羟乙基甲基纤维素虽可保持砂浆的粘结抗拉强度稳定,但却使抗压强度和弹性模量降低,减小剂、矿渣 粉和羟乙基甲基纤维素的共同作用,即增加了砂浆的粘结抗拉强度,又使砂浆有足够的抗压强度、抗折强度和弹性模量,当羟乙基甲基纤维素掺量被抑制在一定范围内时,砂浆便可用作混凝土桥面材料及其修补材料。